Table of Contents
This chapter contains information about
MySQL Cluster, which is a
high-availability, high-redundancy version of MySQL adapted for the
distributed computing environment. Recent MySQL Cluster release
series use version 7 of the NDB
storage
engine (also known as NDBCLUSTER
) to
enable running several computers with MySQL servers and other
software in a cluster. MySQL Cluster NDB 7.5, now available as a
Developer Milestone release, incorporates version 7.5 of the
NDB
storage engine. The latest releases available
for production, MySQL Cluster NDB 7.3 and MySQL Cluster NDB 7.4,
incorporate NDB
versions 7.3 and 7.4,
respectively.
Support for the NDB
storage engine is
not included in standard MySQL Server 5.7 binaries built by Oracle.
Instead, users of MySQL Cluster binaries from Oracle should upgrade
to the most recent binary release of MySQL Cluster for supported
platforms—these include RPMs that should work with most Linux
distributions. MySQL Cluster users who build from source should use
the sources provided for MySQL Cluster. (Locations where the sources
can be obtained are listed later in this section.)
This chapter contains information about MySQL Cluster NDB 7.5 releases through 5.7.13-ndb-7.5.3. MySQL Cluster NDB 7.5 is currently available as a Developer Milestone release. The MySQL Cluster NDB 7.4 and MySQL Cluster NDB 7.3 release series are Generally Available (GA). MySQL Cluster NDB 7.2 is a previous GA release series which is still available. We currently recommend that new deployments for production use MySQL Cluster NDB 7.4. For more information about MySQL Cluster NDB 7.4 and MySQL Cluster NDB 7.3, see MySQL Cluster NDB 7.3 and MySQL Cluster NDB 7.4. For information about MySQL Cluster NDB 7.2, see MySQL Cluster NDB 7.2.
Supported Platforms. MySQL Cluster is currently available and supported on a number of platforms. For exact levels of support available for on specific combinations of operating system versions, operating system distributions, and hardware platforms, please refer to http://www.mysql.com/support/supportedplatforms/cluster.html.
Availability. MySQL Cluster binary and source packages are available for supported platforms from http://dev.mysql.com/downloads/cluster/.
MySQL Cluster release numbers.
MySQL Cluster follows a somewhat different release pattern from
the mainline MySQL Server 5.7 series of releases. In this
Manual and other MySQL documentation, we
identify these and later MySQL Cluster releases employing a
version number that begins with “NDB”. This version
number is that of the NDBCLUSTER
storage engine used in the release, and not of the MySQL server
version on which the MySQL Cluster release is based.
Version strings used in MySQL Cluster software. The version string displayed by MySQL Cluster programs uses this format:
mysql-mysql_server_version
-ndb-ndb_engine_version
mysql_server_version
represents the
version of the MySQL Server on which the MySQL Cluster release is
based. For all MySQL Cluster NDB 7.5 releases, this is
“5.7”. ndb_engine_version
is
the version of the NDB
storage engine
used by this release of the MySQL Cluster software. You can see this
format used in the mysql client, as shown here:
shell>mysql
Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 2 Server version: 5.7.13-ndb-7.5.3 Source distribution Type 'help;' or '\h' for help. Type '\c' to clear the buffer. mysql>SELECT VERSION()\G
*************************** 1. row *************************** VERSION(): 5.7.13-ndb-7.5.3 1 row in set (0.00 sec)
This version string is also displayed in the output of the
SHOW
command in the ndb_mgm
client:
ndb_mgm> SHOW
Connected to Management Server at: localhost:1186
Cluster Configuration
---------------------
[ndbd(NDB)] 2 node(s)
id=1 @10.0.10.6 (5.7.13-ndb-7.5.3, Nodegroup: 0, *)
id=2 @10.0.10.8 (5.7.13-ndb-7.5.3, Nodegroup: 0)
[ndb_mgmd(MGM)] 1 node(s)
id=3 @10.0.10.2 (5.7.13-ndb-7.5.3)
[mysqld(API)] 2 node(s)
id=4 @10.0.10.10 (5.7.13-ndb-7.5.3)
id=5 (not connected, accepting connect from any host)
The version string identifies the mainline MySQL version from which
the MySQL Cluster release was branched and the version of the
NDB
storage engine used. For example,
the full version string for MySQL Cluster NDB 7.4.4 (the first MySQL
Cluster NDB 7.4 GA release) was
mysql-5.6.23-ndb-7.4.4
. From this we can
determine the following:
Since the portion of the version string preceding
“-ndb-
” is the base MySQL Server
version, this means that MySQL Cluster NDB 7.4.4 derived from
MySQL 5.6.23, and contained all feature enhancements and bug
fixes from MySQL 5.6 up to and including MySQL 5.6.23.
Since the portion of the version string following
“-ndb-
” represents the version
number of the NDB
(or
NDBCLUSTER
) storage engine, MySQL
Cluster NDB 7.4.4 used version 7.4.4 of the
NDBCLUSTER
storage engine.
New MySQL Cluster releases are numbered according to updates in the
NDB
storage engine, and do not necessarily
correspond in a one-to-one fashion with mainline MySQL Server
releases. For example, MySQL Cluster NDB 7.4.4 (as previously noted)
was based on MySQL 5.6.23, while MySQL Cluster NDB 7.4.3 was based
on MySQL 5.6.22 (version string:
mysql-5.6.22-ndb-7.4.3
).
Compatibility with standard MySQL 5.7 releases.
While many standard MySQL schemas and applications can work using
MySQL Cluster, it is also true that unmodified applications and
database schemas may be slightly incompatible or have suboptimal
performance when run using MySQL Cluster (see
Section 19.1.6, “Known Limitations of MySQL Cluster”). Most of these issues
can be overcome, but this also means that you are very unlikely to
be able to switch an existing application datastore—that
currently uses, for example, MyISAM
or InnoDB
—to use the
NDB
storage engine without allowing
for the possibility of changes in schemas, queries, and
applications. In addition, the MySQL Server and MySQL Cluster
codebases diverge considerably, so that the standard
mysqld cannot function as a drop-in replacement
for the version of mysqld supplied with MySQL
Cluster.
MySQL Cluster development source trees. MySQL Cluster development trees can also be accessed from https://github.com/mysql/mysql-server.
The MySQL Cluster development sources maintained at https://github.com/mysql/mysql-server are licensed under the GPL. For information about obtaining MySQL sources using Bazaar and building them yourself, see Section 2.9.3, “Installing MySQL Using a Development Source Tree”.
As with MySQL Server 5.7, MySQL Cluster NDB 7.5 releases are built using CMake.
Currently, MySQL Cluster NDB 7.3 and MySQL Cluster NDB 7.4 releases are Generally Available (GA). We recommend that new deployments use MySQL Cluster NDB 7.4. MySQL Cluster NDB 7.1 and earlier versions are no longer in active development. For an overview of major features added in MySQL Cluster NDB 7.4, see What is New in MySQL Cluster NDB 7.4. For similar information about MySQL Cluster NDB 7.3, see What is New in MySQL Cluster NDB 7.3. For an overview of major features added in previous MySQL Cluster releases, see What is New in MySQL Cluster.
The contents of this chapter are subject to revision as MySQL Cluster continues to evolve. Additional information regarding MySQL Cluster can be found on the MySQL Web site at http://www.mysql.com/products/cluster/.
Additional Resources. More information about MySQL Cluster can be found in the following places:
For answers to some commonly asked questions about MySQL Cluster, see Section A.10, “MySQL 5.7 FAQ: MySQL Cluster”.
The MySQL Cluster mailing list: http://lists.mysql.com/cluster.
The MySQL Cluster Forum: http://forums.mysql.com/list.php?25.
Many MySQL Cluster users and developers blog about their experiences with MySQL Cluster, and make feeds of these available through PlanetMySQL.
MySQL Cluster is a technology that enables clustering of in-memory databases in a shared-nothing system. The shared-nothing architecture enables the system to work with very inexpensive hardware, and with a minimum of specific requirements for hardware or software.
MySQL Cluster is designed not to have any single point of failure. In a shared-nothing system, each component is expected to have its own memory and disk, and the use of shared storage mechanisms such as network shares, network file systems, and SANs is not recommended or supported.
MySQL Cluster integrates the standard MySQL server with an in-memory
clustered storage engine called NDB
(which stands for “Network
DataBase”). In our
documentation, the term NDB
refers to
the part of the setup that is specific to the storage engine,
whereas “MySQL Cluster” refers to the combination of
one or more MySQL servers with the NDB
storage engine.
A MySQL Cluster consists of a set of computers, known as hosts, each running one or more processes. These processes, known as nodes, may include MySQL servers (for access to NDB data), data nodes (for storage of the data), one or more management servers, and possibly other specialized data access programs. The relationship of these components in a MySQL Cluster is shown here:
All these programs work together to form a MySQL Cluster (see
Section 19.4, “MySQL Cluster Programs”. When data is stored by the
NDB
storage engine, the tables (and
table data) are stored in the data nodes. Such tables are directly
accessible from all other MySQL servers (SQL nodes) in the cluster.
Thus, in a payroll application storing data in a cluster, if one
application updates the salary of an employee, all other MySQL
servers that query this data can see this change immediately.
Although a MySQL Cluster SQL node uses the mysqld server daemon, it differs in a number of critical respects from the mysqld binary supplied with the MySQL 5.7 distributions, and the two versions of mysqld are not interchangeable.
In addition, a MySQL server that is not connected to a MySQL Cluster
cannot use the NDB
storage engine and
cannot access any MySQL Cluster data.
The data stored in the data nodes for MySQL Cluster can be mirrored; the cluster can handle failures of individual data nodes with no other impact than that a small number of transactions are aborted due to losing the transaction state. Because transactional applications are expected to handle transaction failure, this should not be a source of problems.
Individual nodes can be stopped and restarted, and can then rejoin the system (cluster). Rolling restarts (in which all nodes are restarted in turn) are used in making configuration changes and software upgrades (see Section 19.5.5, “Performing a Rolling Restart of a MySQL Cluster”). Rolling restarts are also used as part of the process of adding new data nodes online (see Section 19.5.14, “Adding MySQL Cluster Data Nodes Online”). For more information about data nodes, how they are organized in a MySQL Cluster, and how they handle and store MySQL Cluster data, see Section 19.1.2, “MySQL Cluster Nodes, Node Groups, Replicas, and Partitions”.
Backing up and restoring MySQL Cluster databases can be done using
the NDB
-native functionality found in the MySQL
Cluster management client and the ndb_restore
program included in the MySQL Cluster distribution. For more
information, see Section 19.5.3, “Online Backup of MySQL Cluster”, and
Section 19.4.20, “ndb_restore — Restore a MySQL Cluster Backup”. You can also
use the standard MySQL functionality provided for this purpose in
mysqldump and the MySQL server. See
Section 5.5.4, “mysqldump — A Database Backup Program”, for more information.
MySQL Cluster nodes can use a number of different transport mechanisms for inter-node communications, including TCP/IP using standard 100 Mbps or faster Ethernet hardware. It is also possible to use the high-speed Scalable Coherent Interface (SCI) protocol with MySQL Cluster, although this is not required to use MySQL Cluster. SCI requires special hardware and software; see Section 19.3.4, “Using High-Speed Interconnects with MySQL Cluster”, for more about SCI and using it with MySQL Cluster.
NDBCLUSTER
(also known as NDB
) is an in-memory
storage engine offering high-availability and data-persistence
features.
The NDBCLUSTER
storage engine can be
configured with a range of failover and load-balancing options,
but it is easiest to start with the storage engine at the cluster
level. MySQL Cluster's NDB
storage
engine contains a complete set of data, dependent only on other
data within the cluster itself.
The “Cluster” portion of MySQL Cluster is configured independently of the MySQL servers. In a MySQL Cluster, each part of the cluster is considered to be a node.
In many contexts, the term “node” is used to indicate a computer, but when discussing MySQL Cluster it means a process. It is possible to run multiple nodes on a single computer; for a computer on which one or more cluster nodes are being run we use the term cluster host.
There are three types of cluster nodes, and in a minimal MySQL Cluster configuration, there will be at least three nodes, one of each of these types:
Management node: The role of this type of node is to manage the other nodes within the MySQL Cluster, performing such functions as providing configuration data, starting and stopping nodes, and running backups. Because this node type manages the configuration of the other nodes, a node of this type should be started first, before any other node. An MGM node is started with the command ndb_mgmd.
Data node: This type of node stores cluster data. There are as many data nodes as there are replicas, times the number of fragments (see Section 19.1.2, “MySQL Cluster Nodes, Node Groups, Replicas, and Partitions”). For example, with two replicas, each having two fragments, you need four data nodes. One replica is sufficient for data storage, but provides no redundancy; therefore, it is recommended to have 2 (or more) replicas to provide redundancy, and thus high availability. A data node is started with the command ndbd (see Section 19.4.1, “ndbd — The MySQL Cluster Data Node Daemon”) or ndbmtd (see Section 19.4.3, “ndbmtd — The MySQL Cluster Data Node Daemon (Multi-Threaded)”).
MySQL Cluster tables are normally stored completely in memory rather than on disk (this is why we refer to MySQL Cluster as an in-memory database). However, some MySQL Cluster data can be stored on disk; see Section 19.5.13, “MySQL Cluster Disk Data Tables”, for more information.
SQL node: This is a node
that accesses the cluster data. In the case of MySQL Cluster,
an SQL node is a traditional MySQL server that uses the
NDBCLUSTER
storage engine. An SQL
node is a mysqld process started with the
--ndbcluster
and
--ndb-connectstring
options, which are
explained elsewhere in this chapter, possibly with additional
MySQL server options as well.
An SQL node is actually just a specialized type of API node, which designates any application which accesses MySQL Cluster data. Another example of an API node is the ndb_restore utility that is used to restore a cluster backup. It is possible to write such applications using the NDB API. For basic information about the NDB API, see Getting Started with the NDB API.
It is not realistic to expect to employ a three-node setup in a production environment. Such a configuration provides no redundancy; to benefit from MySQL Cluster's high-availability features, you must use multiple data and SQL nodes. The use of multiple management nodes is also highly recommended.
For a brief introduction to the relationships between nodes, node groups, replicas, and partitions in MySQL Cluster, see Section 19.1.2, “MySQL Cluster Nodes, Node Groups, Replicas, and Partitions”.
Configuration of a cluster involves configuring each individual node in the cluster and setting up individual communication links between nodes. MySQL Cluster is currently designed with the intention that data nodes are homogeneous in terms of processor power, memory space, and bandwidth. In addition, to provide a single point of configuration, all configuration data for the cluster as a whole is located in one configuration file.
The management server manages the cluster configuration file and the cluster log. Each node in the cluster retrieves the configuration data from the management server, and so requires a way to determine where the management server resides. When interesting events occur in the data nodes, the nodes transfer information about these events to the management server, which then writes the information to the cluster log.
In addition, there can be any number of cluster client processes
or applications. These include standard MySQL clients,
NDB
-specific API programs, and management
clients. These are described in the next few paragraphs.
Standard MySQL clients. MySQL Cluster can be used with existing MySQL applications written in PHP, Perl, C, C++, Java, Python, Ruby, and so on. Such client applications send SQL statements to and receive responses from MySQL servers acting as MySQL Cluster SQL nodes in much the same way that they interact with standalone MySQL servers.
MySQL clients using a MySQL Cluster as a data source can be
modified to take advantage of the ability to connect with multiple
MySQL servers to achieve load balancing and failover. For example,
Java clients using Connector/J 5.0.6 and later can use
jdbc:mysql:loadbalance://
URLs (improved in
Connector/J 5.1.7) to achieve load balancing transparently; for
more information about using Connector/J with MySQL Cluster, see
Using Connector/J with MySQL Cluster.
NDB client programs.
Client programs can be written that access MySQL Cluster data
directly from the NDBCLUSTER
storage engine,
bypassing any MySQL Servers that may be connected to the
cluster, using the NDB
API, a high-level C++ API. Such applications may be
useful for specialized purposes where an SQL interface to the
data is not needed. For more information, see
The NDB API.
NDB
-specific Java applications can also be
written for MySQL Cluster using the
MySQL Cluster Connector for
Java. This MySQL Cluster Connector includes
ClusterJ, a high-level
database API similar to object-relational mapping persistence
frameworks such as Hibernate and JPA that connect directly to
NDBCLUSTER
, and so does not require access to a
MySQL Server. Support is also provided in MySQL Cluster
ClusterJPA, an OpenJPA
implementation for MySQL Cluster that leverages the strengths of
ClusterJ and JDBC; ID lookups and other fast operations are
performed using ClusterJ (bypassing the MySQL Server), while more
complex queries that can benefit from MySQL's query optimizer
are sent through the MySQL Server, using JDBC. See
Java and MySQL Cluster, and
The ClusterJ API and Data Object Model, for more
information.
MySQL Cluster also supports applications written in JavaScript
using Node.js. The MySQL Connector for JavaScript includes
adapters for direct access to the NDB
storage
engine and as well as for the MySQL Server. Applications using
this Connector are typically event-driven and use a domain object
model similar in many ways to that employed by ClusterJ. For more
information, see MySQL NoSQL Connector for JavaScript.
The Memcache API for MySQL Cluster, implemented as the loadable ndbmemcache storage engine for memcached version 1.6 and later, can be used to provide a persistent MySQL Cluster data store, accessed using the memcache protocol.
The standard memcached caching engine is included in the MySQL Cluster NDB 7.5 distribution. Each memcached server has direct access to data stored in MySQL Cluster, but is also able to cache data locally and to serve (some) requests from this local cache.
For more information, see ndbmemcache—Memcache API for MySQL Cluster.
Management clients. These clients connect to the management server and provide commands for starting and stopping nodes gracefully, starting and stopping message tracing (debug versions only), showing node versions and status, starting and stopping backups, and so on. An example of this type of program is the ndb_mgm management client supplied with MySQL Cluster (see Section 19.4.5, “ndb_mgm — The MySQL Cluster Management Client”). Such applications can be written using the MGM API, a C-language API that communicates directly with one or more MySQL Cluster management servers. For more information, see The MGM API.
Oracle also makes available MySQL Cluster Manager, which provides an advanced command-line interface simplifying many complex MySQL Cluster management tasks, such restarting a MySQL Cluster with a large number of nodes. The MySQL Cluster Manager client also supports commands for getting and setting the values of most node configuration parameters as well as mysqld server options and variables relating to MySQL Cluster. See MySQL™ Cluster Manager 1.4.0 User Manual, for more information.
Event logs. MySQL Cluster logs events by category (startup, shutdown, errors, checkpoints, and so on), priority, and severity. A complete listing of all reportable events may be found in Section 19.5.6, “Event Reports Generated in MySQL Cluster”. Event logs are of the two types listed here:
Cluster log: Keeps a record of all desired reportable events for the cluster as a whole.
Node log: A separate log which is also kept for each individual node.
Under normal circumstances, it is necessary and sufficient to keep and examine only the cluster log. The node logs need be consulted only for application development and debugging purposes.
Checkpoint.
Generally speaking, when data is saved to disk, it is said that
a checkpoint has been
reached. More specific to MySQL Cluster, a checkpoint is a point
in time where all committed transactions are stored on disk.
With regard to the NDB
storage
engine, there are two types of checkpoints which work together
to ensure that a consistent view of the cluster's data is
maintained. These are shown in the following list:
Local Checkpoint (LCP): This is a checkpoint that is specific to a single node; however, LCPs take place for all nodes in the cluster more or less concurrently. An LCP involves saving all of a node's data to disk, and so usually occurs every few minutes. The precise interval varies, and depends upon the amount of data stored by the node, the level of cluster activity, and other factors.
Global Checkpoint (GCP): A GCP occurs every few seconds, when transactions for all nodes are synchronized and the redo-log is flushed to disk.
For more information about the files and directories created by local checkpoints and global checkpoints, see MySQL Cluster Data Node File System Directory Files.
This section discusses the manner in which MySQL Cluster divides and duplicates data for storage.
A number of concepts central to an understanding of this topic are discussed in the next few paragraphs.
(Data) Node. An ndbd process, which stores a replica —that is, a copy of the partition (see below) assigned to the node group of which the node is a member.
Each data node should be located on a separate computer. While it is also possible to host multiple ndbd processes on a single computer, such a configuration is not supported.
It is common for the terms “node” and “data node” to be used interchangeably when referring to an ndbd process; where mentioned, management nodes (ndb_mgmd processes) and SQL nodes (mysqld processes) are specified as such in this discussion.
Node Group. A node group consists of one or more nodes, and stores partitions, or sets of replicas (see next item).
The number of node groups in a MySQL Cluster is not directly
configurable; it is a function of the number of data nodes and of
the number of replicas
(NoOfReplicas
configuration parameter), as shown here:
[number_of_node_groups
] =number_of_data_nodes
/NoOfReplicas
Thus, a MySQL Cluster with 4 data nodes has 4 node groups if
NoOfReplicas
is set to 1
in the config.ini
file, 2 node groups if
NoOfReplicas
is set to 2,
and 1 node group if
NoOfReplicas
is set to 4.
Replicas are discussed later in this section; for more information
about NoOfReplicas
, see
Section 19.3.3.6, “Defining MySQL Cluster Data Nodes”.
All node groups in a MySQL Cluster must have the same number of data nodes.
You can add new node groups (and thus new data nodes) online, to a running MySQL Cluster; see Section 19.5.14, “Adding MySQL Cluster Data Nodes Online”, for more information.
Partition. This is a portion of the data stored by the cluster. There are as many cluster partitions as nodes participating in the cluster. Each node is responsible for keeping at least one copy of any partitions assigned to it (that is, at least one replica) available to the cluster.
A replica belongs entirely to a single node; a node can (and usually does) store several replicas.
NDB and user-defined partitioning.
MySQL Cluster normally partitions
NDBCLUSTER
tables automatically.
However, it is also possible to employ user-defined partitioning
with NDBCLUSTER
tables. This is
subject to the following limitations:
Only the KEY
and LINEAR
KEY
partitioning schemes are supported in production
with NDB
tables.
When using ndbd, the maximum number of
partitions that may be defined explicitly for any
NDB
table is 8 *
[
.
(The number of node groups in a MySQL Cluster is determined as
discussed previously in this section.)
number of node groups
]
When using ndbmtd, this maximum is also
affected by the number of local query handler threads, which
is determined by the value of the
MaxNoOfExecutionThreads
configuration parameter. In such cases, the maximum number of
partitions that may be defined explicitly for an
NDB
table is equal to 4
* MaxNoOfExecutionThreads * [
.
number of node
groups
]
See Section 19.4.3, “ndbmtd — The MySQL Cluster Data Node Daemon (Multi-Threaded)”, for more information.
For more information relating to MySQL Cluster and user-defined partitioning, see Section 19.1.6, “Known Limitations of MySQL Cluster”, and Section 20.6.2, “Partitioning Limitations Relating to Storage Engines”.
Replica. This is a copy of a cluster partition. Each node in a node group stores a replica. Also sometimes known as a partition replica. The number of replicas is equal to the number of nodes per node group.
The following diagram illustrates a MySQL Cluster with four data nodes, arranged in two node groups of two nodes each; nodes 1 and 2 belong to node group 0, and nodes 3 and 4 belong to node group 1.
Only data (ndbd) nodes are shown here; although a working cluster requires an ndb_mgm process for cluster management and at least one SQL node to access the data stored by the cluster, these have been omitted in the figure for clarity.
The data stored by the cluster is divided into four partitions, numbered 0, 1, 2, and 3. Each partition is stored—in multiple copies—on the same node group. Partitions are stored on alternate node groups as follows:
Partition 0 is stored on node group 0; a primary replica (primary copy) is stored on node 1, and a backup replica (backup copy of the partition) is stored on node 2.
Partition 1 is stored on the other node group (node group 1); this partition's primary replica is on node 3, and its backup replica is on node 4.
Partition 2 is stored on node group 0. However, the placing of its two replicas is reversed from that of Partition 0; for Partition 2, the primary replica is stored on node 2, and the backup on node 1.
Partition 3 is stored on node group 1, and the placement of its two replicas are reversed from those of partition 1. That is, its primary replica is located on node 4, with the backup on node 3.
What this means regarding the continued operation of a MySQL Cluster is this: so long as each node group participating in the cluster has at least one node operating, the cluster has a complete copy of all data and remains viable. This is illustrated in the next diagram.
In this example, where the cluster consists of two node groups of two nodes each, any combination of at least one node in node group 0 and at least one node in node group 1 is sufficient to keep the cluster “alive” (indicated by arrows in the diagram). However, if both nodes from either node group fail, the remaining two nodes are not sufficient (shown by the arrows marked out with an X); in either case, the cluster has lost an entire partition and so can no longer provide access to a complete set of all cluster data.
One of the strengths of MySQL Cluster is that it can be run on commodity hardware and has no unusual requirements in this regard, other than for large amounts of RAM, due to the fact that all live data storage is done in memory. (It is possible to reduce this requirement using Disk Data tables—see Section 19.5.13, “MySQL Cluster Disk Data Tables”, for more information about these.) Naturally, multiple and faster CPUs can enhance performance. Memory requirements for other MySQL Cluster processes are relatively small.
The software requirements for MySQL Cluster are also modest. Host operating systems do not require any unusual modules, services, applications, or configuration to support MySQL Cluster. For supported operating systems, a standard installation should be sufficient. The MySQL software requirements are simple: all that is needed is a production release of MySQL Cluster. It is not strictly necessary to compile MySQL yourself merely to be able to use MySQL Cluster. We assume that you are using the binaries appropriate to your platform, available from the MySQL Cluster software downloads page at http://dev.mysql.com/downloads/cluster/.
For communication between nodes, MySQL Cluster supports TCP/IP networking in any standard topology, and the minimum expected for each host is a standard 100 Mbps Ethernet card, plus a switch, hub, or router to provide network connectivity for the cluster as a whole. We strongly recommend that a MySQL Cluster be run on its own subnet which is not shared with machines not forming part of the cluster for the following reasons:
Security. Communications between MySQL Cluster nodes are not encrypted or shielded in any way. The only means of protecting transmissions within a MySQL Cluster is to run your MySQL Cluster on a protected network. If you intend to use MySQL Cluster for Web applications, the cluster should definitely reside behind your firewall and not in your network's De-Militarized Zone (DMZ) or elsewhere.
See Section 19.5.12.1, “MySQL Cluster Security and Networking Issues”, for more information.
Efficiency. Setting up a MySQL Cluster on a private or protected network enables the cluster to make exclusive use of bandwidth between cluster hosts. Using a separate switch for your MySQL Cluster not only helps protect against unauthorized access to MySQL Cluster data, it also ensures that MySQL Cluster nodes are shielded from interference caused by transmissions between other computers on the network. For enhanced reliability, you can use dual switches and dual cards to remove the network as a single point of failure; many device drivers support failover for such communication links.
Network communication and latency. MySQL Cluster requires communication between data nodes and API nodes (including SQL nodes), as well as between data nodes and other data nodes, to execute queries and updates. Communication latency between these processes can directly affect the observed performance and latency of user queries. In addition, to maintain consistency and service despite the silent failure of nodes, MySQL Cluster uses heartbeating and timeout mechanisms which treat an extended loss of communication from a node as node failure. This can lead to reduced redundancy. Recall that, to maintain data consistency, a MySQL Cluster shuts down when the last node in a node group fails. Thus, to avoid increasing the risk of a forced shutdown, breaks in communication between nodes should be avoided wherever possible.
The failure of a data or API node results in the abort of all uncommitted transactions involving the failed node. Data node recovery requires synchronization of the failed node's data from a surviving data node, and re-establishment of disk-based redo and checkpoint logs, before the data node returns to service. This recovery can take some time, during which the Cluster operates with reduced redundancy.
Heartbeating relies on timely generation of heartbeat signals by all nodes. This may not be possible if the node is overloaded, has insufficient machine CPU due to sharing with other programs, or is experiencing delays due to swapping. If heartbeat generation is sufficiently delayed, other nodes treat the node that is slow to respond as failed.
This treatment of a slow node as a failed one may or may not be
desirable in some circumstances, depending on the impact of the
node's slowed operation on the rest of the cluster. When
setting timeout values such as
HeartbeatIntervalDbDb
and
HeartbeatIntervalDbApi
for
MySQL Cluster, care must be taken care to achieve quick detection,
failover, and return to service, while avoiding potentially
expensive false positives.
Where communication latencies between data nodes are expected to be higher than would be expected in a LAN environment (on the order of 100 µs), timeout parameters must be increased to ensure that any allowed periods of latency periods are well within configured timeouts. Increasing timeouts in this way has a corresponding effect on the worst-case time to detect failure and therefore time to service recovery.
LAN environments can typically be configured with stable low latency, and such that they can provide redundancy with fast failover. Individual link failures can be recovered from with minimal and controlled latency visible at the TCP level (where MySQL Cluster normally operates). WAN environments may offer a range of latencies, as well as redundancy with slower failover times. Individual link failures may require route changes to propagate before end-to-end connectivity is restored. At the TCP level this can appear as large latencies on individual channels. The worst-case observed TCP latency in these scenarios is related to the worst-case time for the IP layer to reroute around the failures.
SCI support. It is also possible to use the high-speed Scalable Coherent Interface (SCI) with MySQL Cluster, but this is not a requirement. See Section 19.3.4, “Using High-Speed Interconnects with MySQL Cluster”, for more about this protocol and its use with MySQL Cluster.
In this section, we describe changes in the implementation of MySQL Cluster in MySQL MySQL Cluster NDB 7.5 as compared to MySQL Cluster NDB 7.4 and earlier release series. Changes and features most likely to be of interest are shown in the following list:
ndbinfo Enhancements.
A number of changes are made in the
ndbinfo
database, chief of
which is that it now provides detailed information about
MySQL Cluster node configuration parameters.
The config_params
table has
been made read-only, and has been enhanced with additional
columns providing information about each configuration
parameter, including the parameter's type, default value,
maximum and minimum values (where applicable), a brief
description of the parameter, and whether the parameter is
required. This table also provides each parameter with a
unique param_number
.
A row in the config_values
table shows the current value of a given parameter on the node
having a specified ID. The parameter is identified by the
value of the config_param
column, which
maps to the config_params
table's
param_number
.
Using this relationship you can write a join on these two tables to obtain the default, maximum, minimum, and current values for one or more MySQL Cluster configuration parameters by name. An example SQL statement using such a join is shown here:
SELECT p.param_name AS Name, v.node_id AS Node, p.param_type AS Type, p.param_default AS 'Default', p.param_min AS Minimum, p.param_max AS Maximum, CASE p.param_mandatory WHEN 1 THEN 'Y' ELSE 'N' END AS 'Required', v.config_value AS Current FROM config_params p JOIN config_values v ON p.param_number = v.config_param WHERE p. param_name IN ('NodeId', 'HostName','DataMemory', 'IndexMemory');
For more information about these changes, see Section 19.5.10.7, “The ndbinfo config_params Table”. See Section 19.5.10.8, “The ndbinfo config_values Table”, for further information and examples.
In addition, the ndbinfo
database no longer
depends on the MyISAM
storage engine. All
ndbinfo
tables and views now use
NDB
(shown as NDBINFO
).
ndb_binlog_index No Longer Dependent On MyISAM.
As of MySQL Cluster NDB 7.5.2, the
ndb_binlog_index
table employed in MySQL
Cluster Replication now uses the
InnoDB
storage engine instead
of MyISAM
. When upgrading, you can run
mysql_upgrade with
--force
--upgrade-system-tables
to cause it to execute
ALTER TABLE ...
ENGINE=INNODB
on this table. Use of
MyISAM
for this table remains supported
for backward compatibility.
A benefit of this change is that it makes it possible to depend on transactional behavior and lock-free reads for this table, which can help alleviate concurrency issues during purge operations and log rotation, and improve the availability of this table.
ALTER TABLE Changes.
MySQL Cluster formerly supported an alternative syntax for
online ALTER TABLE
. This is
no longer supported in MySQL Cluster NDB 7.5, which makes
exclusive use of ALGORITHM =
DEFAULT|COPY|INPLACE
for table DDL, as in the
standard MySQL Server.
Another change affecting the use of this statement is that
ALTER TABLE ... ALGORITHM=INPLACE RENAME
may now contain DDL operations in addition to the renaming.
ExecuteOnComputer Parameter Deprecated.
The ExecuteOnComputer
configuration
parameter for
management
nodes,
data
nodes, and
API
nodes has been deprecated and is now subject to
removal in a future release of MySQL Cluster. You should use
the equivalent HostName
parameter for all
three types of nodes.
records-per-key Optimization. The NDB handler now uses the records-per-key interface for index statistics implemented for the optimizer in MySQL 5.7.5. Some of the benefits from this change include those listed here:
The optimizer now chooses better execution plans in many cases where a less optimal join index or table join order would previously have been chosen
Row estimates shown by
EXPLAIN
are more accurate
Cardinality estimates shown by SHOW
INDEX
are improved
Connection Pool Node IDs.
MySQL Cluster NDB 7.5.0 adds the mysqld
--ndb-cluster-connection-pool-nodeids
option, which allows a set of node IDs to be set for the
connection pool. This setting overrides
--ndb-nodeid
, which means
that it also overrides both the
--ndb-connectstring
option
and the NDB_CONNECTSTRING
environment
variable.
You can set the size for the connection pool using the
--ndb-cluster-connection-pool
option for mysqld.
create_old_temporals Removed.
The create_old_temporals
system variable
was deprecated in MySQL Cluster NDB 7.4, and has now been
removed.
ndb_mgm Client PROMPT Command.
MySQL Cluster NDB 7.5 adds a new command for setting the
client's command-line prompt. The following example
illustrates the use of the
PROMPT
command:
ndb_mgm>PROMPT mgm#1:
mgm#1:SHOW
Cluster Configuration --------------------- [ndbd(NDB)] 4 node(s) id=5 @10.100.1.1 (mysql-5.7.13-ndb-7.5.3, Nodegroup: 0, *) id=6 @10.100.1.3 (mysql-5.7.13-ndb-7.5.3, Nodegroup: 0) id=7 @10.100.1.9 (mysql-5.7.13-ndb-7.5.3, Nodegroup: 1) id=8 @10.100.1.11 (mysql-5.7.13-ndb-7.5.3, Nodegroup: 1) [ndb_mgmd(MGM)] 1 node(s) id=50 @10.100.1.8 (mysql-5.7.13-ndb-7.5.3) [mysqld(API)] 2 node(s) id=100 @10.100.1.8 (5.7.13-ndb-7.5.3) id=101 @10.100.1.10 (5.7.13-ndb-7.5.3) mgm#1:PROMPT
ndb_mgm>EXIT
jon@valhaj:/usr/local/mysql/bin>
For additional information and examples, see Section 19.5.2, “Commands in the MySQL Cluster Management Client”.
Deprecated Parameters Removed. The following MySQL Cluster data node configuration parameters were deprecated in previous releases of MySQL Cluster, and were removed in MySQL Cluster NDB 7.5.0:
Id
: deprecated in NDB 7.1.9; replaced
by NodeId
.
NoOfDiskPagesToDiskDuringRestartTUP
,
NoOfDiskPagesToDiskDuringRestartACC
:
both deprecated, had no effect; replaced in MySQL 5.1.6 by
DiskCheckpointSpeedInRestart
, which
itself was later deprecated (in NDB 7.4.1) and is now also
removed.
NoOfDiskPagesToDiskAfterRestartACC
,
NoOfDiskPagesToDiskAfterRestartTUP
:
both deprecated, had no effect; replaced in MySQL 5.1.6 by
DiskCheckpointSpeed
, which itself was
later deprecated (in NDB 7.4.1) and is now also removed.
ReservedSendBufferMemory
: deprecated in
NDB 7.2.5; no longer had any effect.
MaxNoOfIndexes
: archaic (pre-MySQL
4.1), had no effect; long since replaced by
MaxNoOfOrderedIndexes
or
MaxNoOfUniqueHashIndexes
.
Discless
: archaic (pre-MySQL 4.1)
synonym for and long since replaced by
Diskless
.
The archaic and unused (and for this reason also previously
undocumented) ByteOrder
computer
configuration parameter was also removed in MySQL Cluster NDB
7.5.0.
The parameters just described are not supported in MySQL Cluster NDB 7.5. Attempting to use any of these parameters in a MySQL Cluster configuration file now results in an error.
DBTC Scan Enhancements.
Scans have been improved by reducing the number of signals
used for communication between the DBTC
and DBDIH
kernel blocks in
NDB
, enabling higher
scalability of data nodes when used for scan operations by
decreasing the use of CPU resources for scan operations, in
some cases by an estimated five percent.
Also as result of these changes response times should be
greatly improved, which could help prevent issues with
overload of the main threads. In addition, scans made in the
BACKUP
kernel block have also been improved
and made more efficient than in previous releases.
JSON column support.
MySQL Cluster NDB 7.5.2 and later supports the
JSON
column type for
NDB
tables and the JSON functions found
in the MySQL Server, subject to the limitation that an
NDB
table can have at most 3
JSON
columns.
Read from any replica; specify number of hashmap partition fragments.
Previously, all reads were directed towards the primary
replica except for simple reads. (A simple read is a reads
that lock the row while reading it.) Beginning with MySQL
Cluster NDB 7.5.2, it is possible to enabling reads from any
replica. This is disabled by default but can be enabled for
a given SQL node using the
ndb_read_backup
system
variable added in this release.
Previously, it was possible to define tables with only one type of partition mapping, with one primary partition on each LDM in each node, but in MySQL Cluster NDB 7.5.2 it becomes possible to be more flexible about the assignment of partitions by setting a fragment count type. Possible count types are one per node, one per node group, one per LDM per node, and one per LDM per node group.
This setting can be controlled for individual tables by means
of a FRAGMENT_COUNT_TYPE
option embedded in
NDB_TABLE
comments in
CREATE TABLE
or
ALTER TABLE
statements.
Settings for table-level READ_BACKUP
are
also supported using this syntax. For more information and
examples, see
Section 14.1.18.7, “Setting NDB_TABLE options in table comments”.
As part of this work, MySQL Cluster NDB 7.5.2 also introduces
the ndb_data_node_neighbour
system variable. This is intended for use, in transaction
hinting, to provide a “nearby” data node to this
SQL node.
ThreadConfig improvements.
A number of enhancements and feature additions are
implemented in MySQL Cluster NDB 7.5.2 for the
ThreadConfig
multithreaded data node
(ndbmtd) configuration parameter,
including support for an increased number of platforms.
These changes are described in the next few paragraphs.
Non-exclusive CPU locking is now supported on FreeBSD and
Windows, using cpubind
and
cpuset
. Exclusive CPU locking is now
supported on Solaris (only) using the
cpubind_exclusive
and
cpuset_exclusive
parameters which are
introduced in this release.
Thread prioritzation is now available, controlled by the new
thread_prio
parameter.
thread_prio
is supported on Linux, FreeBSD,
Windows, and Solaris, and varies somewhat by platform. For
more information, see the description of
ThreadConfig
.
The realtime
parameter is now supported on
Windows platforms.
Partitions larger than 16 GB.
Due to an improvement in the hash index implementation used
by MySQL Cluster data nodes, partitions of
NDB
tables may now contain more than 16
GB of data for fixed columns, and the maximum partition size
for fixed columns is now raised to 128 TB. The previous
limitation was due to the fact that the
DBACC
block in the NDB
kernel used only 32-bit references to the fixed-size part of
a row in the DBTUP
block, although 45-bit
references to this data are used in DBTUP
itself and elsewhere in the kernel outside
DBACC
; all such references in to the data
handled in the DBACC
block now use 45
bits instead.
MySQL Server offers a number of choices in storage engines. Since
both NDB
and
InnoDB
can serve as transactional
MySQL storage engines, users of MySQL Server sometimes become
interested in MySQL Cluster. They see
NDB
as a possible alternative or
upgrade to the default InnoDB
storage
engine in MySQL 5.7. While NDB
and
InnoDB
share common characteristics,
there are differences in architecture and implementation, so that
some existing MySQL Server applications and usage scenarios can be
a good fit for MySQL Cluster, but not all of them.
In this section, we discuss and compare some characteristics of
the NDB
storage engine used by MySQL
Cluster NDB 7.5 with InnoDB
used in
MySQL 5.7. The next few sections provide a technical comparison.
In many instances, decisions about when and where to use MySQL
Cluster must be made on a case-by-case basis, taking all factors
into consideration. While it is beyond the scope of this
documentation to provide specifics for every conceivable usage
scenario, we also attempt to offer some very general guidance on
the relative suitability of some common types of applications for
NDB
as opposed to
InnoDB
backends.
MySQL Cluster NDB 7.5 uses a mysqld based on
MySQL 5.7, including support for
InnoDB
1.1. While it is possible to
use InnoDB
tables with MySQL Cluster, such
tables are not clustered. It is also not possible to use programs
or libraries from a MySQL Cluster NDB 7.5 distribution with MySQL
Server 5.7, or the reverse.
While it is also true that some types of common business
applications can be run either on MySQL Cluster or on MySQL Server
(most likely using the InnoDB
storage
engine), there are some important architectural and implementation
differences. Section 19.1.5.1, “Differences Between the NDB and InnoDB Storage Engines”,
provides a summary of the these differences. Due to the
differences, some usage scenarios are clearly more suitable for
one engine or the other; see
Section 19.1.5.2, “NDB and InnoDB Workloads”. This in turn
has an impact on the types of applications that better suited for
use with NDB
or
InnoDB
. See
Section 19.1.5.3, “NDB and InnoDB Feature Usage Summary”, for a comparison
of the relative suitability of each for use in common types of
database applications.
For information about the relative characteristics of the
NDB
and
MEMORY
storage engines, see
When to Use MEMORY or MySQL Cluster.
See Chapter 16, Alternative Storage Engines, for additional information about MySQL storage engines.
The MySQL Cluster NDB
storage
engine is implemented using a distributed, shared-nothing
architecture, which causes it to behave differently from
InnoDB
in a number of ways. For
those unaccustomed to working with
NDB
, unexpected behaviors can arise
due to its distributed nature with regard to transactions,
foreign keys, table limits, and other characteristics. These are
shown in the following table:
Feature |
|
MySQL Cluster |
---|---|---|
MySQL Server Version | 5.7 | 5.7 |
|
|
|
MySQL Cluster Version | N/A |
|
Storage Limits | 64TB | 3TB (Practical upper limit based on 48 data nodes with 64GB RAM each; can be increased with disk-based data and BLOBs) |
Foreign Keys | Yes | Yes. |
Transactions | All standard types | |
MVCC | Yes | No |
Data Compression | Yes | No (MySQL Cluster checkpoint and backup files can be compressed) |
Large Row Support (> 14K) |
Supported for (Using these types to store very large amounts of data can lower MySQL Cluster performance) | |
Replication Support | Asynchronous and semisynchronous replication using MySQL Replication | Automatic synchronous replication within a MySQL Cluster. Asynchronous replication between MySQL Clusters, using MySQL Replication |
Scaleout for Read Operations | Yes (MySQL Replication) | Yes (Automatic partitioning in MySQL Cluster; MySQL Cluster Replication) |
Scaleout for Write Operations | Requires application-level partitioning (sharding) | Yes (Automatic partitioning in MySQL Cluster is transparent to applications) |
High Availability (HA) | Requires additional software | Yes (Designed for 99.999% uptime) |
Node Failure Recovery and Failover | Requires additional software | Automatic (Key element in MySQL Cluster architecture) |
Time for Node Failure Recovery | 30 seconds or longer | Typically < 1 second |
Real-Time Performance | No | Yes |
In-Memory Tables | No | Yes (Some data can optionally be stored on disk; both in-memory and disk data storage are durable) |
NoSQL Access to Storage Engine | Yes | Yes Multiple APIs, including Memcached, Node.js/JavaScript, Java, JPA, C++, and HTTP/REST |
Concurrent and Parallel Writes | Not supported | Up to 48 writers, optimized for concurrent writes |
Conflict Detection and Resolution (Multiple Replication Masters) | No | Yes |
Hash Indexes | No | Yes |
Online Addition of Nodes | Read-only replicas using MySQL Replication | Yes (all node types) |
Online Upgrades | No | Yes |
Online Schema Modifications | Yes, as part of MySQL 5.6. | Yes. |
MySQL Cluster has a range of unique attributes that make it
ideal to serve applications requiring high availability, fast
failover, high throughput, and low latency. Due to its
distributed architecture and multi-node implementation, MySQL
Cluster also has specific constraints that may keep some
workloads from performing well. A number of major differences in
behavior between the NDB
and
InnoDB
storage engines with regard
to some common types of database-driven application workloads
are shown in the following table::
Workload |
MySQL Cluster ( | |
---|---|---|
High-Volume OLTP Applications | Yes | Yes |
DSS Applications (data marts, analytics) | Yes | Limited (Join operations across OLTP datasets not exceeding 3TB in size) |
Custom Applications | Yes | Yes |
Packaged Applications | Yes | Limited (should be mostly primary key access). MySQL Cluster NDB 7.5 supports foreign keys. |
In-Network Telecoms Applications (HLR, HSS, SDP) | No | Yes |
Session Management and Caching | Yes | Yes |
E-Commerce Applications | Yes | Yes |
User Profile Management, AAA Protocol | Yes | Yes |
When comparing application feature requirements to the
capabilities of InnoDB
with
NDB
, some are clearly more
compatible with one storage engine than the other.
The following table lists supported application features according to the storage engine to which each feature is typically better suited.
Preferred application requirements for
|
Preferred application requirements for
|
---|---|
|
|
In the sections that follow, we discuss known limitations in
current releases of MySQL Cluster as compared with the features
available when using the MyISAM
and
InnoDB
storage engines. If you check the
“Cluster” category in the MySQL bugs database at
http://bugs.mysql.com, you can find known bugs in
the following categories under “MySQL Server:” in the
MySQL bugs database at http://bugs.mysql.com, which
we intend to correct in upcoming releases of MySQL Cluster:
MySQL Cluster
Cluster Direct API (NDBAPI)
Cluster Disk Data
Cluster Replication
ClusterJ
This information is intended to be complete with respect to the conditions just set forth. You can report any discrepancies that you encounter to the MySQL bugs database using the instructions given in Section 1.7, “How to Report Bugs or Problems”. If we do not plan to fix the problem in MySQL Cluster NDB 7.5, we will add it to the list.
See Previous MySQL Cluster Issues Resolved in MySQL Cluster NDB 7.3 for a list of issues in earlier releases that have been resolved in MySQL Cluster NDB 7.5.
Limitations and other issues specific to MySQL Cluster Replication are described in Section 19.6.3, “Known Issues in MySQL Cluster Replication”.
Some SQL statements relating to certain MySQL features produce
errors when used with NDB
tables,
as described in the following list:
Temporary tables.
Temporary tables are not supported. Trying either to
create a temporary table that uses the
NDB
storage engine or to
alter an existing temporary table to use
NDB
fails with the error
Table storage engine 'ndbcluster' does not
support the create option 'TEMPORARY'.
Indexes and keys in NDB tables. Keys and indexes on MySQL Cluster tables are subject to the following limitations:
Column width.
Attempting to create an index on an
NDB
table column whose width is
greater than 3072 bytes succeeds, but only the first
3072 bytes are actually used for the index. In such
cases, a warning Specified key was too
long; max key length is 3072 bytes is
issued, and a SHOW CREATE
TABLE
statement shows the length of the
index as 3072.
TEXT and BLOB columns.
You cannot create indexes on
NDB
table columns that
use any of the TEXT
or
BLOB
data types.
FULLTEXT indexes.
The NDB
storage engine
does not support FULLTEXT
indexes,
which are possible for
MyISAM
and
InnoDB
tables only.
However, you can create indexes on
VARCHAR
columns of
NDB
tables.
USING HASH keys and NULL.
Using nullable columns in unique keys and primary keys
means that queries using these columns are handled as
full table scans. To work around this issue, make the
column NOT NULL
, or re-create the
index without the USING HASH
option.
Prefixes.
There are no prefix indexes; only entire columns can
be indexed. (The size of an NDB
column index is always the same as the width of the
column in bytes, up to and including 3072 bytes, as
described earlier in this section. Also see
Section 19.1.6.6, “Unsupported or Missing Features in MySQL Cluster”,
for additional information.)
BIT columns.
A BIT
column cannot be
a primary key, unique key, or index, nor can it be
part of a composite primary key, unique key, or index.
AUTO_INCREMENT columns.
Like other MySQL storage engines, the
NDB
storage engine can
handle a maximum of one
AUTO_INCREMENT
column per table.
However, in the case of a Cluster table with no
explicit primary key, an
AUTO_INCREMENT
column is
automatically defined and used as a
“hidden” primary key. For this reason,
you cannot define a table that has an explicit
AUTO_INCREMENT
column unless that
column is also declared using the PRIMARY
KEY
option. Attempting to create a table
with an AUTO_INCREMENT
column that
is not the table's primary key, and using the
NDB
storage engine, fails
with an error.
Restrictions on foreign keys.
Support for foreign key constraints in MySQL Cluster NDB
7.5 is comparable to that provided by
InnoDB
, subject to the
following restrictions:
Every column referenced as a foreign key requires an explicit unique key, if it is not the table's primary key.
ON UPDATE CASCADE
is not supported
when the reference is to the parent table's primary
key.
This is because an update of a primary key is
implemented as a delete of the old row (containing the
old primary key) plus an insert of the new row (with a
new primary key). This is not visible to the
NDB
kernel, which views these two
rows as being the same, and thus has no way of knowing
that this update should be cascaded.
SET DEFAULT
is not supported. (Also
not supported by InnoDB
.)
The NO ACTION
keywords are accepted
but treated as RESCRICT
. (Also the
same as with InnoDB
.)
In earlier versions of MySQL Cluster, when creating a table with foreign key referencing an index in another table, it sometimes appeared possible to create the foreign key even if the order of the columns in the indexes did not match, due to the fact that an appropriate error was not always returned internally. A partial fix for this issue improved the error used internally to work in most cases; however, it remains possible for this situation to occur in the event that the parent index is a unique index. (Bug #18094360)
For more information, see Section 14.1.18.3, “Using FOREIGN KEY Constraints”, and Section 1.8.3.2, “FOREIGN KEY Constraints”.
MySQL Cluster and geometry data types.
Geometry data types (WKT
and
WKB
) are supported for
NDB
tables. However, spatial
indexes are not supported.
Character sets and binary log files.
Currently, the ndb_apply_status
and
ndb_binlog_index
tables are created
using the latin1
(ASCII) character set.
Because names of binary logs are recorded in this table,
binary log files named using non-Latin characters are not
referenced correctly in these tables. This is a known
issue, which we are working to fix. (Bug #50226)
To work around this problem, use only Latin-1 characters
when naming binary log files or setting any the
--basedir
,
--log-bin
, or
--log-bin-index
options.
Creating NDB tables with user-defined partitioning.
Support for user-defined partitioning in MySQL Cluster is
restricted to [LINEAR
]
KEY
partitioning. Using any other
partitioning type with ENGINE=NDB
or
ENGINE=NDBCLUSTER
in a
CREATE TABLE
statement
results in an error.
It is possible to override this restriction, but doing so is not supported for use in production settings. For details, see User-defined partitioning and the NDB storage engine (MySQL Cluster).
Default partitioning scheme.
All MySQL Cluster tables are by default partitioned by
KEY
using the table's primary key
as the partitioning key. If no primary key is explicitly
set for the table, the “hidden” primary key
automatically created by the
NDB
storage engine is used
instead. For additional discussion of these and related
issues, see Section 20.2.5, “KEY Partitioning”.
CREATE TABLE
and
ALTER TABLE
statements that
would cause a user-partitioned
NDBCLUSTER
table not to meet
either or both of the following two requirements are not
permitted, and fail with an error:
The table must have an explicit primary key.
All columns listed in the table's partitioning expression must be part of the primary key.
Exception.
If a user-partitioned
NDBCLUSTER
table is created
using an empty column-list (that is, using
PARTITION BY [LINEAR] KEY()
), then no
explicit primary key is required.
Maximum number of partitions for NDBCLUSTER tables.
The maximum number of partitions that can defined for a
NDBCLUSTER
table when
employing user-defined partitioning is 8 per node group.
(See Section 19.1.2, “MySQL Cluster Nodes, Node Groups, Replicas, and Partitions”, for
more information about MySQL Cluster node groups.
DROP PARTITION not supported.
It is not possible to drop partitions from
NDB
tables using
ALTER TABLE ... DROP PARTITION
. The
other partitioning extensions to
ALTER
TABLE
—ADD PARTITION
,
REORGANIZE PARTITION
, and
COALESCE PARTITION
—are supported
for Cluster tables, but use copying and so are not
optimized. See
Section 20.3.1, “Management of RANGE and LIST Partitions” and
Section 14.1.8, “ALTER TABLE Syntax”.
Row-based replication.
When using row-based replication with MySQL Cluster,
binary logging cannot be disabled. That is, the
NDB
storage engine ignores
the value of sql_log_bin
.
JSON data type.
The MySQL JSON
data type is
supported for NDB
tables in the
mysqld supplied with MySQL Cluster NDB
7.5.2 and later.
An NDB
table can have a maximum of 3
JSON
columns.
The NDB API has no special provision for working with
JSON
data, which it views simply as
BLOB
data. Handling data as
JSON
must be performed by the
application.
CPU and thread info ndbinfo tables.
MySQL Cluster 7.5.2 adds several new tables to the
ndbinfo
information
database providing information about CPU and thread
activity by node, thread ID, and thread type. The tables
are listed here:
cpustat
: Provides
per-second, per-thread CPU statistics
cpustat_50ms
: Raw
per-thread CPU statistics data, gathered every 50ms
cpustat_1sec
: Raw
per-thread CPU statistics data, gathered each second
cpustat_20sec
: Raw
per-thread CPU statistics data, gathered every 20
seconds
threads
: Names and
descriptions of thread types
For more information about these tables, see Section 19.5.10, “The ndbinfo MySQL Cluster Information Database”.
Lock info ndbinfo tables.
MySQL Cluster NDB 7.5.3 adds new tables to the
ndbinfo
information
database providing information about locks and lock
attempts in a running MySQL Cluster. These tables are
listed here:
cluster_locks
: Current
lock requests which are waiting for or holding locks;
this information can be useful when investigating stalls
and deadlocks. Analogous to
cluster_operations
.
locks_per_fragment
:
Counts of lock claim requests, and their outcomes per
fragment, as well as total time spent waiting for locks
successfully and unsuccessfully. Analogous to
operations_per_fragment
and
memory_per_fragment
.
server_locks
: Subset
of cluster transactions—those running on the local
mysqld, showing a connection id per
transaction. Analogous to
server_operations
.
In this section, we list limits found in MySQL Cluster that either differ from limits found in, or that are not found in, standard MySQL.
Memory usage and recovery.
Memory consumed when data is inserted into an
NDB
table is not automatically
recovered when deleted, as it is with other storage engines.
Instead, the following rules hold true:
A DELETE
statement on an
NDB
table makes the memory
formerly used by the deleted rows available for re-use by
inserts on the same table only. However, this memory can be
made available for general re-use by performing
OPTIMIZE TABLE
.
A rolling restart of the cluster also frees any memory used by deleted rows. See Section 19.5.5, “Performing a Rolling Restart of a MySQL Cluster”.
A DROP TABLE
or
TRUNCATE TABLE
operation on
an NDB
table frees the memory
that was used by this table for re-use by any
NDB
table, either by the same
table or by another NDB
table.
Recall that TRUNCATE TABLE
drops and re-creates the table. See
Section 14.1.34, “TRUNCATE TABLE Syntax”.
Limits imposed by the cluster's configuration. A number of hard limits exist which are configurable, but available main memory in the cluster sets limits. See the complete list of configuration parameters in Section 19.3.3, “MySQL Cluster Configuration Files”. Most configuration parameters can be upgraded online. These hard limits include:
Database memory size and index memory size
(DataMemory
and
IndexMemory
,
respectively).
DataMemory
is
allocated as 32KB pages. As each
DataMemory
page
is used, it is assigned to a specific table; once
allocated, this memory cannot be freed except by
dropping the table.
See Section 19.3.3.6, “Defining MySQL Cluster Data Nodes”, for more information.
The maximum number of operations that can be performed
per transaction is set using the configuration
parameters
MaxNoOfConcurrentOperations
and
MaxNoOfLocalOperations
.
Bulk loading, TRUNCATE
TABLE
, and ALTER
TABLE
are handled as special cases by
running multiple transactions, and so are not subject
to this limitation.
Different limits related to tables and indexes. For
example, the maximum number of ordered indexes in the
cluster is determined by
MaxNoOfOrderedIndexes
,
and the maximum number of ordered indexes per table is
16.
Node and data object maximums. The following limits apply to numbers of cluster nodes and metadata objects:
The maximum number of data nodes is 48.
A data node must have a node ID in the range of 1 to 48, inclusive. (Management and API nodes may use node IDs in the range 1 to 255, inclusive.)
The total maximum number of nodes in a MySQL Cluster is 255. This number includes all SQL nodes (MySQL Servers), API nodes (applications accessing the cluster other than MySQL servers), data nodes, and management servers.
The maximum number of metadata objects in current versions of MySQL Cluster is 20320. This limit is hard-coded.
See Previous MySQL Cluster Issues Resolved in MySQL Cluster NDB 7.3, for more information.
A number of limitations exist in MySQL Cluster with regard to the handling of transactions. These include the following:
Transaction isolation level.
The NDBCLUSTER
storage engine
supports only the READ
COMMITTED
transaction isolation level.
(InnoDB
, for example, supports
READ COMMITTED
,
READ UNCOMMITTED
,
REPEATABLE READ
, and
SERIALIZABLE
.) See
Section 19.5.3.4, “MySQL Cluster Backup Troubleshooting”,
for information on how this can affect backing up and
restoring Cluster databases.)
Transactions and BLOB or TEXT columns.
NDBCLUSTER
stores only part
of a column value that uses any of MySQL's
BLOB
or
TEXT
data types in the
table visible to MySQL; the remainder of the
BLOB
or
TEXT
is stored in a
separate internal table that is not accessible to MySQL.
This gives rise to two related issues of which you should
be aware whenever executing
SELECT
statements on tables
that contain columns of these types:
For any SELECT
from a
MySQL Cluster table: If the
SELECT
includes a
BLOB
or
TEXT
column, the
READ COMMITTED
transaction isolation level is converted to a read with
read lock. This is done to guarantee consistency.
For any SELECT
which uses
a unique key lookup to retrieve any columns that use any
of the BLOB
or
TEXT
data types and that
is executed within a transaction, a shared read lock is
held on the table for the duration of the
transaction—that is, until the transaction is
either committed or aborted.
This issue does not occur for queries that use index or
table scans, even against
NDB
tables having
BLOB
or
TEXT
columns.
For example, consider the table t
defined by the following CREATE
TABLE
statement:
CREATE TABLE t ( a INT NOT NULL AUTO_INCREMENT PRIMARY KEY, b INT NOT NULL, c INT NOT NULL, d TEXT, INDEX i(b), UNIQUE KEY u(c) ) ENGINE = NDB,
Either of the following queries on t
causes a shared read lock, because the first query uses
a primary key lookup and the second uses a unique key
lookup:
SELECT * FROM t WHERE a = 1; SELECT * FROM t WHERE c = 1;
However, none of the four queries shown here causes a shared read lock:
SELECT * FROM t WHERE b = 1; SELECT * FROM t WHERE d = '1'; SELECT * FROM t; SELECT b,c WHERE a = 1;
This is because, of these four queries, the first uses
an index scan, the second and third use table scans, and
the fourth, while using a primary key lookup, does not
retrieve the value of any
BLOB
or
TEXT
columns.
You can help minimize issues with shared read locks by
avoiding queries that use unique key lookups that
retrieve BLOB
or
TEXT
columns, or, in
cases where such queries are not avoidable, by
committing transactions as soon as possible afterward.
Rollbacks. There are no partial transactions, and no partial rollbacks of transactions. A duplicate key or similar error causes the entire transaction to be rolled back.
This behavior differs from that of other transactional
storage engines such as InnoDB
that may roll back individual statements.
Transactions and memory usage. As noted elsewhere in this chapter, MySQL Cluster does not handle large transactions well; it is better to perform a number of small transactions with a few operations each than to attempt a single large transaction containing a great many operations. Among other considerations, large transactions require very large amounts of memory. Because of this, the transactional behavior of a number of MySQL statements is effected as described in the following list:
TRUNCATE TABLE
is not
transactional when used on
NDB
tables. If a
TRUNCATE TABLE
fails to
empty the table, then it must be re-run until it is
successful.
DELETE FROM
(even with no
WHERE
clause) is
transactional. For tables containing a great many rows,
you may find that performance is improved by using
several DELETE FROM ... LIMIT ...
statements to “chunk” the delete operation.
If your objective is to empty the table, then you may
wish to use TRUNCATE
TABLE
instead.
LOAD DATA statements.
LOAD DATA
INFILE
is not transactional when used on
NDB
tables.
When executing a
LOAD DATA
INFILE
statement, the
NDB
engine performs
commits at irregular intervals that enable better
utilization of the communication network. It is not
possible to know ahead of time when such commits take
place.
ALTER TABLE and transactions.
When copying an NDB
table
as part of an ALTER
TABLE
, the creation of the copy is
nontransactional. (In any case, this operation is
rolled back when the copy is deleted.)
Transactions and the COUNT() function.
When using MySQL Cluster Replication, it is not possible
to guarantee the transactional consistency of the
COUNT()
function on the
slave. In other words, when performing on the master a
series of statements
(INSERT
,
DELETE
, or both) that
changes the number of rows in a table within a single
transaction, executing SELECT COUNT(*) FROM
queries on the
slave may yield intermediate results. This is due to the
fact that table
SELECT COUNT(...)
may perform
dirty reads, and is not a bug in the
NDB
storage engine.
Starting, stopping, or restarting a node may give rise to temporary errors causing some transactions to fail. These include the following cases:
Temporary errors. When first starting a node, it is possible that you may see Error 1204 Temporary failure, distribution changed and similar temporary errors.
Errors due to node failure. The stopping or failure of any data node can result in a number of different node failure errors. (However, there should be no aborted transactions when performing a planned shutdown of the cluster.)
In either of these cases, any errors that are generated must be handled within the application. This should be done by retrying the transaction.
See also Section 19.1.6.2, “Limits and Differences of MySQL Cluster from Standard MySQL Limits”.
Some database objects such as tables and indexes have different
limitations when using the
NDBCLUSTER
storage engine:
Database and table names.
When using the NDB
storage engine, the
maximum allowed length both for database names and for
table names is 63 characters. A statement using a database
name or table name longer than this limit fails with an
appropriate error.
Number of database objects.
The maximum number of all
NDB
database objects in a
single MySQL Cluster—including databases, tables,
and indexes—is limited to 20320.
Attributes per table. The maximum number of attributes (that is, columns and indexes) that can belong to a given table is 512.
Attributes per key. The maximum number of attributes per key is 32.
Row size.
The maximum permitted size of any one row is 14000 bytes.
Each BLOB
or
TEXT
column contributes 256
+ 8 = 264 bytes to this total.
BIT column storage per table.
The maximum combined width for all
BIT
columns used in a given
NDB
table is 4096.
A number of features supported by other storage engines are not
supported for NDB
tables. Trying to
use any of these features in MySQL Cluster does not cause errors
in or of itself; however, errors may occur in applications that
expects the features to be supported or enforced. Statements
referencing such features, even if effectively ignored by
NDB
, must be syntactically and otherwise
valid.
Index prefixes.
Prefixes on indexes are not supported for
NDB
tables. If a prefix is used as part
of an index specification in a statement such as
CREATE TABLE
,
ALTER TABLE
, or
CREATE INDEX
, the prefix is
not created by NDB
.
A statement containing an index prefix, and creating or
modifying an NDB
table, must still be
syntactically valid. For example, the following statement
always fails with Error 1089 Incorrect prefix
key; the used key part isn't a string, the used length is
longer than the key part, or the storage engine doesn't
support unique prefix keys, regardless of
storage engine:
CREATE TABLE
t1 (
c1 INT NOT NULL,
c2 VARCHAR(100),
INDEX i1 (c2(500))
);
This happens on account of the SQL syntax rule that no index may have a prefix larger than itself.
Savepoints and rollbacks.
Savepoints and rollbacks to savepoints are ignored as in
MyISAM
.
Durability of commits. There are no durable commits on disk. Commits are replicated, but there is no guarantee that logs are flushed to disk on commit.
Replication.
Statement-based replication is not supported. Use
--binlog-format=ROW
(or
--binlog-format=MIXED
) when
setting up cluster replication. See
Section 19.6, “MySQL Cluster Replication”, for more
information.
Replication using global transaction identifiers (GTIDs) is
not compatible with MySQL Cluster, and is not supported in
MySQL Cluster NDB 7.5. Do not enable GTIDs when using the
NDB
storage engine, as this is very
likely to cause problems up to and including failure of
MySQL Cluster Replication.
See Section 19.1.6.3, “Limits Relating to Transaction Handling in MySQL Cluster”,
for more information relating to limitations on transaction
handling in NDB
.
The following performance issues are specific to or especially pronounced in MySQL Cluster:
Range scans.
There are query performance issues due to sequential
access to the NDB
storage
engine; it is also relatively more expensive to do many
range scans than it is with either
MyISAM
or InnoDB
.
Reliability of Records in range.
The Records in range
statistic is
available but is not completely tested or officially
supported. This may result in nonoptimal query plans in
some cases. If necessary, you can employ USE
INDEX
or FORCE INDEX
to alter
the execution plan. See Section 9.9.4, “Index Hints”, for
more information on how to do this.
Unique hash indexes.
Unique hash indexes created with USING
HASH
cannot be used for accessing a table if
NULL
is given as part of the key.
The following are limitations specific to the
NDB
storage engine:
Machine architecture. All machines used in the cluster must have the same architecture. That is, all machines hosting nodes must be either big-endian or little-endian, and you cannot use a mixture of both. For example, you cannot have a management node running on a PowerPC which directs a data node that is running on an x86 machine. This restriction does not apply to machines simply running mysql or other clients that may be accessing the cluster's SQL nodes.
Binary logging. MySQL Cluster has the following limitations or restrictions with regard to binary logging:
sql_log_bin
has no
effect on data operations; however, it is supported for
schema operations.
MySQL Cluster cannot produce a binary log for tables
having BLOB
columns but
no primary key.
Only the following schema operations are logged in a cluster binary log which is not on the mysqld executing the statement:
See also Section 19.1.6.10, “Limitations Relating to Multiple MySQL Cluster Nodes”.
Disk Data object maximums and minimums. Disk data objects are subject to the following maximums and minimums:
Maximum number of tablespaces: 232 (4294967296)
Maximum number of data files per tablespace: 216 (65536)
Maximum data file size: The theoretical limit is 64G; however, the practical upper limit is 32G. This is equivalent to 32768 extents of 1M each.
Since a MySQL Cluster Disk Data table can use at most 1
tablespace, this means that the theoretical upper limit to
the amount of data (in bytes) that can be stored on disk by
a single NDB
table is 32G * 65536 =
2251799813685248, or approximately 2 petabytes.
The theoretical maximum number of extents per tablespace data file is 216 (65536); however, for practical purposes, the recommended maximum number of extents per data file is 215 (32768).
The minimum and maximum possible sizes of extents for tablespace data files are 32K and 2G, respectively. See Section 14.1.19, “CREATE TABLESPACE Syntax”, for more information.
Disk Data tables and diskless mode. Use of Disk Data tables is not supported when running the cluster in diskless mode.
Multiple SQL nodes.
The following are issues relating to the use of multiple MySQL
servers as MySQL Cluster SQL nodes, and are specific to the
NDBCLUSTER
storage engine:
No distributed table locks.
A LOCK TABLES
works only
for the SQL node on which the lock is issued; no other SQL
node in the cluster “sees” this lock. This is
also true for a lock issued by any statement that locks
tables as part of its operations. (See next item for an
example.)
ALTER TABLE operations.
ALTER TABLE
is not fully
locking when running multiple MySQL servers (SQL nodes).
(As discussed in the previous item, MySQL Cluster does not
support distributed table locks.)
Multiple management nodes. When using multiple management servers:
If any of the management servers are running on the same host, you must give nodes explicit IDs in connection strings because automatic allocation of node IDs does not work across multiple management servers on the same host. This is not required if every management server resides on a different host.
When a management server starts, it first checks for any
other management server in the same MySQL Cluster, and upon
successful connection to the other management server uses
its configuration data. This means that the management
server --reload
and
--initial
startup options
are ignored unless the management server is the only one
running. It also means that, when performing a rolling
restart of a MySQL Cluster with multiple management nodes,
the management server reads its own configuration file if
(and only if) it is the only management server running in
this MySQL Cluster. See
Section 19.5.5, “Performing a Rolling Restart of a MySQL Cluster”, for more
information.
Multiple network addresses. Multiple network addresses per data node are not supported. Use of these is liable to cause problems: In the event of a data node failure, an SQL node waits for confirmation that the data node went down but never receives it because another route to that data node remains open. This can effectively make the cluster inoperable.
It is possible to use multiple network hardware
interfaces (such as Ethernet cards) for a
single data node, but these must be bound to the same address.
This also means that it not possible to use more than one
[tcp]
section per connection in the
config.ini
file. See
Section 19.3.3.9, “MySQL Cluster TCP/IP Connections”, for more
information.
This section describes the basics for planning, installing, configuring, and running a MySQL Cluster. Whereas the examples in Section 19.3, “Configuration of MySQL Cluster” provide more in-depth information on a variety of clustering options and configuration, the result of following the guidelines and procedures outlined here should be a usable MySQL Cluster which meets the minimum requirements for availability and safeguarding of data.
For information about upgrading or downgrading a MySQL Cluster between release versions, see Section 19.2.8, “Upgrading and Downgrading MySQL Cluster”.
This section covers hardware and software requirements; networking issues; installation of MySQL Cluster; basic configuration issues; starting, stopping, and restarting the cluster; loading of a sample database; and performing queries.
MySQL Cluster NDB 7.5 also provides a MySQL Cluster Auto-Installer, a web-based graphical installer, as part of the MySQL Cluster distribution. The Auto-Installer can be used to perform basic installation and setup of a MySQL Cluster on one (for testing) or more host computers. See Section 19.2.1, “The MySQL Cluster Auto-Installer”, for more information.
Assumptions. The following sections make a number of assumptions regarding the cluster's physical and network configuration. These assumptions are discussed in the next few paragraphs.
Cluster nodes and host computers. The cluster consists of four nodes, each on a separate host computer, and each with a fixed network address on a typical Ethernet network as shown here:
Node | IP Address |
---|---|
Management node (mgmd) | 192.168.0.10 |
SQL node (mysqld) | 192.168.0.20 |
Data node "A" (ndbd) | 192.168.0.30 |
Data node "B" (ndbd) | 192.168.0.40 |
This may be made clearer by the following diagram:
Network addressing.
In the interest of simplicity (and reliability), this
How-To uses only numeric IP addresses.
However, if DNS resolution is available on your network, it is
possible to use host names in lieu of IP addresses in configuring
Cluster. Alternatively, you can use the hosts
file (typically /etc/hosts
for Linux and
other Unix-like operating systems,
C:\WINDOWS\system32\drivers\etc\hosts
on
Windows, or your operating system's equivalent) for providing
a means to do host lookup if such is available.
Potential hosts file issues.
A common problem when trying to use host names for Cluster nodes
arises because of the way in which some operating systems
(including some Linux distributions) set up the system's own
host name in the /etc/hosts
during
installation. Consider two machines with the host names
ndb1
and ndb2
, both in the
cluster
network domain. Red Hat Linux
(including some derivatives such as CentOS and Fedora) places the
following entries in these machines'
/etc/hosts
files:
# ndb1 /etc/hosts
:
127.0.0.1 ndb1.cluster ndb1 localhost.localdomain localhost
# ndb2 /etc/hosts
:
127.0.0.1 ndb2.cluster ndb2 localhost.localdomain localhost
SUSE Linux (including OpenSUSE) places these entries in the
machines' /etc/hosts
files:
# ndb1 /etc/hosts
:
127.0.0.1 localhost
127.0.0.2 ndb1.cluster ndb1
# ndb2 /etc/hosts
:
127.0.0.1 localhost
127.0.0.2 ndb2.cluster ndb2
In both instances, ndb1
routes
ndb1.cluster
to a loopback IP address, but gets a
public IP address from DNS for ndb2.cluster
,
while ndb2
routes ndb2.cluster
to a loopback address and obtains a public address for
ndb1.cluster
. The result is that each data node
connects to the management server, but cannot tell when any other
data nodes have connected, and so the data nodes appear to hang
while starting.
You cannot mix localhost
and other host names
or IP addresses in config.ini
. For these
reasons, the solution in such cases (other than to use IP
addresses for all
config.ini
HostName
entries) is to remove the fully qualified host names from
/etc/hosts
and use these in
config.ini
for all cluster hosts.
Host computer type. Each host computer in our installation scenario is an Intel-based desktop PC running a supported operating system installed to disk in a standard configuration, and running no unnecessary services. The core operating system with standard TCP/IP networking capabilities should be sufficient. Also for the sake of simplicity, we also assume that the file systems on all hosts are set up identically. In the event that they are not, you should adapt these instructions accordingly.
Network hardware. Standard 100 Mbps or 1 gigabit Ethernet cards are installed on each machine, along with the proper drivers for the cards, and that all four hosts are connected through a standard-issue Ethernet networking appliance such as a switch. (All machines should use network cards with the same throughput. That is, all four machines in the cluster should have 100 Mbps cards or all four machines should have 1 Gbps cards.) MySQL Cluster works in a 100 Mbps network; however, gigabit Ethernet provides better performance.
MySQL Cluster is not intended for use in a network for which throughput is less than 100 Mbps or which experiences a high degree of latency. For this reason (among others), attempting to run a MySQL Cluster over a wide area network such as the Internet is not likely to be successful, and is not supported in production.
Sample data.
We use the world
database which is available
for download from the MySQL Web site (see
http://dev.mysql.com/doc/index-other.html). We assume that
each machine has sufficient memory for running the operating
system, required MySQL Cluster processes, and (on the data nodes)
storing the database.
For general information about installing MySQL, see Chapter 2, Installing and Upgrading MySQL. For information about installation of MySQL Cluster on Linux and other Unix-like operating systems, see Section 19.2.2, “Installation of MySQL Cluster on Linux”. For information about installation of MySQL Cluster on Windows operating systems, see Section 19.2.3, “Installing MySQL Cluster on Windows”.
For general information about MySQL Cluster hardware, software, and networking requirements, see Section 19.1.3, “MySQL Cluster Hardware, Software, and Networking Requirements”.
This section describes the web-based graphical configuration installer included as part of the MySQL Cluster distribution. Topics discussed include an overview of the installer and its parts, software and other requirements for running the installer, navigating the GUI, and using the installer to set up and start or stop a MySQL Cluster on one or more host computers.
This section provides information on supported operating platforms and software, required software, and other prerequisites for running the MySQL Cluster Auto-Installer.
Supported platforms. The MySQL Cluster Auto-Installer is available with most MySQL Cluster NDB 7.5.2 and later MySQL Cluster distributions for recent versions of Linux, Windows, Solaris, and MacOS X. For more detailed information about platform support for MySQL Cluster and the MySQL Cluster Auto-Installer, see http://www.mysql.com/support/supportedplatforms/cluster.html.
The MySQL Cluster Auto-Installer is not supported with MySQL Cluster NDB 7.5.0 or 7.5.1 (Bug #79853, Bug #22502247).
Supported Web browsers. The Web-based installer is supported with recent versions of Firefox and Microsoft Internet Explorer. It should also work with recent versions of Opera, Safari, and Chrome, although we have not thoroughly tested for compability with these browsers.
Required software—setup host. The following software must be installed on the host where the Auto-Installer is run:
Python 2.6 or higher. The Auto-Installer requires the Python interpreter and standard libraries. If these are not already installed on the system, you may be able to add them using the system's package manager. Otherwise, they can be downloaded from http://python.org/download/.
Paramiko 1.7.7.1 or higher. This is required to communicate with remote hosts using SSH. You can download it from http://www.lag.net/paramiko/. Paramiko may also be available from your system's package manager.
Pycrypto version 2.6 or higher. This cryptography module is required by Paramiko. If it is not available using your system's package manage, you can download it from https://www.dlitz.net/software/pycrypto/.
All of the software in the preceding list is included in the Windows version of the configuration tool, and does not need to be installed separately.
The Paramiko and Pycrypto libraries are required only if you intend to deploy MySQL Cluster nodes on remote hosts, and are not needed if all nodes are on the same host where the installer is run.
Required software—remote hosts. The only software required for remote hosts where you wish to deploy MySQL Cluster nodes is the SSH server, which is usually installed by default on Linux and Solaris systems. Several alternatives are available for Windows; for an overview of these, see http://en.wikipedia.org/wiki/Comparison_of_SSH_servers.
An additional requirement when using multiple hosts is that it is possible to authenticate to any of the remote hosts using SSH and the proper keys or user credentials, as discussed in the next few paragraphs:
Authentication and security. Three basic security or authentication mechanisms for remote access are available to the Auto-Installer, which we list and describe here:
SSH. A secure shell connection is used to enable the back end to perform actions on remote hosts. For this reason, an SSH server must be running on the remote host. In addition, the system user running the installer must have access to the remote server, either with a user name and password, or by using public and private keys.
You should never use the system root
account for remote access, as this is extremely insecure.
In addition, mysqld cannot normally be
started by system root
. For these and
other reasons, you should provide SSH credentials for a
regular user account on the target system, and not for
system root
. For more information about
this issue, see Section 7.1.5, “How to Run MySQL as a Normal User”.
HTTPS.
Remote communication between the Web browser front end and
the back end is not encrypted by default, which means that
information such as the user's SSH password is
transmitted in clear text that is readable to anyone. For
communication from a remote client to be encrypted, the
back end must have a certificate, and the front end must
communicate with the back end using HTTPS rather than
HTTP. Enabling HTTPS is accomplished most easily through
issuing a self-signed certificate. Once the certificate is
issued, you must make sure that it is used. You can do
this by starting ndb_setup.py from the
command line with the
--use-https
and
--cert-file
options.
Certificate-based authentication.
The back end ndb_setup.py process can
execute commands on the local host as well as remote
hosts. This means that anyone connecting to the back end
can take charge of how commands are executed. To reject
unwanted connections to the back end, a certificate may be
required for authentication of the client. In this case, a
certificate must be issued by the user, installed in the
browser, and made available to the back end for
authentication purposes. You can enact this requirement
(together with or in place of password or key
authentication) by starting
ndb_setup.py with the
--ca-certs-file
option.
There is no need or requirement for secure authentication when the client browser is running on the same host as the Auto-Installer back end.
See also Section 19.5.12, “MySQL Cluster Security Issues”, which discusses security considerations to take into account when deploying MySQL Cluster, as well as Chapter 7, Security, for more general MySQL security information.
The MySQL Cluster Auto-Installer is made up of two components. The front end is a GUI client implemented as a Web page that loads and runs in a standard Web browser such as Firefox or Microsoft Internet Explorer (see Section 19.2.1.1, “MySQL Cluster Auto-Installer Requirements”). The back end is a server process (ndb_setup.py) that runs on the local machine or on another host to which you have access.
These two components (client and server) communicate with each other using standard HTTP requests and responses. The back end can manage MySQL Cluster software programs on any host where the back end user has granted access. If the MySQL Cluster software is on a different host, the back end relies on SSH for access, using the Paramiko library for executing commands remotely (see Section 19.2.1.1, “MySQL Cluster Auto-Installer Requirements”).
The remainder of this section is concerned primarily with the Web client. For more information about using the command-line tool, see Section 19.4.23, “ndb_setup.py — Start browser-based Auto-Installer for MySQL Cluster”.
MySQL Cluster Auto-Installer Interface. This section describes the layout and navigation of the MySQL Cluster Auto-Installer, whose Welcome screen looks similar to what is shown here when it is first opened in the Web browser:
You can access the installer UI by selecting either of the options Create New MySQL Cluster or Continue Previous Cluster Configuration. A typical screen in the Auto-Installer includes the following elements:
Display panel. The central area where data regarding configuration settings and controls for changing them are displayed.
Breadcrumb navigation. Located in the top left and top center of the GUI, the breadcrumb navigation bar consists of a series of titles linking to screens that correspond to steps in the configuration of a MySQL Cluster. The breadcrumb allows you to jump between these stages in arbritrary order.
Sequential navigation. This consists of a set of buttons labelled
, , and , and can be found in the lower right-hand corner of the GUI. The sequential navigation is used to move between steps in the suggested order.Settings and Help menus. These menus can be found in the top right corner of the GUI (to the right of the breadcrumb navigation bar).
provides a way check and possibly alter configuration settings for the Auto-Installer; can be used to access the installer's built-in help files.The locations of the elements just described are shown here in a typical page in the Auto-Installer; the numbers superimposed thereupon correspond to those used in the preceding list.
All of these elements except for the display panel are described in greater detail in the remainder of this section. Section 19.2.1.3, “Using the MySQL Cluster Auto-Installer”, describes the panels shown in the display area as well as the functionality of each panel and the controls it contains.
Arbitrary and sequential navigation. The Auto-Installer can display any of a number of pages covering different stages in the setup and configuration of a MySQL Cluster deployment. You can navigate between pages in either of two ways. The first of these is the breadcrumb trail navigation toolbar displaying the titles of the various pages (in which the title of the current page is highlighted and disabled). From these, any desired page, in any desired order, can be reached by selecting the title of the corresponding page. This toolbar is shown here:
The second navigation mechanism provided by the Auto-Installer consists of the
, , and sequential navigation buttons at the bottom right of the page. These can be used to move to the next or previous page in predetermined order, or to go to the very last page. The buttons are enabled and disabled as needed, so that you cannot, for example, advance beyond the last page.Settings and Help menus. These menus are positioned adjacent to one another in the top right corner of the GUI, as shown earlier in this section. The
menu is shown here in more detail:The entries in the
menu are described here, in the following list:: Remove all hosts and processes; reset all parameter values to their defaults; start the installer over at the first page.
: Save your configuration information—such as host names, process data, and parameter values—as a cookie in the browser. When this option is chosen, all information except any SSH password is saved. This means that you can quit and restart the browser, and continue working on the same configuration from where you left off at the end of the previous session).
Since the SSH password is never saved, you must supply this once again at the beginning of a new session, if one is used.
: Show advanced configuration parameters in the Auto-Installer and make these settable by the user.
Once set, the advanced parameters continue to be used in the configuration file until they are explicitly changed or reset. This is regardless of whether the advanced parameters are currently visible in the installer; in other words, disabling the menu item does not reset the values of any of these parameters.
: Query new hosts automatically for hardware resource information to pre-populate a number of configuration options and values. In this case, the suggested values are not mandatory, but they are used unless explicitly changed using the appropriate editing options in the installer.
As with the installer's navigation elements, one or more of the entries in the
menu may be disabled due to choices you have made previously.The
menu is shown here, as it appears when expanded:The
menu provides several options, described in the following list:: Show the built-in user guide. This is opened in a separate browser window, so that it can be used simultaneously with the installer without interrupting workflow.
: Open the built-in user guide to the section describing the page currently displayed in the installer.
: This will show a small dialog displaying the installer name and the version number of the MySQL Cluster distribution it was supplied with, similar to what is shown here:
The Auto-Installer also provides context-sensitive help in the form of tooltips for most input widgets. One of these tooltips is displayed when the mouse hovers over a widget or the small question mark which can sometimes appear next to a widget label.
In addition, the names of MySQL Cluster configuration parameters are linked to their descriptions in the online MySQL Cluster documentation, so that if you click on the name of a given parameter, the documentation for that parameter is shown in a separate window.
Section 19.2.1.3.1, “Starting the MySQL Cluster Auto-Installer”
Section 19.2.1.3.2, “MySQL Cluster Auto-Installer Welcome Screen”
Section 19.2.1.3.3, “MySQL Cluster Auto-Installer Define Cluster Screen”
Section 19.2.1.3.4, “MySQL Cluster Auto-Installer Define Hosts Screen”
Section 19.2.1.3.5, “MySQL Cluster Auto-Installer Define Processes Screen”
Section 19.2.1.3.6, “MySQL Cluster Auto-Installer Define Attributes Screen”
Section 19.2.1.3.7, “MySQL Cluster Auto-Installer Deploy Cluster Screen”
The MySQL Cluster Auto-Installer consists of several pages, each corresponding to a step in the process used to configure and deploy a MySQL Cluster, and listed here:
Welcome: Begin using the Auto-Installer by choosing either to configure a new MySQL Cluster, or to continue configuring an existing one.
Define Cluster: Set basic information about the cluster as a whole, such as name, hosts, and load type. Here you can also set the SSH authentication type for accessing remote hosts, if needed.
Define Hosts: Identify the hosts where you intend to run MySQL Cluster processes.
Define Processes: Assign one or more processes of a given type or types to each cluster host.
Define Attributes: Set configuration attributes for processes or types of processes.
Deploy Cluster: Deploy the cluster with the configuration set previously; start and stop the deployed cluster.
The following sections describe in greater detail the purpose and function of each of these pages, in the order just listed.
The Auto-Installer is provided together with the MySQL Cluster
software. (See Section 19.2, “MySQL Cluster Installation”.)
The present section explains how to start the installer. You
can do by invoking the ndb_setup.py
executable. ndb_setup.py is found in the
bin
within the MySQL Cluster installation
directory; a typical location might be
/usr/local/mysql/bin
on a Linux system or
C:\Program Files\MySQL\MySQL Server
5.6\bin
on a Windows system, but this can vary
according to where the MySQL Cluster software is installed on
your system.
On Windows, you can also start the installer by running setup.bat in the MySQL Cluster installation directory. When invoked from the command line, it accepts the same options as does ndb_setup.py.
ndb_setup.py can be started with any of several options that affect its operation, but it is usually sufficient to allow the default settings be used, in which case you can start ndb_setup.py by either of the following two methods:
Navigate to the MySQL Cluster bin
directory in a terminal and invoke it from the command
line, without any additional arguments or options, like
this:
shell> ndb_setup
This works regardless of operating platform.
Navigate to the MySQL Cluster bin
directory in a file browser (such Windows Explorer on
Windows, or Konqueror, Dolphin, or Nautilus on Linux) and
activate (usually by double-clicking) the
ndb_setup.py file icon. This works on
Windows, and should work with most common Linux desktops
as well.
On Windows, you can also navigate to the MySQL Cluster installation directory and activate the setup.bat file icon.
In either case, once ndb_setup.py is invoked, the Auto-Installer's Welcome screen should open in the system's default Web browser.
In some cases, you may wish to use non-default settings for the installer, such as specifying a different port for the Auto-Installer's included Web server to run on, in which case you must invoke ndb_setup.py with one or more startup options with values overriding the necessary defaults. The same startup options can be used on Windows systems with the setup.bat file supplied for such platforms in the MySQL Cluster software distribution. This can be done using the command line, but if you want or need to start the installer from a desktop or file browser while emplying one or more of these options, it is also possible to create a script or batch file containing the proper invocation, then to double-click its file icon in the file browser to start the installer. (On Linux systems, you might also need to make the script file executable first.) For information about advanced startup options for the MySQL Cluster Auto-Installer, see Section 19.4.23, “ndb_setup.py — Start browser-based Auto-Installer for MySQL Cluster”.
The Welcome screen is loaded in the default browser when ndb_setup.py is invoked, as shown here:
This screen provides the following two choices for entering the installer, one of which must be selected to continue:
Create New MySQL Cluster: Start the Auto-Installer with a completely new cluster to be set up and deployed.
Continue Previous Cluster Configuration: Start the Auto-Installer at the same point where the previous session ended, with all previous settings preserved.
The second option requires that the browser be able to access its cookies from the previous session, as these provide the mechanism by which configuration and other information generated during a session is stored. In other words, to continue the previous session with the Auto-Installer, you must use the same web browser running on the same host as you did for the previous session.
The Define Cluster screen is the first screen to appear following the choice made in the Welcome screen, and is used for setting general properties of the cluster. The layout of the Define Cluster screen is shown here:
The Define Cluster screen allows you to set a number of general properties for the cluster, as described in this list:
Cluster name: A name that identifies
the cluster. The default is MyCluster
.
Host list: A comma-delimited list of
one or more hosts where cluster processes should run. By
default, this is 127.0.0.1
. If you add
remote hosts to the list, you must be able to connect to
them using the SSH Credentials
supplied.
Application type: Choose one of the following:
Not intended for production environments.
: Minimal resource usage for small-scale testing. This the default.: Maximize performance for the given hardware.
: Maximize performance while maximizing sensitivity to timeouts in order to minimize the time needed to detect failed cluster processes.
Write load: Choose a level for the anticipated number of writes for the cluster as a whole. You can choose any one of the following levels:
: The expected load includes fewer than 100 write transactions for second.
: The expected load includes 100 to 1000 write transactions per second.
: The expected load includes more than 1000 write transactions per second.
SSH Credentials: Choose Key-Based SSH or enter User and Password credentials. The SSH key or a user name with password is required for connecting to any remote hosts specified in the Host list. By default, Key-Based SSH is selected, and the User and Password fileds are blank.
The Define Hosts screen, shown here, provides a means of viewing and specifying several key properties of each cluster host:
The hosts currently entered are displayed in the grid with various pieces of information. You can add hosts by clicking the Define Cluster screen).
button and entering a list of one or more comma-separated host names, IP addresses, or both (as when editing the host list on theSimilarly, you can remove one or more hosts using the button labelled
. When you remove a host in this fashion, any process which was configured for that host is also removed.If Automatically get resource information for new hosts is checked in the , the Auto-Installer attempts to retrieve the platform name, amount of memory, and number of CPU cores and to fill these in automatically. The status of this is displayed in the menuResource info column. Fetching the information from remote hosts is not instantaneous and may take some time, particularly from remote hosts running Windows.
If the SSH user credentials on the Define Cluster screen are changed, the tool tries to refresh the hardware information from any hosts for which information is missing. However, if a given field has already been edited, the user-supplied information is not overwritten by any value fetched from that host.
The hardware resource information, platform name, installation directory, and data directory can be edited by the user by clicking the corresponding cell in the grid, by selecting one or more hosts and clicking the button labelled Edit selected host(s). This causes a dialog box to appear, in which these fields can be edited, as shown here:
When more than one host is selected, any edited values are applied to all selected hosts.
The Define Processes screen, shown here, provides a way to assign MySQL Cluster processes (nodes) to cluster hosts:
The left-hand portion of this screen contains a process tree showing cluster hosts and processes set up to run on each one. On the right is a panel which displays information about the item currently selected in the tree.
When this screen is accessed for the first time for a given cluster, a default set of processes is defined for you, based on the number of hosts. If you later return to the Define Hosts screen, remove all hosts, and add new hosts, this also causes a new default set of processes to be defined.
MySQL Cluster processes are of the following types:
Management node. Performs administrative tasks such as stopping individual data nodes, querying node and cluster status, and making backups. Executable: ndb_mgmd.
Single-threaded data node. Stores data and executes queries. Executable: ndbd.
Multi threaded data node. Stores data and executes queries with multiple worker threads executing in parallel. Executable: ndbmtd.
SQL node.
MySQL server for executing SQL queries against
NDB
. Executable:
mysqld.
API node.
A client accessing data in
NDB
by means of the NDB API
or other low-level client API, rather than by using SQL.
See MySQL Cluster API Developer Guide, for more information.
For more information about process (node) types, see Section 19.1.1, “MySQL Cluster Core Concepts”.
Processes shown in the tree are numbered sequentially by type,
for each host—for example, SQL node
1
, SQL node 2
, and so on—to
simplify identification.
Each management node, data node, or SQL process must be assigned to a specific host, and is not allowed to run on any other host. An API node may be assigned to a single host, but this is not required. Instead, you can assign it to the special entry which the tree also contains in addition to any other hosts, and which acts as a placeholder for processes that are allowed to run on any host. Only API processes may use this . entry
Adding processes. To add a new process to a given host, either right-click that host's entry in the tree, then select the Add process popup when it appears, or select a host in the process tree, and press the button below the process tree. Performing either of these actions opens the add process dialog, as shown here:
Here you can select from among the available process types described earlier this section; you can also enter an arbitrary process name to take the place of the suggested value, if desired.
Removing processes. To delete a process, right-click on a process in the tree and select delete process from the pop up menu that appears, or select a process, then use the button below the process tree.
When a process is selected in the process tree, information about that process is displayed in the panel to the right of the tree, where you can change the process name and possibly its type. Important: Currently, you can change a single-threaded data node (ndbd) to a multi-threaded data node (ndbmtd), or the reverse, only; no other process type changes are allowed. If you want to make a change between any other process types, you must delete the original process first, then add a new process of the desired type.
This screen has a layout similar to that of the Define Processes screen, with a process tree at the left. Unlike that screen's tree, the Define Attributes process tree is organized by process or node type, with single-threaded and multi-threaded data nodes considered to be of the same type for this purpose, in groups labelled , , , and . A panel to the right of this tree displays information regarding the item currently selected. The Define Attributes screen is shown here:
A checkbox labelled Show advanced configuration is located below the process tree. Checking this box makes advanced options visible in the information pane. These options are set and used whether or not they are visible.
You can edit attributes for a single process by selecting that process from the tree, or for all processes of the same type in the cluster by selecting one of the
folders. A per-process value set for a given attribute overrides any per-group setting for that attribute that would otherwise apply to the process in question. An example of such an information panel (for an SQL process) is shown here:For some of the attributes shown in the information panel, a button bearing a plus sign is displayed to the right, which means that the value of this attribute can be overridden. This
button activates an input widget for the attribute, enabling you to change its value. When the value has been overridden, this button changes into a button showing an , as shown here:Clicking the
button next to an attribute undoes any changes made to it; it immediately reverts to the predefined value.All configuration attributes have predefined values calculated by the installer, based such factors as host name, node ID, node type, and so on. In most cases, these values may be left as they are. If you are not familiar with it already, it is highly recommended that you read the applicable documentation before making changes to any of the attribute values. To make finding this information easier, each attribute name shown in the information panel is linked to its description in the online MySQL Cluster documentation.
This screen allows you to perform the following tasks:
Review process startup commands and configuration files to be applied
Distribute configuration files by creating any necessary files and directories on all cluster hosts—that is, deploy the cluster as presently configured
Start and stop the cluster
The Deploy Cluster screen is shown here:
Like the Define Attributes screen, this screens features a process tree, organized by process type, on the left hand side. Next to each process is a status icon whose color indicates the current status of the process: green if it is running; yellow if it is starting or stopping; red if the process is stopped.
To the right of the process tree are two information panels, the upper panel showing the startup command or commands needed to start the selected process. (For some processes, more than one command may be required—for example, if initialization is necessary.) The lower panel shows the contents of the configuration file, if any, for the given process; currently, the management node process is only type of process having a configuration file. Other process types are configured using command-line parameters when starting the process, or by obtaining configuration information from the management nodes as needed in real time.
Three buttons are located immediately below the process tree. These are labelled as and perform the functions described in the following list:
: Verify that the configuration is valid. Create any directories required on the cluster hosts, and distribute the configuration files onto the hosts. A progress bar shows how far the deployment has proceeded.
: The cluster is deployed as with , after which all cluster processes are started in the correct order.
Starting these processes may take some time. If the estimated time to completion is too large, the installer provides an opportunity to cancel or to continue of the startup procedure. A progress bar indicates the current status of the startup procedure, as shown here:
The process status icons adjoining the process tree mentioned previously also update with the status of each process.
: After the cluster has been started, you can stop it using the this. As with starting the cluster, cluster shutdown is not instantaneous, and may require some time complete. A progress bar, similar to that displayed during cluster startup, shows the approximate current status of the cluster shutdown procedure, as do the process status icons adjoining the process tree.
The Auto-Installer generates a my.cnf
file containing the appropriate options for each
mysqld process in the cluster.
This section covers installation methods for MySQL Cluster on Linux and other Unix-like operating systems. While the next few sections refer to a Linux operating system, the instructions and procedures given there should be easily adaptable to other supported Unix-like platforms. For manual installation and setup instructions specific to Windows systems, see Section 19.2.3, “Installing MySQL Cluster on Windows”.
Each MySQL Cluster host computer must have the correct executable programs installed. A host running an SQL node must have installed on it a MySQL Server binary (mysqld). Management nodes require the management server daemon (ndb_mgmd); data nodes require the data node daemon (ndbd or ndbmtd). It is not necessary to install the MySQL Server binary on management node hosts and data node hosts. It is recommended that you also install the management client (ndb_mgm) on the management server host.
Installation of MySQL Cluster on Linux can be done using precompiled binaries from Oracle (downloaded as a .tar.gz archive), with RPM packages (also available from Oracle), or from source code. All three of these installation methods are described in the section that follow.
Regardless of the method used, it is still necessary following installation of the MySQL Cluster binaries to create configuration files for all cluster nodes, before you can start the cluster. See Section 19.2.4, “Initial Configuration of MySQL Cluster”.
This section covers the steps necessary to install the correct executables for each type of Cluster node from precompiled binaries supplied by Oracle.
For setting up a cluster using precompiled binaries, the first
step in the installation process for each cluster host is to
download the latest MySQL Cluster NDB 7.5 binary archive
(mysql-cluster-gpl-7.5.3-linux-i686-glibc23.tar.gz
from the MySQL Cluster
downloads area. We assume that you have placed this file
in each machine's /var/tmp
directory.
(If you do require a custom binary, see
Section 2.9.3, “Installing MySQL Using a Development Source Tree”.)
After completing the installation, do not yet start any of the binaries. We show you how to do so following the configuration of the nodes (see Section 19.2.4, “Initial Configuration of MySQL Cluster”).
SQL nodes.
On each of the machines designated to host SQL nodes, perform
the following steps as the system root
user:
Check your /etc/passwd
and
/etc/group
files (or use whatever tools
are provided by your operating system for managing users and
groups) to see whether there is already a
mysql
group and mysql
user on the system. Some OS distributions create these as
part of the operating system installation process. If they
are not already present, create a new
mysql
user group, and then add a
mysql
user to this group:
shell>groupadd mysql
shell>useradd -g mysql -s /bin/false mysql
The syntax for useradd and groupadd may differ slightly on different versions of Unix, or they may have different names such as adduser and addgroup.
Change location to the directory containing the downloaded
file, unpack the archive, and create a symbolic link named
mysql
to the mysql
directory.
The actual file and directory names vary according to the MySQL Cluster version number.
shell>cd /var/tmp
shell>tar -C /usr/local -xzvf mysql-cluster-gpl-7.5.3-linux2.6.tar.gz
shell>ln -s /usr/local/mysql-cluster-gpl-7.5.3-linux2.6-i686 /usr/local/mysql
Change location to the mysql
directory
and run the supplied script for creating the system
databases:
shell>cd mysql
shell>scripts/mysql_install_db --user=mysql
Set the necessary permissions for the MySQL server and data directories:
shell>chown -R root .
shell>chown -R mysql data
shell>chgrp -R mysql .
Copy the MySQL startup script to the appropriate directory, make it executable, and set it to start when the operating system is booted up:
shell>cp support-files/mysql.server /etc/rc.d/init.d/
shell>chmod +x /etc/rc.d/init.d/mysql.server
shell>chkconfig --add mysql.server
(The startup scripts directory may vary depending on your
operating system and version—for example, in some
Linux distributions, it is
/etc/init.d
.)
Here we use Red Hat's chkconfig for creating links to the startup scripts; use whatever means is appropriate for this purpose on your platform, such as update-rc.d on Debian.
Remember that the preceding steps must be repeated on each machine where an SQL node is to reside.
Data nodes.
Installation of the data nodes does not require the
mysqld binary. Only the MySQL Cluster data
node executable ndbd (single-threaded) or
ndbmtd (multi-threaded) is required. These
binaries can also be found in the .tar.gz
archive. Again, we assume that you have placed this archive in
/var/tmp
.
As system root
(that is, after using
sudo, su root, or your
system's equivalent for temporarily assuming the system
administrator account's privileges), perform the following steps
to install the data node binaries on the data node hosts:
Change location to the /var/tmp
directory, and extract the ndbd and
ndbmtd binaries from the archive into a
suitable directory such as
/usr/local/bin
:
shell>cd /var/tmp
shell>tar -zxvf mysql-5.7.13-ndb-7.5.3-linux-i686-glibc23.tar.gz
shell>cd mysql-5.7.13-ndb-7.5.3-linux-i686-glibc23
shell>cp bin/ndbd /usr/local/bin/ndbd
shell>cp bin/ndbmtd /usr/local/bin/ndbmtd
(You can safely delete the directory created by unpacking
the downloaded archive, and the files it contains, from
/var/tmp
once
ndb_mgm and ndb_mgmd
have been copied to the executables directory.)
Change location to the directory into which you copied the files, and then make both of them executable:
shell>cd /usr/local/bin
shell>chmod +x ndb*
The preceding steps should be repeated on each data node host.
Although only one of the data node executables is required to run a MySQL Cluster data node, we have shown you how to install both ndbd and ndbmtd in the preceding instructions. We recommend that you do this when installing or upgrading MySQL Cluster, even if you plan to use only one of them, since this will save time and trouble in the event that you later decide to change from one to the other.
The data directory on each machine hosting a data node is
/usr/local/mysql/data
. This piece of
information is essential when configuring the management node.
(See Section 19.2.4, “Initial Configuration of MySQL Cluster”.)
Management nodes.
Installation of the management node does not require the
mysqld binary. Only the MySQL Cluster
management server (ndb_mgmd) is required;
you most likely want to install the management client
(ndb_mgm) as well. Both of these binaries
also be found in the .tar.gz
archive.
Again, we assume that you have placed this archive in
/var/tmp
.
As system root
, perform the following steps
to install ndb_mgmd and
ndb_mgm on the management node host:
Change location to the /var/tmp
directory, and extract the ndb_mgm and
ndb_mgmd from the archive into a suitable
directory such as /usr/local/bin
:
shell>cd /var/tmp
shell>tar -zxvf mysql-5.7.13-ndb-7.5.3-linux2.6-i686.tar.gz
shell>cd mysql-5.7.13-ndb-7.5.3-linux2.6-i686
shell>cp bin/ndb_mgm* /usr/local/bin
(You can safely delete the directory created by unpacking
the downloaded archive, and the files it contains, from
/var/tmp
once
ndb_mgm and ndb_mgmd
have been copied to the executables directory.)
Change location to the directory into which you copied the files, and then make both of them executable:
shell>cd /usr/local/bin
shell>chmod +x ndb_mgm*
In Section 19.2.4, “Initial Configuration of MySQL Cluster”, we create configuration files for all of the nodes in our example MySQL Cluster.
This section covers the steps necessary to install the correct executables for each type of MySQL Cluster node using RPM packages supplied by Oracle.
RPMs are available for both 32-bit and 64-bit Linux platforms. The filenames for these RPMs use the following pattern:
MySQL-Cluster-component
-producttype
-ndbversion
.distribution
.architecture
.rpmcomponent
:= {server | client [|other
]}producttype
:= {gpl | advanced}ndbversion
:=major
.minor
.release
distribution
:= {sles10 | rhel5 | el6}architecture
:= {i386 | x86_64}
The component
can be
server
or client
. (Other
values are possible, but since only the
server
and client
components are required for a working MySQL Cluster
installation, we do not discuss them here.) The
producttype
for Community RPMs
downloaded from http://dev.mysql.com/downloads/cluster/ is
always gpl
; advanced
is
used to indicate commercial releases.
ndbversion
represents the three-part
NDB
storage engine version number in
7.5.x
format. The
distribution
can be one of
sles11
(SUSE Enterprise Linux 11),
rhel5
(Oracle Linux 5, Red Hat Enterprise
Linux 4 and 5), or el6
(Oracle Linux 6, Red
Hat Enterprise Linux 6) The
architecture
is
i386
for 32-bit RPMs and
x86_64
for 64-bit versions.
For a MySQL Cluster, one and possibly two RPMs are required:
The server
RPM (for example,
MySQL-Cluster-server-gpl-7.5.3-1.sles11.i386.rpm
),
which supplies the core files needed to run a MySQL Server
with NDBCLUSTER
storage engine
support (that is, as a MySQL Cluster SQL node) as well as
all MySQL Cluster executables, including the management
node, data node, and ndb_mgm client
binaries. This RPM is always required for installing MySQL
Cluster.
If you do not have your own client application capable of
administering a MySQL server, you should also obtain and
install the client
RPM (for example,
MySQL-Cluster-client-gpl-7.5.3-1.sles11.i386.rpm
),
which supplies the mysql client
The MySQL Cluster version number in the RPM file names (shown
here as 7.5.3
) can vary
according to the version which you are actually using.
It is very important that all of the Cluster RPMs to
be installed have the same version number. The
architecture
designation should also
be appropriate to the machine on which the RPM is to be
installed; in particular, you should keep in mind that 64-bit
RPMs cannot be used with 32-bit operating system.
Data nodes.
On a computer that is to host a cluster data node it is
necessary to install only the server
RPM.
To do so, copy this RPM to the data node host, and run the
following command as the system root user, replacing the name
shown for the RPM as necessary to match that of the RPM
downloaded from the MySQL web site:
shell> rpm -Uhv MySQL-Cluster-server-gpl-7.5.3-1.sles11.i386.rpm
Although this installs all MySQL Cluster binaries, only the
program ndbd or ndbmtd
(both in /usr/sbin
) is actually needed to
run a MySQL Cluster data node.
SQL nodes.
On each machine to be used for hosting a cluster SQL node,
install the server
RPM by executing the
following command as the system root user, replacing the name
shown for the RPM as necessary to match the name of the RPM
downloaded from the MySQL web site:
shell> rpm -Uhv MySQL-Cluster-server-gpl-7.5.3-1.sles11.i386.rpm
This installs the MySQL server binary
(mysqld) with
NDB
storage engine support in the
/usr/sbin
directory, as well as all needed
MySQL Server support files. It also installs the
mysql.server and
mysqld_safe startup scripts (in
/usr/share/mysql
and
/usr/bin
, respectively). The RPM installer
should take care of general configuration issues (such as
creating the mysql
user and group, if needed)
automatically.
To administer the SQL node (MySQL server), you should also
install the client
RPM, as shown here:
shell> rpm -Uhv MySQL-Cluster-client-gpl-7.5.3-1.sles11.i386.rpm
This installs the mysql client program.
Management nodes.
To install the MySQL Cluster management server, it is
necessary only to use the server
RPM. Copy
this RPM to the computer intended to host the management node,
and then install it by running the following command as the
system root user (replace the name shown for the RPM as
necessary to match that of the server
RPM
downloaded from the MySQL web site):
shell> rpm -Uhv MySQL-Cluster-server-gpl-7.5.3-1.sles11.i386.rpm
Although this RPM installs many other files, only the management
server binary ndb_mgmd (in the
/usr/sbin
directory) is actually required
for running a management node. The server
RPM
also installs ndb_mgm, the
NDB
management client.
See Section 2.5.5, “Installing MySQL on Linux Using RPM Packages from Oracle”, for general information about installing MySQL using RPMs supplied by Oracle.
After installing from RPM, you still need to configure the cluster as discussed in Section 19.2.4, “Initial Configuration of MySQL Cluster”.
The section provides information about installing MySQL Cluster on Debian and related Linux distributions such Ubuntu using the .deb files supplied by Oracle for this purpose.
Oracle provides .deb
installer files for
MySQL Cluster NDB 7.5 for 32-bit and 64-bit platforms. For a
Debian-based system, only a single installer file is necessary.
This file is named using the pattern shown here, according to
the applicable MySQL Cluster version, Debian version, and
architecture:
mysql-cluster-gpl-ndbver
-debiandebianver
-arch
.deb
Here, ndbver
is the 3-part
NDB
engine version number,
debianver
is the major version of
Debian (6.0
or 7
), and
arch
is one of
i686
or x86_64
.
In the examples that follow, we assume you wish to install MySQL
Cluster NDB 7.5.0 on a 64-bit Debian 7 system; in this case, the
installer file is named
mysql-cluster-gpl-7.5.0-debian7-x86_64.deb
.
Once you have downloaded the appropriate
.deb
file, you can install it from the
command line using dpkg
, like this:
shell> dpkg -i mysql-cluster-gpl-7.5.0-debian7-i686.deb
You can also remove it using dpkg
as shown
here:
shell> dpkg -r mysql
The installer file should also be compatible with most graphical
package managers that work with .deb
files,
such as GDebi
for the Gnome desktop.
The .deb
file installs MySQL Cluster under
/opt/mysql/server-
,
where version
/version
is the 2-part release
series version for the included MySQL server. For MySQL Cluster
NDB 7.5, this is always 5.7
. The directory
layout is the same as that for the generic Linux binary
distribution (see Table 2.3, “MySQL Installation Layout for Generic Unix/Linux Binary Package”),
with the exception that startup scripts and configuration files
are found in support-files
instead of
share
. All MySQL Cluster executables, such
as ndb_mgm, ndbd, and
ndb_mgmd, are placed in the
bin
directory.
This section provides information about compiling MySQL Cluster on Linux and other Unix-like platforms. Building MySQL Cluster from source is similar to building the standard MySQL Server, although it differs in a few key respects discussed here. For general information about building MySQL from source, see Section 2.9, “Installing MySQL from Source”. For information about compiling MySQL Cluster on Windows platforms, see Section 19.2.3.2, “Compiling and Installing MySQL Cluster from Source on Windows”.
Building MySQL Cluster requires using the MySQL Cluster sources.
These are available from the MySQL Cluster downloads page at
http://dev.mysql.com/downloads/cluster/. The archived source
file should have a name similar to
mysql-cluster-gpl-7.5.3.tar.gz
.
You can also obtain MySQL development sources from
launchpad.net. Building MySQL Cluster
from standard MySQL Server 5.7 sources is not
supported.
The WITH_NDBCLUSTER_STORAGE_ENGINE
option for CMake causes the binaries for the
management nodes, data nodes, and other MySQL Cluster programs
to be built; it also causes mysqld to be
compiled with NDB
storage engine
support. This option (or its alias
WITH_NDBCLUSTER
) is required when
building MySQL Cluster.
The WITH_NDB_JAVA
option is
enabled by default. This means that, by default, if
CMake cannot find the location of Java on
your system, the configuration process fails; if you do not
wish to enable Java and ClusterJ support, you must indicate
this explicitly by configuring the build using
-DWITH_NDB_JAVA=OFF
. Use
WITH_CLASSPATH
to provide the
Java classpath if needed.
For more information about CMake options specific to building MySQL Cluster, see Options for Compiling MySQL Cluster.
After you have run make && make install (or your system's equivalent), the result is similar to what is obtained by unpacking a precompiled binary to the same location.
Management nodes.
When building from source and running the default
make install, the management server and
management client binaries (ndb_mgmd and
ndb_mgm) can be found in
/usr/local/mysql/bin
. Only
ndb_mgmd is required to be present on a
management node host; however, it is also a good idea to have
ndb_mgm present on the same host machine.
Neither of these executables requires a specific location on
the host machine's file system.
Data nodes.
The only executable required on a data node host is the data
node binary ndbd or
ndbmtd. (mysqld, for
example, does not have to be present on the host machine.) By
default, when building from source, this file is placed in the
directory /usr/local/mysql/bin
. For
installing on multiple data node hosts, only
ndbd or ndbmtd need be
copied to the other host machine or machines. (This assumes
that all data node hosts use the same architecture and
operating system; otherwise you may need to compile separately
for each different platform.) The data node binary need not be
in any particular location on the host's file system, as long
as the location is known.
When compiling MySQL Cluster from source, no special options are
required for building multi-threaded data node binaries.
Configuring the build with NDB
storage engine support causes ndbmtd to be
built automatically; make install places the
ndbmtd binary in the installation
bin
directory along with
mysqld, ndbd, and
ndb_mgm.
SQL nodes.
If you compile MySQL with clustering support, and perform the
default installation (using make install as
the system root
user),
mysqld is placed in
/usr/local/mysql/bin
. Follow the steps
given in Section 2.9, “Installing MySQL from Source” to make
mysqld ready for use. If you want to run
multiple SQL nodes, you can use a copy of the same
mysqld executable and its associated
support files on several machines. The easiest way to do this
is to copy the entire /usr/local/mysql
directory and all directories and files contained within it to
the other SQL node host or hosts, then repeat the steps from
Section 2.9, “Installing MySQL from Source” on each machine. If you
configure the build with a nondefault PREFIX
option, you must adjust the directory accordingly.
In Section 19.2.4, “Initial Configuration of MySQL Cluster”, we create configuration files for all of the nodes in our example MySQL Cluster.
This section describes installation procedures for MySQL Cluster on Windows hosts. MySQL Cluster NDB 7.5 binaries for Windows can be obtained from http://dev.mysql.com/downloads/cluster/. For information about installing MySQL Cluster on Windows from a binary release provided by Oracle, see Section 19.2.3.1, “Installing MySQL Cluster on Windows from a Binary Release”.
It is also possible to compile and install MySQL Cluster from source on Windows using Microsoft Visual Studio. For more information, see Section 19.2.3.2, “Compiling and Installing MySQL Cluster from Source on Windows”.
This section describes a basic installation of MySQL Cluster on
Windows using a binary no-install
MySQL
Cluster release provided by Oracle, using the same 4-node setup
outlined in the beginning of this section (see
Section 19.2, “MySQL Cluster Installation”), as shown in the
following table:
Node | IP Address |
---|---|
Management (MGMD) node | 192.168.0.10 |
MySQL server (SQL) node | 192.168.0.20 |
Data (NDBD) node "A" | 192.168.0.30 |
Data (NDBD) node "B" | 192.168.0.40 |
As on other platforms, the MySQL Cluster host computer running an SQL node must have installed on it a MySQL Server binary (mysqld.exe). You should also have the MySQL client (mysql.exe) on this host. For management nodes and data nodes, it is not necessary to install the MySQL Server binary; however, each management node requires the management server daemon (ndb_mgmd.exe); each data node requires the data node daemon (ndbd.exe or ndbmtd.exe). For this example, we refer to ndbd.exe as the data node executable, but you can install ndbmtd.exe, the multi-threaded version of this program, instead, in exactly the same way. You should also install the management client (ndb_mgm.exe) on the management server host. This section covers the steps necessary to install the correct Windows binaries for each type of MySQL Cluster node.
As with other Windows programs, MySQL Cluster executables are
named with the .exe
file extension.
However, it is not necessary to include the
.exe
extension when invoking these
programs from the command line. Therefore, we often simply
refer to these programs in this documentation as
mysqld, mysql,
ndb_mgmd, and so on. You should understand
that, whether we refer (for example) to
mysqld or mysqld.exe,
either name means the same thing (the MySQL Server program).
For setting up a MySQL Cluster using Oracles's
no-install
binaries, the first step in the
installation process is to download the latest MySQL Cluster
Windows binary archive from
http://dev.mysql.com/downloads/cluster/. This archive has a
filename of the form
mysql-cluster-gpl-noinstall-
,
where ver
-winarch
.zipver
is the
NDB
storage engine version (such as
7.5.3
), and
arch
is the architecture
(32
for 32-bit binaries, and
64
for 64-bit binaries). For example, the
MySQL Cluster NDB 7.5.3
no-install
archive for 32-bit Windows systems
is named
mysql-cluster-gpl-noinstall-7.5.3-win32.zip
.
You can run 32-bit MySQL Cluster binaries on both 32-bit and 64-bit versions of Windows; however, 64-bit MySQL Cluster binaries can be used only on 64-bit versions of Windows. If you are using a 32-bit version of Windows on a computer that has a 64-bit CPU, then you must use the 32-bit MySQL Cluster binaries.
To minimize the number of files that need to be downloaded from the Internet or copied between machines, we start with the computer where you intend to run the SQL node.
SQL node.
We assume that you have placed a copy of the
no-install
archive in the directory
C:\Documents and
Settings\
on the computer having the IP
address 192.168.0.20, where
username
\My
Documents\Downloadsusername
is the name of the current
user. (You can obtain this name using ECHO
%USERNAME%
on the command line.) To install and run
MySQL Cluster executables as Windows services, this user
should be a member of the Administrators
group.
Extract all the files from the archive. The Extraction Wizard
integrated with Windows Explorer is adequate for this task. (If
you use a different archive program, be sure that it extracts
all files and directories from the archive, and that it
preserves the archive's directory structure.) When you are
asked for a destination directory, enter
C:\
, which causes the Extraction Wizard to
extract the archive to the directory
C:\mysql-cluster-gpl-noinstall-
.
Rename this directory to ver
-winarch
C:\mysql
.
It is possible to install the MySQL Cluster binaries to
directories other than C:\mysql\bin
;
however, if you do so, you must modify the paths shown in this
procedure accordingly. In particular, if the MySQL Server (SQL
node) binary is installed to a location other than
C:\mysql
or C:\Program
Files\MySQL\MySQL Server 5.7
, or if the
SQL node's data directory is in a location other than
C:\mysql\data
or C:\Program
Files\MySQL\MySQL Server 5.7\data
, extra
configuration options must be used on the command line or added
to the my.ini
or
my.cnf
file when starting the SQL node. For
more information about configuring a MySQL Server to run in a
nonstandard location, see
Section 2.3.5, “Installing MySQL on Microsoft Windows Using a noinstall Zip Archive”.
For a MySQL Server with MySQL Cluster support to run as part of
a MySQL Cluster, it must be started with the options
--ndbcluster
and
--ndb-connectstring
. While you
can specify these options on the command line, it is usually
more convenient to place them in an option file. To do this,
create a new text file in Notepad or another text editor. Enter
the following configuration information into this file:
[mysqld] # Options for mysqld process: ndbcluster # run NDB storage engine ndb-connectstring=192.168.0.10 # location of management server
You can add other options used by this MySQL Server if desired
(see Section 2.3.5.2, “Creating an Option File”), but the file
must contain the options shown, at a minimum. Save this file as
C:\mysql\my.ini
. This completes the
installation and setup for the SQL node.
Data nodes.
A MySQL Cluster data node on a Windows host requires only a
single executable, one of either ndbd.exe
or ndbmtd.exe. For this example, we assume
that you are using ndbd.exe, but the same
instructions apply when using ndbmtd.exe.
On each computer where you wish to run a data node (the
computers having the IP addresses 192.168.0.30 and
192.168.0.40), create the directories
C:\mysql
,
C:\mysql\bin
, and
C:\mysql\cluster-data
; then, on the
computer where you downloaded and extracted the
no-install
archive, locate
ndbd.exe
in the
C:\mysql\bin
directory. Copy this file to
the C:\mysql\bin
directory on each of the
two data node hosts.
To function as part of a MySQL Cluster, each data node must be
given the address or hostname of the management server. You can
supply this information on the command line using the
--ndb-connectstring
or
-c
option when starting each data node process.
However, it is usually preferable to put this information in an
option file. To do this, create a new text file in Notepad or
another text editor and enter the following text:
[mysql_cluster] # Options for data node process: ndb-connectstring=192.168.0.10 # location of management server
Save this file as C:\mysql\my.ini
on the
data node host. Create another text file containing the same
information and save it on as
C:mysql\my.ini
on the other data node host,
or copy the my.ini file from the first data node host to the
second one, making sure to place the copy in the second data
node's C:\mysql
directory. Both data
node hosts are now ready to be used in the MySQL Cluster, which
leaves only the management node to be installed and configured.
Management node.
The only executable program required on a computer used for
hosting a MySQL Cluster management node is the management
server program ndb_mgmd.exe. However, in
order to administer the MySQL Cluster once it has been
started, you should also install the MySQL Cluster management
client program ndb_mgm.exe on the same
machine as the management server. Locate these two programs on
the machine where you downloaded and extracted the
no-install
archive; this should be the
directory C:\mysql\bin
on the SQL node
host. Create the directory C:\mysql\bin
on the computer having the IP address 192.168.0.10, then copy
both programs to this directory.
You should now create two configuration files for use by
ndb_mgmd.exe
:
A local configuration file to supply configuration data specific to the management node itself. Typically, this file needs only to supply the location of the MySQL Cluster global configuration file (see item 2).
To create this file, start a new text file in Notepad or another text editor, and enter the following information:
[mysql_cluster] # Options for management node process config-file=C:/mysql/bin/config.ini
Save this file as the text file
C:\mysql\bin\my.ini
.
A global configuration file from which the management node
can obtain configuration information governing the MySQL
Cluster as a whole. At a minimum, this file must contain a
section for each node in the MySQL Cluster, and the IP
addresses or hostnames for the management node and all data
nodes (HostName
configuration parameter).
It is also advisable to include the following additional
information:
The IP address or hostname of any SQL nodes
The data memory and index memory allocated to each data
node (DataMemory
and IndexMemory
configuration parameters)
The number of replicas, using the
NoOfReplicas
configuration parameter (see
Section 19.1.2, “MySQL Cluster Nodes, Node Groups, Replicas, and Partitions”)
The directory where each data node stores it data and
log file, and the directory where the management node
keeps its log files (in both cases, the
DataDir
configuration parameter)
Create a new text file using a text editor such as Notepad, and input the following information:
[ndbd default]
# Options affecting ndbd processes on all data nodes:
NoOfReplicas=2 # Number of replicas
DataDir=C:/mysql/cluster-data # Directory for each data node's data files
# Forward slashes used in directory path,
# rather than backslashes. This is correct;
# see Important note in text
DataMemory=80M # Memory allocated to data storage
IndexMemory=18M # Memory allocated to index storage
# For DataMemory and IndexMemory, we have used the
# default values. Since the "world" database takes up
# only about 500KB, this should be more than enough for
# this example Cluster setup.
[ndb_mgmd]
# Management process options:
HostName=192.168.0.10 # Hostname or IP address of management node
DataDir=C:/mysql/bin/cluster-logs # Directory for management node log files
[ndbd]
# Options for data node "A":
# (one [ndbd] section per data node)
HostName=192.168.0.30 # Hostname or IP address
[ndbd]
# Options for data node "B":
HostName=192.168.0.40 # Hostname or IP address
[mysqld]
# SQL node options:
HostName=192.168.0.20 # Hostname or IP address
Save this file as the text file
C:\mysql\bin\config.ini
.
A single backslash character (\
) cannot be
used when specifying directory paths in program options or
configuration files used by MySQL Cluster on Windows. Instead,
you must either escape each backslash character with a second
backslash (\\
), or replace the backslash
with a forward slash character (/
). For
example, the following line from the
[ndb_mgmd]
section of a MySQL Cluster
config.ini
file does not work:
DataDir=C:\mysql\bin\cluster-logs
Instead, you may use either of the following:
DataDir=C:\\mysql\\bin\\cluster-logs # Escaped backslashes
DataDir=C:/mysql/bin/cluster-logs # Forward slashes
For reasons of brevity and legibility, we recommend that you use forward slashes in directory paths used in MySQL Cluster program options and configuration files on Windows.
Oracle provides precompiled MySQL Cluster binaries for Windows which should be adequate for most users. However, if you wish, it is also possible to compile MySQL Cluster for Windows from source code. The procedure for doing this is almost identical to the procedure used to compile the standard MySQL Server binaries for Windows, and uses the same tools. However, there are two major differences:
To build MySQL Cluster, you must use the MySQL Cluster sources, which you can obtain from http://dev.mysql.com/downloads/cluster/.
Attempting to build MySQL Cluster from the source code for the standard MySQL Server is likely not to be successful, and is not supported by Oracle.
You must configure the build using the
WITH_NDBCLUSTER_STORAGE_ENGINE
or WITH_NDBCLUSTER
option in
addition to any other build options you wish to use with
CMake. (WITH_NDBCLUSTER
is supported as an alias for
WITH_NDBCLUSTER_STORAGE_ENGINE
, and works
in exactly the same way.)
The WITH_NDB_JAVA
option is
enabled by default. This means that, by default, if
CMake cannot find the location of Java on
your system, the configuration process fails; if you do not
wish to enable Java and ClusterJ support, you must indicate
this explicitly by configuring the build using
-DWITH_NDB_JAVA=OFF
. (Bug #12379735) Use
WITH_CLASSPATH
to provide the
Java classpath if needed.
For more information about CMake options specific to building MySQL Cluster, see Options for Compiling MySQL Cluster.
Once the build process is complete, you can create a Zip archive
containing the compiled binaries;
Section 2.9.2, “Installing MySQL Using a Standard Source Distribution” provides the
commands needed to perform this task on Windows systems. The
MySQL Cluster binaries can be found in the
bin
directory of the resulting archive,
which is equivalent to the no-install
archive, and which can be installed and configured in the same
manner. For more information, see
Section 19.2.3.1, “Installing MySQL Cluster on Windows from a Binary Release”.
Once the MySQL Cluster executables and needed configuration files are in place, performing an initial start of the cluster is simply a matter of starting the MySQL Cluster executables for all nodes in the cluster. Each cluster node process must be started separately, and on the host computer where it resides. The management node should be started first, followed by the data nodes, and then finally by any SQL nodes.
On the management node host, issue the following command from the command line to start the management node process. The output should appear similar to what is shown here:
C:\mysql\bin> ndb_mgmd
2010-06-23 07:53:34 [MgmtSrvr] INFO -- NDB Cluster Management Server. mysql-5.7.13-ndb-7.5.3
2010-06-23 07:53:34 [MgmtSrvr] INFO -- Reading cluster configuration from 'config.ini'
The management node process continues to print logging output to the console. This is normal, because the management node is not running as a Windows service. (If you have used MySQL Cluster on a Unix-like platform such as Linux, you may notice that the management node's default behavior in this regard on Windows is effectively the opposite of its behavior on Unix systems, where it runs by default as a Unix daemon process. This behavior is also true of MySQL Cluster data node processes running on Windows.) For this reason, do not close the window in which ndb_mgmd.exe is running; doing so kills the management node process. (See Section 19.2.3.4, “Installing MySQL Cluster Processes as Windows Services”, where we show how to install and run MySQL Cluster processes as Windows services.)
The required -f
option tells the management
node where to find the global configuration file
(config.ini
). The long form of this
option is --config-file
.
A MySQL Cluster management node caches the configuration
data that it reads from config.ini
;
once it has created a configuration cache, it ignores the
config.ini
file on subsequent starts
unless forced to do otherwise. This means that, if the
management node fails to start due to an error in this
file, you must make the management node re-read
config.ini
after you have corrected
any errors in it. You can do this by starting
ndb_mgmd.exe with the
--reload
or
--initial
option on the
command line. Either of these options works to refresh the
configuration cache.
It is not necessary or advisable to use either of these
options in the management node's
my.ini
file.
For additional information about options which can be used with ndb_mgmd, see Section 19.4.4, “ndb_mgmd — The MySQL Cluster Management Server Daemon”, as well as Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
On each of the data node hosts, run the command shown here to start the data node processes:
C:\mysql\bin> ndbd
2010-06-23 07:53:46 [ndbd] INFO -- Configuration fetched from 'localhost:1186', generation: 1
In each case, the first line of output from the data node process should resemble what is shown in the preceding example, and is followed by additional lines of logging output. As with the management node process, this is normal, because the data node is not running as a Windows service. For this reason, do not close the console window in which the data node process is running; doing so kills ndbd.exe. (For more information, see Section 19.2.3.4, “Installing MySQL Cluster Processes as Windows Services”.)
Do not start the SQL node yet; it cannot connect to the
cluster until the data nodes have finished starting, which
may take some time. Instead, in a new console window on the
management node host, start the MySQL Cluster management
client ndb_mgm.exe, which should be in
C:\mysql\bin
on the management node
host. (Do not try to re-use the console window where
ndb_mgmd.exe is running by typing
CTRL+C, as this kills the
management node.) The resulting output should look like
this:
C:\mysql\bin> ndb_mgm
-- NDB Cluster -- Management Client --
ndb_mgm>
When the prompt ndb_mgm>
appears, this
indicates that the management client is ready to receive
MySQL Cluster management commands. You can observe the
status of the data nodes as they start by entering
ALL STATUS
at the
management client prompt. This command causes a running
report of the data nodes's startup sequence, which
should look something like this:
ndb_mgm> ALL STATUS
Connected to Management Server at: localhost:1186
Node 2: starting (Last completed phase 3) (mysql-5.7.13-ndb-7.5.3)
Node 3: starting (Last completed phase 3) (mysql-5.7.13-ndb-7.5.3)
Node 2: starting (Last completed phase 4) (mysql-5.7.13-ndb-7.5.3)
Node 3: starting (Last completed phase 4) (mysql-5.7.13-ndb-7.5.3)
Node 2: Started (version 7.5.3)
Node 3: Started (version 7.5.3)
ndb_mgm>
Commands issued in the management client are not case-sensitive; we use uppercase as the canonical form of these commands, but you are not required to observe this convention when inputting them into the ndb_mgm client. For more information, see Section 19.5.2, “Commands in the MySQL Cluster Management Client”.
The output produced by ALL
STATUS
is likely to vary from what is shown here,
according to the speed at which the data nodes are able to
start, the release version number of the MySQL Cluster
software you are using, and other factors. What is
significant is that, when you see that both data nodes have
started, you are ready to start the SQL node.
You can leave ndb_mgm.exe running; it has no negative impact on the performance of the MySQL Cluster, and we use it in the next step to verify that the SQL node is connected to the cluster after you have started it.
On the computer designated as the SQL node host, open a
console window and navigate to the directory where you
unpacked the MySQL Cluster binaries (if you are following
our example, this is C:\mysql\bin
).
Start the SQL node by invoking mysqld.exe from the command line, as shown here:
C:\mysql\bin> mysqld --console
The --console
option causes
logging information to be written to the console, which can
be helpful in the event of problems. (Once you are satisfied
that the SQL node is running in a satisfactory manner, you
can stop it and restart it out without the
--console
option, so that
logging is performed normally.)
In the console window where the management client
(ndb_mgm.exe) is running on the
management node host, enter the
SHOW
command, which
should produce output similar to what is shown here:
ndb_mgm> SHOW
Connected to Management Server at: localhost:1186
Cluster Configuration
---------------------
[ndbd(NDB)] 2 node(s)
id=2 @192.168.0.30 (Version: 5.7.13-ndb-7.5.3, Nodegroup: 0, *)
id=3 @192.168.0.40 (Version: 5.7.13-ndb-7.5.3, Nodegroup: 0)
[ndb_mgmd(MGM)] 1 node(s)
id=1 @192.168.0.10 (Version: 5.7.13-ndb-7.5.3)
[mysqld(API)] 1 node(s)
id=4 @192.168.0.20 (Version: 5.7.13-ndb-7.5.3)
You can also verify that the SQL node is connected to the
MySQL Cluster in the mysql client
(mysql.exe) using the
SHOW ENGINE NDB STATUS
statement.
You should now be ready to work with database objects and data
using MySQL Cluster's
NDBCLUSTER
storage engine. See
Section 19.2.6, “MySQL Cluster Example with Tables and Data”, for more
information and examples.
You can also install ndb_mgmd.exe, ndbd.exe, and ndbmtd.exe as Windows services. For information on how to do this, see Section 19.2.3.4, “Installing MySQL Cluster Processes as Windows Services”).
Once you are satisfied that MySQL Cluster is running as desired, you can install the management nodes and data nodes as Windows services, so that these processes are started and stopped automatically whenever Windows is started or stopped. This also makes it possible to control these processes from the command line with the appropriate NET START or NET STOP command, or using the Windows graphical Services utility.
Installing programs as Windows services usually must be done using an account that has Administrator rights on the system.
To install the management node as a service on Windows, invoke
ndb_mgmd.exe from the command line on the
machine hosting the management node, using the
--install
option, as shown
here:
C:\> C:\mysql\bin\ndb_mgmd.exe --install
Installing service 'MySQL Cluster Management Server'
as '"C:\mysql\bin\ndbd.exe" "--service=ndb_mgmd"'
Service successfully installed.
When installing a MySQL Cluster program as a Windows service, you should always specify the complete path; otherwise the service installation may fail with the error The system cannot find the file specified.
The --install
option must be
used first, ahead of any other options that might be specified
for ndb_mgmd.exe. However, it is preferable
to specify such options in an options file instead. If your
options file is not in one of the default locations as shown in
the output of ndb_mgmd.exe
--help
, you can specify the
location using the
--config-file
option.
Now you should be able to start and stop the management server like this:
C:\>NET START ndb_mgmd
The MySQL Cluster Management Server service is starting. The MySQL Cluster Management Server service was started successfully. C:\>NET STOP ndb_mgmd
The MySQL Cluster Management Server service is stopping.. The MySQL Cluster Management Server service was stopped successfully.
You can also start or stop the management server as a Windows service using the descriptive name, as shown here:
C:\>NET START 'MySQL Cluster Management Server'
The MySQL Cluster Management Server service is starting. The MySQL Cluster Management Server service was started successfully. C:\>NET STOP 'MySQL Cluster Management Server'
The MySQL Cluster Management Server service is stopping.. The MySQL Cluster Management Server service was stopped successfully.
However, it is usually simpler to specify a short service name
or to permit the default service name to be used when installing
the service, and then reference that name when starting or
stopping the service. To specify a service name other than
ndb_mgmd
, append it to the
--install
option, as shown in
this example:
C:\> C:\mysql\bin\ndb_mgmd.exe --install=mgmd1
Installing service 'MySQL Cluster Management Server'
as '"C:\mysql\bin\ndb_mgmd.exe" "--service=mgmd1"'
Service successfully installed.
Now you should be able to start or stop the service using the name you have specified, like this:
C:\>NET START mgmd1
The MySQL Cluster Management Server service is starting. The MySQL Cluster Management Server service was started successfully. C:\>NET STOP mgmd1
The MySQL Cluster Management Server service is stopping.. The MySQL Cluster Management Server service was stopped successfully.
To remove the management node service, invoke
ndb_mgmd.exe with the
--remove
option, as shown here:
C:\> C:\mysql\bin\ndb_mgmd.exe --remove
Removing service 'MySQL Cluster Management Server'
Service successfully removed.
If you installed the service using a service name other than the
default, you can remove the service by passing this name as the
value of the --remove
option,
like this:
C:\> C:\mysql\bin\ndb_mgmd.exe --remove=mgmd1
Removing service 'mgmd1'
Service successfully removed.
Installation of a MySQL Cluster data node process as a Windows
service can be done in a similar fashion, using the
--install
option for
ndbd.exe (or ndbmtd.exe),
as shown here:
C:\> C:\mysql\bin\ndbd.exe --install
Installing service 'MySQL Cluster Data Node Daemon' as '"C:\mysql\bin\ndbd.exe" "--service=ndbd"'
Service successfully installed.
Now you can start or stop the data node using either the default service name or the descriptive name with net start or net stop, as shown in the following example:
C:\>NET START ndbd
The MySQL Cluster Data Node Daemon service is starting. The MySQL Cluster Data Node Daemon service was started successfully. C:\>NET STOP ndbd
The MySQL Cluster Data Node Daemon service is stopping.. The MySQL Cluster Data Node Daemon service was stopped successfully. C:\>NET START 'MySQL Cluster Data Node Daemon'
The MySQL Cluster Data Node Daemon service is starting. The MySQL Cluster Data Node Daemon service was started successfully. C:\>NET STOP 'MySQL Cluster Data Node Daemon'
The MySQL Cluster Data Node Daemon service is stopping.. The MySQL Cluster Data Node Daemon service was stopped successfully.
To remove the data node service, invoke
ndbd.exe with the
--remove
option, as shown here:
C:\> C:\mysql\bin\ndbd.exe --remove
Removing service 'MySQL Cluster Data Node Daemon'
Service successfully removed.
As with ndb_mgmd.exe (and
mysqld.exe), when installing
ndbd.exe as a Windows service, you can also
specify a name for the service as the value of
--install
, and then use it when
starting or stopping the service, like this:
C:\>C:\mysql\bin\ndbd.exe --install=dnode1
Installing service 'dnode1' as '"C:\mysql\bin\ndbd.exe" "--service=dnode1"' Service successfully installed. C:\>NET START dnode1
The MySQL Cluster Data Node Daemon service is starting. The MySQL Cluster Data Node Daemon service was started successfully. C:\>NET STOP dnode1
The MySQL Cluster Data Node Daemon service is stopping.. The MySQL Cluster Data Node Daemon service was stopped successfully.
If you specified a service name when installing the data node
service, you can use this name when removing it as well, by
passing it as the value of the
--remove
option, as shown here:
C:\> C:\mysql\bin\ndbd.exe --remove=dnode1
Removing service 'dnode1'
Service successfully removed.
Installation of the SQL node as a Windows service, starting the
service, stopping the service, and removing the service are done
in a similar fashion, using mysqld
--install
, NET START,
NET STOP, and mysqld
--remove
. For additional
information, see Section 2.3.5.8, “Starting MySQL as a Windows Service”.
In this section, we discuss manual configuration of an installed MySQL Cluster by creating and editing configuration files.
MySQL Cluster also provides a GUI installer which can be used to perform the configuration without the need to edit text files in a separate application. For more information, see Section 19.2.1, “The MySQL Cluster Auto-Installer”.
For our four-node, four-host MySQL Cluster (see Cluster nodes and host computers), it is necessary to write four configuration files, one per node host.
Each data node or SQL node requires a
my.cnf
file that provides two pieces of
information: a connection
string that tells the node where to find the
management node, and a line telling the MySQL server on this
host (the machine hosting the data node) to enable the
NDBCLUSTER
storage engine.
For more information on connection strings, see Section 19.3.3.3, “MySQL Cluster Connection Strings”.
The management node needs a config.ini
file telling it how many replicas to maintain, how much memory
to allocate for data and indexes on each data node, where to
find the data nodes, where to save data to disk on each data
node, and where to find any SQL nodes.
Configuring the data nodes and SQL nodes.
The my.cnf
file needed for the data nodes
is fairly simple. The configuration file should be located in
the /etc
directory and can be edited using
any text editor. (Create the file if it does not exist.) For
example:
shell> vi /etc/my.cnf
We show vi being used here to create the file, but any text editor should work just as well.
For each data node and SQL node in our example setup,
my.cnf
should look like this:
[mysqld] # Options for mysqld process: ndbcluster # run NDB storage engine [mysql_cluster] # Options for MySQL Cluster processes: ndb-connectstring=192.168.0.10 # location of management server
After entering the preceding information, save this file and exit the text editor. Do this for the machines hosting data node “A”, data node “B”, and the SQL node.
Once you have started a mysqld process with
the ndbcluster
and
ndb-connectstring
parameters in the
[mysqld]
and
[mysql_cluster]
sections of the
my.cnf
file as shown previously, you cannot
execute any CREATE TABLE
or
ALTER TABLE
statements without
having actually started the cluster. Otherwise, these statements
will fail with an error. This is by design.
Configuring the management node.
The first step in configuring the management node is to create
the directory in which the configuration file can be found and
then to create the file itself. For example (running as
root
):
shell>mkdir /var/lib/mysql-cluster
shell>cd /var/lib/mysql-cluster
shell>vi config.ini
For our representative setup, the config.ini
file should read as follows:
[ndbd default] # Options affecting ndbd processes on all data nodes: NoOfReplicas=2 # Number of replicas DataMemory=80M # How much memory to allocate for data storage IndexMemory=18M # How much memory to allocate for index storage # For DataMemory and IndexMemory, we have used the # default values. Since the "world" database takes up # only about 500KB, this should be more than enough for # this example Cluster setup. [tcp default] # TCP/IP options: portnumber=2202 # This the default; however, you can use any # port that is free for all the hosts in the cluster # Note: It is recommended that you do not specify the port # number at all and simply allow the default value to be used # instead [ndb_mgmd] # Management process options: hostname=192.168.0.10 # Hostname or IP address of MGM node datadir=/var/lib/mysql-cluster # Directory for MGM node log files [ndbd] # Options for data node "A": # (one [ndbd] section per data node) hostname=192.168.0.30 # Hostname or IP address datadir=/usr/local/mysql/data # Directory for this data node's data files [ndbd] # Options for data node "B": hostname=192.168.0.40 # Hostname or IP address datadir=/usr/local/mysql/data # Directory for this data node's data files [mysqld] # SQL node options: hostname=192.168.0.20 # Hostname or IP address # (additional mysqld connections can be # specified for this node for various # purposes such as running ndb_restore)
The world
database can be downloaded from
http://dev.mysql.com/doc/index-other.html.
After all the configuration files have been created and these minimal options have been specified, you are ready to proceed with starting the cluster and verifying that all processes are running. We discuss how this is done in Section 19.2.5, “Initial Startup of MySQL Cluster”.
For more detailed information about the available MySQL Cluster configuration parameters and their uses, see Section 19.3.3, “MySQL Cluster Configuration Files”, and Section 19.3, “Configuration of MySQL Cluster”. For configuration of MySQL Cluster as relates to making backups, see Section 19.5.3.3, “Configuration for MySQL Cluster Backups”.
The default port for Cluster management nodes is 1186; the default port for data nodes is 2202. However, the cluster can automatically allocate ports for data nodes from those that are already free.
Starting the cluster is not very difficult after it has been configured. Each cluster node process must be started separately, and on the host where it resides. The management node should be started first, followed by the data nodes, and then finally by any SQL nodes:
On the management host, issue the following command from the system shell to start the management node process:
shell> ndb_mgmd -f /var/lib/mysql-cluster/config.ini
The first time that it is started, ndb_mgmd
must be told where to find its configuration file, using the
-f
or
--config-file
option. (See
Section 19.4.4, “ndb_mgmd — The MySQL Cluster Management Server Daemon”, for
details.)
For additional options which can be used with ndb_mgmd, see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
On each of the data node hosts, run this command to start the ndbd process:
shell> ndbd
If you used RPM files to install MySQL on the cluster host where the SQL node is to reside, you can (and should) use the supplied startup script to start the MySQL server process on the SQL node.
If all has gone well, and the cluster has been set up correctly, the cluster should now be operational. You can test this by invoking the ndb_mgm management node client. The output should look like that shown here, although you might see some slight differences in the output depending upon the exact version of MySQL that you are using:
shell>ndb_mgm
-- NDB Cluster -- Management Client -- ndb_mgm>SHOW
Connected to Management Server at: localhost:1186 Cluster Configuration --------------------- [ndbd(NDB)] 2 node(s) id=2 @192.168.0.30 (Version: 5.7.13-ndb-7.5.3, Nodegroup: 0, *) id=3 @192.168.0.40 (Version: 5.7.13-ndb-7.5.3, Nodegroup: 0) [ndb_mgmd(MGM)] 1 node(s) id=1 @192.168.0.10 (Version: 5.7.13-ndb-7.5.3) [mysqld(API)] 1 node(s) id=4 @192.168.0.20 (Version: 5.7.13-ndb-7.5.3)
The SQL node is referenced here as
[mysqld(API)]
, which reflects the fact that the
mysqld process is acting as a MySQL Cluster API
node.
The IP address shown for a given MySQL Cluster SQL or other API
node in the output of SHOW
is the address used by the SQL or API node to connect to the
cluster data nodes, and not to any management node.
You should now be ready to work with databases, tables, and data in MySQL Cluster. See Section 19.2.6, “MySQL Cluster Example with Tables and Data”, for a brief discussion.
The information in this section applies to MySQL Cluster running on both Unix and Windows platforms.
Working with database tables and data in MySQL Cluster is not much different from doing so in standard MySQL. There are two key points to keep in mind:
For a table to be replicated in the cluster, it must use the
NDBCLUSTER
storage engine. To
specify this, use the ENGINE=NDBCLUSTER
or
ENGINE=NDB
option when creating the table:
CREATE TABLEtbl_name
(col_name
column_definitions
) ENGINE=NDBCLUSTER;
Alternatively, for an existing table that uses a different
storage engine, use ALTER TABLE
to change the table to use
NDBCLUSTER
:
ALTER TABLE tbl_name
ENGINE=NDBCLUSTER;
Every NDBCLUSTER
table has a
primary key. If no primary key is defined by the user when a
table is created, the NDBCLUSTER
storage engine automatically generates a hidden one. Such a
key takes up space just as does any other table index. (It is
not uncommon to encounter problems due to insufficient memory
for accommodating these automatically created indexes.)
If you are importing tables from an existing database using the
output of mysqldump, you can open the SQL
script in a text editor and add the ENGINE
option to any table creation statements, or replace any existing
ENGINE
options. Suppose that you have the
world
sample database on another MySQL server
that does not support MySQL Cluster, and you want to export the
City
table:
shell> mysqldump --add-drop-table world City > city_table.sql
The resulting city_table.sql
file will
contain this table creation statement (and the
INSERT
statements necessary to
import the table data):
DROP TABLE IF EXISTS `City`;
CREATE TABLE `City` (
`ID` int(11) NOT NULL auto_increment,
`Name` char(35) NOT NULL default '',
`CountryCode` char(3) NOT NULL default '',
`District` char(20) NOT NULL default '',
`Population` int(11) NOT NULL default '0',
PRIMARY KEY (`ID`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;
INSERT INTO `City` VALUES (1,'Kabul','AFG','Kabol',1780000);
INSERT INTO `City` VALUES (2,'Qandahar','AFG','Qandahar',237500);
INSERT INTO `City` VALUES (3,'Herat','AFG','Herat',186800);
(remaining INSERT statements omitted)
You need to make sure that MySQL uses the
NDBCLUSTER
storage engine for this
table. There are two ways that this can be accomplished. One of
these is to modify the table definition
before importing it into the Cluster
database. Using the City
table as an example,
modify the ENGINE
option of the definition as
follows:
DROP TABLE IF EXISTS `City`;
CREATE TABLE `City` (
`ID` int(11) NOT NULL auto_increment,
`Name` char(35) NOT NULL default '',
`CountryCode` char(3) NOT NULL default '',
`District` char(20) NOT NULL default '',
`Population` int(11) NOT NULL default '0',
PRIMARY KEY (`ID`)
) ENGINE=NDBCLUSTER DEFAULT CHARSET=latin1;
INSERT INTO `City` VALUES (1,'Kabul','AFG','Kabol',1780000);
INSERT INTO `City` VALUES (2,'Qandahar','AFG','Qandahar',237500);
INSERT INTO `City` VALUES (3,'Herat','AFG','Herat',186800);
(remaining INSERT statements omitted)
This must be done for the definition of each table that is to be
part of the clustered database. The easiest way to accomplish this
is to do a search-and-replace on the file that contains the
definitions and replace all instances of
TYPE=
or
engine_name
ENGINE=
with engine_name
ENGINE=NDBCLUSTER
. If you do not want to
modify the file, you can use the unmodified file to create the
tables, and then use ALTER TABLE
to
change their storage engine. The particulars are given later in
this section.
Assuming that you have already created a database named
world
on the SQL node of the cluster, you can
then use the mysql command-line client to read
city_table.sql
, and create and populate the
corresponding table in the usual manner:
shell> mysql world < city_table.sql
It is very important to keep in mind that the preceding command
must be executed on the host where the SQL node is running (in
this case, on the machine with the IP address
192.168.0.20
).
To create a copy of the entire world
database
on the SQL node, use mysqldump on the
noncluster server to export the database to a file named
world.sql
; for example, in the
/tmp
directory. Then modify the table
definitions as just described and import the file into the SQL
node of the cluster like this:
shell> mysql world < /tmp/world.sql
If you save the file to a different location, adjust the preceding instructions accordingly.
Running SELECT
queries on the SQL
node is no different from running them on any other instance of a
MySQL server. To run queries from the command line, you first need
to log in to the MySQL Monitor in the usual way (specify the
root
password at the Enter
password:
prompt):
shell> mysql -u root -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1 to server version: 5.7.13-ndb-7.5.3
Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
mysql>
We simply use the MySQL server's root
account and assume that you have followed the standard security
precautions for installing a MySQL server, including setting a
strong root
password. For more information, see
Section 2.10.4, “Securing the Initial MySQL Accounts”.
It is worth taking into account that Cluster nodes do
not make use of the MySQL privilege system
when accessing one another. Setting or changing MySQL user
accounts (including the root
account) effects
only applications that access the SQL node, not interaction
between nodes. See
Section 19.5.12.2, “MySQL Cluster and MySQL Privileges”, for
more information.
If you did not modify the ENGINE
clauses in the
table definitions prior to importing the SQL script, you should
run the following statements at this point:
mysql>USE world;
mysql>ALTER TABLE City ENGINE=NDBCLUSTER;
mysql>ALTER TABLE Country ENGINE=NDBCLUSTER;
mysql>ALTER TABLE CountryLanguage ENGINE=NDBCLUSTER;
Selecting a database and running a SELECT query against a table in that database is also accomplished in the usual manner, as is exiting the MySQL Monitor:
mysql>USE world;
mysql>SELECT Name, Population FROM City ORDER BY Population DESC LIMIT 5;
+-----------+------------+ | Name | Population | +-----------+------------+ | Bombay | 10500000 | | Seoul | 9981619 | | São Paulo | 9968485 | | Shanghai | 9696300 | | Jakarta | 9604900 | +-----------+------------+ 5 rows in set (0.34 sec) mysql>\q
Bye shell>
Applications that use MySQL can employ standard APIs to access
NDB
tables. It is important to
remember that your application must access the SQL node, and not
the management or data nodes. This brief example shows how we
might execute the SELECT
statement
just shown by using the PHP 5.X mysqli
extension running on a Web server elsewhere on the network:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type"
content="text/html; charset=iso-8859-1">
<title>SIMPLE mysqli SELECT</title>
</head>
<body>
<?php
# connect to SQL node:
$link = new mysqli('192.168.0.20', 'root', 'root_password
', 'world');
# parameters for mysqli constructor are:
# host, user, password, database
if( mysqli_connect_errno() )
die("Connect failed: " . mysqli_connect_error());
$query = "SELECT Name, Population
FROM City
ORDER BY Population DESC
LIMIT 5";
# if no errors...
if( $result = $link->query($query) )
{
?>
<table border="1" width="40%" cellpadding="4" cellspacing ="1">
<tbody>
<tr>
<th width="10%">City</th>
<th>Population</th>
</tr>
<?
# then display the results...
while($row = $result->fetch_object())
printf("<tr>\n <td align=\"center\">%s</td><td>%d</td>\n</tr>\n",
$row->Name, $row->Population);
?>
</tbody
</table>
<?
# ...and verify the number of rows that were retrieved
printf("<p>Affected rows: %d</p>\n", $link->affected_rows);
}
else
# otherwise, tell us what went wrong
echo mysqli_error();
# free the result set and the mysqli connection object
$result->close();
$link->close();
?>
</body>
</html>
We assume that the process running on the Web server can reach the IP address of the SQL node.
In a similar fashion, you can use the MySQL C API, Perl-DBI, Python-mysql, or MySQL Connectors to perform the tasks of data definition and manipulation just as you would normally with MySQL.
To shut down the cluster, enter the following command in a shell on the machine hosting the management node:
shell> ndb_mgm -e shutdown
The -e
option here is used to pass a command to
the ndb_mgm client from the shell. (See
Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”, for more
information about this option.) The command causes the
ndb_mgm, ndb_mgmd, and any
ndbd or ndbmtd processes to
terminate gracefully. Any SQL nodes can be terminated using
mysqladmin shutdown and other means. On Windows
platforms, assuming that you have installed the SQL node as a
Windows service, you can use NET STOP MYSQL.
To restart the cluster on Unix platforms, run these commands:
On the management host (192.168.0.10
in our
example setup):
shell> ndb_mgmd -f /var/lib/mysql-cluster/config.ini
On each of the data node hosts
(192.168.0.30
and
192.168.0.40
):
shell> ndbd
Use the ndb_mgm client to verify that both data nodes have started successfully.
On the SQL host (192.168.0.20
):
shell> mysqld_safe &
On Windows platforms, assuming that you have installed all MySQL Cluster processes as Windows services using the default service names (see Section 19.2.3.4, “Installing MySQL Cluster Processes as Windows Services”), you can restart the cluster as follows:
On the management host (192.168.0.10
in our
example setup), execute the following command:
C:\> NET START ndb_mgmd
On each of the data node hosts
(192.168.0.30
and
192.168.0.40
), execute the following
command:
C:\> NET START ndbd
On the management node host, use the ndb_mgm client to verify that the management node and both data nodes have started successfully (see Section 19.2.3.3, “Initial Startup of MySQL Cluster on Windows”).
On the SQL node host (192.168.0.20
),
execute the following command:
C:\> NET START mysql
In a production setting, it is usually not desirable to shut down the cluster completely. In many cases, even when making configuration changes, or performing upgrades to the cluster hardware or software (or both), which require shutting down individual host machines, it is possible to do so without shutting down the cluster as a whole by performing a rolling restart of the cluster. For more information about doing this, see Section 19.5.5, “Performing a Rolling Restart of a MySQL Cluster”.
This section provides information about MySQL Cluster software and table file compatibility between different MySQL Cluster NDB 7.5 releases with regard to performing upgrades and downgrades as well as compatibility matrices and notes. You are expected already to be familiar with installing and configuring a MySQL Cluster prior to attempting an upgrade or downgrade. See Section 19.3, “Configuration of MySQL Cluster”.
Only compatibility between MySQL versions with regard to
NDBCLUSTER
is taken into account in
this section, and there are likely other issues to be
considered. As with any other MySQL software upgrade
or downgrade, you are strongly encouraged to review the relevant
portions of the MySQL Manual for the MySQL versions from which
and to which you intend to migrate, before attempting an upgrade
or downgrade of the MySQL Cluster software. See
Section 2.11.1, “Upgrading MySQL”.
A MySQL server that is part of a MySQL Cluster differs in one chief
respect from a normal (nonclustered) MySQL server, in that it
employs the NDB
storage engine. This
engine is also referred to sometimes as
NDBCLUSTER
, although
NDB
is preferred.
To avoid unnecessary allocation of resources, the server is
configured by default with the NDB
storage engine disabled. To enable NDB
,
you must modify the server's my.cnf
configuration file, or start the server with the
--ndbcluster
option.
This MySQL server is a part of the cluster, so it also must know how
to access a management node to obtain the cluster configuration
data. The default behavior is to look for the management node on
localhost
. However, should you need to specify
that its location is elsewhere, this can be done in
my.cnf
, or with the mysql
client. Before the NDB
storage engine
can be used, at least one management node must be operational, as
well as any desired data nodes.
For more information about
--ndbcluster
and other
mysqld options specific to MySQL Cluster, see
Section 19.3.3.8.1, “MySQL Server Options for MySQL Cluster”.
You can use also the MySQL Cluster Auto-Installer to set up and deploy a MySQL Cluster on one or more hosts using a browser-based GUI. For more information, see Section 19.2.1, “The MySQL Cluster Auto-Installer”.
For general information about installing MySQL Cluster, see Section 19.2, “MySQL Cluster Installation”.
To familiarize you with the basics, we will describe the simplest possible configuration for a functional MySQL Cluster. After this, you should be able to design your desired setup from the information provided in the other relevant sections of this chapter.
First, you need to create a configuration directory such as
/var/lib/mysql-cluster
, by executing the
following command as the system root
user:
shell> mkdir /var/lib/mysql-cluster
In this directory, create a file named
config.ini
that contains the following
information. Substitute appropriate values for
HostName
and DataDir
as
necessary for your system.
# file "config.ini" - showing minimal setup consisting of 1 data node, # 1 management server, and 3 MySQL servers. # The empty default sections are not required, and are shown only for # the sake of completeness. # Data nodes must provide a hostname but MySQL Servers are not required # to do so. # If you don't know the hostname for your machine, use localhost. # The DataDir parameter also has a default value, but it is recommended to # set it explicitly. # Note: [db], [api], and [mgm] are aliases for [ndbd], [mysqld], and [ndb_mgmd], # respectively. [db] is deprecated and should not be used in new installations. [ndbd default] NoOfReplicas= 1 [mysqld default] [ndb_mgmd default] [tcp default] [ndb_mgmd] HostName= myhost.example.com [ndbd] HostName= myhost.example.com DataDir= /var/lib/mysql-cluster [mysqld] [mysqld] [mysqld]
You can now start the ndb_mgmd management
server. By default, it attempts to read the
config.ini
file in its current working
directory, so change location into the directory where the file is
located and then invoke ndb_mgmd:
shell>cd /var/lib/mysql-cluster
shell>ndb_mgmd
Then start a single data node by running ndbd:
shell> ndbd
For command-line options which can be used when starting ndbd, see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
By default, ndbd looks for the management
server at localhost
on port 1186.
If you have installed MySQL from a binary tarball, you will need
to specify the path of the ndb_mgmd and
ndbd servers explicitly. (Normally, these
will be found in /usr/local/mysql/bin
.)
Finally, change location to the MySQL data directory (usually
/var/lib/mysql
or
/usr/local/mysql/data
), and make sure that
the my.cnf
file contains the option necessary
to enable the NDB storage engine:
[mysqld] ndbcluster
You can now start the MySQL server as usual:
shell> mysqld_safe --user=mysql &
Wait a moment to make sure the MySQL server is running properly.
If you see the notice mysql ended
, check the
server's .err
file to find out what went
wrong.
If all has gone well so far, you now can start using the cluster.
Connect to the server and verify that the
NDBCLUSTER
storage engine is enabled:
shell>mysql
Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 1 to server version: 5.7.14 Type 'help;' or '\h' for help. Type '\c' to clear the buffer. mysql>SHOW ENGINES\G
... *************************** 12. row *************************** Engine: NDBCLUSTER Support: YES Comment: Clustered, fault-tolerant, memory-based tables *************************** 13. row *************************** Engine: NDB Support: YES Comment: Alias for NDBCLUSTER ...
The row numbers shown in the preceding example output may be different from those shown on your system, depending upon how your server is configured.
Try to create an NDBCLUSTER
table:
shell>mysql
mysql>USE test;
Database changed mysql>CREATE TABLE ctest (i INT) ENGINE=NDBCLUSTER;
Query OK, 0 rows affected (0.09 sec) mysql>SHOW CREATE TABLE ctest \G
*************************** 1. row *************************** Table: ctest Create Table: CREATE TABLE `ctest` ( `i` int(11) default NULL ) ENGINE=ndbcluster DEFAULT CHARSET=latin1 1 row in set (0.00 sec)
To check that your nodes were set up properly, start the management client:
shell> ndb_mgm
Use the SHOW command from within the management client to obtain a report on the cluster's status:
ndb_mgm> SHOW
Cluster Configuration
---------------------
[ndbd(NDB)] 1 node(s)
id=2 @127.0.0.1 (Version: 5.7.13-ndb-7.5.3, Nodegroup: 0, *)
[ndb_mgmd(MGM)] 1 node(s)
id=1 @127.0.0.1 (Version: 5.7.13-ndb-7.5.3)
[mysqld(API)] 3 node(s)
id=3 @127.0.0.1 (Version: 5.7.13-ndb-7.5.3)
id=4 (not connected, accepting connect from any host)
id=5 (not connected, accepting connect from any host)
At this point, you have successfully set up a working MySQL
Cluster. You can now store data in the cluster by using any table
created with ENGINE=NDBCLUSTER
or its alias
ENGINE=NDB
.
The next several sections provide summary tables of MySQL Cluster
node configuration parameters used in the
config.ini
file to govern various aspects of
node behavior, as well as of options and variables read by
mysqld from a my.cnf
file
or from the command line when run as a MySQL Cluster process. Each
of the node parameter tables lists the parameters for a given type
(ndbd
, ndb_mgmd
,
mysqld
, computer
,
tcp
, shm
, or
sci
). All tables include the data type for the
parameter, option, or variable, as well as its default, mimimum,
and maximum values as applicable.
Considerations when restarting nodes.
For node parameters, these tables also indicate what type of
restart is required (node restart or system restart)—and
whether the restart must be done with
--initial
—to change the value of a given
configuration parameter. When performing a node restart or an
initial node restart, all of the cluster's data nodes must
be restarted in turn (also referred to as a
rolling restart). It is
possible to update cluster configuration parameters marked as
node
online—that is, without shutting
down the cluster—in this fashion. An initial node restart
requires restarting each ndbd process with
the --initial
option.
A system restart requires a complete shutdown and restart of the entire cluster. An initial system restart requires taking a backup of the cluster, wiping the cluster file system after shutdown, and then restoring from the backup following the restart.
In any cluster restart, all of the cluster's management servers must be restarted for them to read the updated configuration parameter values.
Values for numeric cluster parameters can generally be increased without any problems, although it is advisable to do so progressively, making such adjustments in relatively small increments. Many of these can be increased online, using a rolling restart.
However, decreasing the values of such parameters—whether this is done using a node restart, node initial restart, or even a complete system restart of the cluster—is not to be undertaken lightly; it is recommended that you do so only after careful planning and testing. This is especially true with regard to those parameters that relate to memory usage and disk space. In addition, it is the generally the case that configuration parameters relating to memory and disk usage can be raised using a simple node restart, but they require an initial node restart to be lowered.
Because some of these parameters can be used for configuring more than one type of cluster node, they may appear in more than one of the tables.
4294967039
often appears as a maximum value
in these tables. This value is defined in the
NDBCLUSTER
sources as
MAX_INT_RNIL
and is equal to
0xFFFFFEFF
, or
232 −
28 − 1
.
The summary table in this section provides information about
parameters used in the [ndbd]
or
[ndbd default]
sections of a
config.ini
file for configuring MySQL
Cluster data nodes. For detailed descriptions and other
additional information about each of these parameters, see
Section 19.3.3.6, “Defining MySQL Cluster Data Nodes”.
These parameters also apply to ndbmtd, the multi-threaded version of ndbd. For more information, see Section 19.4.3, “ndbmtd — The MySQL Cluster Data Node Daemon (Multi-Threaded)”.
Restart types. Changes in MySQL Cluster configuration parameters do not take effect until the cluster is restarted. The type of restart required to change a given parameter is indicated in the summary table as follows:
N
—Node restart: The parameter can
be updated using a rolling restart (see
Section 19.5.5, “Performing a Rolling Restart of a MySQL Cluster”).
S
—System restart: The cluster must
be shut down completely, then restarted, to effect a change
in this parameter.
I
—Initial restart: Data nodes must
be restarted using the
--initial
option.
For more information about restart types, see Section 19.3.2, “Overview of MySQL Cluster Configuration Parameters, Options, and Variables”.
MySQL Cluster also supports the addition of new data node groups online, to a running cluster. For more information, see Section 19.5.14, “Adding MySQL Cluster Data Nodes Online”.
Table 19.1 Data Node Configuration Parameters
Parameter Name | Type or Units | Restart Type | In Version ... (and later) |
---|---|---|---|
Default Value | |||
Minimum/Maximum or Permitted Values | |||
enumeration | N | NDB 7.5.0 | |
Default | |||
Default, Disabled, WaitExternal | |||
milliseconds | N | NDB 7.5.0 | |
7500 | |||
10 / 4294967039 (0xFFFFFEFF) | |||
bytes | N | NDB 7.5.1 | |
16M | |||
512K / 4294967039 (0xFFFFFEFF) | |||
path | IN | NDB 7.5.0 | |
FileSystemPath | |||
... | |||
percent | N | NDB 7.5.0 | |
50 | |||
0 / 90 | |||
bytes | N | NDB 7.5.0 | |
16M | |||
2M / 4294967039 (0xFFFFFEFF) | |||
bytes | N | NDB 7.5.0 | |
1M | |||
256K / 4294967039 (0xFFFFFEFF) | |||
bytes | N | NDB 7.5.0 | |
32M | |||
0 / 4294967039 (0xFFFFFEFF) | |||
seconds | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
bytes | N | NDB 7.5.0 | |
256K | |||
32K / 4294967039 (0xFFFFFEFF) | |||
integer | N | NDB 7.5.0 | |
256 | |||
1 / 992 | |||
numeric | S | NDB 7.5.0 | |
0 | |||
0 / 128 | |||
boolean | N | NDB 7.5.0 | |
false | |||
true, false | |||
boolean | N | NDB 7.5.0 | |
false | |||
true, false | |||
milliseconds | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
boolean | S | NDB 7.5.0 | |
true | |||
true, false | |||
path | IN | NDB 7.5.0 | |
. | |||
... | |||
bytes | N | NDB 7.5.0 | |
80M | |||
1M / 1024G | |||
LDM threads | N | NDB 7.5.0 | |
3840 | |||
0 / 3840 | |||
bytes | N | NDB 7.5.0 | |
undefined | |||
0 / 100 | |||
threads | N | NDB 7.5.0 | |
2 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
true|false (1|0) | IS | NDB 7.5.0 | |
false | |||
true, false | |||
32K pages | N | NDB 7.5.0 | |
10 | |||
1 / 1000 | |||
bytes | N | NDB 7.5.0 | |
64M | |||
4M / 1T | |||
bytes | N | NDB 7.5.0 | |
4M | |||
32K / 4294967039 (0xFFFFFEFF) | |||
name | S | NDB 7.5.0 | |
[none] | |||
... | |||
bytes | N | NDB 7.5.0 | |
0 | |||
0 / 32G | |||
path | IN | NDB 7.5.0 | |
DataDir | |||
... | |||
filename | IN | NDB 7.5.0 | |
[see text] | |||
... | |||
filename | IN | NDB 7.5.0 | |
FileSystemPath | |||
... | |||
filename | IN | NDB 7.5.0 | |
[see text] | |||
... | |||
bytes | IN | NDB 7.5.0 | |
16M | |||
4M / 1G | |||
milliseconds | N | NDB 7.5.0 | |
1500 | |||
100 / 4294967039 (0xFFFFFEFF) | |||
milliseconds | N | NDB 7.5.0 | |
5000 | |||
10 / 4294967039 (0xFFFFFEFF) | |||
numeric | S | NDB 7.5.0 | |
0 | |||
0 / 65535 | |||
name or IP address | N | NDB 7.5.0 | |
localhost | |||
... | |||
bytes | N | NDB 7.5.0 | |
18M | |||
1M / 1T | |||
boolean | S | NDB 7.5.0 | |
false | |||
false, true | |||
boolean | S | NDB 7.5.0 | |
false | |||
false, true | |||
percentage | IN | NDB 7.5.0 | |
100 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
bytes | IN | NDB 7.5.0 | |
32768 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
percentage | IN | NDB 7.5.0 | |
100 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
percentage | IN | NDB 7.5.0 | |
100 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
seconds | IN | NDB 7.5.0 | |
60 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
[see values] | IN | NDB 7.5.0 | |
SPARSE | |||
SPARSE, FULL | |||
string | S | NDB 7.5.0 | |
[see text] | |||
... | |||
files | N | NDB 7.5.0 | |
27 | |||
20 / 4294967039 (0xFFFFFEFF) | |||
string | S | NDB 7.5.0 | |
[see text] | |||
... | |||
numeric | N | NDB 7.5.0 | |
1 | |||
0 / 1 | |||
second | N | NDB 7.5.0 | |
60 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
CPU ID | N | NDB 7.5.0 | |
64K | |||
0 / 64K | |||
CPU ID | N | NDB 7.5.0 | |
[none] | |||
0 / 64K | |||
numeric | N | NDB 7.5.0 | |
0 | |||
0 / 2 | |||
log level | N | NDB 7.5.0 | |
0 | |||
0 / 15 | |||
levelr | N | NDB 7.5.0 | |
0 | |||
0 / 15 | |||
integer | N | NDB 7.5.0 | |
0 | |||
0 / 15 | |||
integer | N | NDB 7.5.0 | |
0 | |||
0 / 15 | |||
integer | N | NDB 7.5.0 | |
0 | |||
0 / 15 | |||
integer | N | NDB 7.5.0 | |
0 | |||
0 / 15 | |||
integer | N | NDB 7.5.0 | |
0 | |||
0 / 15 | |||
integer | N | NDB 7.5.0 | |
1 | |||
0 / 15 | |||
integer | N | NDB 7.5.0 | |
0 | |||
0 / 15 | |||
bytes | N | NDB 7.5.0 | |
64M | |||
512K / 4294967039 (0xFFFFFEFF) | |||
unsigned | N | NDB 7.5.0 | |
32M | |||
1M / 1G | |||
epochs | N | NDB 7.5.0 | |
100 | |||
0 / 100000 | |||
bytes | N | NDB 7.5.0 | |
26214400 | |||
26214400 (0x01900000) / 4294967039 (0xFFFFFEFF) | |||
numeric | S | NDB 7.5.0 | |
20M | |||
1M / 1024G | |||
numeric | S | NDB 7.5.0 | |
50M | |||
1M / 1024G | |||
numeric | S | NDB 7.5.0 | |
200M | |||
1M / 1024G | |||
operations (DML) | N | NDB 7.5.0 | |
4294967295 | |||
32 / 4294967295 | |||
seconds | N | NDB 7.5.0 | |
0 | |||
0 / 600 | |||
integer | N | NDB 7.5.0 | |
1000 | |||
32 / 4294967039 (0xFFFFFEFF) | |||
integer | N | NDB 7.5.0 | |
8K | |||
0 / 4294967039 (0xFFFFFEFF) | |||
integer | N | NDB 7.5.0 | |
32K | |||
32 / 4294967039 (0xFFFFFEFF) | |||
integer | N | NDB 7.5.0 | |
256 | |||
2 / 500 | |||
unsigned | N | NDB 7.5.0 | |
256 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
integer | N | NDB 7.5.0 | |
4096 | |||
32 / 4294967039 (0xFFFFFEFF) | |||
integer | N | NDB 7.5.0 | |
4000 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
integer | N | NDB 7.5.0 | |
UNDEFINED | |||
32 / 4294967039 (0xFFFFFEFF) | |||
integer | N | NDB 7.5.0 | |
[see text] | |||
32 / 4294967039 (0xFFFFFEFF) | |||
unsigned | N | NDB 7.5.0 | |
0 | |||
20 / 4294967039 (0xFFFFFEFF) | |||
integer | N | NDB 7.5.0 | |
128 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
integer | N | NDB 7.5.0 | |
25 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
unsigned | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
unsigned | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
integer | N | NDB 7.5.0 | |
128 | |||
8 / 20320 | |||
integer | N | NDB 7.5.0 | |
768 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
integer | S | NDB 7.5.0 | |
0 | |||
0 / 64 | |||
bytes | N | NDB 7.5.0 | |
256 | |||
1 / 4294967039 (0xFFFFFEFF) | |||
unsigned | N | NDB 7.5.0 | |
3 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
unsigned | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
numeric | S | NDB 7.5.0 | |
10M | |||
1M / 1024G | |||
unsigned | N | NDB 7.5.0 | |
5 | |||
0 / 100 | |||
IS | NDB 7.5.0 | ||
[none] | |||
0 / 65536 | |||
unsigned | IS | NDB 7.5.0 | |
[none] | |||
1 / 48 | |||
integer | IN | NDB 7.5.0 | |
16 | |||
3 / 4294967039 (0xFFFFFEFF) | |||
integer | IS | NDB 7.5.0 | |
2 | |||
1 / 4 | |||
boolean | N | NDB 7.5.0 | |
1 | |||
... | |||
boolean | N | NDB 7.5.0 | |
false | |||
true, false | |||
boolean | N | NDB 7.5.0 | |
false | |||
true, false | |||
bytes | N | NDB 7.5.0 | |
32M | |||
1M / 4294967039 (0xFFFFFEFF) | |||
numeric | N | NDB 7.5.0 | |
3 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
seconds | N | NDB 7.5.0 | |
20 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
error code | N | NDB 7.5.0 | |
2 | |||
0 / 4 | |||
µs | N | NDB 7.5.0 | |
50 | |||
0 / 11000 | |||
integer | S | NDB 7.5.0 | |
5 | |||
0 / 10 | |||
µs | N | NDB 7.5.0 | |
0 | |||
0 / 500 | |||
unsigned | S | NDB 7.5.0 | |
[none] | |||
1 / 64K | |||
bytes | N | NDB 7.5.0 | |
128M | |||
0 / 64T | |||
unsigned | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
milliseconds | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
milliseconds | N | NDB 7.5.0 | |
15000 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
milliseconds | N | NDB 7.5.0 | |
30000 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
milliseconds | N | NDB 7.5.0 | |
60000 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
seconds | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
boolean | N | NDB 7.5.0 | |
1 | |||
0, 1 | |||
% or bytes | S | NDB 7.5.0 | |
25 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
boolean | N | NDB 7.5.0 | |
false | |||
true, false | |||
milliseconds | N | NDB 7.5.0 | |
100 | |||
0 / 32000 | |||
milliseconds | N | NDB 7.5.0 | |
0 | |||
0 / 256000 | |||
milliseconds | N | NDB 7.5.0 | |
2000 | |||
20 / 32000 | |||
milliseconds | N | NDB 7.5.0 | |
120000 | |||
10 / 4294967039 (0xFFFFFEFF) | |||
milliseconds | N | NDB 7.5.0 | |
1000 | |||
1000 / 4294967039 (0xFFFFFEFF) | |||
number of 4-byte words, as a base-2 logarithm | N | NDB 7.5.0 | |
20 | |||
0 / 31 | |||
milliseconds | N | NDB 7.5.0 | |
6000 | |||
70 / 4294967039 (0xFFFFFEFF) | |||
milliseconds | N | NDB 7.5.0 | |
6000 | |||
70 / 4294967039 (0xFFFFFEFF) | |||
bytes | N | NDB 7.5.0 | |
0 | |||
256K / 4294967039 (0xFFFFFEFF) | |||
bytes | N | NDB 7.5.0 | |
1M | |||
1K / 4294967039 (0xFFFFFEFF) | |||
milliseconds | N | NDB 7.5.0 | |
1200 | |||
50 / 4294967039 (0xFFFFFEFF) | |||
milliseconds | N | NDB 7.5.0 | |
[see text] | |||
0 / 4294967039 (0xFFFFFEFF) | |||
boolean | N | NDB 7.5.0 | |
false | |||
true, false | |||
unsigned | N | NDB 7.5.0 | |
16M | |||
1M / 4294967039 (0xFFFFFEFF) | |||
unsigned | N | NDB 7.5.0 | |
2M | |||
1M / 4294967039 (0xFFFFFEFF) |
Table 19.2 Multi-Threaded Data Node Configuration Parameters
Parameter Name | Type or Units | Restart Type | In Version ... (and later) |
---|---|---|---|
Default Value | |||
Minimum/Maximum or Permitted Values | |||
integer | IS | NDB 7.5.0 | |
2 | |||
2 / 72 | |||
numeric | IN | NDB 7.5.0 | |
4 | |||
4, 8, 12, 16, 24, 32 | |||
string | IS | NDB 7.5.0 | |
'' | |||
... |
The summary table in this section provides information about
parameters used in the [ndb_mgmd]
or
[mgm]
sections of a
config.ini
file for configuring MySQL
Cluster management nodes. For detailed descriptions and other
additional information about each of these parameters, see
Section 19.3.3.5, “Defining a MySQL Cluster Management Server”.
Restart types. Changes in MySQL Cluster configuration parameters do not take effect until the cluster is restarted. The type of restart required to change a given parameter is indicated in the summary table as follows:
N
—Node restart: The parameter can
be updated using a rolling restart (see
Section 19.5.5, “Performing a Rolling Restart of a MySQL Cluster”).
S
—System restart: The cluster must
be shut down completely, then restarted, to effect a change
in this parameter.
I
—Initial restart: Data nodes must
be restarted using the
--initial
option.
For more information about restart types, see Section 19.3.2, “Overview of MySQL Cluster Configuration Parameters, Options, and Variables”.
Table 19.3 Management Node Configuration Parameters
Parameter Name | Type or Units | Restart Type | In Version ... (and later) |
---|---|---|---|
Default Value | |||
Minimum/Maximum or Permitted Values | |||
milliseconds | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
0-2 | N | NDB 7.5.0 | |
1 | |||
0 / 2 | |||
path | N | NDB 7.5.0 | |
. | |||
... | |||
name | S | NDB 7.5.0 | |
[none] | |||
... | |||
milliseconds | N | NDB 7.5.0 | |
1500 | |||
100 / 4294967039 (0xFFFFFEFF) | |||
string | S | NDB 7.5.0 | |
[none] | |||
... | |||
name or IP address | N | NDB 7.5.0 | |
[none] | |||
... | |||
unsigned | IS | NDB 7.5.0 | |
[none] | |||
1 / 255 | |||
{CONSOLE|SYSLOG|FILE} | N | NDB 7.5.0 | |
[see text] | |||
... | |||
unsigned | IS | NDB 7.5.0 | |
[none] | |||
1 / 255 | |||
unsigned | S | NDB 7.5.0 | |
1186 | |||
0 / 64K | |||
unsigned | N | NDB 7.5.0 | |
[none] | |||
0 / 64K | |||
bytes | N | NDB 7.5.0 | |
0 | |||
256K / 4294967039 (0xFFFFFEFF) | |||
boolean | N | NDB 7.5.0 | |
false | |||
true, false |
After making changes in a management node's configuration, it is necessary to perform a rolling restart of the cluster for the new configuration to take effect. See Section 19.3.3.5, “Defining a MySQL Cluster Management Server”, for more information.
To add new management servers to a running MySQL Cluster, it
is also necessary perform a rolling restart of all cluster
nodes after modifying any existing
config.ini
files. For more information
about issues arising when using multiple management nodes, see
Section 19.1.6.10, “Limitations Relating to Multiple MySQL Cluster Nodes”.
The summary table in this section provides information about
parameters used in the [mysqld]
and
[api]
sections of a
config.ini
file for configuring MySQL
Cluster SQL nodes and API nodes. For detailed descriptions and
other additional information about each of these parameters, see
Section 19.3.3.7, “Defining SQL and Other API Nodes in a MySQL Cluster”.
For a discussion of MySQL server options for MySQL Cluster, see Section 19.3.3.8.1, “MySQL Server Options for MySQL Cluster”; for information about MySQL server system variables relating to MySQL Cluster, see Section 19.3.3.8.2, “MySQL Cluster System Variables”.
Restart types. Changes in MySQL Cluster configuration parameters do not take effect until the cluster is restarted. The type of restart required to change a given parameter is indicated in the summary table as follows:
N
—Node restart: The parameter can
be updated using a rolling restart (see
Section 19.5.5, “Performing a Rolling Restart of a MySQL Cluster”).
S
—System restart: The cluster must
be shut down completely, then restarted, to effect a change
in this parameter.
I
—Initial restart: Data nodes must
be restarted using the
--initial
option.
For more information about restart types, see Section 19.3.2, “Overview of MySQL Cluster Configuration Parameters, Options, and Variables”.
Table 19.4 SQL Node / API Node Configuration Parameters
Parameter Name | Type or Units | Restart Type | In Version ... (and later) |
---|---|---|---|
Default Value | |||
Minimum/Maximum or Permitted Values | |||
bytes | N | NDB 7.5.2 | |
undefined | |||
0 / 100 | |||
milliseconds | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
0-2 | N | NDB 7.5.0 | |
0 | |||
0 / 2 | |||
boolean | N | NDB 7.5.0 | |
false | |||
true, false | |||
bytes | N | NDB 7.5.0 | |
16K | |||
1024 / 1M | |||
records | N | NDB 7.5.0 | |
256 | |||
1 / 992 | |||
integer | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
string | N | NDB 7.5.0 | |
[none] | |||
... | |||
buckets | N | NDB 7.5.0 | |
3840 | |||
0 / 3840 | |||
enumeration | S | NDB 7.5.0 | |
QUEUE | |||
ABORT, QUEUE | |||
bytes | S | NDB 7.5.0 | |
8192 | |||
0 / 64K | |||
name | S | NDB 7.5.0 | |
[none] | |||
... | |||
bytes | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
string | S | NDB 7.5.0 | |
[none] | |||
... | |||
name or IP address | N | NDB 7.5.0 | |
[none] | |||
... | |||
unsigned | IS | NDB 7.5.0 | |
[none] | |||
1 / 255 | |||
bytes | N | NDB 7.5.0 | |
256K | |||
32K / 16M | |||
unsigned | IS | NDB 7.5.0 | |
[none] | |||
1 / 255 | |||
integer | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
bytes | N | NDB 7.5.0 | |
0 | |||
256K / 4294967039 (0xFFFFFEFF) | |||
boolean | N | NDB 7.5.0 | |
false | |||
true, false |
To add new SQL or API nodes to the configuration of a running
MySQL Cluster, it is necessary to perform a rolling restart of
all cluster nodes after adding new [mysqld]
or [api]
sections to the
config.ini
file (or files, if you are
using more than one management server). This must be done
before the new SQL or API nodes can connect to the cluster.
It is not necessary to perform any restart of the cluster if new SQL or API nodes can employ previously unused API slots in the cluster configuration to connect to the cluster.
The summary tables in this section provide information about
parameters used in the [computer]
,
[tcp]
, [shm]
, and
[sci]
sections of a
config.ini
file for configuring MySQL
Cluster management nodes. For detailed descriptions and other
additional information about individual parameters, see
Section 19.3.3.9, “MySQL Cluster TCP/IP Connections”,
Section 19.3.3.11, “MySQL Cluster Shared-Memory Connections”, or
Section 19.3.3.12, “SCI Transport Connections in MySQL Cluster”, as appropriate.
Restart types. Changes in MySQL Cluster configuration parameters do not take effect until the cluster is restarted. The type of restart required to change a given parameter is indicated in the summary tables as follows:
N
—Node restart: The parameter can
be updated using a rolling restart (see
Section 19.5.5, “Performing a Rolling Restart of a MySQL Cluster”).
S
—System restart: The cluster must
be shut down completely, then restarted, to effect a change
in this parameter.
I
—Initial restart: Data nodes must
be restarted using the
--initial
option.
For more information about restart types, see Section 19.3.2, “Overview of MySQL Cluster Configuration Parameters, Options, and Variables”.
Table 19.6 TCP Configuration Parameters
Parameter Name | Type or Units | Restart Type | In Version ... (and later) |
---|---|---|---|
Default Value | |||
Minimum/Maximum or Permitted Values | |||
boolean | N | NDB 7.5.0 | |
false | |||
true, false | |||
| unsigned | N | NDB 7.5.0 |
55 | |||
0 / 200 | |||
numeric | N | NDB 7.5.0 | |
[none] | |||
... | |||
numeric | N | NDB 7.5.0 | |
[none] | |||
... | |||
| numeric | N | NDB 7.5.0 |
[none] | |||
... | |||
bytes | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
unsigned | S | NDB 7.5.0 | |
[none] | |||
0 / 64K | |||
| string | N | NDB 7.5.0 |
[none] | |||
... | |||
bytes | N | NDB 7.5.0 | |
2M | |||
16K / 4294967039 (0xFFFFFEFF) | |||
unsigned | N | NDB 7.5.0 | |
2M | |||
256K / 4294967039 (0xFFFFFEFF) | |||
boolean | N | NDB 7.5.0 | |
[see text] | |||
true, false | |||
unsigned | N | NDB 7.5.0 | |
0 | |||
0 / 2G | |||
unsigned | N | NDB 7.5.0 | |
0 | |||
0 / 2G | |||
unsigned | N | NDB 7.5.0 | |
0 | |||
0 / 2G | |||
boolean | N | NDB 7.5.0 | |
false | |||
true, false |
Table 19.7 Shared Memory Configuration Parameters
Parameter Name | Type or Units | Restart Type | In Version ... (and later) |
---|---|---|---|
Default Value | |||
Minimum/Maximum or Permitted Values | |||
boolean | N | NDB 7.5.0 | |
true | |||
true, false | |||
| unsigned | N | NDB 7.5.0 |
35 | |||
0 / 200 | |||
numeric | N | NDB 7.5.0 | |
[none] | |||
... | |||
numeric | N | NDB 7.5.0 | |
[none] | |||
... | |||
| numeric | N | NDB 7.5.0 |
[none] | |||
... | |||
bytes | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
| unsigned | S | NDB 7.5.0 |
[none] | |||
0 / 64K | |||
boolean | N | NDB 7.5.0 | |
false | |||
true, false | |||
unsigned | N | NDB 7.5.0 | |
[none] | |||
0 / 4294967039 (0xFFFFFEFF) | |||
bytes | N | NDB 7.5.0 | |
1M | |||
64K / 4294967039 (0xFFFFFEFF) | |||
unsigned | N | NDB 7.5.0 | |
[none] | |||
0 / 4294967039 (0xFFFFFEFF) |
Table 19.8 SCI Configuration Parameters
Parameter Name | Type or Units | Restart Type | In Version ... (and later) |
---|---|---|---|
Default Value | |||
Minimum/Maximum or Permitted Values | |||
boolean | N | NDB 7.5.0 | |
false | |||
true, false | |||
| unsigned | N | NDB 7.5.0 |
15 | |||
0 / 200 | |||
unsigned | N | NDB 7.5.0 | |
[none] | |||
0 / 4294967039 (0xFFFFFEFF) | |||
unsigned | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
unsigned | N | NDB 7.5.0 | |
[none] | |||
0 / 4294967039 (0xFFFFFEFF) | |||
unsigned | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
numeric | N | NDB 7.5.0 | |
[none] | |||
... | |||
numeric | N | NDB 7.5.0 | |
[none] | |||
... | |||
| numeric | N | NDB 7.5.0 |
[none] | |||
... | |||
bytes | N | NDB 7.5.0 | |
0 | |||
0 / 4294967039 (0xFFFFFEFF) | |||
| unsigned | S | NDB 7.5.0 |
[none] | |||
0 / 64K | |||
unsigned | N | NDB 7.5.0 | |
8K | |||
128 / 32K | |||
boolean | N | NDB 7.5.0 | |
true | |||
true, false | |||
unsigned | N | NDB 7.5.0 | |
10M | |||
64K / 4294967039 (0xFFFFFEFF) |
The following table provides a list of the command-line options,
server and status variables applicable within
mysqld
when it is running as an SQL node in a
MySQL Cluster. For a table showing all
command-line options, server and status variables available for
use with mysqld, see
Section 6.1.1, “Server Option and Variable Reference”.
Table 19.9 MySQL Server Options and Variables for MySQL Cluster: MySQL Cluster NDB 7.4
Option or Variable Name | ||
---|---|---|
Command Line | System Variable | Status Variable |
Option File | Scope | Dynamic |
Notes | ||
No | No | Yes |
No | Both | No |
DESCRIPTION: Count of SHOW NDB STATUS statements |
||
No | No | Yes |
No | Both | No |
DESCRIPTION: Number of times that tables have been discovered |
||
Yes | Yes | No |
Yes | Global | No |
DESCRIPTION: Size (in bytes) to use for NDB transaction batches |
||
Yes | Yes | No |
Yes | Both | Yes |
DESCRIPTION: Specifies size in bytes that large BLOB reads should be batched into. 0 = no limit. |
||
Yes | Yes | No |
Yes | Both | Yes |
DESCRIPTION: Specifies size in bytes that large BLOB writes should be batched into. 0 = no limit. |
||
Yes | Yes | Yes |
Yes | Global | No |
DESCRIPTION: Number of connections to the cluster used by MySQL |
||
Yes | Yes | No |
Yes | Global | No |
DESCRIPTION: Comma-separated list of node IDs for connections to the cluster used by MySQL; the number of nodes in the list must be the same as the value set for --ndb-cluster-connection-pool |
||
Yes | No | No |
Yes | No | |
DESCRIPTION: Point to the management server that distributes the cluster configuration |
||
Yes | Yes | No |
Yes | Both | Yes |
DESCRIPTION: Specifies that constraint checks on unique indexes (where these are supported) should be deferred until commit time. Not normally needed or used; for testing purposes only. |
||
Yes | Yes | No |
Yes | Global | Yes |
DESCRIPTION: Default distribution for new tables in NDBCLUSTER (KEYHASH or LINHASH, default is KEYHASH) |
||
Yes | Yes | No |
Yes | Global | No |
DESCRIPTION: Cause a MySQL server acting as a slave to log mysql.ndb_apply_status updates received from its immediate master in its own binary log, using its own server ID. Effective only if the server is started with the --ndbcluster option. |
||
Yes | Yes | No |
Yes | Global | Yes |
DESCRIPTION: When enabled, causes epochs in which there were no changes to be written to the ndb_apply_status and ndb_binlog_index tables, even when --log-slave-updates is enabled. |
||
Yes | Yes | No |
Yes | Both | Yes |
DESCRIPTION: Log primary key reads with exclusive locks; allow conflict resolution based on read conflicts. |
||
Yes | Yes | No |
Yes | Global | No |
DESCRIPTION: Log originating server id and epoch in mysql.ndb_binlog_index table. |
||
Yes | Yes | No |
Yes | Global | No |
DESCRIPTION: Write NDB transaction IDs in the binary log. Requires --log-bin-v1-events=OFF. |
||
Yes | No | No |
Yes | No | |
DESCRIPTION: Set the host (and port, if desired) for connecting to management server |
||
Yes | No | Yes |
Yes | Global | No |
DESCRIPTION: MySQL Cluster node ID for this MySQL server |
||
Yes | No | No |
Yes | No | |
DESCRIPTION: Activation threshold when receive thread takes over the polling of the cluster connection (measured in concurrently active threads) |
||
Yes | No | No |
Yes | No | |
DESCRIPTION: CPU mask for locking receiver threads to specific CPUs; specified as hexadecimal. See documentation for details. |
||
Yes | No | No |
No | No | |
DESCRIPTION: Enable or disable the ndb_transid_mysql_connection_map plugin; that is, enable or disable the INFORMATION_SCHEMA table having that name. |
||
Yes | Yes | No |
Yes | Global | No |
DESCRIPTION: Time (in seconds) for the MySQL server to wait for connection to cluster management and data nodes before accepting MySQL client connections. |
||
Yes | Yes | No |
Yes | Global | No |
DESCRIPTION: Time (in seconds) for the MySQL server to wait for NDB engine setup to complete. |
||
Yes | Yes | No |
Yes | Both | Yes |
DESCRIPTION: Set to OFF to keep ALTER TABLE from using copying operations on NDB tables |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Amount of data (in bytes) received from the data nodes by this MySQL Server (SQL node). |
||
No | No | Yes |
No | Session | No |
DESCRIPTION: Amount of data (in bytes) received from the data nodes in this client session. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Amount of data (in bytes) received from the data nodes by this slave. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Amount of data (in bytes) sent to the data nodes by this MySQL Server (SQL node). |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Amount of data (in bytes) sent to the data nodes by this slave. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of bytes of events received by the NDB binary log injector thread. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of row change events received by the NDB binary log injector thread. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of events received, other than row change events, by the NDB binary log injector thread. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of operations based on or using primary keys by this MySQL Server (SQL node). |
||
No | No | Yes |
No | Session | No |
DESCRIPTION: Number of operations based on or using primary keys in this client session. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of operations based on or using primary keys by this slave. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of scans that have been pruned to a single partition by this MySQL Server (SQL node). |
||
No | No | Yes |
No | Session | No |
DESCRIPTION: Number of scans that have been pruned to a single partition in this client session. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of range scans that have been started by this slave. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Total number of rows that have been read by this MySQL Server (SQL node). |
||
No | No | Yes |
No | Session | No |
DESCRIPTION: Total number of rows that have been read in this client session. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of batches of rows received by this slave. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of table scans that have been started, including scans of internal tables, by this MySQL Server (SQL node). |
||
No | No | Yes |
No | Session | No |
DESCRIPTION: Number of table scans that have been started, including scans of internal tables, in this client session. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of transactions aborted by this MySQL Server (SQL node). |
||
No | No | Yes |
No | Session | No |
DESCRIPTION: Number of transactions aborted in this client session. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of transactions aborted by this slave. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of transactions aborted (may be greater than the sum of TransCommitCount and TransAbortCount) by this MySQL Server (SQL node). |
||
No | No | Yes |
No | Session | No |
DESCRIPTION: Number of transactions aborted (may be greater than the sum of TransCommitCount and TransAbortCount) in this client session. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of transactions aborted (may be greater than the sum of TransCommitCount and TransAbortCount) by this slave. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of transactions committed by this MySQL Server (SQL node). |
||
No | No | Yes |
No | Session | No |
DESCRIPTION: Number of transactions committed in this client session. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of transactions committed by this slave. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Total number of rows that have been read by this slave. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of transactions started by this MySQL Server (SQL node). |
||
No | No | Yes |
No | Session | No |
DESCRIPTION: Number of transactions started in this client session. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of transactions started by this slave. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of operations based on or using unique keys by this MySQL Server (SQL node). |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of operations based on or using unique keys by this slave. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of times thread has been blocked while waiting for execution of an operation to complete by this MySQL Server (SQL node). |
||
No | No | Yes |
No | Session | No |
DESCRIPTION: Number of times thread has been blocked while waiting for execution of an operation to complete in this client session. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of times thread has been blocked while waiting for execution of an operation to complete by this slave. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of times thread has been blocked waiting for a metadata-based signal by this MySQL Server (SQL node). |
||
No | No | Yes |
No | Session | No |
DESCRIPTION: Number of times thread has been blocked waiting for a metadata-based signal in this client session. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Total time (in nanoseconds) spent waiting for some type of signal from the data nodes by this MySQL Server (SQL node). |
||
No | No | Yes |
No | Session | No |
DESCRIPTION: Total time (in nanoseconds) spent waiting for some type of signal from the data nodes in this client session. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Total time (in nanoseconds) spent waiting for some type of signal from the data nodes by this slave. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of times thread has been blocked while waiting for a scan-based signal by this MySQL Server (SQL node). |
||
No | No | Yes |
No | Session | No |
DESCRIPTION: Number of times thread has been blocked while waiting for a scan-based signal in this client session. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of times thread has been blocked while waiting for a scan-based signal by this slave. |
||
Yes | Yes | No |
Yes | Both | Yes |
DESCRIPTION: NDB auto-increment prefetch size |
||
Yes | Yes | No |
Yes | Global | Yes |
DESCRIPTION: Number of milliseconds between checks of cluster SQL nodes made by the MySQL query cache |
||
Yes | Yes | No |
No | Global | Yes |
DESCRIPTION: Causes RESET SLAVE to clear all rows from the ndb_apply_status table. ON by default. |
||
No | No | Yes |
No | Both | No |
DESCRIPTION: If the server is acting as a MySQL Cluster node, then the value of this variable its node ID in the cluster |
||
No | No | Yes |
No | Both | No |
DESCRIPTION: The host name or IP address of the Cluster management server. Formerly Ndb_connected_host |
||
No | No | Yes |
No | Both | No |
DESCRIPTION: The port for connecting to Cluster management server. Formerly Ndb_connected_port |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of rows that have been found in conflict by the NDB$EPOCH_TRANS() conflict detection function |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: If the server is part of a MySQL Cluster involved in cluster replication, the value of this variable indicates the number of times that conflict resolution based on "greater timestamp wins" has been applied |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: If the server is part of a MySQL Cluster involved in cluster replication, the value of this variable indicates the number of times that "same timestamp wins" conflict resolution has been applied |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of internal iterations required to commit an epoch transaction. Should be (slightly) greater than or equal to Ndb_conflict_trans_conflict_commit_count. |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Total number of rows realigned after being found in conflict by a transactional conflict function. Includes Ndb_conflict_trans_row_conflict_count and any rows included in or dependent on conflicting transactions. |
||
Yes | Yes | No |
Yes | Global | Yes |
DESCRIPTION: Specifies cluster data node "closest" to this MySQL Server, for transaction hinting and fully replicated tables |
||
Yes | Yes | No |
Yes | Both | Yes |
DESCRIPTION: Specifies that constraint checks should be deferred (where these are supported). Not normally needed or used; for testing purposes only. |
||
Yes | Yes | No |
Yes | Global | Yes |
DESCRIPTION: Default distribution for new tables in NDBCLUSTER (KEYHASH or LINHASH, default is KEYHASH) |
||
Yes | Yes | No |
Yes | Global | Yes |
DESCRIPTION: Percentage of free memory that should be available in event buffer before resumption of buffering, after reaching limit set by ndb_eventbuffer_max_alloc. |
||
Yes | Yes | No |
Yes | Global | Yes |
DESCRIPTION: Maximum memory that can be allocated for buffering events by the NDB API. Defaults to 0 (no limit). |
||
Yes | Yes | No |
Yes | Global | Yes |
DESCRIPTION: Controls logging of MySQL Cluster schema, connection, and data distribution events in the MySQL error log |
||
Yes | Yes | No |
Yes | Both | Yes |
DESCRIPTION: Forces sending of buffers to NDB immediately, without waiting for other threads |
||
Yes | Yes | No |
Yes | Both | Yes |
DESCRIPTION: Whether new NDB tables are fully replicated |
||
Yes | Yes | No |
Yes | Both | Yes |
DESCRIPTION: Use NDB index statistics in query optimization |
||
Yes | Yes | No |
Yes | Both | Yes |
DESCRIPTION: Comma-separated list of tunable options for NDB index statistics; the list should contain no spaces |
||
No | Yes | No |
No | Both | Yes |
DESCRIPTION: Enables pushing down of joins to data nodes |
||
Yes | Yes | No |
Yes | Global | No |
DESCRIPTION: Whether or not a MySQL server acting as a slave logs mysql.ndb_apply_status updates received from its immediate master in its own binary log, using its own server ID. |
||
Yes | Yes | No |
No | Both | Yes |
DESCRIPTION: Write updates to NDB tables in the binary log. Effective only if binary logging is enabled with --log-bin. |
||
Yes | Yes | No |
No | Global | Yes |
DESCRIPTION: Insert mapping between epochs and binary log positions into the ndb_binlog_index table. Defaults to ON. Effective only if binary logging is enabled on the server. |
||
Yes | Yes | No |
Yes | Global | Yes |
DESCRIPTION: When enabled, epochs in which there were no changes are written to the ndb_apply_status and ndb_binlog_index tables, even when log_slave_updates is enabled. |
||
Yes | Yes | No |
Yes | Both | Yes |
DESCRIPTION: Log primary key reads with exclusive locks; allow conflict resolution based on read conflicts. |
||
Yes | Yes | No |
Yes | Global | No |
DESCRIPTION: Whether the id and epoch of the originating server are recorded in the mysql.ndb_binlog_index table. Set using the --ndb-log-orig option when starting mysqld. |
||
No | Yes | No |
No | Global | No |
DESCRIPTION: Whether NDB transaction IDs are written into the binary log. (Read-only.) |
||
Yes | Yes | No |
Yes | Global | Yes |
DESCRIPTION: Log complete rows (ON) or updates only (OFF) |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: If the server is part of a MySQL Cluster, the value of this variable is the number of data nodes in the cluster |
||
No | Yes | No |
No | Global | Yes |
DESCRIPTION: Sets the number of milliseconds to wait between processing sets of rows by OPTIMIZE TABLE on NDB tables. |
||
Yes | Yes | No |
Yes | Global | No |
DESCRIPTION: Determines how an SQL node chooses a cluster data node to use as transaction coordinator |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of joins that API nodes have attempted to push down to the data nodes |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: Number of joins successfully pushed down and executed on the data nodes |
||
Yes | Yes | No |
Yes | Global | Yes |
DESCRIPTION: Enable read from any replica |
||
No | No | No |
No | No | |
DESCRIPTION: Activation threshold when receive thread takes over the polling of the cluster connection (measured in concurrently active threads) |
||
No | Yes | No |
No | Global | Yes |
DESCRIPTION: CPU mask for locking receiver threads to specific CPUs; specified as hexadecimal. See documentation for details. |
||
Yes | No | No |
Yes | No | |
DESCRIPTION: This is a threshold on the number of epochs to be behind before reporting binary log status |
||
Yes | No | No |
Yes | No | |
DESCRIPTION: This is a threshold on the percentage of free memory remaining before reporting binary log status |
||
No | No | Yes |
No | Global | No |
DESCRIPTION: The total number of scans executed by NDB since the cluster was last started |
||
Yes | Yes | No |
Yes | Global | Yes |
DESCRIPTION: Show the mock tables used to support foreign_key_checks=0. |
||
Yes | Yes | No |
Yes | Global | Yes |
DESCRIPTION: Role for slave to play in conflict detection and resolution. Value is one of PRIMARY, SECONDARY, PASS, or NONE (default). Can be changed only when slave SQL thread is stopped. See documentation for further information. |
||
No | Yes | No |
No | Global | No |
DESCRIPTION: The most recently committed NDB epoch on this slave. When this value is greater than or equal to Ndb_conflict_last_conflict_epoch, no conflicts have yet been detected. |
||
No | Yes | No |
No | Session | Yes |
DESCRIPTION: NDB tables created when this setting is enabled are not checkpointed to disk (although table schema files are created). The setting in effect when the table is created with or altered to use NDBCLUSTER persists for the lifetime of the table. |
||
No | Yes | No |
No | Session | Yes |
DESCRIPTION: NDB tables are not persistent on disk: no schema files are created and the tables are not logged |
||
No | Yes | No |
No | Both | Yes |
DESCRIPTION: Use exact row count when planning queries |
||
Yes | Yes | No |
Yes | Both | Yes |
DESCRIPTION: Forces NDB to use a count of records during SELECT COUNT(*) query planning to speed up this type of query |
||
No | Yes | No |
No | Global | No |
DESCRIPTION: Shows build and NDB engine version as an integer. |
||
No | Yes | No |
No | Global | No |
DESCRIPTION: Shows build information including NDB engine version in ndb-x.y.z format. |
||
Yes | No | No |
Yes | No | |
DESCRIPTION: Enable NDB Cluster (if this version of MySQL supports it)
Disabled by |
||
No | Yes | No |
No | Global | No |
DESCRIPTION: The name used for the NDB information database; read only. |
||
Yes | Yes | No |
No | Both | Yes |
DESCRIPTION: Used for debugging only. |
||
Yes | Yes | No |
No | Both | Yes |
DESCRIPTION: Used for debugging only. |
||
No | Yes | No |
No | Global | Yes |
DESCRIPTION: Put the ndbinfo database into offline mode, in which no rows are returned from tables or views. |
||
Yes | Yes | No |
No | Both | Yes |
DESCRIPTION: Whether to show ndbinfo internal base tables in the mysql client. The default is OFF. |
||
Yes | Yes | No |
No | Both | Yes |
DESCRIPTION: The prefix to use for naming ndbinfo internal base tables |
||
No | Yes | No |
No | Global | No |
DESCRIPTION: The version of the ndbinfo engine; read only. |
||
Yes | Yes | No |
Yes | Global | No |
DESCRIPTION: Sets the number of least significant bits in the server_id actually used for identifying the server, permitting NDB API applications to store application data in the most significant bits. server_id must be less than 2 to the power of this value. |
||
Yes | Yes | No |
Yes | Global | No |
DESCRIPTION: The effective value of server_id if the server was started with the --server-id-bits option set to a nondefault value. |
||
Yes | Yes | No |
Yes | Global | Yes |
DESCRIPTION: Turns update batching on and off for a replication slave |
||
No | Yes | No |
No | Session | Yes |
DESCRIPTION: Allows batching of statements within a transaction. Disable AUTOCOMMIT to use. |
Configuring MySQL Cluster requires working with two files:
my.cnf
: Specifies options for all MySQL
Cluster executables. This file, with which you should be
familiar with from previous work with MySQL, must be
accessible by each executable running in the cluster.
config.ini
: This file, sometimes known as
the global configuration
file, is read only by the MySQL Cluster management
server, which then distributes the information contained
therein to all processes participating in the cluster.
config.ini
contains a description of each
node involved in the cluster. This includes configuration
parameters for data nodes and configuration parameters for
connections between all nodes in the cluster. For a quick
reference to the sections that can appear in this file, and
what sorts of configuration parameters may be placed in each
section, see
Sections of
the config.ini
File.
Caching of configuration data.
NDB
uses stateful
configuration. Rather than reading the global
configuration file every time the management server is
restarted, the management server caches the configuration the
first time it is started, and thereafter, the global
configuration file is read only when one of the following
conditions is true:
The management server is started using the --initial option.
When --initial
is used, the
global configuration file is re-read, any existing cache
files are deleted, and the management server creates a new
configuration cache.
The management server is started using the --reload option.
The --reload
option causes
the management server to compare its cache with the global
configuration file. If they differ, the management server
creates a new configuration cache; any existing
configuration cache is preserved, but not used. If the
management server's cache and the global configuration
file contain the same configuration data, then the existing
cache is used, and no new cache is created.
The management server is started using --config-cache=FALSE.
This disables
--config-cache
(enabled by
default), and can be used to force the management server to
bypass configuration caching altogether. In this case, the
management server ignores any configuration files that may
be present, always reading its configuration data from the
config.ini
file instead.
No configuration cache is found. In this case, the management server reads the global configuration file and creates a cache containing the same configuration data as found in the file.
Configuration cache files.
The management server by default creates configuration cache
files in a directory named mysql-cluster
in
the MySQL installation directory. (If you build MySQL Cluster
from source on a Unix system, the default location is
/usr/local/mysql-cluster
.) This can be
overridden at runtime by starting the management server with the
--configdir
option.
Configuration cache files are binary files named according to
the pattern
ndb_
,
where node_id
_config.bin.seq_id
node_id
is the management
server's node ID in the cluster, and
seq_id
is a cache idenitifer. Cache
files are numbered sequentially using
seq_id
, in the order in which they
are created. The management server uses the latest cache file as
determined by the seq_id
.
It is possible to roll back to a previous configuration by
deleting later configuration cache files, or by renaming an
earlier cache file so that it has a higher
seq_id
. However, since configuration
cache files are written in a binary format, you should not
attempt to edit their contents by hand.
For more information about the
--configdir
,
--config-cache
,
--initial
, and
--reload
options for the MySQL
Cluster management server, see
Section 19.4.4, “ndb_mgmd — The MySQL Cluster Management Server Daemon”.
We are continuously making improvements in Cluster configuration and attempting to simplify this process. Although we strive to maintain backward compatibility, there may be times when introduce an incompatible change. In such cases we will try to let Cluster users know in advance if a change is not backward compatible. If you find such a change and we have not documented it, please report it in the MySQL bugs database using the instructions given in Section 1.7, “How to Report Bugs or Problems”.
To support MySQL Cluster, you will need to update
my.cnf
as shown in the following example.
You may also specify these parameters on the command line when
invoking the executables.
The options shown here should not be confused with those that
are used in config.ini
global
configuration files. Global configuration options are
discussed later in this section.
# my.cnf # example additions to my.cnf for MySQL Cluster # (valid in MySQL 5.7) # enable ndbcluster storage engine, and provide connection string for # management server host (default port is 1186) [mysqld] ndbcluster ndb-connectstring=ndb_mgmd.mysql.com # provide connection string for management server host (default port: 1186) [ndbd] connect-string=ndb_mgmd.mysql.com # provide connection string for management server host (default port: 1186) [ndb_mgm] connect-string=ndb_mgmd.mysql.com # provide location of cluster configuration file [ndb_mgmd] config-file=/etc/config.ini
(For more information on connection strings, see Section 19.3.3.3, “MySQL Cluster Connection Strings”.)
# my.cnf # example additions to my.cnf for MySQL Cluster # (will work on all versions) # enable ndbcluster storage engine, and provide connection string for management # server host to the default port 1186 [mysqld] ndbcluster ndb-connectstring=ndb_mgmd.mysql.com:1186
Once you have started a mysqld process with
the NDBCLUSTER
and
ndb-connectstring
parameters in the
[mysqld]
in the my.cnf
file as shown previously, you cannot execute any
CREATE TABLE
or
ALTER TABLE
statements without
having actually started the cluster. Otherwise, these
statements will fail with an error. This is by
design.
You may also use a separate [mysql_cluster]
section in the cluster my.cnf
file for
settings to be read and used by all executables:
# cluster-specific settings [mysql_cluster] ndb-connectstring=ndb_mgmd.mysql.com:1186
For additional NDB
variables that
can be set in the my.cnf
file, see
Section 19.3.3.8.2, “MySQL Cluster System Variables”.
The MySQL Cluster global configuration file is by convention
named config.ini
(but this is not
required). If needed, it is read by ndb_mgmd
at startup and can be placed in any location that can be read by
it. The location and name of the configuration are specified
using
--config-file=
with ndb_mgmd on the command line. This
option has no default value, and is ignored if
ndb_mgmd uses the configuration cache.
path_name
The global configuration file for MySQL Cluster uses INI format,
which consists of sections preceded by section headings
(surrounded by square brackets), followed by the appropriate
parameter names and values. One deviation from the standard INI
format is that the parameter name and value can be separated by
a colon (“:
”) as well as the
equal sign (“=
”); however, the
equal sign is preferred. Another deviation is that sections are
not uniquely identified by section name. Instead, unique
sections (such as two different nodes of the same type) are
identified by a unique ID specified as a parameter within the
section.
Default values are defined for most parameters, and can also be
specified in config.ini
. To create a
default value section, simply add the word
default
to the section name. For example, an
[ndbd]
section contains parameters that apply
to a particular data node, whereas an [ndbd
default]
section contains parameters that apply to all
data nodes. Suppose that all data nodes should use the same data
memory size. To configure them all, create an [ndbd
default]
section that contains a
DataMemory
line to
specify the data memory size.
In some older releases of MySQL Cluster, there was no default
value for
NoOfReplicas
, which
always had to be specified explicitly in the [ndbd
default]
section. Although this parameter now has a
default value of 2, which is the recommended setting in most
common usage scenarios, it is still recommended practice to
set this parameter explicitly.
The global configuration file must define the computers and nodes involved in the cluster and on which computers these nodes are located. An example of a simple configuration file for a cluster consisting of one management server, two data nodes and two MySQL servers is shown here:
# file "config.ini" - 2 data nodes and 2 SQL nodes # This file is placed in the startup directory of ndb_mgmd (the # management server) # The first MySQL Server can be started from any host. The second # can be started only on the host mysqld_5.mysql.com [ndbd default] NoOfReplicas= 2 DataDir= /var/lib/mysql-cluster [ndb_mgmd] Hostname= ndb_mgmd.mysql.com DataDir= /var/lib/mysql-cluster [ndbd] HostName= ndbd_2.mysql.com [ndbd] HostName= ndbd_3.mysql.com [mysqld] [mysqld] HostName= mysqld_5.mysql.com
The preceding example is intended as a minimal starting configuration for purposes of familiarization with MySQL Cluster, and is almost certain not to be sufficient for production settings. See Section 19.3.3.2, “Recommended Starting Configuration for MySQL Cluster”, which provides a more complete example starting configuration.
Each node has its own section in the
config.ini
file. For example, this cluster
has two data nodes, so the preceding configuration file contains
two [ndbd]
sections defining these nodes.
Do not place comments on the same line as a section heading in
the config.ini
file; this causes the
management server not to start because it cannot parse the
configuration file in such cases.
There are six different sections that you can use in the
config.ini
configuration file, as described
in the following list:
[computer]
: Defines cluster hosts. This
is not required to configure a viable MySQL Cluster, but be
may used as a convenience when setting up a large cluster.
See Section 19.3.3.4, “Defining Computers in a MySQL Cluster”, for
more information.
[ndbd]
: Defines a cluster data node
(ndbd process). See
Section 19.3.3.6, “Defining MySQL Cluster Data Nodes”, for
details.
[mysqld]
: Defines the cluster's MySQL
server nodes (also called SQL or API nodes). For a
discussion of SQL node configuration, see
Section 19.3.3.7, “Defining SQL and Other API Nodes in a MySQL Cluster”.
[mgm]
or [ndb_mgmd]
:
Defines a cluster management server (MGM) node. For
information concerning the configuration of management
nodes, see Section 19.3.3.5, “Defining a MySQL Cluster Management Server”.
[tcp]
: Defines a TCP/IP connection
between cluster nodes, with TCP/IP being the default
connection protocol. Normally, [tcp]
or
[tcp default]
sections are not required
to set up a MySQL Cluster, as the cluster handles this
automatically; however, it may be necessary in some
situations to override the defaults provided by the cluster.
See Section 19.3.3.9, “MySQL Cluster TCP/IP Connections”, for
information about available TCP/IP configuration parameters
and how to use them. (You may also find
Section 19.3.3.10, “MySQL Cluster TCP/IP Connections Using Direct Connections” to be
of interest in some cases.)
[shm]
: Defines shared-memory connections
between nodes. In MySQL 5.7, it is enabled by
default, but should still be considered experimental. For a
discussion of SHM interconnects, see
Section 19.3.3.11, “MySQL Cluster Shared-Memory Connections”.
[sci]
:Defines
Scalable Coherent
Interface connections between cluster data nodes.
Such connections require software which, while freely
available, is not part of the MySQL Cluster distribution, as
well as specialized hardware. See
Section 19.3.3.12, “SCI Transport Connections in MySQL Cluster” for detailed
information about SCI interconnects.
You can define default
values for each
section. All Cluster parameter names are case-insensitive, which
differs from parameters specified in my.cnf
or my.ini
files.
Achieving the best performance from a MySQL Cluster depends on a number of factors including the following:
MySQL Cluster software version
Numbers of data nodes and SQL nodes
Hardware
Operating system
Amount of data to be stored
Size and type of load under which the cluster is to operate
Therefore, obtaining an optimum configuration is likely to be an iterative process, the outcome of which can vary widely with the specifics of each MySQL Cluster deployment. Changes in configuration are also likely to be indicated when changes are made in the platform on which the cluster is run, or in applications that use the MySQL Cluster's data. For these reasons, it is not possible to offer a single configuration that is ideal for all usage scenarios. However, in this section, we provide a recommended base configuration.
Starting config.ini file.
The following config.ini
file is a
recommended starting point for configuring a cluster running
MySQL Cluster NDB 7.5:
# TCP PARAMETERS [tcp default]SendBufferMemory
=2MReceiveBufferMemory
=2M # Increasing the sizes of these 2 buffers beyond the default values # helps prevent bottlenecks due to slow disk I/O. # MANAGEMENT NODE PARAMETERS [ndb_mgmd default]DataDir
=path/to/management/server/data/directory
# It is possible to use a different data directory for each management # server, but for ease of administration it is preferable to be # consistent. [ndb_mgmd]HostName
=management-server-A-hostname
#NodeId
=management-server-A-nodeid
[ndb_mgmd]HostName
=management-server-B-hostname
#NodeId
=management-server-B-nodeid
# Using 2 management servers helps guarantee that there is always an # arbitrator in the event of network partitioning, and so is # recommended for high availability. Each management server must be # identified by a HostName. You may for the sake of convenience specify # a NodeId for any management server, although one will be allocated # for it automatically; if you do so, it must be in the range 1-255 # inclusive and must be unique among all IDs specified for cluster # nodes. # DATA NODE PARAMETERS [ndbd default]NoOfReplicas
=2 # Using 2 replicas is recommended to guarantee availability of data; # using only 1 replica does not provide any redundancy, which means # that the failure of a single data node causes the entire cluster to # shut down. We do not recommend using more than 2 replicas, since 2 is # sufficient to provide high availability, and we do not currently test # with greater values for this parameter.LockPagesInMainMemory
=1 # On Linux and Solaris systems, setting this parameter locks data node # processes into memory. Doing so prevents them from swapping to disk, # which can severely degrade cluster performance.DataMemory
=3072MIndexMemory
=384M # The values provided for DataMemory and IndexMemory assume 4 GB RAM # per data node. However, for best results, you should first calculate # the memory that would be used based on the data you actually plan to # store (you may find the ndb_size.pl utility helpful in estimating # this), then allow an extra 20% over the calculated values. Naturally, # you should ensure that each data node host has at least as much # physical memory as the sum of these two values. #ODirect
=1 # Enabling this parameter causes NDBCLUSTER to try using O_DIRECT # writes for local checkpoints and redo logs; this can reduce load on # CPUs. We recommend doing so when using MySQL Cluster on systems running # Linux kernel 2.6 or later.NoOfFragmentLogFiles
=300DataDir
=path/to/data/node/data/directory
MaxNoOfConcurrentOperations
=100000SchedulerSpinTimer
=400SchedulerExecutionTimer
=100RealTimeScheduler
=1 # Setting these parameters allows you to take advantage of real-time scheduling # of NDB threads to achieve increased throughput when using ndbd. They # are not needed when using ndbmtd; in particular, you should not set #RealTimeScheduler
for ndbmtd data nodes.TimeBetweenGlobalCheckpoints
=1000TimeBetweenEpochs
=200RedoBuffer
=32M #CompressedLCP
=1 #CompressedBackup
=1 # Enabling CompressedLCP and CompressedBackup causes, respectively, local checkpoint files and backup files to be compressed, which can result in a space savings of up to 50% over noncompressed LCPs and backups. #MaxNoOfLocalScans
=64MaxNoOfTables
=1024MaxNoOfOrderedIndexes
=256 [ndbd]HostName
=data-node-A-hostname
#NodeId
=data-node-A-nodeid
LockExecuteThreadToCPU
=1LockMaintThreadsToCPU
=0 # On systems with multiple CPUs, these parameters can be used to lock NDBCLUSTER # threads to specific CPUs [ndbd]HostName
=data-node-B-hostname
#NodeId
=data-node-B-nodeid
LockExecuteThreadToCPU
=1LockMaintThreadsToCPU
=0 # You must have an [ndbd] section for every data node in the cluster; # each of these sections must include a HostName. Each section may # optionally include a NodeId for convenience, but in most cases, it is # sufficient to allow the cluster to allocate node IDs dynamically. If # you do specify the node ID for a data node, it must be in the range 1 # to 48 inclusive and must be unique among all IDs specified for # cluster nodes. # SQL NODE / API NODE PARAMETERS [mysqld] #HostName
=sql-node-A-hostname
#NodeId
=sql-node-A-nodeid
[mysqld] [mysqld] # Each API or SQL node that connects to the cluster requires a [mysqld] # or [api] section of its own. Each such section defines a connection # “slot”; you should have at least as many of these sections in the # config.ini file as the total number of API nodes and SQL nodes that # you wish to have connected to the cluster at any given time. There is # no performance or other penalty for having extra slots available in # case you find later that you want or need more API or SQL nodes to # connect to the cluster at the same time. # If no HostName is specified for a given [mysqld] or [api] section, # then any API or SQL node may use that slot to connect to the # cluster. You may wish to use an explicit HostName for one connection slot # to guarantee that an API or SQL node from that host can always # connect to the cluster. If you wish to prevent API or SQL nodes from # connecting from other than a desired host or hosts, then use a # HostName for every [mysqld] or [api] section in the config.ini file. # You can if you wish define a node ID (NodeId parameter) for any API or # SQL node, but this is not necessary; if you do so, it must be in the # range 1 to 255 inclusive and must be unique among all IDs specified # for cluster nodes.
Recommended my.cnf options for SQL nodes.
MySQL Servers acting as MySQL Cluster SQL nodes must always be
started with the --ndbcluster
and --ndb-connectstring
options, either on
the command line or in my.cnf
. In
addition, set the following options for all
mysqld processes in the cluster, unless
your setup requires otherwise:
--ndb-use-exact-count=0
--ndb-index-stat-enable=0
--ndb-force-send=1
--engine-condition-pushdown=1
With the exception of the MySQL Cluster management server (ndb_mgmd), each node that is part of a MySQL Cluster requires a connection string that points to the management server's location. This connection string is used in establishing a connection to the management server as well as in performing other tasks depending on the node's role in the cluster. The syntax for a connection string is as follows:
[nodeid=node_id
, ]host-definition
[,host-definition
[, ...]]host-definition
:host_name
[:port_number
]
node_id
is an integer greater than or equal
to 1 which identifies a node in config.ini
.
host_name
is a string representing a
valid Internet host name or IP address.
port_number
is an integer referring
to a TCP/IP port number.
example 1 (long): "nodeid=2,myhost1:1100,myhost2:1100,192.168.0.3:1200" example 2 (short): "myhost1"
localhost:1186
is used as the default
connection string value if none is provided. If
port_num
is omitted from the
connection string, the default port is 1186. This port should
always be available on the network because it has been assigned
by IANA for this purpose (see
http://www.iana.org/assignments/port-numbers for
details).
By listing multiple host definitions, it is possible to designate several redundant management servers. A MySQL Cluster data or API node attempts to contact successive management servers on each host in the order specified, until a successful connection has been established.
It is also possible to specify in a connection string one or more bind addresses to be used by nodes having multiple network interfaces for connecting to management servers. A bind address consists of a hostname or network address and an optional port number. This enhanced syntax for connection strings is shown here:
[nodeid=node_id
, ] [bind-address=host-definition
, ]host-definition
[; bind-address=host-definition
]host-definition
[; bind-address=host-definition
] [, ...]]host-definition
:host_name
[:port_number
]
If a single bind address is used in the connection string
prior to specifying any management hosts,
then this address is used as the default for connecting to any
of them (unless overridden for a given management server; see
later in this section for an example). For example, the
following connection string causes the node to use
192.168.178.242
regardless of the management
server to which it connects:
bind-address=192.168.178.242, poseidon:1186, perch:1186
If a bind address is specified following a management host definition, then it is used only for connecting to that management node. Consider the following connection string:
poseidon:1186;bind-address=localhost, perch:1186;bind-address=192.168.178.242
In this case, the node uses localhost
to
connect to the management server running on the host named
poseidon
and
192.168.178.242
to connect to the management
server running on the host named perch
.
You can specify a default bind address and then override this
default for one or more specific management hosts. In the
following example, localhost
is used for
connecting to the management server running on host
poseidon
; since
192.168.178.242
is specified first (before
any management server definitions), it is the default bind
address and so is used for connecting to the management servers
on hosts perch
and orca
:
bind-address=192.168.178.242,poseidon:1186;bind-address=localhost,perch:1186,orca:2200
There are a number of different ways to specify the connection string:
Each executable has its own command-line option which enables specifying the management server at startup. (See the documentation for the respective executable.)
It is also possible to set the connection string for all
nodes in the cluster at once by placing it in a
[mysql_cluster]
section in the management
server's my.cnf
file.
For backward compatibility, two other options are available, using the same syntax:
Set the NDB_CONNECTSTRING
environment
variable to contain the connection string.
Write the connection string for each executable into a
text file named Ndb.cfg
and place
this file in the executable's startup directory.
However, these are now deprecated and should not be used for new installations.
The recommended method for specifying the connection string is
to set it on the command line or in the
my.cnf
file for each executable.
The [computer]
section has no real
significance other than serving as a way to avoid the need of
defining host names for each node in the system. All parameters
mentioned here are required.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | string | [none] | ... | IS |
This is a unique identifier, used to refer to the host computer elsewhere in the configuration file.
The computer ID is not the same as
the node ID used for a management, API, or data node.
Unlike the case with node IDs, you cannot use
NodeId
in place of
Id
in the [computer]
section of the config.ini
file.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | name or IP address | [none] | ... | N |
This is the computer's hostname or IP address.
The [ndb_mgmd]
section is used to configure
the behavior of the management server. If multiple management
servers are employed, you can specify parameters common to all
of them in an [ndb_mgmd default]
section.
[mgm]
and [mgm default]
are older aliases for these, supported for backward
compatibility.
All parameters in the following list are optional and assume their default values if omitted.
If neither the ExecuteOnComputer
nor the
HostName
parameter is present, the default
value localhost
will be assumed for both.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | [none] | 1 - 255 | IS |
Each node in the cluster has a unique identity. For a management node, this is represented by an integer value in the range 1 to 255, inclusive. This ID is used by all internal cluster messages for addressing the node, and so must be unique for each MySQL Cluster node, regardless of the type of node.
Data node IDs must be less than 49. If you plan to deploy a large number of data nodes, it is a good idea to limit the node IDs for management nodes (and API nodes) to values greater than 48.
The use of the Id
parameter for
identifying management nodes is deprecated in favor of
NodeId
. Although
Id
continues to be supported for backward
compatibility, it now generates a warning and is subject to
removal in a future version of MySQL Cluster.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | [none] | 1 - 255 | IS |
Each node in the cluster has a unique identity. For a management node, this is represented by an integer value in the range 1 to 255 inclusive. This ID is used by all internal cluster messages for addressing the node, and so must be unique for each MySQL Cluster node, regardless of the type of node.
Data node IDs must be less than 49. If you plan to deploy a large number of data nodes, it is a good idea to limit the node IDs for management nodes (and API nodes) to values greater than 48.
NodeId
is the preferred parameter name to
use when identifying management nodes. Although the older
Id
continues to be
supported for backward compatibility, it is now deprecated
and generates a warning when used; it is also subject to
removal in a future MySQL Cluster release.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | name | [none] | ... | S |
This refers to the Id
set for one of the
computers defined in a [computer]
section
of the config.ini
file.
This parameter is deprecated as of MySQL Cluster NDB
7.5.0, and is subject to removal in a future release. Use
the HostName
parameter instead.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 1186 | 0 - 64K | S |
This is the port number on which the management server listens for configuration requests and management commands.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | name or IP address | [none] | ... | N |
Specifying this parameter defines the hostname of the
computer on which the management node is to reside. To
specify a hostname other than localhost
,
either this parameter or
ExecuteOnComputer
is required.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | {CONSOLE|SYSLOG|FILE} | [see text] | ... | N |
This parameter specifies where to send cluster logging
information. There are three options in this
regard—CONSOLE
,
SYSLOG
, and
FILE
—with FILE
being the default:
CONSOLE
outputs the log to
stdout
:
CONSOLE
SYSLOG
sends the log to a
syslog
facility, possible values
being one of auth
,
authpriv
, cron
,
daemon
, ftp
,
kern
, lpr
,
mail
, news
,
syslog
, user
,
uucp
, local0
,
local1
, local2
,
local3
, local4
,
local5
, local6
, or
local7
.
Not every facility is necessarily supported by every operating system.
SYSLOG:facility=syslog
FILE
pipes the cluster log output to
a regular file on the same machine. The following values
can be specified:
filename
: The name of the log
file.
The default log file name used in such cases is
ndb_
.
nodeid
_cluster.log
maxsize
: The maximum size (in
bytes) to which the file can grow before logging
rolls over to a new file. When this occurs, the old
log file is renamed by appending
.N
to the file name,
where N
is the next
number not yet used with this name.
maxfiles
: The maximum number of
log files.
FILE:filename=cluster.log,maxsize=1000000,maxfiles=6
The default value for the FILE
parameter is
FILE:filename=ndb_
,
where node_id
_cluster.log,maxsize=1000000,maxfiles=6node_id
is the ID of
the node.
It is possible to specify multiple log destinations separated by semicolons as shown here:
CONSOLE;SYSLOG:facility=local0;FILE:filename=/var/log/mgmd
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | 0-2 | 1 | 0 - 2 | N |
This parameter is used to define which nodes can act as
arbitrators. Only management nodes and SQL nodes can be
arbitrators. ArbitrationRank
can take one
of the following values:
0
: The node will never be used as an
arbitrator.
1
: The node has high priority; that
is, it will be preferred as an arbitrator over
low-priority nodes.
2
: Indicates a low-priority node
which be used as an arbitrator only if a node with a
higher priority is not available for that purpose.
Normally, the management server should be configured as an
arbitrator by setting its ArbitrationRank
to 1 (the default for management nodes) and those for all
SQL nodes to 0 (the default for SQL nodes).
You can disable arbitration completely either by setting
ArbitrationRank
to 0 on all management
and SQL nodes, or by setting the
Arbitration
parameter in the [ndbd default]
section
of the config.ini
global configuration
file. Setting
Arbitration
causes
any settings for ArbitrationRank
to be
disregarded.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
An integer value which causes the management server's responses to arbitration requests to be delayed by that number of milliseconds. By default, this value is 0; it is normally not necessary to change it.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | path | . | ... | N |
This specifies the directory where output files from the
management server will be placed. These files include
cluster log files, process output files, and the daemon's
process ID (PID) file. (For log files, this location can be
overridden by setting the FILE
parameter
for LogDestination
as discussed previously in this section.)
The default value for this parameter is the directory in which ndb_mgmd is located.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | [none] | 0 - 64K | N |
This parameter specifies the port number used to obtain statistical information from a MySQL Cluster management server. It has no default value.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | false | true, false | N |
Use WAN TCP setting as default.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | string | [none] | ... | S |
Set the scheduling policy and priority of heartbeat threads for management and API nodes.
The syntax for setting this parameter is shown here:
HeartbeatThreadPriority =policy
[,priority
]policy
: {FIFO | RR}
When setting this parameter, you must specify a policy. This
is one of FIFO
(first in, first out) or
RR
(round robin). The policy value is
followed optionally by the priority (an integer).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 0 | 256K - 4294967039 (0xFFFFFEFF) | N |
This parameter is used to determine the total amount of memory to allocate on this node for shared send buffer memory among all configured transporters.
If this parameter is set, its minimum permitted value is 256KB; 0 indicates that the parameter has not been set. For more detailed information, see Section 19.3.3.13, “Configuring MySQL Cluster Send Buffer Parameters”.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 1500 | 100 - 4294967039 (0xFFFFFEFF) | N |
Specify the interval between heartbeat messages used to determine whether another management node is on contact with this one. The management node waits after 3 of these intervals to declare the connection dead; thus, the default setting of 1500 milliseconds causes the management node to wait for approximately 1600 ms before timing out.
After making changes in a management node's configuration, it is necessary to perform a rolling restart of the cluster for the new configuration to take effect.
To add new management servers to a running MySQL Cluster, it
is also necessary to perform a rolling restart of all cluster
nodes after modifying any existing
config.ini
files. For more information
about issues arising when using multiple management nodes, see
Section 19.1.6.10, “Limitations Relating to Multiple MySQL Cluster Nodes”.
The [ndbd]
and [ndbd
default]
sections are used to configure the behavior
of the cluster's data nodes.
[ndbd]
and [ndbd default]
are always used as the section names whether you are using
ndbd or ndbmtd binaries
for the data node processes.
There are many parameters which control buffer sizes, pool
sizes, timeouts, and so forth. The only mandatory parameter is
either one of ExecuteOnComputer
or
HostName
; this must be defined in the local
[ndbd]
section.
The parameter
NoOfReplicas
should be
defined in the [ndbd default]
section, as it
is common to all Cluster data nodes. It is not strictly
necessary to set
NoOfReplicas
, but it is
good practice to set it explicitly.
Most data node parameters are set in the [ndbd
default]
section. Only those parameters explicitly
stated as being able to set local values are permitted to be
changed in the [ndbd]
section. Where present,
HostName
, NodeId
and
ExecuteOnComputer
must
be defined in the local [ndbd]
section, and
not in any other section of config.ini
. In
other words, settings for these parameters are specific to one
data node.
For those parameters affecting memory usage or buffer sizes, it
is possible to use K
, M
,
or G
as a suffix to indicate units of 1024,
1024×1024, or 1024×1024×1024. (For example,
100K
means 100 × 1024 = 102400.)
Parameter names and values are currently case-sensitive.
Information about configuration parameters specific to MySQL Cluster Disk Data tables can be found later in this section (see Disk Data Configuration Parameters).
All of these parameters also apply to ndbmtd
(the multi-threaded version of ndbd). Three
additional data node configuration
parameters—MaxNoOfExecutionThreads
,
ThreadConfig
, and
NoOfFragmentLogParts
—apply
to ndbmtd only; these have no effect when
used with ndbd. For more information, see
Multi-Threading Configuration Parameters (ndbmtd).
See also Section 19.4.3, “ndbmtd — The MySQL Cluster Data Node Daemon (Multi-Threaded)”.
Identifying data nodes.
The NodeId
or Id
value
(that is, the data node identifier) can be allocated on the
command line when the node is started or in the configuration
file.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | [none] | 1 - 48 | IS |
A unique node ID is used as the node's address for all cluster internal messages. For data nodes, this is an integer in the range 1 to 48 inclusive. Each node in the cluster must have a unique identifier.
NodeId
is the only supported parameter
name to use when identifying data nodes.
(Id
was removed in MySQL Cluster NDB
7.5.0.)
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | name | [none] | ... | S |
This refers to the Id
set for one of the
computers defined in a [computer]
section.
This parameter is deprecated as of MySQL Cluster NDB
7.5.0, and is subject to removal in a future release. Use
the HostName
parameter instead.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | name or IP address | localhost | ... | N |
Specifying this parameter defines the hostname of the
computer on which the data node is to reside. To specify a
hostname other than localhost
, either
this parameter or ExecuteOnComputer
is
required.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | [none] | 1 - 64K | S |
Each node in the cluster uses a port to connect to other nodes. By default, this port is allocated dynamically in such a way as to ensure that no two nodes on the same host computer receive the same port number, so it should normally not be necessary to specify a value for this parameter.
However, if you need to be able to open specific ports in a
firewall to permit communication between data nodes and API
nodes (including SQL nodes), you can set this parameter to
the number of the desired port in an
[ndbd]
section or (if you need to do this
for multiple data nodes) the [ndbd
default]
section of the
config.ini
file, and then open the port
having that number for incoming connections from SQL nodes,
API nodes, or both.
Connections from data nodes to management nodes is done
using the ndb_mgmd management port (the
management server's
PortNumber
) so
outgoing connections to that port from any data nodes
should always be permitted.
Setting this parameter to TRUE
or
1
binds IP_ADDR_ANY
so
that connections can be made from anywhere (for
autogenerated connections). The default is
FALSE
(0
).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | [none] | 0 - 65536 | IS |
This parameter can be used to assign a data node to a
specific node group. It is read only when the cluster is
started for the first time, and cannot be used to reassign a
data node to a different node group online. It is generally
not desirable to use this parameter in the [ndbd
default]
section of the
config.ini
file, and care must be taken
not to assign nodes to node groups in such a way that an
invalid numbers of nodes are assigned to any node groups.
The NodeGroup
parameter is chiefly intended for use in adding a new node
group to a running MySQL Cluster without having to perform a
rolling restart. For this purpose, you should set it to
65536 (the maximum value). You are not required to set a
NodeGroup
value for
all cluster data nodes, only for those nodes which are to be
started and added to the cluster as a new node group at a
later time. For more information, see
Section 19.5.14.3, “Adding MySQL Cluster Data Nodes Online: Detailed Example”.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 2 | 1 - 4 | IS |
This global parameter can be set only in the [ndbd
default]
section, and defines the number of
replicas for each table stored in the cluster. This
parameter also specifies the size of node groups. A node
group is a set of nodes all storing the same information.
Node groups are formed implicitly. The first node group is
formed by the set of data nodes with the lowest node IDs,
the next node group by the set of the next lowest node
identities, and so on. By way of example, assume that we
have 4 data nodes and that
NoOfReplicas
is set
to 2. The four data nodes have node IDs 2, 3, 4 and 5. Then
the first node group is formed from nodes 2 and 3, and the
second node group by nodes 4 and 5. It is important to
configure the cluster in such a manner that nodes in the
same node groups are not placed on the same computer because
a single hardware failure would cause the entire cluster to
fail.
If no node IDs are provided, the order of the data nodes
will be the determining factor for the node group. Whether
or not explicit assignments are made, they can be viewed in
the output of the management client's
SHOW
command.
The default value for
NoOfReplicas
is 2,
which is the recommended setting in most common usage
scenarios.
The maximum possible value is 4; currently, only the values 1 and 2 are actually supported.
Setting
NoOfReplicas
to 1
means that there is only a single copy of all Cluster
data; in this case, the loss of a single data node causes
the cluster to fail because there are no additional copies
of the data stored by that node.
The value for this parameter must divide evenly into the
number of data nodes in the cluster. For example, if there
are two data nodes, then
NoOfReplicas
must be
equal to either 1 or 2, since 2/3 and 2/4 both yield
fractional values; if there are four data nodes, then
NoOfReplicas
must be
equal to 1, 2, or 4.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | path | . | ... | IN |
This parameter specifies the directory where trace files, log files, pid files and error logs are placed.
The default is the data node process working directory.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | path | DataDir | ... | IN |
This parameter specifies the directory where all files
created for metadata, REDO logs, UNDO logs (for Disk Data
tables), and data files are placed. The default is the
directory specified by DataDir
.
This directory must exist before the ndbd process is initiated.
The recommended directory hierarchy for MySQL Cluster
includes /var/lib/mysql-cluster
, under
which a directory for the node's file system is created. The
name of this subdirectory contains the node ID. For example,
if the node ID is 2, this subdirectory is named
ndb_2_fs
.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | path | [see text] | ... | IN |
This parameter specifies the directory in which backups are placed.
The string '/BACKUP
' is always appended
to this value. For example, if you set the value of
BackupDataDir
to
/var/lib/cluster-data
, then all
backups are stored under
/var/lib/cluster-data/BACKUP
. This
also means that the effective default
backup location is the directory named
BACKUP
under the location specified
by the
FileSystemPath
parameter.
DataMemory
and
IndexMemory
are
[ndbd]
parameters specifying the size of
memory segments used to store the actual records and their
indexes. In setting values for these, it is important to
understand how
DataMemory
and
IndexMemory
are used, as
they usually need to be updated to reflect actual usage by the
cluster:
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 80M | 1M - 1024G | N |
This parameter defines the amount of space (in bytes) available for storing database records. The entire amount specified by this value is allocated in memory, so it is extremely important that the machine has sufficient physical memory to accommodate it.
The memory allocated by
DataMemory
is used
to store both the actual records and indexes. There is a
16-byte overhead on each record; an additional amount for
each record is incurred because it is stored in a 32KB page
with 128 byte page overhead (see below). There is also a
small amount wasted per page due to the fact that each
record is stored in only one page.
For variable-size table attributes, the data is stored on
separate data pages, allocated from
DataMemory
.
Variable-length records use a fixed-size part with an extra
overhead of 4 bytes to reference the variable-size part. The
variable-size part has 2 bytes overhead plus 2 bytes per
attribute.
The maximum record size is 14000 bytes.
The memory space defined by
DataMemory
is also
used to store ordered indexes, which use about 10 bytes per
record. Each table row is represented in the ordered index.
A common error among users is to assume that all indexes are
stored in the memory allocated by
IndexMemory
, but
this is not the case: Only primary key and unique hash
indexes use this memory; ordered indexes use the memory
allocated by
DataMemory
. However,
creating a primary key or unique hash index also creates an
ordered index on the same keys, unless you specify
USING HASH
in the index creation
statement. This can be verified by running ndb_desc
-d db_name
table_name
in the
management client.
Currently, MySQL Cluster can use a maximum of 512 MB for
hash indexes per partition, which means in some cases it is
possible to get Table is full errors
in MySQL client applications even when ndb_mgm -e
"ALL REPORT MEMORYUSAGE" shows significant free
DataMemory
. This can
also pose a problem with data node restarts on nodes that
are heavily loaded with data. You can force
NDB
to create extra partitions
for MySQL Cluster tables and thus have more memory available
for hash indexes by using the MAX_ROWS
option for CREATE TABLE
. In
general, setting MAX_ROWS
to twice the
number of rows that you expect to store in the table should
be sufficient. You can also use the
MinFreePct
configuration parameter to help avoid problems with node
restarts. (Bug #13436216)
The memory space allocated by
DataMemory
consists
of 32KB pages, which are allocated to table fragments. Each
table is normally partitioned into the same number of
fragments as there are data nodes in the cluster. Thus, for
each node, there are the same number of fragments as are set
in NoOfReplicas
.
Once a page has been allocated, it is currently not possible
to return it to the pool of free pages, except by deleting
the table. (This also means that
DataMemory
pages,
once allocated to a given table, cannot be used by other
tables.) Performing a data node recovery also compresses the
partition because all records are inserted into empty
partitions from other live nodes.
The DataMemory
memory space also contains UNDO information: For each
update, a copy of the unaltered record is allocated in the
DataMemory
. There is
also a reference to each copy in the ordered table indexes.
Unique hash indexes are updated only when the unique index
columns are updated, in which case a new entry in the index
table is inserted and the old entry is deleted upon commit.
For this reason, it is also necessary to allocate enough
memory to handle the largest transactions performed by
applications using the cluster. In any case, performing a
few large transactions holds no advantage over using many
smaller ones, for the following reasons:
Large transactions are not any faster than smaller ones
Large transactions increase the number of operations that are lost and must be repeated in event of transaction failure
Large transactions use more memory
The default value for
DataMemory
is 80MB;
the minimum is 1MB. There is no maximum size, but in reality
the maximum size has to be adapted so that the process does
not start swapping when the limit is reached. This limit is
determined by the amount of physical RAM available on the
machine and by the amount of memory that the operating
system may commit to any one process. 32-bit operating
systems are generally limited to 2−4GB per process;
64-bit operating systems can use more. For large databases,
it may be preferable to use a 64-bit operating system for
this reason.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 18M | 1M - 1T | N |
This parameter controls the amount of storage used for hash indexes in MySQL Cluster. Hash indexes are always used for primary key indexes, unique indexes, and unique constraints. When defining a primary key or a unique index, two indexes are created, one of which is a hash index used for all tuple accesses as well as lock handling. This index is also used to enforce unique constraints.
You can estimate the size of a hash index using this formula:
size = ( (fragments
* 32K) + (rows
* 18) ) *replicas
fragments
is the number of
fragments, replicas
is the number
of replicas (normally 2), and
rows
is the number of rows. If a
table has one million rows, 8 fragments, and 2 replicas, the
expected index memory usage is calculated as shown here:
((8 * 32K) + (1000000 * 18)) * 2 = ((8 * 32768) + (1000000 * 18)) * 2 = (262144 + 18000000) * 2 = 18262144 * 2 = 36524288 bytes = ~35MB
Index statistics for ordered indexes (when these are
enabled) are stored in the
mysql.ndb_index_stat_sample
table. Since
this table has a hash index, this adds to index memory
usage. An upper bound to the number of rows for a given
ordered index can be calculated as follows:
sample_size= key_size + ((key_attributes + 1) * 4) sample_rows =IndexStatSaveSize
* ((0.01 *IndexStatSaveScale
* log2(rows * sample_size)) + 1) / sample_size
In the preceding formula,
key_size
is the size of the
ordered index key in bytes,
key_attributes
is the number ot
attributes in the ordered index key, and
rows
is the number of rows in the
base table.
Assume that table t1
has 1 million rows
and an ordered index named ix1
on two
four-byte integers. Assume in addition that
IndexStatSaveSize
and
IndexStatSaveScale
are set to their default values (32K and 100, respectively).
Using the previous 2 formulas, we can calculate as follows:
sample_size = 8 + ((1 + 2) * 4) = 20 bytes sample_rows = 32K * ((0.01 * 100 * log2(1000000*20)) + 1) / 20 = 32768 * ( (1 * ~16.811) +1) / 20 = 32768 * ~17.811 / 20 = ~29182 rows
The expected index memory usage is thus 2 * 18 * 29182 = ~1050550 bytes.
The default value for
IndexMemory
is 18MB.
The minimum is 1MB.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | % or bytes | 25 | 0 - 4294967039 (0xFFFFFEFF) | S |
This parameter determines how much memory is allocated for
strings such as table names, and is specified in an
[ndbd]
or [ndbd
default]
section of the
config.ini
file. A value between
0
and 100
inclusive is
interpreted as a percent of the maximum default value, which
is calculated based on a number of factors including the
number of tables, maximum table name size, maximum size of
.FRM
files,
MaxNoOfTriggers
,
maximum column name size, and maximum default column value.
A value greater than 100
is interpreted
as a number of bytes.
The default value is 25—that is, 25 percent of the default maximum.
Under most circumstances, the default value should be
sufficient, but when you have a great many Cluster tables
(1000 or more), it is possible to get Error 773
Out of string memory, please modify StringMemory
config parameter: Permanent error: Schema error,
in which case you should increase this value.
25
(25 percent) is not excessive, and
should prevent this error from recurring in all but the most
extreme conditions.
The following example illustrates how memory is used for a table. Consider this table definition:
CREATE TABLE example ( a INT NOT NULL, b INT NOT NULL, c INT NOT NULL, PRIMARY KEY(a), UNIQUE(b) ) ENGINE=NDBCLUSTER;
For each record, there are 12 bytes of data plus 12 bytes
overhead. Having no nullable columns saves 4 bytes of overhead.
In addition, we have two ordered indexes on columns
a
and b
consuming roughly
10 bytes each per record. There is a primary key hash index on
the base table using roughly 29 bytes per record. The unique
constraint is implemented by a separate table with
b
as primary key and a
as
a column. This other table consumes an additional 29 bytes of
index memory per record in the example
table
as well 8 bytes of record data plus 12 bytes of overhead.
Thus, for one million records, we need 58MB for index memory to handle the hash indexes for the primary key and the unique constraint. We also need 64MB for the records of the base table and the unique index table, plus the two ordered index tables.
You can see that hash indexes takes up a fair amount of memory space; however, they provide very fast access to the data in return. They are also used in MySQL Cluster to handle uniqueness constraints.
Currently, the only partitioning algorithm is hashing and ordered indexes are local to each node. Thus, ordered indexes cannot be used to handle uniqueness constraints in the general case.
An important point for both
IndexMemory
and
DataMemory
is that the
total database size is the sum of all data memory and all index
memory for each node group. Each node group is used to store
replicated information, so if there are four nodes with two
replicas, there will be two node groups. Thus, the total data
memory available is 2 ×
DataMemory
for each data
node.
It is highly recommended that
DataMemory
and
IndexMemory
be set to
the same values for all nodes. Data distribution is even over
all nodes in the cluster, so the maximum amount of space
available for any node can be no greater than that of the
smallest node in the cluster.
DataMemory
and
IndexMemory
can be
changed, but decreasing either of these can be risky; doing so
can easily lead to a node or even an entire MySQL Cluster that
is unable to restart due to there being insufficient memory
space. Increasing these values should be acceptable, but it is
recommended that such upgrades are performed in the same manner
as a software upgrade, beginning with an update of the
configuration file, and then restarting the management server
followed by restarting each data node in turn.
MinFreePct.
A proportion (5% by default) of data node resources including
DataMemory
and
IndexMemory
is kept in
reserve to insure that the data node does not exhaust its
memory when performing a restart. This can be adjusted using
the MinFreePct
data
node configuration parameter (default 5).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 5 | 0 - 100 | N |
Updates do not increase the amount of index memory used. Inserts take effect immediately; however, rows are not actually deleted until the transaction is committed.
Transaction parameters.
The next few [ndbd]
parameters that we
discuss are important because they affect the number of
parallel transactions and the sizes of transactions that can
be handled by the system.
MaxNoOfConcurrentTransactions
sets the number of parallel transactions possible in a node.
MaxNoOfConcurrentOperations
sets the number of records that can be in update phase or
locked simultaneously.
Both of these parameters (especially
MaxNoOfConcurrentOperations
)
are likely targets for users setting specific values and not
using the default value. The default value is set for systems
using small transactions, to ensure that these do not use
excessive memory.
MaxDMLOperationsPerTransaction
sets the maximum number of DML operations that can be performed
in a given transaction.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 4096 | 32 - 4294967039 (0xFFFFFEFF) | N |
Each cluster data node requires a transaction record for each active transaction in the cluster. The task of coordinating transactions is distributed among all of the data nodes. The total number of transaction records in the cluster is the number of transactions in any given node times the number of nodes in the cluster.
Transaction records are allocated to individual MySQL servers. Each connection to a MySQL server requires at least one transaction record, plus an additional transaction object per table accessed by that connection. This means that a reasonable minimum for the total number of transactions in the cluster can be expressed as
MinTotalNoOfConcurrentTransactions = (maximum number of tables accessed in any single transaction + 1) * number of SQL nodes
Suppose that there are 10 SQL nodes using the cluster. A
single join involving 10 tables requires 11 transaction
records; if there are 10 such joins in a transaction, then
10 * 11 = 110 transaction records are required for this
transaction, per MySQL server, or 110 * 10 = 1100
transaction records total. Each data node can be expected to
handle MinTotalNoOfConcurrentTransactions / number of data
nodes. For a MySQL Cluster having 4 data nodes, this would
mean setting
MaxNoOfConcurrentTransactions
on each
data node to 1100 / 4 = 275. In addition, you should provide
for failure recovery by ensuring that a single node group
can accommodate all concurrent transactions; in other words,
that each data node's MaxNoOfConcurrentTransactions is
sufficient to cover a number of transactions equal to
MinTotalNoOfConcurrentTransactions / number of node groups.
If this cluster has a single node group, then
MaxNoOfConcurrentTransactions
should be
set to 1100 (the same as the total number of concurrent
transactions for the entire cluster).
In addition, each transaction involves at least one
operation; for this reason, the value set for
MaxNoOfConcurrentTransactions
should
always be no more than the value of
MaxNoOfConcurrentOperations
.
This parameter must be set to the same value for all cluster data nodes. This is due to the fact that, when a data node fails, the oldest surviving node re-creates the transaction state of all transactions that were ongoing in the failed node.
It is possible to change this value using a rolling restart, but the amount of traffic on the cluster must be such that no more transactions occur than the lower of the old and new levels while this is taking place.
The default value is 4096.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 32K | 32 - 4294967039 (0xFFFFFEFF) | N |
It is a good idea to adjust the value of this parameter according to the size and number of transactions. When performing transactions which involve only a few operations and records, the default value for this parameter is usually sufficient. Performing large transactions involving many records usually requires that you increase its value.
Records are kept for each transaction updating cluster data, both in the transaction coordinator and in the nodes where the actual updates are performed. These records contain state information needed to find UNDO records for rollback, lock queues, and other purposes.
This parameter should be set at a minimum to the number of
records to be updated simultaneously in transactions,
divided by the number of cluster data nodes. For example, in
a cluster which has four data nodes and which is expected to
handle one million concurrent updates using transactions,
you should set this value to 1000000 / 4 = 250000. To help
provide resiliency against failures, it is suggested that
you set this parameter to a value that is high enough to
permit an individual data node to handle the load for its
node group. In other words, you should set the value equal
to total number of concurrent operations / number
of node groups
. (In the case where there is a
single node group, this is the same as the total number of
concurrent operations for the entire cluster.)
Because each transaction always involves at least one
operation, the value of
MaxNoOfConcurrentOperations
should always
be greater than or equal to the value of
MaxNoOfConcurrentTransactions
.
Read queries which set locks also cause operation records to be created. Some extra space is allocated within individual nodes to accommodate cases where the distribution is not perfect over the nodes.
When queries make use of the unique hash index, there are actually two operation records used per record in the transaction. The first record represents the read in the index table and the second handles the operation on the base table.
The default value is 32768.
This parameter actually handles two values that can be configured separately. The first of these specifies how many operation records are to be placed with the transaction coordinator. The second part specifies how many operation records are to be local to the database.
A very large transaction performed on an eight-node cluster
requires as many operation records in the transaction
coordinator as there are reads, updates, and deletes
involved in the transaction. However, the operation records
of the are spread over all eight nodes. Thus, if it is
necessary to configure the system for one very large
transaction, it is a good idea to configure the two parts
separately.
MaxNoOfConcurrentOperations
will always be used to calculate the number of operation
records in the transaction coordinator portion of the node.
It is also important to have an idea of the memory requirements for operation records. These consume about 1KB per record.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | UNDEFINED | 32 - 4294967039 (0xFFFFFEFF) | N |
By default, this parameter is calculated as 1.1 ×
MaxNoOfConcurrentOperations
.
This fits systems with many simultaneous transactions, none
of them being very large. If there is a need to handle one
very large transaction at a time and there are many nodes,
it is a good idea to override the default value by
explicitly specifying this parameter.
MaxDMLOperationsPerTransaction
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | operations (DML) | 4294967295 | 32 - 4294967295 | N |
This parameter limits the size of a transaction. The
transaction is aborted if it requires more than this many
DML operations. The minimum number of operations per
transaction is 32; however, you can set
MaxDMLOperationsPerTransaction
to 0 to
disable any limitation on the number of DML operations per
transaction. The maximum (and default) is 4294967295.
Transaction temporary storage.
The next set of [ndbd]
parameters is used
to determine temporary storage when executing a statement that
is part of a Cluster transaction. All records are released
when the statement is completed and the cluster is waiting for
the commit or rollback.
The default values for these parameters are adequate for most situations. However, users with a need to support transactions involving large numbers of rows or operations may need to increase these values to enable better parallelism in the system, whereas users whose applications require relatively small transactions can decrease the values to save memory.
MaxNoOfConcurrentIndexOperations
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 8K | 0 - 4294967039 (0xFFFFFEFF) | N |
For queries using a unique hash index, another temporary set
of operation records is used during a query's execution
phase. This parameter sets the size of that pool of records.
Thus, this record is allocated only while executing a part
of a query. As soon as this part has been executed, the
record is released. The state needed to handle aborts and
commits is handled by the normal operation records, where
the pool size is set by the parameter
MaxNoOfConcurrentOperations
.
The default value of this parameter is 8192. Only in rare cases of extremely high parallelism using unique hash indexes should it be necessary to increase this value. Using a smaller value is possible and can save memory if the DBA is certain that a high degree of parallelism is not required for the cluster.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 4000 | 0 - 4294967039 (0xFFFFFEFF) | N |
The default value of
MaxNoOfFiredTriggers
is 4000, which is sufficient for most situations. In some
cases it can even be decreased if the DBA feels certain the
need for parallelism in the cluster is not high.
A record is created when an operation is performed that affects a unique hash index. Inserting or deleting a record in a table with unique hash indexes or updating a column that is part of a unique hash index fires an insert or a delete in the index table. The resulting record is used to represent this index table operation while waiting for the original operation that fired it to complete. This operation is short-lived but can still require a large number of records in its pool for situations with many parallel write operations on a base table containing a set of unique hash indexes.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 1M | 1K - 4294967039 (0xFFFFFEFF) | N |
The memory affected by this parameter is used for tracking operations fired when updating index tables and reading unique indexes. This memory is used to store the key and column information for these operations. It is only very rarely that the value for this parameter needs to be altered from the default.
The default value for
TransactionBufferMemory
is 1MB.
Normal read and write operations use a similar buffer, whose
usage is even more short-lived. The compile-time parameter
ZATTRBUF_FILESIZE
(found in
ndb/src/kernel/blocks/Dbtc/Dbtc.hpp
)
set to 4000 × 128 bytes (500KB). A similar buffer for
key information, ZDATABUF_FILESIZE
(also
in Dbtc.hpp
) contains 4000 × 16 =
62.5KB of buffer space. Dbtc
is the
module that handles transaction coordination.
Scans and buffering.
There are additional [ndbd]
parameters in
the Dblqh
module (in
ndb/src/kernel/blocks/Dblqh/Dblqh.hpp
)
that affect reads and updates. These include
ZATTRINBUF_FILESIZE
, set by default to
10000 × 128 bytes (1250KB) and
ZDATABUF_FILE_SIZE
, set by default to
10000*16 bytes (roughly 156KB) of buffer space. To date, there
have been neither any reports from users nor any results from
our own extensive tests suggesting that either of these
compile-time limits should be increased.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 256 | 2 - 500 | N |
This parameter is used to control the number of parallel
scans that can be performed in the cluster. Each transaction
coordinator can handle the number of parallel scans defined
for this parameter. Each scan query is performed by scanning
all partitions in parallel. Each partition scan uses a scan
record in the node where the partition is located, the
number of records being the value of this parameter times
the number of nodes. The cluster should be able to sustain
MaxNoOfConcurrentScans
scans concurrently from all nodes in the cluster.
Scans are actually performed in two cases. The first of these cases occurs when no hash or ordered indexes exists to handle the query, in which case the query is executed by performing a full table scan. The second case is encountered when there is no hash index to support the query but there is an ordered index. Using the ordered index means executing a parallel range scan. The order is kept on the local partitions only, so it is necessary to perform the index scan on all partitions.
The default value of
MaxNoOfConcurrentScans
is 256. The maximum value is 500.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | [see text] | 32 - 4294967039 (0xFFFFFEFF) | N |
Specifies the number of local scan records if many scans are not fully parallelized. When the number of local scan records is not provided, it is calculated as shown here:
4 * MaxNoOfConcurrentScans
* [# data nodes] + 2
The minimum value is 32.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 256 | 1 - 992 | N |
This parameter is used to calculate the number of lock records used to handle concurrent scan operations.
BatchSizePerLocalScan
has a strong
connection to the
BatchSize
defined in
the SQL nodes.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 64M | 512K - 4294967039 (0xFFFFFEFF) | N |
This is an internal buffer used for passing messages within individual nodes and between nodes. The default is 64MB.
This parameter seldom needs to be changed from the default.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 0 | 0 - 64 | S |
This parameter sets the parallelization used in the copy
phase of a node restart or system restart, when a node that
is currently just starting is synchronised with a node that
already has current data by copying over any changed records
from the node that is up to date. Because full parallelism
in such cases can lead to overload situations,
MaxParallelCopyInstances
provides a means
to decrease it. This parameter's default value 0. This
value means that the effective parallelism is equal to the
number of LDM instances in the node just starting as well as
the node updating it.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 256 | 1 - 4294967039 (0xFFFFFEFF) | N |
It is possible to configure the maximum number of parallel
scans (TUP
scans and
TUX
scans) allowed before they begin
queuing for serial handling. You can increase this to take
advantage of any unused CPU when performing large number of
scans in parallel and improve their performance.
The default value for this parameter is 256.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 32M | 1M - 1G | N |
This is the maximum size of the memory unit to use when
allocating memory for tables. In cases where
NDB
gives Out of
memory errors, but it is evident by examining the
cluster logs or the output of DUMP
1000
that all available memory has not yet been used,
you can increase the value of this parameter (or
MaxNoOfTables
, or both)
to cause NDB
to make sufficient
memory available.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | LDM threads | 3840 | 0 - 3840 | N |
The size of the table hash maps used by
NDB
is configurable using this
parameter. DefaultHashMapSize
can take any of
three possible values (0, 240, 3840). These values and their
effects are described in the following table:
Value | Description / Effect |
---|---|
0 | Use the lowest value set, if any, for this parameter among all data nodes and API nodes in the cluster; if it is not set on any data or API node, use the default value. |
240 | Original hash map size (used by default in all MySQL Cluster releases prior to NDB 7.2.7) |
3840 | Larger hash map size (used by default beginning with NDB 7.2.7) |
The original intended use for this parameter was to facilitate upgrades and especially downgrades to and from very old releases with differing default hash map sizes. This is not an issue when upgrading from MySQL Cluster NDB 7.4 to MySQL Cluster NDB 7.5.
Logging and checkpointing.
The following [ndbd]
parameters control log
and checkpoint behavior.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 16 | 3 - 4294967039 (0xFFFFFEFF) | IN |
This parameter sets the number of REDO log files for the node, and thus the amount of space allocated to REDO logging. Because the REDO log files are organized in a ring, it is extremely important that the first and last log files in the set (sometimes referred to as the “head” and “tail” log files, respectively) do not meet. When these approach one another too closely, the node begins aborting all transactions encompassing updates due to a lack of room for new log records.
A REDO
log record is not removed until
both required local checkpoints have been completed since
that log record was inserted. Checkpointing frequency is
determined by its own set of configuration parameters
discussed elsewhere in this chapter.
The default parameter value is 16, which by default means 16
sets of 4 16MB files for a total of 1024MB. The size of the
individual log files is configurable using the
FragmentLogFileSize
parameter. In scenarios requiring a great many updates, the
value for
NoOfFragmentLogFiles
may need to be set as high as 300 or even higher to provide
sufficient space for REDO logs.
If the checkpointing is slow and there are so many writes to
the database that the log files are full and the log tail
cannot be cut without jeopardizing recovery, all updating
transactions are aborted with internal error code 410
(Out of log file space temporarily
). This
condition prevails until a checkpoint has completed and the
log tail can be moved forward.
This parameter cannot be changed “on the
fly”; you must restart the node using
--initial
. If you wish to change this
value for all data nodes in a running cluster, you can do
so using a rolling node restart (using
--initial
when starting each data node).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 16M | 4M - 1G | IN |
Setting this parameter enables you to control directly the size of redo log files. This can be useful in situations when MySQL Cluster is operating under a high load and it is unable to close fragment log files quickly enough before attempting to open new ones (only 2 fragment log files can be open at one time); increasing the size of the fragment log files gives the cluster more time before having to open each new fragment log file. The default value for this parameter is 16M.
For more information about fragment log files, see the
description for
NoOfFragmentLogFiles
.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | [see values] | SPARSE | SPARSE, FULL | IN |
By default, fragment log files are created sparsely when
performing an initial start of a data node—that is,
depending on the operating system and file system in use,
not all bytes are necessarily written to disk. However, it
is possible to override this behavior and force all bytes to
be written, regardless of the platform and file system type
being used, by means of this parameter.
InitFragmentLogFiles
takes either of two values:
SPARSE
. Fragment log files are
created sparsely. This is the default value.
FULL
. Force all bytes of the fragment
log file to be written to disk.
Depending on your operating system and file system, setting
InitFragmentLogFiles=FULL
may help
eliminate I/O errors on writes to the REDO log.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 0 | 20 - 4294967039 (0xFFFFFEFF) | N |
This parameter sets a ceiling on how many internal threads to allocate for open files. Any situation requiring a change in this parameter should be reported as a bug.
The default value is 0. However, the minimum value to which this parameter can be set is 20.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | files | 27 | 20 - 4294967039 (0xFFFFFEFF) | N |
This parameter sets the initial number of internal threads to allocate for open files.
The default value is 27.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 25 | 0 - 4294967039 (0xFFFFFEFF) | N |
This parameter sets the maximum number of errors written in the error log as well as the maximum number of trace files that are kept before overwriting the existing ones. Trace files are generated when, for whatever reason, the node crashes.
The default is 25, which sets these maximums to 25 error messages and 25 trace files.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | seconds | 0 | 0 - 600 | N |
In parallel data node recovery, only table data is actually copied and synchronized in parallel; synchronization of metadata such as dictionary and checkpoint information is done in a serial fashion. In addition, recovery of dictionary and checkpoint information cannot be executed in parallel with performing of local checkpoints. This means that, when starting or restarting many data nodes concurrently, data nodes may be forced to wait while a local checkpoint is performed, which can result in longer node recovery times.
It is possible to force a delay in the local checkpoint to
permit more (and possibly all) data nodes to complete
metadata synchronization; once each data node's
metadata synchronization is complete, all of the data nodes
can recover table data in parallel, even while the local
checkpoint is being executed. To force such a delay, set
MaxLCPStartDelay
,
which determines the number of seconds the cluster can wait
to begin a local checkpoint while data nodes continue to
synchronize metadata. This parameter should be set in the
[ndbd default]
section of the
config.ini
file, so that it is the same
for all data nodes. The maximum value is 600; the default is
0.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | second | 60 | 0 - 4294967039 (0xFFFFFEFF) | N |
A local checkpoint fragment scan watchdog checks
periodically for no progress in each fragment scan performed
as part of a local checkpoint, and shuts down the node if
there is no progress after a given amount of time has
elapsed. This interval can be set using the
LcpScanProgressTimeout
data node configuration parameter, which sets the maximum
time for which the local checkpoint can be stalled before
the LCP fragment scan watchdog shuts down the node.
The default value is 60 seconds (providing compatibility with previous releases). Setting this parameter to 0 disables the LCP fragment scan watchdog altogether.
Metadata objects.
The next set of [ndbd]
parameters defines
pool sizes for metadata objects, used to define the maximum
number of attributes, tables, indexes, and trigger objects
used by indexes, events, and replication between clusters.
These act merely as “suggestions” to the cluster, and any that are not specified revert to the default values shown.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 1000 | 32 - 4294967039 (0xFFFFFEFF) | N |
This parameter sets a suggested maximum number of attributes
that can be defined in the cluster; like
MaxNoOfTables
, it is
not intended to function as a hard upper limit.
(In older MySQL Cluster releases, this parameter was
sometimes treated as a hard limit for certain operations.
This caused problems with MySQL Cluster Replication, when it
was possible to create more tables than could be replicated,
and sometimes led to confusion when it was possible [or not
possible, depending on the circumstances] to create more
than MaxNoOfAttributes
attributes.)
The default value is 1000, with the minimum possible value being 32. The maximum is 4294967039. Each attribute consumes around 200 bytes of storage per node due to the fact that all metadata is fully replicated on the servers.
When setting
MaxNoOfAttributes
,
it is important to prepare in advance for any
ALTER TABLE
statements that
you might want to perform in the future. This is due to the
fact, during the execution of ALTER
TABLE
on a Cluster table, 3 times the number of
attributes as in the original table are used, and a good
practice is to permit double this amount. For example, if
the MySQL Cluster table having the greatest number of
attributes
(greatest_number_of_attributes
)
has 100 attributes, a good starting point for the value of
MaxNoOfAttributes
would be 6 *
.
greatest_number_of_attributes
=
600
You should also estimate the average number of attributes
per table and multiply this by
MaxNoOfTables
. If
this value is larger than the value obtained in the previous
paragraph, you should use the larger value instead.
Assuming that you can create all desired tables without any
problems, you should also verify that this number is
sufficient by trying an actual ALTER
TABLE
after configuring the parameter. If this is
not successful, increase
MaxNoOfAttributes
by
another multiple of
MaxNoOfTables
and
test it again.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 128 | 8 - 20320 | N |
A table object is allocated for each table and for each
unique hash index in the cluster. This parameter sets a
suggested maximum number of table objects for the cluster as
a whole; like
MaxNoOfAttributes
,
it is not intended to function as a hard upper limit.
(In older MySQL Cluster releases, this parameter was
sometimes treated as a hard limit for certain operations.
This caused problems with MySQL Cluster Replication, when it
was possible to create more tables than could be replicated,
and sometimes led to confusion when it was possible [or not
possible, depending on the circumstances] to create more
than MaxNoOfTables
tables.)
For each attribute that has a
BLOB
data type an extra table
is used to store most of the
BLOB
data. These tables also
must be taken into account when defining the total number of
tables.
The default value of this parameter is 128. The minimum is 8 and the maximum is 20320. Each table object consumes approximately 20KB per node.
The sum of
MaxNoOfTables
and
MaxNoOfOrderedIndexes
must not exceed 232
− 2
(4294967294).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 128 | 0 - 4294967039 (0xFFFFFEFF) | N |
For each ordered index in the cluster, an object is
allocated describing what is being indexed and its storage
segments. By default, each index so defined also defines an
ordered index. Each unique index and primary key has both an
ordered index and a hash index.
MaxNoOfOrderedIndexes
sets the total number of ordered indexes that can be in use
in the system at any one time.
The default value of this parameter is 128. Each index object consumes approximately 10KB of data per node.
The sum of
MaxNoOfTables
and
MaxNoOfOrderedIndexes
must not exceed 232
− 2
(4294967294).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 768 | 0 - 4294967039 (0xFFFFFEFF) | N |
Internal update, insert, and delete triggers are allocated for each unique hash index. (This means that three triggers are created for each unique hash index.) However, an ordered index requires only a single trigger object. Backups also use three trigger objects for each normal table in the cluster.
Replication between clusters also makes use of internal triggers.
This parameter sets the maximum number of trigger objects in the cluster.
The default value is 768.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
Each NDB
table in a MySQL
Cluster requires a subscription in the NDB kernel. For some
NDB API applications, it may be necessary or desirable to
change this parameter. However, for normal usage with MySQL
servers acting as SQL nodes, there is not any need to do so.
The default value for
MaxNoOfSubscriptions
is 0, which is treated as equal to
MaxNoOfTables
. Each
subscription consumes 108 bytes.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
This parameter is of interest only when using MySQL Cluster
Replication. The default value is 0, which is treated as
2 * MaxNoOfTables
; that is, there is one
subscription per NDB
table for
each of two MySQL servers (one acting as the replication
master and the other as the slave). Each subscriber uses 16
bytes of memory.
When using circular replication, multi-master replication,
and other replication setups involving more than 2 MySQL
servers, you should increase this parameter to the number of
mysqld processes included in replication
(this is often, but not always, the same as the number of
clusters). For example, if you have a circular replication
setup using three MySQL Clusters, with one
mysqld attached to each cluster, and each
of these mysqld processes acts as a
master and as a slave, you should set
MaxNoOfSubscribers
equal to 3 * MaxNoOfTables
.
For more information, see Section 19.6, “MySQL Cluster Replication”.
MaxNoOfConcurrentSubOperations
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 256 | 0 - 4294967039 (0xFFFFFEFF) | N |
This parameter sets a ceiling on the number of operations that can be performed by all API nodes in the cluster at one time. The default value (256) is sufficient for normal operations, and might need to be adjusted only in scenarios where there are a great many API nodes each performing a high volume of operations concurrently.
Boolean parameters.
The behavior of data nodes is also affected by a set of
[ndbd]
parameters taking on boolean values.
These parameters can each be specified as
TRUE
by setting them equal to
1
or Y
, and as
FALSE
by setting them equal to
0
or N
.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | numeric | 1 | 0 - 1 | N |
Allocate memory for this data node after a connection to the management server has been established. Enabled by default.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | numeric | 0 | 0 - 2 | N |
For a number of operating systems, including Solaris and Linux, it is possible to lock a process into memory and so avoid any swapping to disk. This can be used to help guarantee the cluster's real-time characteristics.
This parameter takes one of the integer values
0
, 1
, or
2
, which act as shown in the following
list:
0
: Disables locking. This is the
default value.
1
: Performs the lock after allocating
memory for the process.
2
: Performs the lock before memory
for the process is allocated.
If the operating system is not configured to permit
unprivileged users to lock pages, then the data node process
making use of this parameter may have to be run as system
root.
(LockPagesInMainMemory
uses the mlockall
function. From Linux
kernel 2.6.9, unprivileged users can lock memory as limited
by max locked memory
. For more
information, see ulimit -l and
http://linux.die.net/man/2/mlock).
In older MySQL Cluster releases, this parameter was a
Boolean. 0
or false
was the default setting, and disabled locking.
1
or true
enabled
locking of the process after its memory was allocated.
MySQL Cluster NDB 7.5 treats true
or
false
for the value of this parameter
as an error.
Beginning with glibc
2.10,
glibc
uses per-thread arenas to reduce
lock contention on a shared pool, which consumes real
memory. In general, a data node process does not need
per-thread arenas, since it does not perform any memory
allocation after startup. (This difference in allocators
does not appear to affect performance significantly.)
The glibc
behavior is intended to be
configurable via the MALLOC_ARENA_MAX
environment variable, but a bug in this mechanism prior to
glibc
2.16 meant that this variable
could not be set to less than 8, so that the wasted memory
could not be reclaimed. (Bug #15907219; see also
http://sourceware.org/bugzilla/show_bug.cgi?id=13137
for more information concerning this issue.)
One possible workaround for this problem is to use the
LD_PRELOAD
environment variable to
preload a jemalloc
memory allocation
library to take the place of that supplied with
glibc
.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | 1 | 0, 1 | N |
This parameter specifies whether a data node process should exit or perform an automatic restart when an error condition is encountered.
This parameter's default value is 1
;
this means that, by default, an error causes the data node
process to halt.
Users of MySQL Cluster Manager should note that, when
StopOnError
equals 1, this prevents the
MySQL Cluster Manager agent from restarting any data nodes after it has
performed its own restart and recovery. See
Starting and Stopping the Agent on Linux, for more
information.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | true | true, false | S |
When this parameter is enabled, it forces a data node to shut down whenever it encounters a corrupted tuple. In MySQL Cluster NDB 7.5, it is enabled by default.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | true|false (1|0) | false | true, false | IS |
It is possible to specify MySQL Cluster tables as diskless, meaning that tables are not checkpointed to disk and that no logging occurs. Such tables exist only in main memory. A consequence of using diskless tables is that neither the tables nor the records in those tables survive a crash. However, when operating in diskless mode, it is possible to run ndbd on a diskless computer.
This feature causes the entire cluster to operate in diskless mode.
When this feature is enabled, Cluster online backup is disabled. In addition, a partial start of the cluster is not possible.
Diskless
is disabled
by default.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | false | true, false | N |
Enabling this parameter causes
NDB
to attempt using
O_DIRECT
writes for LCP, backups, and
redo logs, often lowering kswapd and CPU
usage. When using MySQL Cluster on Linux, enable
ODirect
if you are
using a 2.6 or later kernel.
ODirect
is disabled
by default.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | error code | 2 | 0 - 4 | N |
This feature is accessible only when building the debug version where it is possible to insert errors in the execution of individual blocks of code as part of testing.
This feature is disabled by default.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | false | true, false | N |
Setting this parameter to 1
causes backup
files to be compressed. The compression used is equivalent
to gzip --fast, and can save 50% or more
of the space required on the data node to store uncompressed
backup files. Compressed backups can be enabled for
individual data nodes, or for all data nodes (by setting
this parameter in the [ndbd default]
section of the config.ini
file).
You cannot restore a compressed backup to a cluster running a MySQL version that does not support this feature.
The default value is 0
(disabled).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | false | true, false | N |
Setting this parameter to 1
causes local
checkpoint files to be compressed. The compression used is
equivalent to gzip --fast, and can save
50% or more of the space required on the data node to store
uncompressed checkpoint files. Compressed LCPs can be
enabled for individual data nodes, or for all data nodes (by
setting this parameter in the [ndbd
default]
section of the
config.ini
file).
You cannot restore a compressed local checkpoint to a cluster running a MySQL version that does not support this feature.
The default value is 0
(disabled).
There are a number of [ndbd]
parameters
specifying timeouts and intervals between various actions in
Cluster data nodes. Most of the timeout values are specified in
milliseconds. Any exceptions to this are mentioned where
applicable.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 6000 | 70 - 4294967039 (0xFFFFFEFF) | N |
To prevent the main thread from getting stuck in an endless loop at some point, a “watchdog” thread checks the main thread. This parameter specifies the number of milliseconds between checks. If the process remains in the same state after three checks, the watchdog thread terminates it.
This parameter can easily be changed for purposes of experimentation or to adapt to local conditions. It can be specified on a per-node basis although there seems to be little reason for doing so.
The default timeout is 6000 milliseconds (6 seconds).
TimeBetweenWatchDogCheckInitial
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 6000 | 70 - 4294967039 (0xFFFFFEFF) | N |
This is similar to the
TimeBetweenWatchDogCheck
parameter, except that
TimeBetweenWatchDogCheckInitial
controls the amount of time that passes between execution
checks inside a database node in the early start phases
during which memory is allocated.
The default timeout is 6000 milliseconds (6 seconds).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 30000 | 0 - 4294967039 (0xFFFFFEFF) | N |
This parameter specifies how long the Cluster waits for all data nodes to come up before the cluster initialization routine is invoked. This timeout is used to avoid a partial Cluster startup whenever possible.
This parameter is overridden when performing an initial start or initial restart of the cluster.
The default value is 30000 milliseconds (30 seconds). 0 disables the timeout, in which case the cluster may start only if all nodes are available.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 60000 | 0 - 4294967039 (0xFFFFFEFF) | N |
If the cluster is ready to start after waiting for
StartPartialTimeout
milliseconds but is still possibly in a partitioned state,
the cluster waits until this timeout has also passed. If
StartPartitionedTimeout
is set to 0, the cluster waits indefinitely.
This parameter is overridden when performing an initial start or initial restart of the cluster.
The default timeout is 60000 milliseconds (60 seconds).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
If a data node has not completed its startup sequence within the time specified by this parameter, the node startup fails. Setting this parameter to 0 (the default value) means that no data node timeout is applied.
For nonzero values, this parameter is measured in milliseconds. For data nodes containing extremely large amounts of data, this parameter should be increased. For example, in the case of a data node containing several gigabytes of data, a period as long as 10−15 minutes (that is, 600000 to 1000000 milliseconds) might be required to perform a node restart.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 15000 | 0 - 4294967039 (0xFFFFFEFF) | N |
When a data node is configured with
Nodegroup = 65536
,
is regarded as not being assigned to any node group. When
that is done, the cluster waits
StartNoNodegroupTimeout
milliseconds,
then treats such nodes as though they had been added to the
list passed to the
--nowait-nodes
option, and
starts. The default value is 15000
(that
is, the management server waits 15 seconds). Setting this
parameter equal to 0
means that the
cluster waits indefinitely.
StartNoNodegroupTimeout
must be the same
for all data nodes in the cluster; for this reason, you
should always set it in the [ndbd
default]
section of the
config.ini
file, rather than for
individual data nodes.
See Section 19.5.14, “Adding MySQL Cluster Data Nodes Online”, for more information.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 5000 | 10 - 4294967039 (0xFFFFFEFF) | N |
One of the primary methods of discovering failed nodes is by the use of heartbeats. This parameter states how often heartbeat signals are sent and how often to expect to receive them. After missing three heartbeat intervals in a row, the node is declared dead. Thus, the maximum time for discovering a failure through the heartbeat mechanism is four times the heartbeat interval.
The default heartbeat interval is 5000 milliseconds (5 seconds). This parameter must not be changed drastically and should not vary widely between nodes. If one node uses 5000 milliseconds and the node watching it uses 1000 milliseconds, obviously the node will be declared dead very quickly. This parameter can be changed during an online software upgrade, but only in small increments.
See also Network communication and latency.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 1500 | 100 - 4294967039 (0xFFFFFEFF) | N |
Each data node sends heartbeat signals to each MySQL server
(SQL node) to ensure that it remains in contact. If a MySQL
server fails to send a heartbeat in time it is declared
“dead,” in which case all ongoing transactions
are completed and all resources released. The SQL node
cannot reconnect until all activities initiated by the
previous MySQL instance have been completed. The
three-heartbeat criteria for this determination are the same
as described for
HeartbeatIntervalDbDb
.
The default interval is 1500 milliseconds (1.5 seconds). This interval can vary between individual data nodes because each data node watches the MySQL servers connected to it, independently of all other data nodes.
For more information, see Network communication and latency.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | numeric | 0 | 0 - 65535 | S |
Data nodes send heartbeats to one another in a circular fashion whereby each data node monitors the previous one. If a heartbeat is not detected by a given data node, this node declares the previous data node in the circle “dead” (that is, no longer accessible by the cluster). The determination that a data node is dead is done globally; in other words; once a data node is declared dead, it is regarded as such by all nodes in the cluster.
It is possible for heartbeats between data nodes residing on different hosts to be too slow compared to heartbeats between other pairs of nodes (for example, due to a very low heartbeat interval or temporary connection problem), such that a data node is declared dead, even though the node can still function as part of the cluster. .
In this type of situation, it may be that the order in which heartbeats are transmitted between data nodes makes a difference as to whether or not a particular data node is declared dead. If this declaration occurs unnecessarily, this can in turn lead to the unnecessary loss of a node group and as thus to a failure of the cluster.
Consider a setup where there are 4 data nodes A, B, C, and D
running on 2 host computers host1
and
host2
, and that these data nodes make up
2 node groups, as shown in the following table:
Node Group |
Nodes Running on | Nodes Running on host2 |
---|---|---|
Node Group 0: | Node A | Node B |
Node Group 1: | Node C | Node D |
Suppose the heartbeats are transmitted in the order A->B->C->D->A. In this case, the loss of the heartbeat between the hosts causes node B to declare node A dead and node C to declare node B dead. This results in loss of Node Group 0, and so the cluster fails. On the other hand, if the order of transmission is A->B->D->C->A (and all other conditions remain as previously stated), the loss of the heartbeat causes nodes A and D to be declared dead; in this case, each node group has one surviving node, and the cluster survives.
The HeartbeatOrder
configuration parameter makes the order of heartbeat
transmission user-configurable. The default value for
HeartbeatOrder
is
zero; allowing the default value to be used on all data
nodes causes the order of heartbeat transmission to be
determined by NDB
. If this parameter is
used, it must be set to a nonzero value (maximum 65535) for
every data node in the cluster, and this value must be
unique for each data node; this causes the heartbeat
transmission to proceed from data node to data node in the
order of their
HeartbeatOrder
values from lowest to highest (and then directly from the
data node having the highest
HeartbeatOrder
to
the data node having the lowest value, to complete the
circle). The values need not be consecutive; for example, to
force the heartbeat transmission order
A->B->D->C->A in the scenario outlined
previously, you could set the
HeartbeatOrder
values as shown here:
Node | HeartbeatOrder |
---|---|
A | 10 |
B | 20 |
C | 30 |
D | 25 |
To use this parameter to change the heartbeat transmission
order in a running MySQL Cluster, you must first set
HeartbeatOrder
for
each data node in the cluster in the global configuration
(config.ini
) file (or files). To cause
the change to take effect, you must perform either of the
following:
A complete shutdown and restart of the entire cluster.
2 rolling restarts of the cluster in succession. All nodes must be restarted in the same order in both rolling restarts.
You can use DUMP 908
to
observe the effect of this parameter in the data node logs.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
This parameter enables connection checking between data
nodes. A data node that fails to respond within an interval
of ConnectCheckIntervalDelay
milliseconds
is considered suspect, and is considered dead after two such
intervals.
The default value for this parameter is 0.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | number of 4-byte words, as a base-2 logarithm | 20 | 0 - 31 | N |
This parameter is an exception in that it does not specify a time to wait before starting a new local checkpoint; rather, it is used to ensure that local checkpoints are not performed in a cluster where relatively few updates are taking place. In most clusters with high update rates, it is likely that a new local checkpoint is started immediately after the previous one has been completed.
The size of all write operations executed since the start of the previous local checkpoints is added. This parameter is also exceptional in that it is specified as the base-2 logarithm of the number of 4-byte words, so that the default value 20 means 4MB (4 × 220) of write operations, 21 would mean 8MB, and so on up to a maximum value of 31, which equates to 8GB of write operations.
All the write operations in the cluster are added together.
Setting
TimeBetweenLocalCheckpoints
to 6 or less means that local checkpoints will be executed
continuously without pause, independent of the cluster's
workload.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 2000 | 20 - 32000 | N |
When a transaction is committed, it is committed in main memory in all nodes on which the data is mirrored. However, transaction log records are not flushed to disk as part of the commit. The reasoning behind this behavior is that having the transaction safely committed on at least two autonomous host machines should meet reasonable standards for durability.
It is also important to ensure that even the worst of cases—a complete crash of the cluster—is handled properly. To guarantee that this happens, all transactions taking place within a given interval are put into a global checkpoint, which can be thought of as a set of committed transactions that has been flushed to disk. In other words, as part of the commit process, a transaction is placed in a global checkpoint group. Later, this group's log records are flushed to disk, and then the entire group of transactions is safely committed to disk on all computers in the cluster.
This parameter defines the interval between global checkpoints. The default is 2000 milliseconds.
TimeBetweenGlobalCheckpointsTimeout
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 120000 | 10 - 4294967039 (0xFFFFFEFF) | N |
This parameter defines the minimum timeout between global checkpoints. The default is 120000 milliseconds.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 100 | 0 - 32000 | N |
This parameter defines the interval between synchronization epochs for MySQL Cluster Replication. The default value is 100 milliseconds.
TimeBetweenEpochs
is
part of the implementation of “micro-GCPs”,
which can be used to improve the performance of MySQL
Cluster Replication.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 0 | 0 - 256000 | N |
This parameter defines a timeout for synchronization epochs for MySQL Cluster Replication. If a node fails to participate in a global checkpoint within the time determined by this parameter, the node is shut down. The default value is 0; in other words, the timeout is disabled.
TimeBetweenEpochsTimeout
is part of the implementation of “micro-GCPs”,
which can be used to improve the performance of MySQL
Cluster Replication.
The current value of this parameter and a warning are written to the cluster log whenever a GCP save takes longer than 1 minute or a GCP save takes longer than 10 seconds.
Setting this parameter to zero has the effect of disabling GCP stops caused by save timeouts, commit timeouts, or both. The maximum possible value for this parameter is 256000 milliseconds.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | epochs | 100 | 0 - 100000 | N |
The number of unprocessed epochs by which a subscribing node can lag behind. Exceeding this number causes a lagging subscriber to be disconnected.
The default value of 100 is sufficient for most normal
operations. If a subscribing node does lag enough to cause
disconnections, it is usually due to network or scheduling
issues with regard to processes or threads. (In rare
circumstances, the problem may be due to a bug in the
NDB
client.) It may be
desirable to set the value lower than the default when
epochs are longer.
Disconnection prevents client issues from affecting the data node service, running out of memory to buffer data, and eventually shutting down. Instead, only the client is affected as a result of the disconnect (by, for example gap events in the binary log), forcing the client to reconnect or restart the process.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 26214400 | 26214400 (0x01900000) - 4294967039 (0xFFFFFEFF) | N |
The total number of bytes allocated for buffering epochs by this node.
TimeBetweenInactiveTransactionAbortCheck
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 1000 | 1000 - 4294967039 (0xFFFFFEFF) | N |
Timeout handling is performed by checking a timer on each transaction once for every interval specified by this parameter. Thus, if this parameter is set to 1000 milliseconds, every transaction will be checked for timing out once per second.
The default value is 1000 milliseconds (1 second).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | [see text] | 0 - 4294967039 (0xFFFFFEFF) | N |
This parameter states the maximum time that is permitted to lapse between operations in the same transaction before the transaction is aborted.
The default for this parameter is 4G
(also the maximum). For a real-time database that needs to
ensure that no transaction keeps locks for too long, this
parameter should be set to a relatively small value. The
unit is milliseconds.
TransactionDeadlockDetectionTimeout
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 1200 | 50 - 4294967039 (0xFFFFFEFF) | N |
When a node executes a query involving a transaction, the node waits for the other nodes in the cluster to respond before continuing. A failure to respond can occur for any of the following reasons:
The node is “dead”
The operation has entered a lock queue
The node requested to perform the action could be heavily overloaded.
This timeout parameter states how long the transaction coordinator waits for query execution by another node before aborting the transaction, and is important for both node failure handling and deadlock detection.
The default timeout value is 1200 milliseconds (1.2 seconds).
The minimum for this parameter is 50 milliseconds.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 4M | 32K - 4294967039 (0xFFFFFEFF) | N |
This is the maximum number of bytes to store before flushing
data to a local checkpoint file. This is done to prevent
write buffering, which can impede performance significantly.
This parameter is not intended to take
the place of
TimeBetweenLocalCheckpoints
.
When ODirect
is
enabled, it is not necessary to set
DiskSyncSize
; in
fact, in such cases its value is simply ignored.
The default value is 4M (4 megabytes).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | numeric | 20M | 1M - 1024G | S |
Set the maximum rate for writing to disk, in bytes per second, by local checkpoints and backup operations when no restarts (by this data node or any other data node) are taking place in this MySQL Cluster.
For setting the maximum rate of disk writes allowed while
this data node is restarting, use
MaxDiskWriteSpeedOwnRestart
.
For setting the maximum rate of disk writes allowed while
other data nodes are restarting, use
MaxDiskWriteSpeedOtherNodeRestart
.
The minimum speed for disk writes by all LCPs and backup
operations can be adjusted by setting
MinDiskWriteSpeed
.
MaxDiskWriteSpeedOtherNodeRestart
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | numeric | 50M | 1M - 1024G | S |
Set the maximum rate for writing to disk, in bytes per second, by local checkpoints and backup operations when one or more data nodes in this MySQL Cluster are restarting, other than this node.
For setting the maximum rate of disk writes allowed while
this data node is restarting, use
MaxDiskWriteSpeedOwnRestart
.
For setting the maximum rate of disk writes allowed when no
data nodes are restarting anywhere in the cluster, use
MaxDiskWriteSpeed
.
The minimum speed for disk writes by all LCPs and backup
operations can be adjusted by setting
MinDiskWriteSpeed
.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | numeric | 200M | 1M - 1024G | S |
Set the maximum rate for writing to disk, in bytes per second, by local checkpoints and backup operations while this data node is restarting.
For setting the maximum rate of disk writes allowed while
other data nodes are restarting, use
MaxDiskWriteSpeedOtherNodeRestart
.
For setting the maximum rate of disk writes allowed when no
data nodes are restarting anywhere in the cluster, use
MaxDiskWriteSpeed
.
The minimum speed for disk writes by all LCPs and backup
operations can be adjusted by setting
MinDiskWriteSpeed
.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | numeric | 10M | 1M - 1024G | S |
Set the minimum rate for writing to disk, in bytes per second, by local checkpoints and backup operations.
The maximum rates of disk writes allowed for LCPs and
backups under various conditions are adjustable using the
parameters
MaxDiskWriteSpeed
,
MaxDiskWriteSpeedOwnRestart
,
and
MaxDiskWriteSpeedOtherNodeRestart
.
See the descriptions of these parameters for more
information.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 7500 | 10 - 4294967039 (0xFFFFFEFF) | N |
This parameter specifies how long data nodes wait for a response from the arbitrator to an arbitration message. If this is exceeded, the network is assumed to have split.
The default value is 7500 milliseconds (7.5 seconds).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | enumeration | Default | Default, Disabled, WaitExternal | N |
The Arbitration
parameter enables a choice of arbitration schemes,
corresponding to one of 3 possible values for this
parameter:
Default.
This enables arbitration to proceed normally, as
determined by the ArbitrationRank
settings for the management and API nodes. This is the
default value.
Disabled.
Setting Arbitration = Disabled
in
the [ndbd default]
section of the
config.ini
file to accomplishes
the same task as setting
ArbitrationRank
to 0 on all
management and API nodes. When
Arbitration
is set in this way, any
ArbitrationRank
settings are
ignored.
WaitExternal.
The
Arbitration
parameter also makes it possible to configure
arbitration in such a way that the cluster waits until
after the time determined by
ArbitrationTimeout
has passed for an external cluster manager application
to perform arbitration instead of handling arbitration
internally. This can be done by setting
Arbitration = WaitExternal
in the
[ndbd default]
section of the
config.ini
file. For best results
with the WaitExternal
setting, it
is recommended that
ArbitrationTimeout
be 2 times as long as the interval required by the
external cluster manager to perform arbitration.
This parameter should be used only in the [ndbd
default]
section of the cluster configuration
file. The behavior of the cluster is unspecified when
Arbitration
is set
to different values for individual data nodes.
RestartSubscriberConnectTimeout
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | ms | 12000 | 0 - 4294967039 (0xFFFFFEFF) | S |
This parameter determines the time that a data node waits
for subscribing API nodes to connect. Once this timeout
expires, any “missing” API nodes are
disconnected from the cluster. To disable this timeout, set
RestartSubscriberConnectTimeout
to 0.
While this parameter is specified in milliseconds, the timeout itself is resolved to the next-greatest whole second.
Buffering and logging.
Several [ndbd]
configuration parameters
enable the advanced user to have more control over the
resources used by node processes and to adjust various buffer
sizes at need.
These buffers are used as front ends to the file system when
writing log records to disk. If the node is running in diskless
mode, these parameters can be set to their minimum values
without penalty due to the fact that disk writes are
“faked” by the NDB
storage engine's file system abstraction layer.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 2M | 1M - 4294967039 (0xFFFFFEFF) | N |
The UNDO index buffer, whose size is set by this parameter,
is used during local checkpoints. The
NDB
storage engine uses a
recovery scheme based on checkpoint consistency in
conjunction with an operational REDO log. To produce a
consistent checkpoint without blocking the entire system for
writes, UNDO logging is done while performing the local
checkpoint. UNDO logging is activated on a single table
fragment at a time. This optimization is possible because
tables are stored entirely in main memory.
The UNDO index buffer is used for the updates on the primary key hash index. Inserts and deletes rearrange the hash index; the NDB storage engine writes UNDO log records that map all physical changes to an index page so that they can be undone at system restart. It also logs all active insert operations for each fragment at the start of a local checkpoint.
Reads and updates set lock bits and update a header in the hash index entry. These changes are handled by the page-writing algorithm to ensure that these operations need no UNDO logging.
This buffer is 2MB by default. The minimum value is 1MB,
which is sufficient for most applications. For applications
doing extremely large or numerous inserts and deletes
together with large transactions and large primary keys, it
may be necessary to increase the size of this buffer. If
this buffer is too small, the NDB storage engine issues
internal error code 677 (Index UNDO buffers
overloaded
).
It is not safe to decrease the value of this parameter during a rolling restart.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 16M | 1M - 4294967039 (0xFFFFFEFF) | N |
This parameter sets the size of the UNDO data buffer, which performs a function similar to that of the UNDO index buffer, except the UNDO data buffer is used with regard to data memory rather than index memory. This buffer is used during the local checkpoint phase of a fragment for inserts, deletes, and updates.
Because UNDO log entries tend to grow larger as more operations are logged, this buffer is also larger than its index memory counterpart, with a default value of 16MB.
This amount of memory may be unnecessarily large for some applications. In such cases, it is possible to decrease this size to a minimum of 1MB.
It is rarely necessary to increase the size of this buffer. If there is such a need, it is a good idea to check whether the disks can actually handle the load caused by database update activity. A lack of sufficient disk space cannot be overcome by increasing the size of this buffer.
If this buffer is too small and gets congested, the NDB storage engine issues internal error code 891 (Data UNDO buffers overloaded).
It is not safe to decrease the value of this parameter during a rolling restart.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 32M | 1M - 4294967039 (0xFFFFFEFF) | N |
All update activities also need to be logged. The REDO log makes it possible to replay these updates whenever the system is restarted. The NDB recovery algorithm uses a “fuzzy” checkpoint of the data together with the UNDO log, and then applies the REDO log to play back all changes up to the restoration point.
RedoBuffer
sets the size of the buffer in
which the REDO log is written. The default value is 32MB;
the minimum value is 1MB.
If this buffer is too small, the
NDB
storage engine issues error
code 1221 (REDO log buffers
overloaded). For this reason, you should
exercise care if you attempt to decrease the value of
RedoBuffer
as part of an online change in
the cluster's configuration.
ndbmtd allocates a separate buffer for
each LDM thread (see
ThreadConfig
). For
example, with 4 LDM threads, an ndbmtd
data node actually has 4 buffers and allocates
RedoBuffer
bytes to each one, for a total
of 4 * RedoBuffer
bytes.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 8192 | 0 - 64K | S |
Controls the size of the circular buffer used for NDB log events within data nodes.
Controlling log messages.
In managing the cluster, it is very important to be able to
control the number of log messages sent for various event
types to stdout
. For each event category,
there are 16 possible event levels (numbered 0 through 15).
Setting event reporting for a given event category to level 15
means all event reports in that category are sent to
stdout
; setting it to 0 means that there
will be no event reports made in that category.
By default, only the startup message is sent to
stdout
, with the remaining event reporting
level defaults being set to 0. The reason for this is that these
messages are also sent to the management server's cluster log.
An analogous set of levels can be set for the management client to determine which event levels to record in the cluster log.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 1 | 0 - 15 | N |
The reporting level for events generated during startup of the process.
The default level is 1.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 0 | 0 - 15 | N |
The reporting level for events generated as part of graceful shutdown of a node.
The default level is 0.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 0 | 0 - 15 | N |
The reporting level for statistical events such as number of primary key reads, number of updates, number of inserts, information relating to buffer usage, and so on.
The default level is 0.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | log level | 0 | 0 - 15 | N |
The reporting level for events generated by local and global checkpoints.
The default level is 0.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 0 | 0 - 15 | N |
The reporting level for events generated during node restart.
The default level is 0.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 0 | 0 - 15 | N |
The reporting level for events generated by connections between cluster nodes.
The default level is 0.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 0 | 0 - 15 | N |
The reporting level for events generated by errors and warnings by the cluster as a whole. These errors do not cause any node failure but are still considered worth reporting.
The default level is 0.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | levelr | 0 | 0 - 15 | N |
The reporting level for events generated by congestion. These errors do not cause node failure but are still considered worth reporting.
The default level is 0.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 0 | 0 - 15 | N |
The reporting level for events generated for information about the general state of the cluster.
The default level is 0.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
This parameter controls how often data node memory usage reports are recorded in the cluster log; it is an integer value representing the number of seconds between reports.
Each data node's data memory and index memory usage is
logged as both a percentage and a number of 32 KB pages of
the DataMemory
and
IndexMemory
,
respectively, set in the config.ini
file. For example, if
DataMemory
is equal
to 100 MB, and a given data node is using 50 MB for data
memory storage, the corresponding line in the cluster log
might look like this:
2006-12-24 01:18:16 [MgmSrvr] INFO -- Node 2: Data usage is 50%(1280 32K pages of total 2560)
MemReportFrequency
is not a required parameter. If used, it can be set for all
cluster data nodes in the [ndbd default]
section of config.ini
, and can also be
set or overridden for individual data nodes in the
corresponding [ndbd]
sections of the
configuration file. The minimum value—which is also
the default value—is 0, in which case memory reports
are logged only when memory usage reaches certain
percentages (80%, 90%, and 100%), as mentioned in the
discussion of statistics events in
Section 19.5.6.2, “MySQL Cluster Log Events”.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | seconds | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
When a data node is started with the
--initial
, it initializes the
redo log file during Start Phase 4 (see
Section 19.5.1, “Summary of MySQL Cluster Start Phases”). When very
large values are set for
NoOfFragmentLogFiles
,
FragmentLogFileSize
,
or both, this initialization can take a long time.You can
force reports on the progress of this process to be logged
periodically, by means of the
StartupStatusReportFrequency
configuration parameter. In this case, progress is reported
in the cluster log, in terms of both the number of files and
the amount of space that have been initialized, as shown
here:
2009-06-20 16:39:23 [MgmSrvr] INFO -- Node 1: Local redo log file initialization status: #Total files: 80, Completed: 60 #Total MBytes: 20480, Completed: 15557 2009-06-20 16:39:23 [MgmSrvr] INFO -- Node 2: Local redo log file initialization status: #Total files: 80, Completed: 60 #Total MBytes: 20480, Completed: 15570
These reports are logged each
StartupStatusReportFrequency
seconds during Start Phase 4. If
StartupStatusReportFrequency
is 0 (the default), then reports are written to the cluster
log only when at the beginning and at the completion of the
redo log file initialization process.
Data Node Debugging Parameters.
It is also possible to cause logging of traces for events
generated by creating and dropping tables using
DictTrace
. This
parameter is useful only in debugging NDB kernel code.
DictTrace
takes an
integer value. 0 (default - no logging) and 1 (logging
enabled) are the only supported values prior to MySQL Cluster
NDB 7.5.2. In MySQL Cluster NDB 7.5.2 and later, setting this
parameter to 2 enables logging of additional
DBDICT
debugging output (Bug #20368450).
Backup parameters.
The [ndbd]
parameters discussed in this
section define memory buffers set aside for execution of
online backups.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 16M | 512K - 4294967039 (0xFFFFFEFF) | N |
NDB 7.5.0 | bytes | 16M | 2M - 4294967039 (0xFFFFFEFF) | N |
NDB 7.5.1 | bytes | 16M | 512K - 4294967039 (0xFFFFFEFF) | N |
In creating a backup, there are two buffers used for sending
data to the disk. The backup data buffer is used to fill in
data recorded by scanning a node's tables. Once this buffer
has been filled to the level specified as
BackupWriteSize
, the
pages are sent to disk. While flushing data to disk, the
backup process can continue filling this buffer until it
runs out of space. When this happens, the backup process
pauses the scan and waits until some disk writes have
completed freeing up memory so that scanning may continue.
The default value for this parameter is 16MB. The minimum was changed from 2M to 512K in MySQL Cluster NDB 7.5.1. (Bug #22749509)
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | percent | 50 | 0 - 90 | N |
During normal operation, data nodes attempt to maximize the
disk write speed used for local checkpoints and backups
while remaining within the bounds set by
MinDiskWriteSpeed
and
MaxDiskWriteSpeed
.
Disk write throttling gives each LDM thread an equal share
of the total budget. This allows parallel LCPs to take place
without exceeding the disk I/O budget. Because a backup is
executed by only one LDM thread, this effectively caused a
budget cut, resulting in longer backup completion times,
and—if the rate of change is sufficiently
high—in failure to complete the backup when the backup
log buffer fill rate is higher than the achievable write
rate.
This problem can be addressed by using the
BackupDiskWriteSpeedPct
configuration
parameter, which takes a value in the range 0-90 (inclusive)
which is interpreted as the percentage of the node's
maximum write rate budget that is reserved prior to sharing
out the remainder of the budget among LDM threads for LCPs.
The LDM thread running the backup receives the whole write
rate budget for the backup, plus its (reduced) share of the
write rate budget for local checkpoints. (This makes the
disk write rate budget behave similarly to how it was
handled in MySQL Cluster NDB 7.3 and earlier.)
The default value for this parameter is 50 (interpreted as 50%).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 16M | 2M - 4294967039 (0xFFFFFEFF) | N |
The backup log buffer fulfills a role similar to that played by the backup data buffer, except that it is used for generating a log of all table writes made during execution of the backup. The same principles apply for writing these pages as with the backup data buffer, except that when there is no more space in the backup log buffer, the backup fails. For that reason, the size of the backup log buffer must be large enough to handle the load caused by write activities while the backup is being made. See Section 19.5.3.3, “Configuration for MySQL Cluster Backups”.
The default value for this parameter should be sufficient for most applications. In fact, it is more likely for a backup failure to be caused by insufficient disk write speed than it is for the backup log buffer to become full. If the disk subsystem is not configured for the write load caused by applications, the cluster is unlikely to be able to perform the desired operations.
It is preferable to configure cluster nodes in such a manner that the processor becomes the bottleneck rather than the disks or the network connections.
The default value for this parameter is 16MB.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 32M | 0 - 4294967039 (0xFFFFFEFF) | N |
This parameter is deprecated, and subject to removal in a future version of MySQL Cluster. Any setting made for it is ignored.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | seconds | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
This parameter controls how often backup status reports are
issued in the management client during a backup, as well as
how often such reports are written to the cluster log
(provided cluster event logging is configured to permit
it—see
Logging and checkpointing).
BackupReportFrequency
represents the time in seconds between backup status
reports.
The default value is 0.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 256K | 32K - 4294967039 (0xFFFFFEFF) | N |
This parameter specifies the default size of messages written to disk by the backup log and backup data buffers.
The default value for this parameter is 256KB.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 1M | 256K - 4294967039 (0xFFFFFEFF) | N |
This parameter specifies the maximum size of messages written to disk by the backup log and backup data buffers.
The default value for this parameter is 1MB.
When specifying these parameters, the following relationships must hold true. Otherwise, the data node will be unable to start.
BackupDataBufferSize >= BackupWriteSize +
188KB
BackupLogBufferSize >= BackupWriteSize +
16KB
BackupMaxWriteSize >= BackupWriteSize
The [ndbd]
parameters discussed in this
section are used in scheduling and locking of threads to
specific CPUs on multiprocessor data node hosts.
To make use of these parameters, the data node process must be run as system root.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | CPU ID | 64K | 0 - 64K | N |
When used with ndbd, this parameter (now
a string) specifies the ID of the CPU assigned to handle the
NDBCLUSTER
execution thread.
When used with ndbmtd, the value of this
parameter is a comma-separated list of CPU IDs assigned to
handle execution threads. Each CPU ID in the list should be
an integer in the range 0 to 65535 (inclusive).
The number of IDs specified should match the number of
execution threads determined by
MaxNoOfExecutionThreads
.
However, there is no guarantee that threads are assigned to
CPUs in any given order when using this parameter. You can
obtain more finely-grained control of this type using
ThreadConfig
.
LockExecuteThreadToCPU
has no default value.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | CPU ID | [none] | 0 - 64K | N |
This parameter specifies the ID of the CPU assigned to
handle NDBCLUSTER
maintenance
threads.
The value of this parameter is an integer in the range 0 to 65535 (inclusive). There is no default value.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | false | true, false | N |
Setting this parameter to 1 enables real-time scheduling of data node threads.
The default is 0 (scheduling disabled).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | µs | 50 | 0 - 11000 | N |
This parameter specifies the time in microseconds for threads to be executed in the scheduler before being sent. Setting it to 0 minimizes the response time; to achieve higher throughput, you can increase the value at the expense of longer response times.
The default is 50 μsec, which our testing shows to increase throughput slightly in high-load cases without materially delaying requests.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 5 | 0 - 10 | S |
Set the balance in the NDB
scheduler
between speed and throughput. This parameter takes an
integer whose value is in the range 0-10 inclusive, with 5
as the default. Higher values provide better response times
relative to throughput. Lower values provide increased
throughput at the expense of longer response times.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | µs | 0 | 0 - 500 | N |
This parameter specifies the time in microseconds for threads to be executed in the scheduler before sleeping.
The default value is 0.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | numeric | 0 | 0 - 128 | S |
This parameter determines the number of threads to create
when rebuilding ordered indexes during a system or node
start, as well as when running
ndb_restore
--rebuild-indexes
. It is
supported only when there is more than one fragment for the
table per data node (for example, when the
MAX_ROWS
option has been used with
CREATE TABLE
).
Setting this parameter to 0 (the default) disables multi-threaded building of ordered indexes.
This parameter is supported when using ndbd or ndbmtd.
You can enable multi-threaded builds during data node
initial restarts by setting the
TwoPassInitialNodeRestartCopy
data node configuration parameter to
TRUE
.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | false | true, false | N |
Multi-threaded building of ordered indexes can be enabled
for initial restarts of data nodes by setting this
configuration parameter to TRUE
, which
enables two-pass copying of data during initial node
restarts.
You must also set
BuildIndexThreads
to
a nonzero value.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | 1 | ... | N |
This parameter determines whether Non-Uniform Memory Access
(NUMA) is controlled by the operating or by the data node
process, whether the data node uses ndbd
or ndbmtd. By default,
NDB
attempts to use an interleaved NUMA
memory allocation policy on any data node where the host
operating system provides NUMA support.
Setting Numa = 0
means that the datanode
process does not itself attempt to set a policy for memory
allocation, and permits this behavior to be determined by
the operating system, which may be further guided by the
separate numactl tool. That is,
Numa = 0
yields the system default
behavior, which can be customised by
numactl. For many Linux systems, the
system default behavior is to allocate socket-local memory
to any given process at allocation time. This can be
problematic when using ndbmtd; this is
because nbdmtd allocates all memory at
startup, leading to an imbalance, giving different access
speeds for different sockets, especially when locking pages
in main memory.
Setting Numa = 1
means that the data node
process uses libnuma
to request
interleaved memory allocation. (This can also be
accomplished manually, on the operating system level, using
numactl.) Using interleaved allocation in
effect tells the data node process to ignore non-uniform
memory access but does not attempt to take any advantage of
fast local memory; instead, the data node process tries to
avoid imbalances due to slow remote memory. If interleaved
allocation is not desired, set Numa
to 0
so that the desired behavior can be determined on the
operating system level.
The Numa
configuration parameter is
supported only on Linux systems where
libnuma.so
is available.
Multi-Threading Configuration Parameters (ndbmtd).
ndbmtd runs by default as a single-threaded
process and must be configured to use multiple threads, using
either of two methods, both of which require setting
configuration parameters in the
config.ini
file. The first method is
simply to set an appropriate value for the
MaxNoOfExecutionThreads
configuration parameter. A second method, makes it possible to
set up more complex rules for ndbmtd
multi-threading using
ThreadConfig
. The
next few paragraphs provide information about these parameters
and their use with multi-threaded data nodes.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 2 | 2 - 72 | IS |
This parameter directly controls the number of execution
threads used by ndbmtd, up to a maximum
of 72. Although this parameter is set in
[ndbd]
or [ndbd
default]
sections of the
config.ini
file, it is exclusive to
ndbmtd and does not apply to
ndbd.
Setting MaxNoOfExecutionThreads
sets the
number of threads for each type as determined by a matrix in
the file
storage/ndb/src/kernel/vm/mt_thr_config.cpp
.
This table shows these numbers of threads for possible
values of MaxNoOfExecutionThreads
.
MaxNoOfExecutionThreads Value | LDM Threads | TC Threads | Send Threads | Receive Threads |
---|---|---|---|---|
0 .. 3 | 1 | 1 | 0 | 1 |
4 .. 6 | 2 | 1 | 0 | 1 |
7 .. 8 | 4 | 1 | 0 | 1 |
9 | 4 | 2 | 0 | 1 |
10 | 4 | 2 | 1 | 1 |
11 | 4 | 3 | 1 | 1 |
12 | 6 | 2 | 1 | 1 |
13 | 6 | 3 | 1 | 1 |
14 | 6 | 3 | 1 | 2 |
15 | 6 | 3 | 2 | 2 |
16 | 8 | 3 | 1 | 2 |
17 | 8 | 4 | 1 | 2 |
18 | 8 | 4 | 2 | 2 |
19 | 8 | 5 | 2 | 2 |
20 | 10 | 4 | 2 | 2 |
21 | 10 | 5 | 2 | 2 |
22 | 10 | 5 | 2 | 3 |
23 | 10 | 6 | 2 | 3 |
24 | 12 | 5 | 2 | 3 |
25 | 12 | 6 | 2 | 3 |
26 | 12 | 6 | 3 | 3 |
27 | 12 | 7 | 3 | 3 |
28 | 12 | 7 | 3 | 4 |
29 | 12 | 8 | 3 | 4 |
30 | 12 | 8 | 4 | 4 |
31 | 12 | 9 | 4 | 4 |
32 | 16 | 8 | 3 | 3 |
33 | 16 | 8 | 3 | 4 |
34 | 16 | 8 | 4 | 4 |
35 | 16 | 9 | 4 | 4 |
36 | 16 | 10 | 4 | 4 |
37 | 16 | 10 | 4 | 5 |
38 | 16 | 11 | 4 | 5 |
39 | 16 | 11 | 5 | 5 |
40 | 20 | 10 | 4 | 4 |
41 | 20 | 10 | 4 | 5 |
42 | 20 | 11 | 4 | 5 |
43 | 20 | 11 | 5 | 5 |
44 | 20 | 12 | 5 | 5 |
45 | 20 | 12 | 5 | 6 |
46 | 20 | 13 | 5 | 6 |
47 | 20 | 13 | 6 | 6 |
48 | 24 | 12 | 5 | 5 |
49 | 24 | 12 | 5 | 6 |
50 | 24 | 13 | 5 | 6 |
51 | 24 | 13 | 6 | 6 |
52 | 24 | 14 | 6 | 6 |
53 | 24 | 14 | 6 | 7 |
54 | 24 | 15 | 6 | 7 |
55 | 24 | 15 | 7 | 7 |
56 | 24 | 16 | 7 | 7 |
57 | 24 | 16 | 7 | 8 |
58 | 24 | 17 | 7 | 8 |
59 | 24 | 17 | 8 | 8 |
60 | 24 | 18 | 8 | 8 |
61 | 24 | 18 | 8 | 9 |
62 | 24 | 19 | 8 | 9 |
63 | 24 | 19 | 9 | 9 |
64 | 32 | 16 | 7 | 7 |
65 | 32 | 16 | 7 | 8 |
66 | 32 | 17 | 7 | 8 |
67 | 32 | 17 | 8 | 8 |
68 | 32 | 18 | 8 | 8 |
69 | 32 | 18 | 8 | 9 |
70 | 32 | 19 | 8 | 9 |
71 | 32 | 20 | 8 | 9 |
72 | 32 | 20 | 8 | 10 |
There is always one SUMA (replication) thread.
The number of LDM threads must not exceed
NoOfFragmentLogParts
.
If this parameter's value is the default (4), this
means that you must increase it as well, when setting
MaxNoOfExecutionThreads
to 16 or greater;
that is, you should set
NoOfFragmentLogParts
to the corresponding
number of LDM threads value shown for that value of
MaxNoOfExecutionThreads
in the preceding
table.
The thread types are described later in this section (see
ThreadConfig
).
Setting this parameter outside the permitted range of values
causes the management server to abort on startup with the
error Error line
number
: Illegal value
value
for parameter
MaxNoOfExecutionThreads.
For MaxNoOfExecutionThreads
, a value of 0
or 1 is rounded up internally by
NDB
to 2, so that 2 is
considered this parameter's default and minimum value.
MaxNoOfExecutionThreads
is generally
intended to be set equal to the number of CPU threads
available, and to allocate a number of threads of each type
suitable to typical workloads. It does not assign particular
threads to specified CPUs. For cases where it is desirable
to vary from the settings provided, or to bind threads to
CPUs, you should use
ThreadConfig
instead, which allows you to allocate each thread directly
to a desired type, CPU, or both.
The multi-threaded data node process always spawns, at a minimum, the threads listed here:
1 local query handler (LDM) thread
1 transaction coordinator (TC) thread
1 receive thread
1 subscription manager (SUMA or replication) thread
Changing the number of LDM threads always requires a system
restart, whether it is changed using this parameter or
ThreadConfig
. If
the cluster's
IndexMemory
usage is
greater than 50%, changing this requires an initial restart
of the cluster. (A maximum of 30-35%
IndexMemory
usage is recommended in such
cases.) Otherwise, resource usage and LDM thread allocation
cannot be balanced between nodes, which can result in
underutilized and overutilized LDM threads, and ultimately
data node failures.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | numeric | 4 | 4, 8, 12, 16, 24, 32 | IN |
Set the number of log file groups for redo logs belonging to this ndbmtd. The maximum value is 32; the value set must be an even multiple of 4.
The number of LQH threads used by ndbmtd
must not exceed NoOfFragmentLogParts
, and
this number may increase when increasing
MaxNoOfExecutionThreads
;
see the description of this parameter for more information.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | string | '' | ... | IS |
This parameter is used with ndbmtd to assign threads of different types to different CPUs. Its value is a string whose format has the following syntax:
ThreadConfig :=entry
[,entry
[,...]]entry
:=type
={param
[,param
[,...]]}type
:= ldm | main | recv | send | rep | io | tc | watchdogparam
:= count=number
| cpubind=cpu_list
| cpuset=cpu_list
| spintime=number
| realtime={0|1} | thread_prio={0..10} | cpubind_exclusive=cpu_list
| cpuset_exclusive=cpu_list
The curly braces
({
...}
) surrounding
the list of parameters are required, even if there is only
one parameter in the list.
A param
(parameter) specifies any
or all of the following information:
The number of threads of the given type
(count
).
The set of CPUs to which the threads of the given type
are to be nonexclusively bound. Thsi is determined by
either one of cpubind
or
cpuset
). cpubind
causes each thread to be bound (nonexclusively) to a CPU
in the set; cpuset
means that each
thread is bound (nonexclusively) to the set of CPUs
specified.
On Solaris, you can instead specify a set of CPUs to
which the threads of the given type are to be bound
exclusively. cpubind_exclusive
causes
each thread to be bound exclusively to a CPU in the set;
cpuset_exclsuive
means that each
thread is bound exclusively to the set of CPUs
specified.
Only one of cpubind
,
cpuset
,
cpubind_exclusive
, or
cpuset_exclusive
can be provided in a
single configuration.
spintime
determines the wait time in
microseconds the thread spins before going to sleep.
The default value for spintime
is the
value of the
SchedulerSpinTimer
data node configuration parameter.
spintime
does not apply to I/O
threads or watchdog threads and so cannot be set for
these thread types.
realtime
can be set to 0 or 1. If it
is set to 1, the threads run with real-time priority.
This also means that thread_prio
cannot be set.
The realtime
parameter is set by
default to the value of the
RealtimeScheduler
data node configuration parameter.
thread_prio
is a thread priority
level that can be set from 0 to 10, with 10 representing
the greatest priority. The default is 5. The precise
effects of this parameter are platform-specific, and are
described later in this section.
thread_prio settings and effects by platform.
The implementation of thread_prio
differs between Linux/FreeBSD, Solaris, and Windows. In
the following list, we discuss its effects on each of
these platforms in turn:
Linux and FreeBSD: We map
thread_prio
to a value to be supplied
to the nice
system call. Since a
lower niceness value for a process indicates a higher
process priority, increasing
thread_prio
has the effect of
lowering the nice
value.
thread_prio value | nice value |
---|---|
0 | 19 |
1 | 16 |
2 | 12 |
3 | 8 |
4 | 4 |
5 | 0 |
6 | -4 |
7 | -8 |
8 | -12 |
9 | -16 |
10 | -20 |
Some operating systems may provide for a maximum process
niceness level of 20, but this is not supported by all
targeted versions; for this reason, we choose 19 as the
maximum nice
value that can be set.
Solaris: Setting
thread_prio
on Solaris sets the
Solaris FX priority, with mappings as shown in the
following table:
thread_prio value | Solaris FX priority |
---|---|
0 | 15 |
1 | 20 |
2 | 25 |
3 | 30 |
4 | 35 |
5 | 40 |
6 | 45 |
7 | 50 |
8 | 55 |
9 | 59 |
10 | 60 |
A thread_prio
setting of 9 is mapped
on Solaris to the special FX priority value 59, which
means that the operating system also attempts to force
the thread to run alone on its own CPU core.
Windows: We map
thread_prio
to a Windows thread
priority value passed to the Windows API
SetThreadPriority()
function. This
mapping is shown in the following table:
thread_prio value | Windows thread priority |
---|---|
0 - 1 | THREAD_PRIORITY_LOWEST |
2 - 3 | THREAD_PRIORITY_BELOW_NORMAL |
4 - 5 | THREAD_PRIORITY_NORMAL |
6 - 7 | THREAD_PRIORITY_ABOVE_NORMAL |
8 - 10 | THREAD_PRIORITY_HIGHEST |
The type
attribute represents an
NDB thread type. The thread types supported, and the range
of permitted count
values for each, are
provided in the following list:
ldm
: Local query handler
(DBLQH
kernel block) that handles
data. The more LDM threads that are used, the more
highly partitioned the data becomes. Each LDM thread
maintains its own sets of data and index partitions, as
well as its own redo log. The value set for
ldm
must be one of the values 1, 2,
4, 6, 8, 12, 16, 24, or 32.
Changing the number of LDM threads requires a system
restart to be effective and safe for cluster
operations. (This is also true when this is done using
MaxNoOfExecutionThreads
.)
If IndexMemory
usage is in excess of 50%, an initial restart of the
cluster is required; a maximum of 30-35%
IndexMemory
usage is recommended in
such cases. Otherwise, IndexMemory
and DataMemory
usage as well as the allocation of LDM threads cannot
be balanced between nodes, which can ultimately lead
to data node failures.
tc
: Transaction coordinator thread
(DBTC
kernel block) containing the
state of an ongoing transaction. The maximum number of
TC threads is 32.
Optimally, every new transaction can be assigned to a new TC thread. In most cases 1 TC thread per 2 LDM threads is sufficient to guarantee that this can happen. In cases where the number of writes is relatively small when compared to the number of reads, it is possible that only 1 TC thread per 4 LQH threads is required to maintain transaction states. Conversely, in applications that perform a great many updates, it may be necessary for the ratio of TC threads to LDM threads to approach 1 (for example, 3 TC threads to 4 LDM threads).
Range: 1 - 32
main
: Data dictionary and transaction
coordinator (DBDIH
and
DBTC
kernel blocks), providing schema
management. This is always handled by a single dedicated
thread.
Range: 1 only.
recv
: Receive thread
(CMVMI
kernel block). Each receive
thread handles one or more sockets for communicating
with other nodes in a MySQL Cluster, with one socket per
node. MySQL Cluster supports multiple receive threads;
the maximum is 16 such threads.
Range: 1 - 16
send
: Send thread
(CMVMI
kernel block). To increase
throughput, it is possible to perform sends from one or
more separate, dedicated threads (maximum 8).
Previously, all threads handled their own sending
directly; this can still be made to happen by setting
the number of send threads to 0 (this also happens when
MaxNoOfExecutionThreads
is set less than 10). While doing so can have an
adeverse impact on throughput, it can also in some cases
provide decreased latency.
Range: 0 - 16
rep
: Replication thread
(SUMA
kernel block). Asynchronous
replication operations are always handled by a single,
dedicated thread.
Range: 1 only.
io
: File system and other
miscellaneous operations. These are not demanding tasks,
and are always handled as a group by a single, dedicated
I/O thread.
Range: 1 only.
watchdog
: Settings to this parameter
are actually applied to several threads of this type
having specific uses. These threads include the
SocketServer
thread which receives
connection setups from other nodes, the
SocketClient
thread which attempts to
set up connections to other nodes, and the thread
watchdog thread that checks that threads are
progressing.
Range: 1 only.
Simple examples:
# Example 1. ThreadConfig=ldm={count=2,cpubind=1,2},main={cpubind=12},rep={cpubind=11} # Example 2. Threadconfig=main={cpubind=0},ldm={count=4,cpubind=1,2,5,6},io={cpubind=3}
It is usually desirable when configuring thread usage for a data
node host to reserve one or more number of CPUs for operating
system and other tasks. Thus, for a host machine with 24 CPUs,
you might want to use 20 CPU threads (leaving 4 for other uses),
with 8 LDM threads, 4 TC threads (half the number of LDM
threads), 3 send threads, 3 receive threads, and 1 thread each
for schema management, asynchronous replication, and I/O
operations. (This is almost the same distribution of threads
used when
MaxNoOfExecutionThreads
is set equal to 20.) The following
ThreadConfig
setting performs these
assignments, additionally binding all of these threads to
specific CPUs:
ThreadConfig=ldm{count=8,cpubind=1,2,3,4,5,6,7,8},main={cpubind=9},io={cpubind=9}, \ rep={cpubind=10},tc{count=4,cpubind=11,12,13,14},recv={count=3,cpubind=15,16,17}, \ send{count=3,cpubind=18,19,20}
It should be possible in most cases to bind the main (schema management) thread and the I/O thread to the same CPU, as we have done in the example just shown.
The following example incorporates groups of CPUs defined using
both cpuset
and cpubind
,
as well as use of thread prioritization.
ThreadConfig=ldm={count=4,cpuset=0-3,thread_prio=8,spintime=200}, \ ldm={count=4,cpubind=4-7,thread_prio=8,spintime=200}, \ tc={count=4,cpuset=8-9,thread_prio=6},send={count=2,thread_prio=10,cpubind=10-11}, \ main={count=1,cpubind=10},rep={count=1,cpubind=11}
In this case we create two LDM groups; the first uses
cpubind
and the second uses
cpuset
. thread_prio
and
spintime
are set to the same values for each
group. This means there are eight LDM threads in total. (You
should ensure that
NoOfFragmentLogParts
is also set to 8.) The four TC threads use only two CPUs; it is
possible when using cpuset
to specify fewer
CPUs than threads in the group. (This is not true for
cpubind
.) The send threads use two threads
using cpubind
to bind these threads to CPUs
10 and 11. The main and rep threads can reuse these CPUs.
This example shows how ThreadConfig
and
NoOfFragmentLogParts
might be set up for a
24-CPU host with hyperthreading, leaving CPUs 10, 11, 22, and 23
available for operating system functions and interrupts:
NoOfFragmentLogParts=10 ThreadConfig=ldm={count=10,cpubind=0-4,12-16,thread_prio=9,spintime=200}, \ tc={count=4,cpuset=6-7,18-19,thread_prio=8},send={count=1,cpuset=8}, \ recv={count=1,cpuset=20},main={count=1,cpuset=9,21},rep={count=1,cpuset=9,21}, \ io={count=1,cpuset=9,21,thread_prio=8},watchdog={count=1,cpuset=9,21,thread_prio=9}
In order to take advantage of the enhanced stability that the
use of ThreadConfig
offers, it is necessary
to insure that CPUs are isolated, and that they not subject to
interrupts, or to being scheduled for other tasks by the
operating system. On many Linux systems, you can do this by
setting IRQBALANCE_BANNED_CPUS
in
/etc/sysconfig/irqbalance
to
0xFFFFF0
, and by using the
isolcpus
boot option in
grub.conf
. For specific information, see
your operating system or platform documentation.
Disk Data Configuration Parameters. Configuration parameters affecting Disk Data behavior include the following:
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | 32K pages | 10 | 1 - 1000 | N |
This is the number of page entries (page references) to
allocate. It is specified as a number of 32K pages in
DiskPageBufferMemory
.
The default is sufficient for most cases but you may need to
increase the value of this parameter if you encounter
problems with very large transactions on Disk Data tables.
Each page entry requires approximately 100 bytes.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 64M | 4M - 1T | N |
This determines the amount of space used for caching pages
on disk, and is set in the [ndbd]
or
[ndbd default]
section of the
config.ini
file. It is measured in
bytes. Each page takes up 32 KB. This means that MySQL
Cluster Disk Data storage always uses
N
* 32 KB memory where
N
is some nonnegative integer.
The default value for this parameter is
64M
(2000 pages of 32 KB each).
You can query the
ndbinfo.diskpagebuffer
table to help determine whether the value for this parameter
should be increased to minimize unnecessary disk seeks. See
Section 19.5.10.18, “The ndbinfo diskpagebuffer Table”, for
more information.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 128M | 0 - 64T | N |
This parameter determines the amount of memory that is used
for log buffers, disk operations (such as page requests and
wait queues), and metadata for tablespaces, log file groups,
UNDO
files, and data files. The shared
global memory pool also provides memory used for satisfying
the memory requirements of the
UNDO_BUFFER_SIZE
option used with
CREATE LOGFILE GROUP
and
ALTER LOGFILE GROUP
statements, including any default value implied for this
options by the setting of the
InitialLogFileGroup
data node configuration parameter.
SharedGlobalMemory
can be set in the
[ndbd]
or [ndbd
default]
section of the
config.ini
configuration file, and is
measured in bytes.
The default value is 128M
.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | threads | 2 | 0 - 4294967039 (0xFFFFFEFF) | N |
This parameter determines the number of unbound threads used
for Disk Data file access. Before
DiskIOThreadPool
was
introduced, exactly one thread was spawned for each Disk
Data file, which could lead to performance issues,
particularly when using very large data files. With
DiskIOThreadPool
,
you can—for example—access a single large data
file using several threads working in parallel.
This parameter applies to Disk Data I/O threads only.
The optimum value for this parameter depends on your hardware and configuration, and includes these factors:
Physical distribution of Disk Data files.
You can obtain better performance by placing data
files, undo log files, and the data node file system
on separate physical disks. If you do this with some
or all of these sets of files, then you can set
DiskIOThreadPool
higher to enable separate threads to handle the files
on each disk.
Disk performance and types.
The number of threads that can be accommodated for
Disk Data file handling is also dependent on the speed
and throughput of the disks. Faster disks and higher
throughput allow for more disk I/O threads. Our test
results indicate that solid-state disk drives can
handle many more disk I/O threads than conventional
disks, and thus higher values for
DiskIOThreadPool
.
The default value for this parameter is 2.
Disk Data file system parameters. The parameters in the following list make it possible to place MySQL Cluster Disk Data files in specific directories without the need for using symbolic links.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | filename | [see text] | ... | IN |
If this parameter is specified, then MySQL Cluster Disk
Data data files and undo log files are placed in the
indicated directory. This can be overridden for data
files, undo log files, or both, by specifying values for
FileSystemPathDataFiles
,
FileSystemPathUndoFiles
,
or both, as explained for these parameters. It can also
be overridden for data files by specifying a path in the
ADD DATAFILE
clause of a
CREATE TABLESPACE
or
ALTER TABLESPACE
statement, and for undo log files by specifying a path
in the ADD UNDOFILE
clause of a
CREATE LOGFILE GROUP
or
ALTER LOGFILE GROUP
statement. If
FileSystemPathDD
is not specified, then
FileSystemPath
is used.
If a
FileSystemPathDD
directory is specified for a given data node (including
the case where the parameter is specified in the
[ndbd default]
section of the
config.ini
file), then starting
that data node with --initial
causes
all files in the directory to be deleted.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | filename | [see text] | ... | IN |
If this parameter is specified, then MySQL Cluster Disk
Data data files are placed in the indicated directory.
This overrides any value set for
FileSystemPathDD
.
This parameter can be overridden for a given data file
by specifying a path in the ADD
DATAFILE
clause of a
CREATE TABLESPACE
or
ALTER TABLESPACE
statement used to create that data file. If
FileSystemPathDataFiles
is not specified, then
FileSystemPathDD
is used (or
FileSystemPath
,
if
FileSystemPathDD
has also not been set).
If a
FileSystemPathDataFiles
directory is specified for a given data node (including
the case where the parameter is specified in the
[ndbd default]
section of the
config.ini
file), then starting
that data node with --initial
causes
all files in the directory to be deleted.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | filename | [see text] | ... | IN |
If this parameter is specified, then MySQL Cluster Disk
Data undo log files are placed in the indicated
directory. This overrides any value set for
FileSystemPathDD
.
This parameter can be overridden for a given data file
by specifying a path in the ADD UNDO
clause of a CREATE LOGFILE
GROUP
or ALTER LOGFILE
GROUP
statement used to create that data file.
If
FileSystemPathUndoFiles
is not specified, then
FileSystemPathDD
is used (or
FileSystemPath
,
if
FileSystemPathDD
has also not been set).
If a
FileSystemPathUndoFiles
directory is specified for a given data node (including
the case where the parameter is specified in the
[ndbd default]
section of the
config.ini
file), then starting
that data node with --initial
causes
all files in the directory to be deleted.
For more information, see Section 19.5.13.1, “MySQL Cluster Disk Data Objects”.
Disk Data object creation parameters. The next two parameters enable you—when starting the cluster for the first time—to cause a Disk Data log file group, tablespace, or both, to be created without the use of SQL statements.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | string | [see text] | ... | S |
This parameter can be used to specify a log file group
that is created when performing an initial start of the
cluster.
InitialLogFileGroup
is specified as shown here:
InitialLogFileGroup = [name=name
;] [undo_buffer_size=size
;]file-specification-list
file-specification-list
:file-specification
[;file-specification
[; ...]]file-specification
:filename
:size
The name
of the log file group is
optional and defaults to DEFAULT-LG
.
The undo_buffer_size
is also
optional; if omitted, it defaults to
64M
. Each
file-specification
corresponds to an undo log file, and at least one must
be specified in the
file-specification-list
. Undo
log files are placed according to any values that have
been set for
FileSystemPath
,
FileSystemPathDD
,
and
FileSystemPathUndoFiles
,
just as if they had been created as the result of a
CREATE LOGFILE GROUP
or
ALTER LOGFILE GROUP
statement.
Consider the following:
InitialLogFileGroup = name=LG1; undo_buffer_size=128M; undo1.log:250M; undo2.log:150M
This is equivalent to the following SQL statements:
CREATE LOGFILE GROUP LG1 ADD UNDOFILE 'undo1.log' INITIAL_SIZE 250M UNDO_BUFFER_SIZE 128M ENGINE NDBCLUSTER; ALTER LOGFILE GROUP LG1 ADD UNDOFILE 'undo2.log' INITIAL_SIZE 150M ENGINE NDBCLUSTER;
This logfile group is created when the data nodes are
started with --initial
.
Resources for the initial log file group are added to
the global memory pool along with those indicated by the
value of
SharedGlobalMemory
.
This parameter, if used, should always be set in the
[ndbd default]
section of the
config.ini
file. The behavior of a
MySQL Cluster when different values are set on different
data nodes is not defined.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | string | [see text] | ... | S |
This parameter can be used to specify a MySQL Cluster
Disk Data tablespace that is created when performing an
initial start of the cluster.
InitialTablespace
is specified as shown here:
InitialTablespace = [name=name
;] [extent_size=size
;]file-specification-list
The name
of the tablespace is
optional and defaults to DEFAULT-TS
.
The extent_size
is also optional; it
defaults to 1M
. The
file-specification-list
uses
the same syntax as shown with the
InitialLogfileGroup
parameter, the only difference being that each
file-specification
used with
InitialTablespace
corresponds to a data file. At least one must be
specified in the
file-specification-list
. Data
files are placed according to any values that have been
set for
FileSystemPath
,
FileSystemPathDD
,
and
FileSystemPathDataFiles
,
just as if they had been created as the result of a
CREATE TABLESPACE
or
ALTER TABLESPACE
statement.
For example, consider the following line specifying
InitialTablespace
in the [ndbd default]
section of the
config.ini
file (as with
InitialLogfileGroup
,
this parameter should always be set in the
[ndbd default]
section, as the
behavior of a MySQL Cluster when different values are
set on different data nodes is not defined):
InitialTablespace = name=TS1; extent_size=8M; data1.dat:2G; data2.dat:4G
This is equivalent to the following SQL statements:
CREATE TABLESPACE TS1 ADD DATAFILE 'data1.dat' EXTENT_SIZE 8M INITIAL_SIZE 2G ENGINE NDBCLUSTER; ALTER TABLESPACE TS1 ADD DATAFILE 'data2.dat' INITIAL_SIZE 4G ENGINE NDBCLUSTER;
This tablespace is created when the data nodes are
started with --initial
, and can be used
whenever creating MySQL Cluster Disk Data tables
thereafter.
Disk Data and GCP Stop errors.
Errors encountered when using Disk Data tables such as
Node nodeid
killed this
node because GCP stop was detected (error 2303)
are often referred to as “GCP stop errors”. Such
errors occur when the redo log is not flushed to disk quickly
enough; this is usually due to slow disks and insufficient
disk throughput.
You can help prevent these errors from occurring by using faster
disks, and by placing Disk Data files on a separate disk from
the data node file system. Reducing the value of
TimeBetweenGlobalCheckpoints
tends to decrease the amount of data to be written for each
global checkpoint, and so may provide some protection against
redo log buffer overflows when trying to write a global
checkpoint; however, reducing this value also permits less time
in which to write the GCP, so this must be done with caution.
In addition to the considerations given for
DiskPageBufferMemory
as
explained previously, it is also very important that the
DiskIOThreadPool
configuration parameter be set correctly; having
DiskIOThreadPool
set too
high is very likely to cause GCP stop errors (Bug #37227).
GCP stops can be caused by save or commit timeouts; the
TimeBetweenEpochsTimeout
data node configuration parameter determines the timeout for
commits. However, it is possible to disable both types of
timeouts by setting this parameter to 0.
Parameters for configuring send buffer memory allocation.
Send buffer memory is allocated dynamically from a memory pool
shared between all transporters, which means that the size of
the send buffer can be adjusted as necessary. (Previously, the
NDB kernel used a fixed-size send buffer for every node in the
cluster, which was allocated when the node started and could
not be changed while the node was running.) The
TotalSendBufferMemory
and OverLoadLimit
data
node configuration parameters permit the setting of limits on
this memory allocation. For more information about the use of
these parameters (as well as
SendBufferMemory
), see
Section 19.3.3.13, “Configuring MySQL Cluster Send Buffer Parameters”.
This parameter specifies the amount of transporter send
buffer memory to allocate in addition to any set using
TotalSendBufferMemory
,
SendBufferMemory
, or
both.
This parameter is used to determine the total amount of memory to allocate on this node for shared send buffer memory among all configured transporters.
If this parameter is set, its minimum permitted value is 256KB; 0 indicates that the parameter has not been set. For more detailed information, see Section 19.3.3.13, “Configuring MySQL Cluster Send Buffer Parameters”.
See also Section 19.5.14, “Adding MySQL Cluster Data Nodes Online”.
Redo log over-commit handling.
It is possible to control a data node's handling of
operations when too much time is taken flushing redo logs to
disk. This occurs when a given redo log flush takes longer
than
RedoOverCommitLimit
seconds, more than
RedoOverCommitCounter
times, causing any pending transactions to be aborted. When
this happens, the API node that sent the transaction can
handle the operations that should have been committed either
by queuing the operations and re-trying them, or by aborting
them, as determined by
DefaultOperationRedoProblemAction
.
The data node configuration parameters for setting the timeout
and number of times it may be exceeded before the API node
takes this action are described in the following list:
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | numeric | 3 | 0 - 4294967039 (0xFFFFFEFF) | N |
When
RedoOverCommitLimit
is exceeded when trying to write a given redo log to disk
this many times or more, any transactions that were not
committed as a result are aborted, and an API node where any
of these transactions originated handles the operations
making up those transactions according to its value for
DefaultOperationRedoProblemAction
(by either queuing the operations to be re-tried, or
aborting them).
RedoOverCommitCounter
defaults to 3. Set
it to 0 to disable the limit.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | seconds | 20 | 0 - 4294967039 (0xFFFFFEFF) | N |
This parameter sets an upper limit in seconds for trying to
write a given redo log to disk before timing out. The number
of times the data node tries to flush this redo log, but
takes longer than RedoOverCommitLimit
, is
kept and compared with
RedoOverCommitCounter
,
and when flushing takes too long more times than the value
of that parameter, any transactions that were not committed
as a result of the flush timeout are aborted. When this
occurs, the API node where any of these transactions
originated handles the operations making up those
transactions according to its
DefaultOperationRedoProblemAction
setting (it either queues the operations to be re-tried, or
aborts them).
By default, RedoOverCommitLimit
is 20
seconds. Set to 0 to disable checking for redo log flush
timeouts.
Controlling restart attempts.
It is possible to exercise finely-grained control over restart
attempts by data nodes when they fail to start using the
MaxStartFailRetries
and
StartFailRetryDelay
data node configuration parameters.
MaxStartFailRetries
limits the total number of retries made before giving up on
starting the data node,
StartFailRetryDelay
sets
the number of seconds between retry attempts. These parameters
are listed here:
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
Use this parameter to set the number of seconds between restart attempts by the data node in the event on failure on startup. The default is 0 (no delay).
Both this parameter and
MaxStartFailRetries
are ignored unless
StopOnError
is equal
to 0.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 3 | 0 - 4294967039 (0xFFFFFEFF) | N |
Use this parameter to limit the number restart attempts made by the data node in the event that it fails on startup. The default is 3 attempts.
Both this parameter and
StartFailRetryDelay
are ignored unless
StopOnError
is equal
to 0.
NDB index statistics parameters. The parameters in the following list relate to NDB index statistics generation.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | false | false, true | S |
Enable or disable automatic statistics collection when indexes are created. Disabled by default.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | false | false, true | S |
Enable or disable monitoring of indexes for changes and
trigger automatic statistics updates these are detected. The
amount and degree of change needed to trigger the updates
are determined by the settings for the
IndexStatTriggerPct
and
IndexStatTriggerScale
options.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 32768 | 0 - 4294967039 (0xFFFFFEFF) | IN |
Maximum space in bytes allowed for the saved statistics of
any given index in the NDB
system tables and in the mysqld memory
cache. This consumes
IndexMemory
.
At least one sample is always produced, regardless of any
size limit. This size is scaled by
IndexStatSaveScale
.
The size specified by
IndexStatSaveSize
is
scaled by the value of
IndexStatTriggerPct
for a large index,
times 0.01. This is further multiplied by the logarithm to
the base 2 of the index size. Setting
IndexStatTriggerPct
equal to 0 disables
the scaling effect.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | percentage | 100 | 0 - 4294967039 (0xFFFFFEFF) | IN |
The size specified by
IndexStatSaveSize
is
scaled by the value of
IndexStatTriggerPct
for a large index,
times 0.01. This is further multiplied by the logarithm to
the base 2 of the index size. Setting
IndexStatTriggerPct
equal to 0 disables
the scaling effect.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | percentage | 100 | 0 - 4294967039 (0xFFFFFEFF) | IN |
Percentage change in updates that triggers an index
statistics update. The value is scaled by
IndexStatTriggerScale
.
You can disable this trigger altogether by setting
IndexStatTriggerPct
to 0.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | percentage | 100 | 0 - 4294967039 (0xFFFFFEFF) | IN |
Scale
IndexStatTriggerPct
by this amount times 0.01 for a large index. A value of 0
disables scaling.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | seconds | 60 | 0 - 4294967039 (0xFFFFFEFF) | IN |
Minimum delay in seconds between automatic index statistics updates for a given index. Setting this variable to 0 disables any delay. The default is 60 seconds.
The [mysqld]
and [api]
sections in the config.ini
file define the
behavior of the MySQL servers (SQL nodes) and other applications
(API nodes) used to access cluster data. None of the parameters
shown is required. If no computer or host name is provided, any
host can use this SQL or API node.
Generally speaking, a [mysqld]
section is
used to indicate a MySQL server providing an SQL interface to
the cluster, and an [api]
section is used for
applications other than mysqld processes
accessing cluster data, but the two designations are actually
synonymous; you can, for instance, list parameters for a MySQL
server acting as an SQL node in an [api]
section.
For a discussion of MySQL server options for MySQL Cluster, see Section 19.3.3.8.1, “MySQL Server Options for MySQL Cluster”; for information about MySQL server system variables relating to MySQL Cluster, see Section 19.3.3.8.2, “MySQL Cluster System Variables”.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | [none] | 1 - 255 | IS |
The Id
is an integer value used to
identify the node in all cluster internal messages. The
permitted range of values is 1 to 255 inclusive. This value
must be unique for each node in the cluster, regardless of
the type of node.
Data node IDs must be less than 49, regardless of the MySQL Cluster version used. If you plan to deploy a large number of data nodes, it is a good idea to limit the node IDs for API nodes (and management nodes) to values greater than 48.
NodeId
is the
preferred parameter name to use when identifying API nodes.
(Id
continues to be supported for
backward compatibility, but is now deprecated and generates
a warning when used. It is also subject to future removal.)
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | string | [none] | ... | N |
Specifies which data nodes to connect.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | [none] | 1 - 255 | IS |
The NodeId
is an integer value used to
identify the node in all cluster internal messages. The
permitted range of values is 1 to 255 inclusive. This value
must be unique for each node in the cluster, regardless of
the type of node.
Data node IDs must be less than 49, regardless of the MySQL Cluster version used. If you plan to deploy a large number of data nodes, it is a good idea to limit the node IDs for API nodes (and management nodes) to values greater than 48.
NodeId
is the
preferred parameter name to use when identifying management
nodes. An alias, Id
, was used for this
purpose in very old versions of MySQL Cluster, and continues
to be supported for backward compatibility; it is now
deprecated and generates a warning when used, and is subject
to removal in a future release of MySQL Cluster.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | name | [none] | ... | S |
This refers to the Id
set for one of the
computers (hosts) defined in a [computer]
section of the configuration file.
This parameter is deprecated as of MySQL Cluster NDB
7.5.0, and is subject to removal in a future release. Use
the HostName
parameter instead.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | name or IP address | [none] | ... | N |
Specifying this parameter defines the hostname of the
computer on which the SQL node (API node) is to reside. To
specify a hostname, either this parameter or
ExecuteOnComputer
is required.
If no HostName
or
ExecuteOnComputer
is specified in a given
[mysql]
or [api]
section of the config.ini
file, then an
SQL or API node may connect using the corresponding
“slot” from any host which can establish a
network connection to the management server host machine.
This differs from the default behavior for data
nodes, where localhost
is assumed for
HostName
unless otherwise
specified.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | 0-2 | 0 | 0 - 2 | N |
This parameter defines which nodes can act as arbitrators.
Both management nodes and SQL nodes can be arbitrators. A
value of 0 means that the given node is never used as an
arbitrator, a value of 1 gives the node high priority as an
arbitrator, and a value of 2 gives it low priority. A normal
configuration uses the management server as arbitrator,
setting its ArbitrationRank
to 1 (the
default for management nodes) and those for all SQL nodes to
0 (the default for SQL nodes).
By setting ArbitrationRank
to 0 on all
management and SQL nodes, you can disable arbitration
completely. You can also control arbitration by overriding
this parameter; to do so, set the
Arbitration
parameter in the [ndbd default]
section
of the config.ini
global configuration
file.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | milliseconds | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
Setting this parameter to any other value than 0 (the default) means that responses by the arbitrator to arbitration requests will be delayed by the stated number of milliseconds. It is usually not necessary to change this value.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 16K | 1024 - 1M | N |
For queries that are translated into full table scans or
range scans on indexes, it is important for best performance
to fetch records in properly sized batches. It is possible
to set the proper size both in terms of number of records
(BatchSize
) and in
terms of bytes (BatchByteSize
). The
actual batch size is limited by both parameters.
The speed at which queries are performed can vary by more than 40% depending upon how this parameter is set.
This parameter is measured in bytes. The default value is 16K.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | records | 256 | 1 - 992 | N |
This parameter is measured in number of records and is by default set to 256. The maximum size is 992.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
This parameter specifies the amount of transporter send
buffer memory to allocate in addition to any that has been
set using
TotalSendBufferMemory
,
SendBufferMemory
, or
both.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | string | [none] | ... | S |
Use this parameter to set the scheduling policy and priority of heartbeat threads for management and API nodes. The syntax for setting this parameter is shown here:
HeartbeatThreadPriority =policy
[,priority
]policy
: {FIFO | RR}
When setting this parameter, you must specify a policy. This
is one of FIFO
(first in, first in) or
RR
(round robin). This followed
optionally by the priority (an integer).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 256K | 32K - 16M | N |
The batch size is the size of each batch sent from each data node. Most scans are performed in parallel to protect the MySQL Server from receiving too much data from many nodes in parallel; this parameter sets a limit to the total batch size over all nodes.
The default value of this parameter is set to 256KB. Its maximum size is 16MB.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 0 | 256K - 4294967039 (0xFFFFFEFF) | N |
This parameter is used to determine the total amount of memory to allocate on this node for shared send buffer memory among all configured transporters.
If this parameter is set, its minimum permitted value is 256KB; 0 indicates that the parameter has not been set. For more detailed information, see Section 19.3.3.13, “Configuring MySQL Cluster Send Buffer Parameters”.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | false | true, false | N |
This parameter is false
by default. This
forces disconnected API nodes (including MySQL Servers
acting as SQL nodes) to use a new connection to the cluster
rather than attempting to re-use an existing one, as re-use
of connections can cause problems when using
dynamically-allocated node IDs. (Bug #45921)
This parameter can be overridden using the NDB API. For more information, see Ndb_cluster_connection::set_auto_reconnect(), and Ndb_cluster_connection::get_auto_reconnect().
DefaultOperationRedoProblemAction
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | enumeration | QUEUE | ABORT, QUEUE | S |
This parameter (along with
RedoOverCommitLimit
and
RedoOverCommitCounter
)
controls the data node's handling of operations when
too much time is taken flushing redo logs to disk. This
occurs when a given redo log flush takes longer than
RedoOverCommitLimit
seconds, more than
RedoOverCommitCounter
times, causing any pending transactions to be aborted.
When this happens, the node can respond in either of two
ways, according to the value of
DefaultOperationRedoProblemAction
, listed
here:
ABORT
: Any pending operations from
aborted transactions are also aborted.
QUEUE
: Pending operations from
transactions that were aborted are queued up to be
re-tried. This the default. Pending operations are still
aborted when the redo log runs out of space—that
is, when P_TAIL_PROBLEM errors
occur.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | buckets | 3840 | 0 - 3840 | N |
The size of the table hash maps used by
NDB
is configurable using this
parameter. DefaultHashMapSize
can take
any of three possible values (0, 240, 3840). These values
and their effects are described in the following table.
Value | Description / Effect |
---|---|
0 | Use the lowest value set, if any, for this parameter among all data nodes and API nodes in the cluster; if it is not set on any data or API node, use the default value. |
240 | Original hash map size (used by default prior to MySQL Cluster NDB 7.2.7. |
3840 | Larger hash map size as (used by default in MySQL Cluster NDB 7.2.7 and later |
The original intended use for this parameter was to facilitate upgrades and downgrades to and from older MySQL Cluster versions, in which the hash map size differed, due to the fact that this change was not otherwise backward compatible. This is not an issue when upgrading or downgrading from MySQL Cluster NDB 7.5.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | false | true, false | N |
Use WAN TCP setting as default.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
In a MySQL Cluster with many unstarted data nodes, the value
of this parameter can be raised to circumvent connection
attempts to data nodes which have not yet begun to function
in the cluster, as well as moderate high traffic to
management nodes. As long as the API node is not connected
to any new data nodes, the value of the
StartConnectBackoffMaxTime
parameter is applied; otherwise,
ConnectBackoffMaxTime
is used to
determine the length of time in milliseconds to wait between
connection attempts.
Time elapsed during node connection
attempts is not taken into account when calculating elapsed
time for this parameter. The timeout is applied with
approximately 100 ms resolution, starting with a 100 ms
delay; for each subsequent attempt, the length of this
period is doubled until it reaches
ConnectBackoffMaxTime
milliseconds, up to
a maximum of 100000 ms (100s).
Once the API node is connected to a data node and that node
reports (in a heartbeat message) that it has connected to
other data nodes, connection attempts to those data nodes
are no longer affected by this parameter, and are made every
100 ms thereafter until connected. Once a data node has
started, it can take up
HeartbeatIntervalDbApi
for the API node to be notified that this has occurred.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | integer | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
In a MySQL Cluster with many unstarted data nodes, the value
of this parameter can be raised to circumvent connection
attempts to data nodes which have not yet begun to function
in the cluster, as well as moderate high traffic to
management nodes. As long as the API node is not connected
to any new data nodes, the value of the
StartConnectBackoffMaxTime
parameter is
applied; otherwise,
ConnectBackoffMaxTime
is used to determine the length of time in milliseconds to
wait between connection attempts.
Time elapsed during node connection
attempts is not taken into account when calculating elapsed
time for this parameter. The timeout is applied with
approximately 100 ms resolution, starting with a 100 ms
delay; for each subsequent attempt, the length of this
period is doubled until it reaches
StartConnectBackoffMaxTime
milliseconds,
up to a maximum of 100000 ms (100s).
Once the API node is connected to a data node and that node
reports (in a heartbeat message) that it has connected to
other data nodes, connection attempts to those data nodes
are no longer affected by this parameter, and are made every
100 ms thereafter until connected. Once a data node has
started, it can take up
HeartbeatIntervalDbApi
for the API node to be notified that this has occurred.
API Node Debugging Parameters.
Beginning with MySQL Cluster NDB 7.5.2, you can use the
ApiVerbose
configuration parameter to
enable debugging output from a given API node. This parameter
takes an integer value. 0 is the default, and disables such
debugging; 1 enables debugging output to the cluster log; 2
adds DBDICT
debugging output as well. (Bug
#20638450) See also
DUMP 1229.
You can also obtain information from a MySQL server running as a
MySQL Cluster SQL node using SHOW
STATUS
in the mysql client, as
shown here:
mysql> SHOW STATUS LIKE 'ndb%';
+-----------------------------+---------------+
| Variable_name | Value |
+-----------------------------+---------------+
| Ndb_cluster_node_id | 5 |
| Ndb_config_from_host | 192.168.0.112 |
| Ndb_config_from_port | 1186 |
| Ndb_number_of_storage_nodes | 4 |
+-----------------------------+---------------+
4 rows in set (0.02 sec)
For information about the status variables appearing in the output from this statement, see Section 19.3.3.8.3, “MySQL Cluster Status Variables”.
To add new SQL or API nodes to the configuration of a running
MySQL Cluster, it is necessary to perform a rolling restart of
all cluster nodes after adding new [mysqld]
or [api]
sections to the
config.ini
file (or files, if you are
using more than one management server). This must be done
before the new SQL or API nodes can connect to the cluster.
It is not necessary to perform any restart of the cluster if new SQL or API nodes can employ previously unused API slots in the cluster configuration to connect to the cluster.
This section provides information about MySQL server options, server and status variables that are specific to MySQL Cluster. For general information on using these, and for other options and variables not specific to MySQL Cluster, see Section 6.1, “The MySQL Server”.
For MySQL Cluster configuration parameters used in the cluster
configuration file (usually named
config.ini
), see
Section 19.3, “Configuration of MySQL Cluster”.
This section provides descriptions of mysqld server options relating to MySQL Cluster. For information about mysqld options not specific to MySQL Cluster, and for general information about the use of options with mysqld, see Section 6.1.3, “Server Command Options”.
For information about command-line options used with other
MySQL Cluster processes (ndbd,
ndb_mgmd, and ndb_mgm),
see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
For information about command-line options used with
NDB
utility programs (such as
ndb_desc, ndb_size.pl,
and ndb_show_tables), see
Section 19.4, “MySQL Cluster Programs”.
--ndb-allow-copying-alter-table=[ON|OFF]
Table 19.10 Type and value information for ndb-allow-copying-alter-table
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Both | Yes |
NDB 7.4 | boolean | ON |
DESCRIPTION: Set to OFF to keep ALTER TABLE from using copying operations on NDB tables |
Let ALTER TABLE
and other
DDL statements use copying operations on
NDB
tables. Set to
OFF
to keep this from happening.
Table 19.11 Type and value information for ndb-batch-size
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | No |
NDB 7.4 | integer | 32768 / 0 - 31536000 |
DESCRIPTION: Size (in bytes) to use for NDB transaction batches |
This sets the size in bytes that is used for NDB transaction batches.
--ndb-cluster-connection-pool=
#
Table 19.12 Type and value information for ndb-cluster-connection-pool
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | Yes |
Yes | Global | No |
NDB 7.4 | integer | 1 / 1 - 63 |
DESCRIPTION: Number of connections to the cluster used by MySQL |
By setting this option to a value greater than 1 (the
default), a mysqld process can use
multiple connections to the cluster, effectively mimicking
several SQL nodes. Each connection requires its own
[api]
or [mysqld]
section in the cluster configuration
(config.ini
) file, and counts against
the maximum number of API connections supported by the
cluster.
Suppose that you have 2 cluster host computers, each
running an SQL node whose mysqld
process was started with
--ndb-cluster-connection-pool=4
; this
means that the cluster must have 8 API slots available for
these connections (instead of 2). All of these connections
are set up when the SQL node connects to the cluster, and
are allocated to threads in a round-robin fashion.
This option is useful only when running mysqld on host machines having multiple CPUs, multiple cores, or both. For best results, the value should be smaller than the total number of cores available on the host machine. Setting it to a value greater than this is likely to degrade performance severely.
Because each SQL node using connection pooling occupies multiple API node slots—each slot having its own node ID in the cluster—you must not use a node ID as part of the cluster connection string when starting any mysqld process that employs connection pooling.
Setting a node ID in the connection string when using
the --ndb-cluster-connection-pool
option causes node ID allocation errors when the SQL
node attempts to connect to the cluster.
--ndb-cluster-connection-pool-nodeids=
list
Table 19.13 Type and value information for ndb-cluster-connection-pool-nodeids
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | No |
NDB 7.4 | set | / |
DESCRIPTION: Comma-separated list of node IDs for connections to the cluster used by MySQL; the number of nodes in the list must be the same as the value set for --ndb-cluster-connection-pool |
Specifies a comma-separated list of node IDs for
connections to the cluster used by an SQL node. The number
of nodes in this list must be the same as the value set
for the
--ndb-cluster-connection-pool
option.
--ndb-cluster-connection-pool-nodeids
was
added in MySQL Cluster NDB 7.5.0.
--ndb-blob-read-batch-bytes=
bytes
Table 19.14 Type and value information for ndb-blob-read-batch-bytes
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Both | Yes |
NDB 7.4 | integer | 65536 / 0 - 4294967295 |
DESCRIPTION: Specifies size in bytes that large BLOB reads should be batched into. 0 = no limit. |
This option can be used to set the size (in bytes) for
batching of BLOB
data reads
in MySQL Cluster applications. When this batch size is
exceeded by the amount of
BLOB
data to be read within
the current transaction, any pending
BLOB
read operations are
immediately executed.
The maximum value for this option is 4294967295; the
default is 65536. Setting it to 0 has the effect of
disabling BLOB
read
batching.
In NDB API applications, you can control
BLOB
write batching with
the
setMaxPendingBlobReadBytes()
and
getMaxPendingBlobReadBytes()
methods.
--ndb-blob-write-batch-bytes=
bytes
Table 19.15 Type and value information for ndb-blob-write-batch-bytes
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Both | Yes |
NDB 7.4 | integer | 65536 / 0 - 4294967295 |
DESCRIPTION: Specifies size in bytes that large BLOB writes should be batched into. 0 = no limit. |
This option can be used to set the size (in bytes) for
batching of BLOB
data
writes in MySQL Cluster applications. When this batch size
is exceeded by the amount of
BLOB
data to be written
within the current transaction, any pending
BLOB
write operations are
immediately executed.
The maximum value for this option is 4294967295; the
default is 65536. Setting it to 0 has the effect of
disabling BLOB
write
batching.
In NDB API applications, you can control
BLOB
write batching with
the
setMaxPendingBlobWriteBytes()
and
getMaxPendingBlobWriteBytes()
methods.
--ndb-connectstring=
connection_string
Table 19.16 Type and value information for ndb-connectstring
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | No | No |
Yes | No | |
NDB 7.4 | string | |
DESCRIPTION: Point to the management server that distributes the cluster configuration |
When using the NDBCLUSTER
storage engine, this option specifies the management
server that distributes cluster configuration data. See
Section 19.3.3.3, “MySQL Cluster Connection Strings”, for
syntax.
--ndb-deferred-constraints=[0|1]
Table 19.17 Type and value information for ndb-deferred-constraints
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Both | Yes |
NDB 7.4 | integer | 0 / 0 - 1 |
DESCRIPTION: Specifies that constraint checks on unique indexes (where these are supported) should be deferred until commit time. Not normally needed or used; for testing purposes only. |
Controls whether or not constraint checks on unique
indexes are deferred until commit time, where such checks
are supported. 0
is the default.
This option is not normally needed for operation of MySQL Cluster or MySQL Cluster Replication, and is intended primarily for use in testing.
--ndb-distribution=[KEYHASH|LINHASH]
Table 19.18 Type and value information for ndb-distribution
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | Yes |
NDB 7.4 | enumeration | KEYHASH / LINHASH, KEYHASH |
DESCRIPTION: Default distribution for new tables in NDBCLUSTER (KEYHASH or LINHASH, default is KEYHASH) |
Controls the default distribution method for
NDB
tables. Can be set to
either of KEYHASH
(key hashing) or
LINHASH
(linear hashing).
KEYHASH
is the default.
Table 19.19 Type and value information for ndb-mgmd-host
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | No | No |
Yes | No | |
NDB 7.4 | string | localhost:1186 |
DESCRIPTION: Set the host (and port, if desired) for connecting to management server |
Can be used to set the host and port number of a single
management server for the program to connect to. If the
program requires node IDs or references to multiple
management servers (or both) in its connection
information, use the
--ndb-connectstring
option
instead.
Table 19.20 Type and value information for ndbcluster
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | No | No |
Yes | No | |
NDB 7.4 | boolean | FALSE |
DESCRIPTION: Enable NDB Cluster (if this version of MySQL supports it)
Disabled by |
The NDBCLUSTER
storage engine
is necessary for using MySQL Cluster. If a
mysqld binary includes support for the
NDBCLUSTER
storage engine,
the engine is disabled by default. Use the
--ndbcluster
option to
enable it. Use --skip-ndbcluster
to
explicitly disable the engine.
Table 19.21 Type and value information for ndb-log-apply-status
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | No |
NDB 7.4 | boolean | OFF |
DESCRIPTION: Cause a MySQL server acting as a slave to log mysql.ndb_apply_status updates received from its immediate master in its own binary log, using its own server ID. Effective only if the server is started with the --ndbcluster option. |
Causes a slave mysqld to log any
updates received from its immediate master to the
mysql.ndb_apply_status
table in its own
binary log using its own server ID rather than the server
ID of the master. In a circular or chain replication
setting, this allows such updates to propagate to the
mysql.ndb_apply_status
tables of any
MySQL servers configured as slaves of the current
mysqld.
In a chain replication setup, using this option allows downstream (slave) clusters to be aware of their positions relative to all of their upstream contributors (masters).
In a circular replication setup, this option causes
changes to ndb_apply_status
tables to
complete the entire circuit, eventually propagating back
to the originating MySQL Cluster. This also allows a
cluster acting as a master to see when its changes
(epochs) have been applied to the other clusters in the
circle.
This option has no effect unless the MySQL server is
started with the
--ndbcluster
option.
Table 19.22 Type and value information for ndb-log-empty-epochs
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | Yes |
NDB 7.4 | boolean | OFF |
DESCRIPTION: When enabled, causes epochs in which there were no changes to be written to the ndb_apply_status and ndb_binlog_index tables, even when --log-slave-updates is enabled. |
Causes epochs during which there were no changes to be
written to the ndb_apply_status
and
ndb_binlog_index
tables, even when
--log-slave-updates
is
enabled.
By default this option is disabled. Disabling
--ndb-log-empty-epochs
causes epoch
transactions with no changes not to be written to the
binary log, although a row is still written even for an
empty epoch in ndb_binlog_index
.
Because --ndb-log-empty-epochs=1
causes
the size of ndb_binlog_index
table to
increase independently of the size of the binary log,
users should be prepared to manage the growth of this
table, even if they expect the cluster to be idle a large
part of the time.
--ndb-log-exclusive-reads=[0|1]
Table 19.23 Type and value information for ndb-log-exclusive-reads
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Both | Yes |
NDB 7.4 | boolean | 0 |
DESCRIPTION: Log primary key reads with exclusive locks; allow conflict resolution based on read conflicts. |
Starting the server with this option causes primary key
reads to be logged with exclusive locks, which allows for
MySQL Cluster Replication conflict detection and
resolution based on read conflicts. You can also enable
and disable these locks at runtime by setting the value of
the
ndb_log_exclusive_reads
system variable to 1 or 0, respectively. 0 (disable
locking) is the default.
For more information, see Read conflict detection and resolution.
Table 19.24 Type and value information for ndb-log-orig
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | No |
NDB 7.4 | boolean | OFF |
DESCRIPTION: Log originating server id and epoch in mysql.ndb_binlog_index table. |
Log the originating server ID and epoch in the
ndb_binlog_index
table.
This makes it possible for a given epoch to have
multiple rows in ndb_binlog_index
,
one for each originating epoch.
For more information, see Section 19.6.4, “MySQL Cluster Replication Schema and Tables”.
Table 19.25 Type and value information for ndb-log-transaction-id
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | No |
NDB 7.4 | boolean | OFF |
DESCRIPTION: Write NDB transaction IDs in the binary log. Requires --log-bin-v1-events=OFF. |
Causes a slave mysqld to write the NDB
transaction ID in each row of the binary log. Such logging
requires the use of the Version 2 event format for the
binary log; thus,
--log-bin-use-v1-row-events
must be set to FALSE
in order to use
this option.
This option is not supported in mainline MySQL Server
5.7. It is required to enable MySQL Cluster
Replication conflict detection and resolution using the
NDB$EPOCH_TRANS()
function (see
NDB$EPOCH_TRANS()).
The default value is FALSE
.
For more information, see Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”.
Table 19.26 Type and value information for ndb-nodeid
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | No | Yes |
Yes | Global | No |
5.0.45 | integer | / 1 - 63 |
5.1.5 | integer | / 1 - 255 |
DESCRIPTION: MySQL Cluster node ID for this MySQL server |
Set this MySQL server's node ID in a MySQL Cluster.
The --ndb-nodeid
option overrides any
node ID set with
--ndb-connectstring
,
regardless of the order in which the two options are used.
In addition, if --ndb-nodeid
is used,
then either a matching node ID must be found in a
[mysqld]
or [api]
section of config.ini
, or there must
be an “open” [mysqld]
or
[api]
section in the file (that is, a
section without a NodeId
or
Id
parameter specified). This is also
true if the node ID is specified as part of the connection
string.
Regardless of how the node ID is determined, its is shown
as the value of the global status variable
Ndb_cluster_node_id
in the output of
SHOW STATUS
, and as
cluster_node_id
in the
connection
row of the output of
SHOW ENGINE
NDBCLUSTER STATUS
.
For more information about node IDs for MySQL Cluster SQL nodes, see Section 19.3.3.7, “Defining SQL and Other API Nodes in a MySQL Cluster”.
--ndb_optimization_delay=
milliseconds
Table 19.27 Type and value information for ndb_optimization_delay
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
No | Yes | No |
No | Global | Yes |
NDB 7.4 | integer | 10 / 0 - 100000 |
DESCRIPTION: Sets the number of milliseconds to wait between processing sets of rows by OPTIMIZE TABLE on NDB tables. |
Set the number of milliseconds to wait between sets of
rows by OPTIMIZE TABLE
statements on NDB
tables. The
default is 10.
--ndb-recv-thread-activation-threshold=
threshold
Table 19.28 Type and value information for ndb-recv-thread-activation-threshold
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | No | No |
Yes | No | |
5.6.10-ndb-7.3.1 | integer | 8 / 0 (MIN_ACTIVATION_THRESHOLD) - 16 (MAX_ACTIVATION_THRESHOLD) |
DESCRIPTION: Activation threshold when receive thread takes over the polling of the cluster connection (measured in concurrently active threads) |
When this number of concurrently active threads is reached, the receive thread takes over polling of the cluster connection.
--ndb-recv-thread-cpu-mask=
bitmask
Table 19.29 Type and value information for ndb-recv-thread-cpu-mask
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | No | No |
Yes | No | |
NDB 7.4 | bitmap | [empty] |
DESCRIPTION: CPU mask for locking receiver threads to specific CPUs; specified as hexadecimal. See documentation for details. |
Set a CPU mask for locking receiver threads to specific
CPUs. This is specified as a hexadecimal bitmask; for
example, 0x33
means that one CPU is
used per receiver thread. An empty string (no locking of
receiver threads) is the default.
ndb-transid-mysql-connection-map=
state
Table 19.30 Type and value information for ndb-transid-mysql-connection-map
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | No | No |
No | No | |
NDB 7.4 | enumeration | ON / ON, OFF, FORCE |
DESCRIPTION: Enable or disable the ndb_transid_mysql_connection_map plugin; that is, enable or disable the INFORMATION_SCHEMA table having that name. |
Enables or disables the plugin that handles the
ndb_transid_mysql_connection_map
table in the INFORMATION_SCHEMA
database. Takes one of the values ON
,
OFF
, or FORCE
.
ON
(the default) enables the plugin.
OFF
disables the plugin, which makes
ndb_transid_mysql_connection_map
inaccessible. FORCE
keeps the MySQL
Server from starting if the plugin fails to load and
start.
You can see whether the
ndb_transid_mysql_connection_map
table plugin is running by checking the output of
SHOW PLUGINS
.
Table 19.31 Type and value information for ndb-wait-connected
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | No |
NDB 7.4 | integer | 0 / 0 - 31536000 |
5.1.56-ndb-7.1.16, 5.1.56-ndb-7.0.27 | integer | 30 / 0 - 31536000 |
DESCRIPTION: Time (in seconds) for the MySQL server to wait for connection to cluster management and data nodes before accepting MySQL client connections. |
This option sets the period of time that the MySQL server
waits for connections to MySQL Cluster management and data
nodes to be established before accepting MySQL client
connections. The time is specified in seconds. The default
value is 30
.
Table 19.32 Type and value information for ndb-wait-setup
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | No |
NDB 7.4 | integer | 15 / 0 - 31536000 |
5.1.56-ndb-7.0.27, 5.1.56-ndb-7.1.16 | integer | 30 / 0 - 31536000 |
DESCRIPTION: Time (in seconds) for the MySQL server to wait for NDB engine setup to complete. |
This variable shows the period of time that the MySQL
server waits for the NDB
storage engine to complete setup before timing out and
treating NDB
as unavailable.
The time is specified in seconds. The default value is
30
.
Table 19.33 Type and value information for server-id-bits
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | No |
NDB 7.4 | integer | 32 / 7 - 32 |
DESCRIPTION: Sets the number of least significant bits in the server_id actually used for identifying the server, permitting NDB API applications to store application data in the most significant bits. server_id must be less than 2 to the power of this value. |
This option indicates the number of least significant bits
within the 32-bit
server_id
which actually
identify the server. Indicating that the server is
actually identified by fewer than 32 bits makes it
possible for some of the remaining bits to be used for
other purposes, such as storing user data generated by
applications using the NDB API's Event API within the
AnyValue
of an
OperationOptions
structure (MySQL Cluster uses the
AnyValue
to store the server ID).
When extracting the effective server ID from
server_id
for purposes
such as detection of replication loops, the server ignores
the remaining bits. The --server-id-bits
option is used to mask out any irrelevant bits of
server_id
in the IO and
SQL threads when deciding whether an event should be
ignored based on the server ID.
This data can be read from the binary log by
mysqlbinlog, provided that it is run
with its own
--server-id-bits
option set to 32 (the default).
The value of server_id
must be less than 2 ^
server_id_bits
;
otherwise, mysqld refuses to start.
This system variable is supported only by MySQL Cluster. It is not supported in the standard MySQL 5.7 Server.
Table 19.34 Type and value information for skip-ndbcluster
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | No | No |
Yes | No | |
DESCRIPTION: Disable the NDB Cluster storage engine |
Disable the NDBCLUSTER
storage engine. This is the default for binaries that were
built with NDBCLUSTER
storage
engine support; the server allocates memory and other
resources for this storage engine only if the
--ndbcluster
option is
given explicitly. See
Section 19.3.1, “Quick Test Setup of MySQL Cluster”, for an example.
This section provides detailed information about MySQL server
system variables that are specific to MySQL Cluster and the
NDB
storage engine. For system
variables not specific to MySQL Cluster, see
Section 6.1.4, “Server System Variables”. For general
information on using system variables, see
Section 6.1.5, “Using System Variables”.
Table 19.35 Type and value information for ndb_autoincrement_prefetch_sz
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Both | Yes |
NDB 7.4 | integer | 32 / 1 - 256 |
5.0.56 | integer | 1 / 1 - 256 |
5.1.1 | integer | 32 / 1 - 256 |
5.1.23 | integer | 1 / 1 - 256 |
5.1.16-ndb-6.2.0 | integer | 32 / 1 - 256 |
5.1.23-ndb-6.2.10 | integer | 1 / 1 - 256 |
5.1.19-ndb-6.3.0 | integer | 32 / 1 - 256 |
5.1.23-ndb-6.3.7 | integer | 1 / 1 - 256 |
5.1.41-ndb-6.3.31 | integer | 1 / 1 - 65536 |
5.1.30-ndb-6.4.0 | integer | 32 / 1 - 256 |
5.1.41-ndb-7.0.11 | integer | 1 / 1 - 65536 |
5.5.15-ndb-7.2.1 | integer | 1 / 1 - 65536 |
DESCRIPTION: NDB auto-increment prefetch size |
Determines the probability of gaps in an autoincremented
column. Set it to 1
to minimize this.
Setting it to a high value for optimization makes inserts
faster, but decreases the likelihood that consecutive
autoincrement numbers will be used in a batch of inserts.
The mininum and default value is 1. The maximum value for
ndb_autoincrement_prefetch_sz
is 65536.
This variable affects only the number of
AUTO_INCREMENT
IDs that are fetched
between statements; within a given statement, at least 32
IDs are obtained at a time. The default value is 1.
This variable does not affect inserts performed using
INSERT
... SELECT
.
Table 19.36 Type and value information for ndb_cache_check_time
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | Yes |
NDB 7.4 | integer | 0 / - |
DESCRIPTION: Number of milliseconds between checks of cluster SQL nodes made by the MySQL query cache |
The number of milliseconds that elapse between checks of MySQL Cluster SQL nodes by the MySQL query cache. Setting this to 0 (the default and minimum value) means that the query cache checks for validation on every query.
The recommended maximum value for this variable is 1000, which means that the check is performed once per second. A larger value means that the check is performed and possibly invalidated due to updates on different SQL nodes less often. It is generally not desirable to set this to a value greater than 2000.
Table 19.37 Type and value information for ndb_clear_apply_status
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
No | Global | Yes |
NDB 7.4 | boolean | ON |
DESCRIPTION: Causes RESET SLAVE to clear all rows from the ndb_apply_status table. ON by default. |
By the default, executing RESET
SLAVE
causes a MySQL Cluster replication slave
to purge all rows from its
ndb_apply_status
table. In MySQL
Cluster NDB 7.4.9 and later you can disable this by
setting ndb_clear_apply_status=OFF
.
Table 19.38 Type and value information for ndb_data_node_neighbour
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | Yes |
5.7.12-ndb-7.5.2 | integer | 0 / 0 - 255 |
DESCRIPTION: Specifies cluster data node "closest" to this MySQL Server, for transaction hinting and fully replicated tables |
Sets the ID of a “nearest” data node, to ensure that a backup replica is also selected for placing the transaction coordinator. This used to ensure that when a fully replicated table is accessed, we access it on this data node, to ensure that the local copy of the table is always used for fully replicated tables. This can also be used for providing hints for transactions.
See Section 14.1.18.7, “Setting NDB_TABLE options in table comments”, for further information.
Added in MySQL Cluster NDB 7.5.2.
Table 19.39 Type and value information for ndb_deferred_constraints
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Both | Yes |
NDB 7.4 | integer | 0 / 0 - 1 |
DESCRIPTION: Specifies that constraint checks should be deferred (where these are supported). Not normally needed or used; for testing purposes only. |
Controls whether or not constraint checks are deferred,
where these are supported. 0
is the
default.
This variable is not normally needed for operation of MySQL Cluster or MySQL Cluster Replication, and is intended primarily for use in testing.
Table 19.40 Type and value information for ndb_distribution
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | Yes |
NDB 7.4 | enumeration | KEYHASH / LINHASH, KEYHASH |
DESCRIPTION: Default distribution for new tables in NDBCLUSTER (KEYHASH or LINHASH, default is KEYHASH) |
Controls the default distribution method for
NDB
tables. Can be set to
either of KEYHASH
(key hashing) or
LINHASH
(linear hashing).
KEYHASH
is the default.
Table 19.41 Type and value information for ndb_eventbuffer_free_percent
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | Yes |
NDB 7.4 | integer | 20 / 1 - 99 |
DESCRIPTION: Percentage of free memory that should be available in event buffer before resumption of buffering, after reaching limit set by ndb_eventbuffer_max_alloc. |
Sets the percentage of the maximum memory allocated to the event buffer (ndb_eventbuffer_max_alloc) that should be available in event buffer after reaching the maximum, before starting to buffer again.
Table 19.42 Type and value information for ndb_eventbuffer_max_alloc
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | Yes |
NDB 7.4 | integer | 0 / 0 - 4294967295 |
DESCRIPTION: Maximum memory that can be allocated for buffering events by the NDB API. Defaults to 0 (no limit). |
Sets the maximum amount memory (in bytes) that can be allocated for buffering events by the NDB API. 0 means that no limit is imposed, and is the default.
Table 19.43 Type and value information for ndb_extra_logging
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | Yes |
NDB 7.4 | integer | 0 / - |
5.1.19-ndb-6.3.0 | integer | 1 / - |
DESCRIPTION: Controls logging of MySQL Cluster schema, connection, and data distribution events in the MySQL error log |
This variable enables recording in the MySQL error log of
information specific to the
NDB
storage engine.
When this variable is set to 0, the only information
specific to NDB
that is written to the
MySQL error log relates to transaction handling. If it set
to a value greater than 0 but less than 10,
NDB
table schema and connection events
are also logged, as well as whether or not conflict
resolution is in use, and other NDB
errors and information. If the value is set to 10 or more,
information about NDB
internals, such
as the progress of data distribution among cluster nodes,
is also written to the MySQL error log. The default is 1.
Table 19.44 Type and value information for ndb_force_send
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Both | Yes |
NDB 7.4 | boolean | TRUE |
DESCRIPTION: Forces sending of buffers to NDB immediately, without waiting for other threads |
Forces sending of buffers to
NDB
immediately, without
waiting for other threads. Defaults to
ON
.
Table 19.45 Type and value information for ndb_fully_replicated
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Both | Yes |
5.7.12-ndb-7-5-2 | boolean | OFF |
DESCRIPTION: Whether new NDB tables are fully replicated |
Determines whether new NDB
tables are
fully replicated. This setting can be overridden for an
individual table using
COMMENT="NDB_TABLE=FULLY_REPLICATED=..."
in a CREATE TABLE
or
ALTER TABLE
statement; see
Section 14.1.18.7, “Setting NDB_TABLE options in table comments”,
for syntax and other information.
Added in MySQL Cluster NDB 7.5.2.
Table 19.46 Type and value information for ndb_index_stat_enable
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Both | Yes |
NDB 7.4 | boolean | OFF |
5.5.15-ndb-7.2.1 | boolean | ON |
DESCRIPTION: Use NDB index statistics in query optimization |
Use NDB
index statistics in
query optimization. The default is ON
.
Table 19.47 Type and value information for ndb_index_stat_option
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Both | Yes |
NDB 7.4 | string | loop_enable=1000ms,loop_idle=1000ms,loop_busy=100ms, update_batch=1,read_batch=4,idle_batch=32,check_batch=8, check_delay=10m,delete_batch=8, clean_delay=1m,error_batch=4, error_delay=1m,evict_batch=8,evict_delay=1m,cache_limit=32M, cache_lowpct=90,zero_total=0 |
5.1.56-ndb-7.1.17 | string | loop_checkon=1000ms,loop_idle=1000ms,loop_busy=100ms, update_batch=1,read_batch=4,idle_batch=32,check_batch=32, check_delay=1m,delete_batch=8,clean_delay=0,error_batch=4, error_delay=1m,evict_batch=8,evict_delay=1m,cache_limit=32M, cache_lowpct=90 |
DESCRIPTION: Comma-separated list of tunable options for NDB index statistics; the list should contain no spaces |
This variable is used for providing tuning options for NDB index statistics generation. The list consist of comma-separated name-value pairs of option names and values, and this list must not contain any space characters.
Options not used when setting
ndb_index_stat_option
are not changed
from their default values. For example, you can set
ndb_index_stat_option =
'loop_idle=1000ms,cache_limit=32M'
.
Time values can be optionally suffixed with
h
(hours), m
(minutes), or s
(seconds). Millisecond
values can optionally be specified using
ms
; millisecond values cannot be
specified using h
,
m
, or s
.) Integer
values can be suffixed with K
,
M
, or G
.
The names of the options that can be set using this variable are shown in the table that follows. The table also provides brief descriptions of the options, their default values, and (where applicable) their minimum and maximum values.
Name | Description | Default/Units | Minimum/Maximum |
---|---|---|---|
loop_enable | 1000 ms | 0/4G | |
loop_idle | Time to sleep when idle | 1000 ms | 0/4G |
loop_busy | Time to sleep when more work is waiting | 100 ms | 0/4G |
update_batch | 1 | 0/4G | |
read_batch | 4 | 1/4G | |
idle_batch | 32 | 1/4G | |
check_batch | 8 | 1/4G | |
check_delay | How often to check for new statistics | 10 m | 1/4G |
delete_batch | 8 | 0/4G | |
clean_delay | 1 m | 0/4G | |
error_batch | 4 | 1/4G | |
error_delay | 1 m | 1/4G | |
evict_batch | 8 | 1/4G | |
evict_delay | Clean LRU cache, from read time | 1 m | 0/4G |
cache_limit | Maximum amount of memory in bytes used for cached index statistics by this mysqld; clean up the cache when this is exceeded. | 32 M | 0/4G |
cache_lowpct | 90 | 0/100 | |
zero_total | Setting this to 1 resets all accumulating counters in
ndb_index_stat_status to 0.
This option value is also reset to 0 when this is
done. | 0 | 0/1 |
Table 19.48 Type and value information for ndb_join_pushdown
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
No | Yes | No |
No | Both | Yes |
5.1.51-ndb-7.2.0 | boolean | TRUE |
DESCRIPTION: Enables pushing down of joins to data nodes |
This variable controls whether joins on
NDB
tables are pushed down to
the NDB kernel (data nodes). Previously, a join was
handled using multiple accesses of
NDB
by the SQL node; however,
when ndb_join_pushdown
is
enabled, a pushable join is sent in its entirety to the
data nodes, where it can be distributed among the data
nodes and executed in parallel on multiple copies of the
data, with a single, merged result being returned to
mysqld. This can reduce greatly the
number of round trips between an SQL node and the data
nodes required to handle such a join.
By default,
ndb_join_pushdown
is
enabled.
Conditions for NDB pushdown joins. In order for a join to be pushable, it must meet the following conditions:
Only columns can be compared, and all columns to be joined must use exactly the same data type.
This means that expressions such as t1.a =
t2.a +
cannot be pushed down, and that (for example) a join
on an constant
INT
column and a
BIGINT
column also
cannot be pushed down.
Explicit locking is not supported; however, the
NDB
storage engine's
characteristic implicit row-based locking is enforced.
This means that a join using FOR
UPDATE
cannot be pushed down.
In order for a join to be pushed down, child tables in
the join must be accessed using one of the
ref
,
eq_ref
, or
const
access methods,
or some combination of these methods.
Outer joined child tables can only be pushed using
eq_ref
.
If the root of the pushed join is an
eq_ref
or
const
, only child
tables joined by
eq_ref
can be
appended. (A table joined by
ref
is likely to
become the root of another pushed join.)
If the query optimizer decides on Using join
cache
for a candidate child table, that
table cannot be pushed as a child. However, it may be
the root of another set of pushed tables.
Joins referencing tables explicitly partitioned by
[LINEAR] HASH
,
LIST
, or RANGE
currently cannot be pushed down.
You can see whether a given join can be pushed down by
checking it with EXPLAIN
;
when the join can be pushed down, you can see references
to the pushed join
in the
Extra
column of the output, as shown in
this example:
mysql>EXPLAIN
->SELECT e.first_name, e.last_name, t.title, d.dept_name
->FROM employees e
->JOIN dept_emp de ON e.emp_no=de.emp_no
->JOIN departments d ON d.dept_no=de.dept_no
->JOIN titles t ON e.emp_no=t.emp_no\G
*************************** 1. row *************************** id: 1 select_type: SIMPLE table: d type: ALL possible_keys: PRIMARY key: NULL key_len: NULL ref: NULL rows: 9 Extra: Parent of 4 pushed join@1 *************************** 2. row *************************** id: 1 select_type: SIMPLE table: de type: ref possible_keys: PRIMARY,emp_no,dept_no key: dept_no key_len: 4 ref: employees.d.dept_no rows: 5305 Extra: Child of 'd' in pushed join@1 *************************** 3. row *************************** id: 1 select_type: SIMPLE table: e type: eq_ref possible_keys: PRIMARY key: PRIMARY key_len: 4 ref: employees.de.emp_no rows: 1 Extra: Child of 'de' in pushed join@1 *************************** 4. row *************************** id: 1 select_type: SIMPLE table: t type: ref possible_keys: PRIMARY,emp_no key: emp_no key_len: 4 ref: employees.de.emp_no rows: 19 Extra: Child of 'e' in pushed join@1 4 rows in set (0.00 sec)
If inner joined child tables are joined by
ref
,
and the result is ordered or
grouped by a sorted index, this index cannot provide
sorted rows, which forces writing to a sorted tempfile.
Two additional sources of information about pushed join performance are available:
The status variables
Ndb_pushed_queries_defined
,
Ndb_pushed_queries_dropped
,
Ndb_pushed_queries_executed
,
and
Ndb_pushed_reads
.
The counters in the
ndbinfo.counters
table that belong to the DBSPJ
kernel block. See
Section 19.5.10.9, “The ndbinfo counters Table”, for
information about these counters. See also
The DBSPJ Block,
in the MySQL Cluster API Developer
Guide.
Table 19.49 Type and value information for ndb_log_apply_status
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | No |
NDB 7.4 | boolean | OFF |
DESCRIPTION: Whether or not a MySQL server acting as a slave logs mysql.ndb_apply_status updates received from its immediate master in its own binary log, using its own server ID. |
A read-only variable which shows whether the server was
started with the
--ndb-log-apply-status
option.
Table 19.50 Type and value information for ndb_log_bin
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
No | Both | Yes |
NDB 7.4 | boolean | ON |
DESCRIPTION: Write updates to NDB tables in the binary log. Effective only if binary logging is enabled with --log-bin. |
Causes updates to NDB
tables to be
written to the binary log. Setting this variable has no
effect if binary logging is not already enabled for the
server using log_bin
.
ndb_log_bin
defaults to 1 (ON);
normally, there is never any need to change this value in
a production environment.
Table 19.51 Type and value information for ndb_log_binlog_index
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
No | Global | Yes |
NDB 7.4 | boolean | ON |
DESCRIPTION: Insert mapping between epochs and binary log positions into the ndb_binlog_index table. Defaults to ON. Effective only if binary logging is enabled on the server. |
Causes a mapping of epochs to positions in the binary log
to be inserted into the
ndb_binlog_index
table. Setting this
variable has no effect if binary logging is not already
enabled for the server using
log_bin
. (In addition,
ndb_log_bin
must not be
disabled.) ndb_log_binlog_index
defaults to 1
(ON
);
normally, there is never any need to change this value in
a production environment.
Table 19.52 Type and value information for ndb_log_empty_epochs
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | Yes |
NDB 7.4 | boolean | OFF |
DESCRIPTION: When enabled, epochs in which there were no changes are written to the ndb_apply_status and ndb_binlog_index tables, even when log_slave_updates is enabled. |
When this variable is set to 0, epoch transactions with no
changes are not written to the binary log, although a row
is still written even for an empty epoch in
ndb_binlog_index
.
Table 19.53 Type and value information for ndb_log_exclusive_reads
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Both | Yes |
NDB 7.4 | boolean | 0 |
DESCRIPTION: Log primary key reads with exclusive locks; allow conflict resolution based on read conflicts. |
This variable determines whether primary key reads are
logged with exclusive locks, which allows for MySQL
Cluster Replication conflict detection and resolution
based on read conflicts. To enable these locks, set the
value of ndb_log_exclusive_reads
to 1.
0, which disables such locking, is the default.
For more information, see Read conflict detection and resolution.
Table 19.54 Type and value information for ndb_log_orig
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | No |
NDB 7.4 | boolean | OFF |
DESCRIPTION: Whether the id and epoch of the originating server are recorded in the mysql.ndb_binlog_index table. Set using the --ndb-log-orig option when starting mysqld. |
Shows whether the originating server ID and epoch are
logged in the ndb_binlog_index
table.
Set using the
--ndb-log-orig
server
option.
Table 19.55 Type and value information for ndb_log_transaction_id
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
No | Yes | No |
No | Global | No |
NDB 7.4 | boolean | OFF |
DESCRIPTION: Whether NDB transaction IDs are written into the binary log. (Read-only.) |
This read-only, Boolean system variable shows whether a
slave mysqld writes NDB transaction IDs
in the binary log (required to use
“active-active” MySQL Cluster Replication
with NDB$EPOCH_TRANS()
conflict
detection). To change the setting, use the
--ndb-log-transaction-id
option.
ndb_log_transaction_id
is
not supported in mainline MySQL Server 5.7.
For more information, see Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”.
Table 19.56 Type and value information for ndb_optimized_node_selection
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | No |
NDB 7.4 | boolean | ON |
5.1.22-ndb-6.3.4 | integer | 3 / 0 - 3 |
DESCRIPTION: Determines how an SQL node chooses a cluster data node to use as transaction coordinator |
There are two forms of optimized node selection, described here:
The SQL node uses
promixity to
determine the transaction coordinator; that is, the
“closest” data node to the SQL node is
chosen as the transaction coordinator. For this
purpose, a data node having a shared memory connection
with the SQL node is considered to be
“closest” to the SQL node; the next
closest (in order of decreasing proximity) are: TCP
connection to localhost
; SCI
connection; TCP connection from a host other than
localhost
.
The SQL thread uses distribution awareness to select the data node. That is, the data node housing the cluster partition accessed by the first statement of a given transaction is used as the transaction coordinator for the entire transaction. (This is effective only if the first statement of the transaction accesses no more than one cluster partition.)
This option takes one of the integer values
0
, 1
,
2
, or 3
.
3
is the default. These values affect
node selection as follows:
0
: Node selection is not optimized.
Each data node is employed as the transaction
coordinator 8 times before the SQL thread proceeds to
the next data node.
1
: Proximity to the SQL node is
used to determine the transaction coordinator.
2
: Distribution awareness is used
to select the transaction coordinator. However, if the
first statement of the transaction accesses more than
one cluster partition, the SQL node reverts to the
round-robin behavior seen when this option is set to
0
.
3
: If distribution awareness can be
employed to determine the transaction coordinator,
then it is used; otherwise proximity is used to select
the transaction coordinator. (This is the default
behavior.)
Table 19.57 Type and value information for ndb_read_backup
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | Yes |
5.7.12-ndb-7.5.2 | boolean | OFF |
DESCRIPTION: Enable read from any replica |
Enable read from any replica for any
NDB
table subsequently created.
Added in MySQL Cluster NDB 7.5.2.
ndb_recv_thread_activation_threshold
Table 19.58 Type and value information for ndb_recv_thread_activation_threshold
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
No | No | No |
No | No | |
5.6.10-ndb-7.3.1 | integer | 8 / 0 (MIN_ACTIVATION_THRESHOLD) - 16 (MAX_ACTIVATION_THRESHOLD) |
DESCRIPTION: Activation threshold when receive thread takes over the polling of the cluster connection (measured in concurrently active threads) |
When this number of concurrently active threads is reached, the receive thread takes over polling of the cluster connection.
This variable is global in scope. It can also be set on
startup using the
--ndb-recv-thread-activation-threshold
option.
Table 19.59 Type and value information for ndb_recv_thread_cpu_mask
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
No | Yes | No |
No | Global | Yes |
NDB 7.4 | bitmap | [empty] |
DESCRIPTION: CPU mask for locking receiver threads to specific CPUs; specified as hexadecimal. See documentation for details. |
CPU mask for locking receiver threads to specific CPUs.
This is specified as a hexadecimal bitmask; for example,
0x33
means that one CPU is used per
receiver thread. An empty string is the default; setting
ndb_recv_thread_cpu_mask
to this value
removes any receiver thread locks previously set.
This variable is global in scope. It can also be set on
startup using the
--ndb-recv-thread-cpu-mask
option.
ndb_report_thresh_binlog_epoch_slip
Table 19.60 Type and value information for ndb_report_thresh_binlog_epoch_slip
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | No | No |
Yes | No | |
NDB 7.4 | integer | 3 / 0 - 256 |
DESCRIPTION: This is a threshold on the number of epochs to be behind before reporting binary log status |
This is a threshold on the number of epochs to be behind
before reporting binary log status. For example, a value
of 3
(the default) means that if the
difference between which epoch has been received from the
storage nodes and which epoch has been applied to the
binary log is 3 or more, a status message will be sent to
the cluster log.
ndb_report_thresh_binlog_mem_usage
Table 19.61 Type and value information for ndb_report_thresh_binlog_mem_usage
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | No | No |
Yes | No | |
NDB 7.4 | integer | 10 / 0 - 10 |
DESCRIPTION: This is a threshold on the percentage of free memory remaining before reporting binary log status |
This is a threshold on the percentage of free memory
remaining before reporting binary log status. For example,
a value of 10
(the default) means that
if the amount of available memory for receiving binary log
data from the data nodes falls below 10%, a status message
will be sent to the cluster log.
Table 19.62 Type and value information for slave_allow_batching
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | Yes |
NDB 7.4 | boolean | off |
DESCRIPTION: Turns update batching on and off for a replication slave |
Whether or not batched updates are enabled on MySQL Cluster replication slaves.
Currently, this variable is available for mysqld only as supplied with MySQL Cluster or built from the MySQL Cluster sources. For more information, see Section 19.6.6, “Starting MySQL Cluster Replication (Single Replication Channel)”.
ndb_show_foreign_key_mock_tables
Table 19.63 Type and value information for ndb_show_foreign_key_mock_tables
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | Yes |
NDB 7.4 | boolean | OFF |
DESCRIPTION: Show the mock tables used to support foreign_key_checks=0. |
Show the mock tables used by NDB
to
support
foreign_key_checks=0
.
When this is enabled, extra warnings are shown when
creating and dropping the tables. The real (internal) name
of the table can be seen in the output of
SHOW CREATE TABLE
.
Table 19.64 Type and value information for ndb_slave_conflict_role
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | Yes |
NDB 7.4 | enumeration | NONE / NONE, PRIMARY, SECONDARY, PASS |
DESCRIPTION: Role for slave to play in conflict detection and resolution. Value is one of PRIMARY, SECONDARY, PASS, or NONE (default). Can be changed only when slave SQL thread is stopped. See documentation for further information. |
Determine the role of this SQL node (and MySQL Cluster) in
a circular (“active-active”) replication
setup. ndb_slave_conflict_role
can take
any one of the values PRIMARY
,
SECONDARY
, PASS
, or
NULL
(the default). The slave SQL
thread must be stopped before you can change
ndb_slave_conflict_role
. In addition,
it is not possible to change directly between
PASS
and either of
PRIMARY
or SECONDARY
directly; in such cases, you must ensure that the SQL
thread is stopped, then execute
SET
@@GLOBAL.ndb_slave_conflict_role = 'NONE'
first.
For more information, see Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”.
Table 19.65 Type and value information for ndb_table_no_logging
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
No | Yes | No |
No | Session | Yes |
NDB 7.4 | boolean | FALSE |
DESCRIPTION: NDB tables created when this setting is enabled are not checkpointed to disk (although table schema files are created). The setting in effect when the table is created with or altered to use NDBCLUSTER persists for the lifetime of the table. |
When this variable is set to ON
or
1
, it causes
NDB
tables not to be
checkpointed to disk. More specifically, this setting
applies to tables which are created or altered using
ENGINE NDB
when
ndb_table_no_logging
is
enabled, and continues to apply for the lifetime of the
table, even if
ndb_table_no_logging
is
later changed. Suppose that A
,
B
, C
, and
D
are tables that we create (and
perhaps also alter), and that we also change the setting
for ndb_table_no_logging
as shown here:
SET @@ndb_table_no_logging = 1; CREATE TABLE A ... ENGINE NDB; CREATE TABLE B ... ENGINE MYISAM; CREATE TABLE C ... ENGINE MYISAM; ALTER TABLE B ENGINE NDB; SET @@ndb_table_no_logging = 0; CREATE TABLE D ... ENGINE NDB; ALTER TABLE C ENGINE NDB; SET @@ndb_table_no_logging = 1;
After the previous sequence of events, tables
A
and B
are not
checkpointed; A
was created with
ENGINE NDB
and B was altered to use
NDB
, both while
ndb_table_no_logging
was enabled.
However, tables C
and
D
are logged; C
was
altered to use NDB
and
D
was created using ENGINE
NDB
, both while
ndb_table_no_logging
was
disabled. Setting
ndb_table_no_logging
back
to 1
or ON
does
not cause table C
or D
to be checkpointed.
ndb_table_no_logging
has no effect on the creation of
NDB
table schema files; to
suppress these, use
ndb_table_temporary
instead.
Table 19.66 Type and value information for ndb_table_temporary
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
No | Yes | No |
No | Session | Yes |
NDB 7.4 | boolean | FALSE |
DESCRIPTION: NDB tables are not persistent on disk: no schema files are created and the tables are not logged |
When set to ON
or 1
,
this variable causes NDB
tables not to be written to disk: This means that no table
schema files are created, and that the tables are not
logged.
Setting this variable currently has no effect. This is a known issue; see Bug #34036.
Table 19.67 Type and value information for ndb_use_copying_alter_table
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
No | Yes | No |
No | Both | No |
DESCRIPTION: Use copying ALTER TABLE operations in MySQL Cluster |
Forces NDB
to use copying of
tables in the event of problems with online
ALTER TABLE
operations. The
default value is OFF
.
Table 19.68 Type and value information for ndb_use_exact_count
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
No | Yes | No |
No | Both | Yes |
NDB 7.4 | boolean | ON |
5.1.47-ndb-7.1.8 | boolean | OFF |
DESCRIPTION: Use exact row count when planning queries |
Forces NDB
to use a count of
records during SELECT COUNT(*)
query
planning to speed up this type of query. The default value
is OFF
, which allows for faster queries
overall.
Table 19.69 Type and value information for ndb_use_transactions
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Both | Yes |
NDB 7.4 | boolean | ON |
DESCRIPTION: Forces NDB to use a count of records during SELECT COUNT(*) query planning to speed up this type of query |
You can disable NDB
transaction support by setting this variable's values to
OFF
(not recommended). The default is
ON
.
Table 19.70 Type and value information for ndb_version
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
No | Yes | No |
No | Global | No |
NDB 7.4 | string | |
DESCRIPTION: Shows build and NDB engine version as an integer. |
NDB
engine version, as a composite
integer.
Table 19.71 Type and value information for ndb_version_string
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
No | Yes | No |
No | Global | No |
NDB 7.4 | string | |
DESCRIPTION: Shows build information including NDB engine version in ndb-x.y.z format. |
NDB
engine version in
ndb-
format.
x.y.z
Table 19.72 Type and value information for server_id_bits
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
Yes | Global | No |
NDB 7.4 | integer | 32 / 7 - 32 |
DESCRIPTION: The effective value of server_id if the server was started with the --server-id-bits option set to a nondefault value. |
The effective value of
server_id
if the server
was started with the
--server-id-bits
option set
to a nondefault value.
If the value of server_id
greater than or equal to 2 to the power of
server_id_bits
,
mysqld refuses to start.
This system variable is supported only by MySQL Cluster.
server_id_bits
is not
supported by the standard MySQL Server.
Table 19.73 Type and value information for transaction_allow_batching
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
No | Yes | No |
No | Session | Yes |
NDB 7.4 | boolean | FALSE |
DESCRIPTION: Allows batching of statements within a transaction. Disable AUTOCOMMIT to use. |
When set to 1
or ON
,
this variable enables batching of statements within the
same transaction. To use this variable,
autocommit
must first be
disabled by setting it to 0
or
OFF
; otherwise, setting
transaction_allow_batching
has no effect.
It is safe to use this variable with transactions that
performs writes only, as having it enabled can lead to
reads from the “before” image. You should
ensure that any pending transactions are committed (using
an explicit COMMIT
if
desired) before issuing a
SELECT
.
transaction_allow_batching
should not be used whenever there is the possibility
that the effects of a given statement depend on the
outcome of a previous statement within the same
transaction.
This variable is currently supported for MySQL Cluster only.
The system variables in the following list all relate to the
ndbinfo
information
database.
Table 19.74 Type and value information for ndbinfo_database
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
No | Yes | No |
No | Global | No |
NDB 7.4 | string | ndbinfo |
DESCRIPTION: The name used for the NDB information database; read only. |
Shows the name used for the NDB
information database; the default is
ndbinfo
. This is a read-only variable
whose value is determined at compile time; you can set it
by starting the server using
--ndbinfo-database=
,
which sets the value shown for this variable but does not
actually change the name used for the NDB information
database.
name
Table 19.75 Type and value information for ndbinfo_max_bytes
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
No | Both | Yes |
NDB 7.4 | integer | 0 / - |
DESCRIPTION: Used for debugging only. |
Used in testing and debugging only.
Table 19.76 Type and value information for ndbinfo_max_rows
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
No | Both | Yes |
NDB 7.4 | integer | 10 / - |
DESCRIPTION: Used for debugging only. |
Used in testing and debugging only.
Table 19.77 Type and value information for ndbinfo_offline
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
No | Yes | No |
No | Global | Yes |
NDB 7.4 | boolean | OFF |
DESCRIPTION: Put the ndbinfo database into offline mode, in which no rows are returned from tables or views. |
Place the ndbinfo
database into offline mode, in which tables and views can
be opened even when they do not actually exist, or when
they exist but have different definitions in
NDB
. No rows are returned
from such tables (or views).
Whether or not the
ndbinfo
database's
underlying internal tables are shown in the
mysql
client. The default is
OFF
.
Table 19.79 Type and value information for ndbinfo_table_prefix
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
Yes | Yes | No |
No | Both | Yes |
NDB 7.4 | string | ndb$ |
DESCRIPTION: The prefix to use for naming ndbinfo internal base tables |
The prefix used in naming the ndbinfo database's base
tables (normally hidden, unless exposed by setting
ndbinfo_show_hidden
).
This is a read-only variable whose default value is
“ndb$
”. You can start the
server with the --ndbinfo-table-prefix
option, but this merely sets the variable and does not
change the actual prefix used to name the hidden base
tables; the prefix itself is determined at compile time.
Table 19.80 Type and value information for ndbinfo_version
Command Line | System Variable | Status Variable |
---|---|---|
Option File | Scope | Dynamic |
From Version | Type | Default, Range |
Notes | ||
No | Yes | No |
No | Global | No |
NDB 7.4 | string | |
DESCRIPTION: The version of the ndbinfo engine; read only. |
Shows the version of the
ndbinfo
engine in use;
read-only.
This section provides detailed information about MySQL server
status variables that relate to MySQL Cluster and the
NDB
storage engine. For status
variables not specific to MySQL Cluster, and for general
information on using status variables, see
Section 6.1.6, “Server Status Variables”.
The MySQL server can ask the
NDBCLUSTER
storage engine if
it knows about a table with a given name. This is called
discovery.
Handler_discover
indicates the number of times that tables have been
discovered using this mechanism.
Ndb_api_bytes_sent_count_session
Amount of data (in bytes) sent to the data nodes in this client session.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_bytes_sent_count_slave
Amount of data (in bytes) sent to the data nodes by this slave.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Amount of data (in bytes) sent to the data nodes by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_bytes_received_count_session
Amount of data (in bytes) received from the data nodes in this client session.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_bytes_received_count_slave
Amount of data (in bytes) received from the data nodes by this slave.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Amount of data (in bytes) received from the data nodes by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_event_data_count_injector
The number of row change events received by the NDB binlog injector thread.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of row change events received by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_event_nondata_count_injector
The number of events received, other than row change events, by the NDB binary log injector thread.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of events received, other than row change events, by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_event_bytes_count_injector
The number of bytes of events received by the NDB binlog injector thread.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of bytes of events received by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of operations in this client session based on or using primary keys. This includes operations on blob tables, implicit unlock operations, and auto-increment operations, as well as user-visible primary key operations.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of operations by this slave based on or using primary keys. This includes operations on blob tables, implicit unlock operations, and auto-increment operations, as well as user-visible primary key operations.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of operations by this MySQL Server (SQL node) based on or using primary keys. This includes operations on blob tables, implicit unlock operations, and auto-increment operations, as well as user-visible primary key operations.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_pruned_scan_count_session
The number of scans in this client session that have been pruned to a single partition.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_pruned_scan_count_slave
The number of scans by this slave that have been pruned to a single partition.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of scans by this MySQL Server (SQL node) that have been pruned to a single partition.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_range_scan_count_session
The number of range scans that have been started in this client session.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_range_scan_count_slave
The number of range scans that have been started by this slave.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of range scans that have been started by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_read_row_count_session
The total number of rows that have been read in this client session. This includes all rows read by any primary key, unique key, or scan operation made in this client session.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The total number of rows that have been read by this slave. This includes all rows read by any primary key, unique key, or scan operation made by this slave.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The total number of rows that have been read by this MySQL Server (SQL node). This includes all rows read by any primary key, unique key, or scan operation made by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_scan_batch_count_session
The number of batches of rows received in this client session. 1 batch is defined as 1 set of scan results from a single fragment.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_scan_batch_count_slave
The number of batches of rows received by this slave. 1 batch is defined as 1 set of scan results from a single fragment.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of batches of rows received by this MySQL Server (SQL node). 1 batch is defined as 1 set of scan results from a single fragment.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_table_scan_count_session
The number of table scans that have been started in this client session, including scans of internal tables,.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_table_scan_count_slave
The number of table scans that have been started by this slave, including scans of internal tables,.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of table scans that have been started by this MySQL Server (SQL node), including scans of internal tables,.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_abort_count_session
The number of transactions aborted in this client session.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_abort_count_slave
The number of transactions aborted by this slave.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of transactions aborted by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_close_count_session
The number of transactions closed in this client session.
This value may be greater than the sum of
Ndb_api_trans_commit_count_session
and
Ndb_api_trans_abort_count_session
,
since some transactions may have been rolled back.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_close_count_slave
The number of transactions closed by this slave. This
value may be greater than the sum of
Ndb_api_trans_commit_count_slave
and
Ndb_api_trans_abort_count_slave
,
since some transactions may have been rolled back.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of transactions closed by this MySQL Server
(SQL node). This value may be greater than the sum of
Ndb_api_trans_commit_count
and
Ndb_api_trans_abort_count
,
since some transactions may have been rolled back.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_commit_count_session
The number of transactions committed in this client session.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_commit_count_slave
The number of transactions committed by this slave.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of transactions committed by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_local_read_row_count_session
The total number of rows that have been read in this client session. This includes all rows read by any primary key, unique key, or scan operation made in this client session.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_local_read_row_count_slave
The total number of rows that have been read by this slave. This includes all rows read by any primary key, unique key, or scan operation made by this slave.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_local_read_row_count
The total number of rows that have been read by this MySQL Server (SQL node). This includes all rows read by any primary key, unique key, or scan operation made by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_start_count_session
The number of transactions started in this client session.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_start_count_slave
The number of transactions started by this slave.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of transactions started by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of operations in this client session based on or using unique keys.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of operations by this slave based on or using unique keys.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
The number of operations by this MySQL Server (SQL node) based on or using unique keys.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_exec_complete_count_session
The number of times a thread has been blocked in this
client session while waiting for execution of an operation
to complete. This includes all
execute()
calls as well as implicit implicit executes for blob and
auto-increment operations not visible to clients.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_exec_complete_count_slave
The number of times a thread has been blocked by this
slave while waiting for execution of an operation to
complete. This includes all
execute()
calls as well as implicit implicit executes for blob and
auto-increment operations not visible to clients.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_exec_complete_count
The number of times a thread has been blocked by this
MySQL Server (SQL node) while waiting for execution of an
operation to complete. This includes all
execute()
calls as well as implicit implicit executes for blob and
auto-increment operations not visible to clients.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_meta_request_count_session
The number of times a thread has been blocked in this client session waiting for a metadata-based signal, such as is expected for DDL requests, new epochs, and seizure of transaction records.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_meta_request_count_slave
The number of times a thread has been blocked by this slave waiting for a metadata-based signal, such as is expected for DDL requests, new epochs, and seizure of transaction records.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_meta_request_count
The number of times a thread has been blocked by this MySQL Server (SQL node) waiting for a metadata-based signal, such as is expected for DDL requests, new epochs, and seizure of transaction records.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_nanos_count_session
Total time (in nanoseconds) spent in this client session waiting for any type of signal from the data nodes.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_nanos_count_slave
Total time (in nanoseconds) spent by this slave waiting for any type of signal from the data nodes.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Total time (in nanoseconds) spent by this MySQL Server (SQL node) waiting for any type of signal from the data nodes.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_scan_result_count_session
The number of times a thread has been blocked in this client session while waiting for a scan-based signal, such as when waiting for more results from a scan, or when waiting for a scan to close.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it relates to the current session only,
and is not affected by any other clients of this
mysqld.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_scan_result_count_slave
The number of times a thread has been blocked by this slave while waiting for a scan-based signal, such as when waiting for more results from a scan, or when waiting for a scan to close.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope. If
this MySQL server does not act as a replication slave, or
does not use NDB tables, this value is always 0.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_scan_result_count
The number of times a thread has been blocked by this MySQL Server (SQL node) while waiting for a scan-based signal, such as when waiting for more results from a scan, or when waiting for a scan to close.
Although this variable can be read using either
SHOW GLOBAL
STATUS
or
SHOW SESSION
STATUS
, it is effectively global in scope.
For more information, see Section 19.5.16, “NDB API Statistics Counters and Variables”.
If the server is acting as a MySQL Cluster node, then the value of this variable its node ID in the cluster.
If the server is not part of a MySQL Cluster, then the value of this variable is 0.
If the server is part of a MySQL Cluster, the value of this variable is the host name or IP address of the Cluster management server from which it gets its configuration data.
If the server is not part of a MySQL Cluster, then the value of this variable is an empty string.
If the server is part of a MySQL Cluster, the value of this variable is the number of the port through which it is connected to the Cluster management server from which it gets its configuration data.
If the server is not part of a MySQL Cluster, then the value of this variable is 0.
Shows the number of times that a row was rejected on the
current SQL node due to MySQL Cluster Replication conflict
resolution using NDB$MAX_DELETE_WIN()
,
since the last time that this mysqld
was started.
For more information, see Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”.
Used in MySQL Cluster Replication conflict resolution, this variable shows the number of times that a row was not applied on the current SQL node due to “greatest timestamp wins” conflict resolution since the last time that this mysqld was started.
For more information, see Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”.
Used in MySQL Cluster Replication conflict resolution, this variable shows the number of times that a row was not applied as the result of “same timestamp wins” conflict resolution on a given mysqld since the last time it was restarted.
For more information, see Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”.
Used in MySQL Cluster Replication conflict resolution,
this variable shows the number of rows found to be in
conflict using NDB$EPOCH()
conflict
resolution on a given mysqld since the
last time it was restarted.
For more information, see Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”.
Shows the number of rows found to be in conflict in MySQL
Cluster Replication conflict resolution, when using
NDB$EPOCH2()
, on the master designated
as the primary since the last time it was restarted.
For more information, see NDB$EPOCH2().
Used in MySQL Cluster Replication conflict resolution,
this variable shows the number of rows found to be in
conflict using NDB$EPOCH_TRANS()
conflict resolution on a given mysqld
since the last time it was restarted.
For more information, see Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”.
Used in MySQL Cluster Replication conflict resolution,
this variable shows the number of rows found to be in
conflict using NDB$EPOCH_TRANS2()
conflict resolution on a given mysqld
since the last time it was restarted.
For more information, see NDB$EPOCH2_TRANS().
Ndb_conflict_last_conflict_epoch
The most recent epoch in which a conflict was detected on
this slave. You can compare this value with
Ndb_slave_max_replicated_epoch
;
if Ndb_slave_max_replicated_epoch
is
greater than
Ndb_conflict_last_conflict_epoch
, no
conflicts have yet been detected.
See Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”, for more information.
Ndb_conflict_reflected_op_discard_count
When using MySQL Cluster Replication conflict resolution, this is the number of reflected operations that were not applied on the secondary, due to encountering an error during execution.
See Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”, for more information.
Ndb_conflict_reflected_op_prepare_count
When using conflict resolution with MySQL Cluster Replication, this status variable contains the number of reflected operations that have been defined (that is, prepared for execution on the secondary).
See Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”.
When using conflict resolution with MySQL Cluster Replication, this gives the number of refresh operations that have been prepared for execution on the secondary.
See Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”, for more information.
Ndb_conflict_last_stable_epoch
Number of rows found to be in conflict by a transactional conflict function
See Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”, for more information.
Ndb_conflict_trans_row_conflict_count
Used in MySQL Cluster Replication conflict resolution, this status variable shows the number of rows found to be directly in-conflict by a transactional conflict function on a given mysqld since the last time it was restarted.
Currently, the only transactional conflict detection
function supported by MySQL Cluster is NDB$EPOCH_TRANS(),
so this status variable is effectively the same as
Ndb_conflict_fn_epoch_trans
.
For more information, see Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”.
Ndb_conflict_trans_row_reject_count
Used in MySQL Cluster Replication conflict resolution,
this status variable shows the total number of rows
realigned due to being determined as conflicting by a
transactional conflict detection function. This includes
not only
Ndb_conflict_trans_row_conflict_count
,
but any rows in or dependent on conflicting transactions.
For more information, see Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”.
Ndb_conflict_trans_reject_count
Used in MySQL Cluster Replication conflict resolution, this status variable shows the number of transactions found to be in conflict by a transactional conflict detection function.
For more information, see Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”.
Ndb_conflict_trans_detect_iter_count
Used in MySQL Cluster Replication conflict resolution,
this shows the number of internal iterations required to
commit an epoch transaction. Should be (slightly) greater
than or equal to
Ndb_conflict_trans_conflict_commit_count
.
For more information, see Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”.
Ndb_conflict_trans_conflict_commit_count
Used in MySQL Cluster Replication conflict resolution, this shows the number of epoch transactions committed after they required transactional conflict handling.
For more information, see Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”.
When using delete-delete conflict detection, this is the number of delete-delete conflicts detected, where a delete operation is applied, but the indicated row does not exist.
Provides the number of round trips to the
NDB
kernel made by
operations.
The epoch most recently committed by
NDB
.
The epoch most recently committed by this
NDB
client.
If the server is part of a MySQL Cluster, the value of this variable is the number of data nodes in the cluster.
If the server is not part of a MySQL Cluster, then the value of this variable is 0.
The total number of joins pushed down to the NDB kernel for distributed handling on the data nodes.
Joins tested using
EXPLAIN
that can be
pushed down contribute to this number.
The number of joins that were pushed down to the NDB kernel but that could not be handled there.
The number of joins successfully pushed down to
NDB
and executed there.
The number of rows returned to mysqld from the NDB kernel by joins that were pushed down.
This variable holds a count of the number of scans
executed by NDBCLUSTER
since
the MySQL Cluster was last started where
NDBCLUSTER
was able to use
partition pruning.
Using this variable together with
Ndb_scan_count
can be
helpful in schema design to maximize the ability of the
server to prune scans to a single table partition, thereby
involving only a single data node.
This variable holds a count of the total number of scans
executed by NDBCLUSTER
since
the MySQL Cluster was last started.
Ndb_slave_max_replicated_epoch
The most recently committed epoch on this slave. You can
compare this value with
Ndb_conflict_last_conflict_epoch
;
if Ndb_slave_max_replicated_epoch
is
the greater of the two, no conflicts have yet been
detected.
For more information, see Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”.
TCP/IP is the default transport mechanism for all connections between nodes in a MySQL Cluster. Normally it is not necessary to define TCP/IP connections; MySQL Cluster automatically sets up such connections for all data nodes, management nodes, and SQL or API nodes.
For an exception to this rule, see Section 19.3.3.10, “MySQL Cluster TCP/IP Connections Using Direct Connections”.
To override the default connection parameters, it is necessary
to define a connection using one or more
[tcp]
sections in the
config.ini
file. Each
[tcp]
section explicitly defines a TCP/IP
connection between two MySQL Cluster nodes, and must contain at
a minimum the parameters
NodeId1
and
NodeId2
, as well as any
connection parameters to override.
It is also possible to change the default values for these
parameters by setting them in the [tcp
default]
section.
Any [tcp]
sections in the
config.ini
file should be listed
last, following all other sections in the
file. However, this is not required for a [tcp
default]
section. This requirement is a known issue
with the way in which the config.ini
file
is read by the MySQL Cluster management server.
Connection parameters which can be set in
[tcp]
and [tcp default]
sections of the config.ini
file are listed
here:
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | numeric | [none] | ... | N |
To identify a connection between two nodes it is necessary
to provide their node IDs in the [tcp]
section of the configuration file as the values of
NodeId1
and
NodeId2
. These are
the same unique Id
values for each of
these nodes as described in
Section 19.3.3.7, “Defining SQL and Other API Nodes in a MySQL Cluster”.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | numeric | [none] | ... | N |
To identify a connection between two nodes it is necessary
to provide their node IDs in the [tcp]
section of the configuration file as the values of
NodeId1
and
NodeId2
. These are the same unique
Id
values for each of these nodes as
described in Section 19.3.3.7, “Defining SQL and Other API Nodes in a MySQL Cluster”.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | name or IP address | [none] | ... | N |
The HostName1
and
HostName2
parameters
can be used to specify specific network interfaces to be
used for a given TCP connection between two nodes. The
values used for these parameters can be host names or IP
addresses.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | name or IP address | [none] | ... | N |
The HostName1
and
HostName2
parameters can be used to
specify specific network interfaces to be used for a given
TCP connection between two nodes. The values used for these
parameters can be host names or IP addresses.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
When more than this many unsent bytes are in the send buffer, the connection is considered overloaded.
This parameter can be used to determine the amount of unsent data that must be present in the send buffer before the connection is considered overloaded. See Section 19.3.3.13, “Configuring MySQL Cluster Send Buffer Parameters”, for more information.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 2M | 256K - 4294967039 (0xFFFFFEFF) | N |
TCP transporters use a buffer to store all messages before performing the send call to the operating system. When this buffer reaches 64KB its contents are sent; these are also sent when a round of messages have been executed. To handle temporary overload situations it is also possible to define a bigger send buffer.
If this parameter is set explicitly, then the memory is not
dedicated to each transporter; instead, the value used
denotes the hard limit for how much memory (out of the total
available memory—that is,
TotalSendBufferMemory
) that may be used
by a single transporter. For more information about
configuring dynamic transporter send buffer memory
allocation in MySQL Cluster, see
Section 19.3.3.13, “Configuring MySQL Cluster Send Buffer Parameters”.
The default size of the send buffer is 2MB, which is the size recommended in most situations. The minimum size is 64 KB; the theoretical maximum is 4 GB.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | [see text] | true, false | N |
To be able to retrace a distributed message datagram, it is
necessary to identify each message. When this parameter is
set to Y
, message IDs are transported
over the network. This feature is disabled by default in
production builds, and enabled in -debug
builds.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | false | true, false | N |
This parameter is a boolean parameter (enabled by setting it
to Y
or 1
, disabled by
setting it to N
or 0
).
It is disabled by default. When it is enabled, checksums for
all messages are calculated before they placed in the send
buffer. This feature ensures that messages are not corrupted
while waiting in the send buffer, or by the transport
mechanism.
This parameter formerly specified the port number to be used
for listening for connections from other nodes. It is now
deprecated (and removed in MySQL Cluster NDB 7.5); use the
ServerPort
data node
configuration parameter for this purpose instead (Bug
#77405, Bug #21280456).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 2M | 16K - 4294967039 (0xFFFFFEFF) | N |
Specifies the size of the buffer used when receiving data from the TCP/IP socket.
The default value of this parameter is 2MB. The minimum possible value is 16KB; the theoretical maximum is 4GB.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 0 | 0 - 2G | N |
Determines the size of the receive buffer set during TCP transporter initialization. The default and minimum value is 0, which allows the operating system or platform to set this value. The default is recommended for most common usage cases.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 0 | 0 - 2G | N |
Determines the size of the send buffer set during TCP transporter initialization. The default and minimum value is 0, which allows the operating system or platform to set this value. The default is recommended for most common usage cases.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 0 | 0 - 2G | N |
Determines the size of the memory set during TCP transporter initialization. The default is recommended for most common usage cases.
Setting this parameter to TRUE
or
1
binds IP_ADDR_ANY
so
that connections can be made from anywhere (for
autogenerated connections). The default is
FALSE
(0
).
Setting up a cluster using direct connections between data nodes
requires specifying explicitly the crossover IP addresses of the
data nodes so connected in the [tcp]
section
of the cluster config.ini
file.
In the following example, we envision a cluster with at least
four hosts, one each for a management server, an SQL node, and
two data nodes. The cluster as a whole resides on the
172.23.72.*
subnet of a LAN. In addition to
the usual network connections, the two data nodes are connected
directly using a standard crossover cable, and communicate with
one another directly using IP addresses in the
1.1.0.*
address range as shown:
# Management Server [ndb_mgmd] Id=1 HostName=172.23.72.20 # SQL Node [mysqld] Id=2 HostName=172.23.72.21 # Data Nodes [ndbd] Id=3 HostName=172.23.72.22 [ndbd] Id=4 HostName=172.23.72.23 # TCP/IP Connections [tcp] NodeId1=3 NodeId2=4 HostName1=1.1.0.1 HostName2=1.1.0.2
The HostName1
and
HostName2
parameters are
used only when specifying direct connections.
The use of direct TCP connections between data nodes can improve the cluster's overall efficiency by enabling the data nodes to bypass an Ethernet device such as a switch, hub, or router, thus cutting down on the cluster's latency.
To take the best advantage of direct connections in this fashion with more than two data nodes, you must have a direct connection between each data node and every other data node in the same node group.
MySQL Cluster attempts to use the shared memory transporter and
configure it automatically where possible.
[shm]
sections in the
config.ini
file explicitly define
shared-memory connections between nodes in the cluster. When
explicitly defining shared memory as the connection method, it
is necessary to define at least
NodeId1
,
NodeId2
, and
ShmKey
. All other
parameters have default values that should work well in most
cases.
SHM functionality is considered experimental only. It is not officially supported in any current MySQL Cluster release, and testing results indicate that SHM performance is not appreciably greater than when using TCP/IP for the transporter.
For these reasons, you must determine for yourself or by using our free resources (forums, mailing lists) whether SHM can be made to work correctly in your specific case.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | numeric | [none] | ... | N |
To identify a connection between two nodes it is necessary
to provide node identifiers for each of them, as
NodeId1
and
NodeId2
.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | numeric | [none] | ... | N |
To identify a connection between two nodes it is necessary
to provide node identifiers for each of them, as
NodeId1
and
NodeId2
.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | name or IP address | [none] | ... | N |
The HostName1
and
HostName2
parameters
can be used to specify specific network interfaces to be
used for a given SHM connection between two nodes. The
values used for these parameters can be host names or IP
addresses.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | name or IP address | [none] | ... | N |
The HostName1
and
HostName2
parameters can be used to
specify specific network interfaces to be used for a given
SHM connection between two nodes. The values used for these
parameters can be host names or IP addresses.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
When more than this many unsent bytes are in the send buffer, the connection is considered overloaded.
This parameter can be used to determine the amount of unsent data that must be present in the send buffer before the connection is considered overloaded. See Section 19.3.3.13, “Configuring MySQL Cluster Send Buffer Parameters”, for more information.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | [none] | 0 - 4294967039 (0xFFFFFEFF) | N |
When setting up shared memory segments, a node ID, expressed as an integer, is used to identify uniquely the shared memory segment to use for the communication. There is no default value.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 1M | 64K - 4294967039 (0xFFFFFEFF) | N |
Each SHM connection has a shared memory segment where
messages between nodes are placed by the sender and read by
the reader. The size of this segment is defined by
ShmSize
. The default
value is 1MB.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | false | true, false | N |
To retrace the path of a distributed message, it is
necessary to provide each message with a unique identifier.
Setting this parameter to Y
causes these
message IDs to be transported over the network as well. This
feature is disabled by default in production builds, and
enabled in -debug
builds.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | true | true, false | N |
This parameter is a boolean
(Y
/N
) parameter which
is disabled by default. When it is enabled, checksums for
all messages are calculated before being placed in the send
buffer.
This feature prevents messages from being corrupted while waiting in the send buffer. It also serves as a check against data being corrupted during transport.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | [none] | 0 - 4294967039 (0xFFFFFEFF) | N |
When using the shared memory transporter, a process sends an operating system signal to the other process when there is new data available in the shared memory. Should that signal conflict with an existing signal, this parameter can be used to change it. This is a possibility when using SHM due to the fact that different operating systems use different signal numbers.
The default value of
SigNum
is 0;
therefore, it must be set to avoid errors in the cluster log
when using the shared memory transporter. Typically, this
parameter is set to 10 in the [shm
default]
section of the
config.ini
file.
[sci]
sections in the
config.ini
file explicitly define SCI
(Scalable Coherent Interface) connections between cluster nodes.
Using SCI transporters in MySQL Cluster is supported only when
the MySQL binaries are built using
--with-ndb-sci=
.
The /your/path/to/SCI
path
should point to a directory
that contains at a minimum lib
and
include
directories containing SISCI
libraries and header files. (See
Section 19.3.4, “Using High-Speed Interconnects with MySQL Cluster” for more
information about SCI.)
In addition, SCI requires specialized hardware.
It is strongly recommended to use SCI Transporters only for communication between ndbd processes. Using SCI Transporters means that the ndbd processes never sleep. For this reason, SCI Transporters should be used only on machines having at least two CPUs dedicated for use by ndbd processes. There should be at least one CPU per ndbd process, with at least one CPU left in reserve to handle operating system activities.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | numeric | [none] | ... | N |
To identify a connection between two nodes it is necessary
to provide node identifiers for each of them, as
NodeId1
and
NodeId2
.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | numeric | [none] | ... | N |
To identify a connection between two nodes it is necessary
to provide node identifiers for each of them, as
NodeId1
and
NodeId2
.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | [none] | 0 - 4294967039 (0xFFFFFEFF) | N |
This identifies the SCI node ID on the first Cluster node
(identified by
NodeId1
).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
It is possible to set up SCI Transporters for failover between two SCI cards which then should use separate networks between the nodes. This identifies the node ID and the second SCI card to be used on the first node.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | [none] | 0 - 4294967039 (0xFFFFFEFF) | N |
This identifies the SCI node ID on the second Cluster node
(identified by
NodeId2
).
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
When using two SCI cards to provide failover, this parameter identifies the second SCI card to be used on the second node.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | name or IP address | [none] | ... | N |
The HostName1
and
HostName2
parameters
can be used to specify specific network interfaces to be
used for a given SCI connection between two nodes. The
values used for these parameters can be host names or IP
addresses.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | name or IP address | [none] | ... | N |
The HostName1
and
HostName2
parameters can be used to
specify specific network interfaces to be used for a given
SCI connection between two nodes. The values used for these
parameters can be host names or IP addresses.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 10M | 64K - 4294967039 (0xFFFFFEFF) | N |
Each SCI transporter has a shared memory segment used for communication between the two nodes. Setting the size of this segment to the default value of 1MB should be sufficient for most applications. Using a smaller value can lead to problems when performing many parallel inserts; if the shared buffer is too small, this can also result in a crash of the ndbd process.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | unsigned | 8K | 128 - 32K | N |
A small buffer in front of the SCI media stores messages before transmitting them over the SCI network. By default, this is set to 8KB. Our benchmarks show that performance is best at 64KB but 16KB reaches within a few percent of this, and there was little if any advantage to increasing it beyond 8KB.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | true | true, false | N |
To trace a distributed message it is necessary to identify
each message uniquely. When this parameter is set to
Y
, message IDs are transported over the
network. This feature is disabled by default in production
builds, and enabled in -debug
builds.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | boolean | false | true, false | N |
This parameter is a boolean value, and is disabled by
default. When Checksum
is enabled,
checksums are calculated for all messages before they are
placed in the send buffer. This feature prevents messages
from being corrupted while waiting in the send buffer. It
also serves as a check against data being corrupted during
transport.
Effective Version | Type/Units | Default | Range/Values | Restart Type |
---|---|---|---|---|
NDB 7.4.0 | bytes | 0 | 0 - 4294967039 (0xFFFFFEFF) | N |
When more than this many unsent bytes are in the send buffer, the connection is considered overloaded. See Section 19.3.3.13, “Configuring MySQL Cluster Send Buffer Parameters”, for more information.
The NDB
kernel employs a unified send buffer
whose memory is allocated dynamically from a pool shared by all
transporters. This means that the size of the send buffer can be
adjusted as necessary. Configuration of the unified send buffer
can accomplished by setting the following parameters:
TotalSendBufferMemory.
This parameter can be set for all types of MySQL Cluster
nodes—that is, it can be set in the
[ndbd]
, [mgm]
, and
[api]
(or [mysql]
)
sections of the config.ini
file. It
represents the total amount of memory (in bytes) to be
allocated by each node for which it is set for use among
all configured transporters. If set, its minimum is 256KB;
the maximum is 4294967039.
To be backward-compatible with existing configurations, this parameter takes as its default value the sum of the maximum send buffer sizes of all configured transporters, plus an additional 32KB (one page) per transporter. The maximum depends on the type of transporter, as shown in the following table:
Transporter | Maximum Send Buffer Size (bytes) |
---|---|
TCP | SendBufferMemory (default = 2M) |
SCI | SendLimit (default = 8K) plus 16K |
SHM | 20K |
This enables existing configurations to function in close to the same way as they did with MySQL Cluster NDB 6.3 and earlier, with the same amount of memory and send buffer space available to each transporter. However, memory that is unused by one transporter is not available to other transporters.
OverloadLimit.
This parameter is used in the
config.ini
file
[tcp]
section, and denotes the amount
of unsent data (in bytes) that must be present in the send
buffer before the connection is considered overloaded.
When such an overload condition occurs, transactions that
affect the overloaded connection fail with NDB API Error
1218 (Send Buffers overloaded in NDB
kernel) until the overload status passes. The
default value is 0, in which case the effective overload
limit is calculated as SendBufferMemory *
0.8
for a given connection. The maximum value
for this parameter is 4G.
SendBufferMemory.
This value denotes a hard limit for the amount of memory
that may be used by a single transporter out of the entire
pool specified by
TotalSendBufferMemory
.
However, the sum of SendBufferMemory
for all configured transporters may be greater than the
TotalSendBufferMemory
that is set for a given node. This is a way to save memory
when many nodes are in use, as long as the maximum amount
of memory is never required by all transporters at the
same time.
ReservedSendBufferMemory. Removed in MySQL Cluster NDB 7.5.2.
Prior to MySQL Cluster NDB 7.5.2, this data node parameter was present, but was not actually used (Bug #77404, Bug #21280428).
Even before design of NDBCLUSTER
began in 1996, it was evident that one of the major problems to be
encountered in building parallel databases would be communication
between the nodes in the network. For this reason,
NDBCLUSTER
was designed from the very
beginning to permit the use of a number of different data
transport mechanisms. In this Manual, we use the term
transporter for these.
The MySQL Cluster codebase provides for four different transporters:
TCP/IP using 100 Mbps or gigabit Ethernet, as discussed in Section 19.3.3.9, “MySQL Cluster TCP/IP Connections”.
Direct (machine-to-machine) TCP/IP; although this transporter uses the same TCP/IP protocol as mentioned in the previous item, it requires setting up the hardware differently and is configured differently as well. For this reason, it is considered a separate transport mechanism for MySQL Cluster. See Section 19.3.3.10, “MySQL Cluster TCP/IP Connections Using Direct Connections”, for details.
Shared memory (SHM). For more information about SHM, see Section 19.3.3.11, “MySQL Cluster Shared-Memory Connections”.
SHM is considered experimental only, and is not officially supported.
Scalable Coherent Interface (SCI), as described in the next section of this chapter, Section 19.3.3.12, “SCI Transport Connections in MySQL Cluster”.
Most users today employ TCP/IP over Ethernet because it is ubiquitous. TCP/IP is also by far the best-tested transporter for use with MySQL Cluster.
We are working to make sure that communication with the ndbd process is made in “chunks” that are as large as possible because this benefits all types of data transmission.
For users who desire it, it is also possible to use cluster interconnects to enhance performance even further. There are two ways to achieve this: Either a custom transporter can be designed to handle this case, or you can use socket implementations that bypass the TCP/IP stack to one extent or another. We have experimented with both of these techniques using the SCI (Scalable Coherent Interface) technology developed by Dolphin Interconnect Solutions.
It is possible employing Scalable Coherent Interface (SCI) technology to achieve a significant increase in connection speeds and throughput between MySQL Cluster data and SQL nodes. To use SCI, it is necessary to obtain and install Dolphin SCI network cards and to use the drivers and other software supplied by Dolphin. You can get information on obtaining these, from Dolphin Interconnect Solutions. SCI SuperSocket or SCI Transporter support is available for 32-bit and 64-bit Linux, Solaris, Windows, and other platforms. See the Dolphin documentation referenced later in this section for more detailed information regarding platforms supported for SCI.
Once you have acquired the required Dolphin hardware and software, you can obtain detailed information on how to adapt a MySQL Cluster configured for normal TCP/IP communication to use SCI from the from the Dolphin SCI online documentation.
The ndbd process has a number of simple constructs which are used to access the data in a MySQL Cluster. We have created a very simple benchmark to check the performance of each of these and the effects which various interconnects have on their performance.
There are four access methods:
Primary key access. This is access of a record through its primary key. In the simplest case, only one record is accessed at a time, which means that the full cost of setting up a number of TCP/IP messages and a number of costs for context switching are borne by this single request. In the case where multiple primary key accesses are sent in one batch, those accesses share the cost of setting up the necessary TCP/IP messages and context switches. If the TCP/IP messages are for different destinations, additional TCP/IP messages need to be set up.
Unique key access. Unique key accesses are similar to primary key accesses, except that a unique key access is executed as a read on an index table followed by a primary key access on the table. However, only one request is sent from the MySQL Server, and the read of the index table is handled by ndbd. Such requests also benefit from batching.
Full table scan. When no indexes exist for a lookup on a table, a full table scan is performed. This is sent as a single request to the ndbd process, which then divides the table scan into a set of parallel scans on all cluster ndbd processes. In future versions of MySQL Cluster, an SQL node will be able to filter some of these scans.
Range scan using ordered index. When an ordered index is used, it performs a scan in the same manner as the full table scan, except that it scans only those records which are in the range used by the query transmitted by the MySQL server (SQL node). All partitions are scanned in parallel when all bound index attributes include all attributes in the partitioning key.
With benchmarks developed internally by MySQL for testing simple and batched primary and unique key accesses, we have found that using SCI sockets improves performance by approximately 100% over TCP/IP, except in rare instances when communication performance is not an issue. This can occur when scan filters make up most of processing time or when very large batches of primary key accesses are achieved. In that case, the CPU processing in the ndbd processes becomes a fairly large part of the overhead.
Using the SCI transporter instead of SCI Sockets is only of interest in communicating between ndbd processes. Using the SCI transporter is also only of interest if a CPU can be dedicated to the ndbd process because the SCI transporter ensures that this process will never go to sleep. It is also important to ensure that the ndbd process priority is set in such a way that the process does not lose priority due to running for an extended period of time, as can be done by locking processes to CPUs in Linux 2.6. If such a configuration is possible, the ndbd process will benefit by 10−70% as compared with using SCI sockets. (The larger figures will be seen when performing updates and probably on parallel scan operations as well.)
There are several other optimized socket implementations for computer clusters, including Myrinet, Gigabit Ethernet, Infiniband and the VIA interface. However, we have tested MySQL Cluster so far only with SCI sockets. See Section 19.3.4.1, “Configuring MySQL Cluster to use SCI Sockets”, for information on how to set up SCI sockets using ordinary TCP/IP for MySQL Cluster.
Using and managing a MySQL Cluster requires several specialized programs, which we describe in this chapter. We discuss the purposes of these programs in a MySQL Cluster, how to use the programs, and what startup options are available for each of them.
These programs include the MySQL Cluster data, management, and SQL node processes (ndbd, ndbmtd, ndb_mgmd, and mysqld) and the management client (ndb_mgm).
Information about the program ndb_setup.py, used to start the MySQL Cluster Auto-Installer, is also included in this section. You should be aware that Section 19.4.23, “ndb_setup.py — Start browser-based Auto-Installer for MySQL Cluster”, contains information about the command-line client only; for information about using the GUI installer spawned by this program to configure and deploy a MySQL Cluster, see Section 19.2.1, “The MySQL Cluster Auto-Installer”.
For information about using mysqld as a MySQL Cluster process, see Section 19.5.4, “MySQL Server Usage for MySQL Cluster”.
Other NDB
utility, diagnostic, and
example programs are included with the MySQL Cluster distribution.
These include ndb_restore,
ndb_show_tables, and
ndb_config. These programs are also covered in
this section.
The final portion of this section contains tables of options that are common to all the various MySQL Cluster programs.
ndbd is the process that is used to handle all the data in tables using the NDB Cluster storage engine. This is the process that empowers a data node to accomplish distributed transaction handling, node recovery, checkpointing to disk, online backup, and related tasks.
In a MySQL Cluster, a set of ndbd processes cooperate in handling data. These processes can execute on the same computer (host) or on different computers. The correspondences between data nodes and Cluster hosts is completely configurable.
The following table includes command options specific to the MySQL Cluster data node program ndbd. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndbd), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.81 This table describes command-line options for the ndbd program
Format | Description | Added or Removed |
---|---|---|
Perform initial start of ndbd, including cleaning the file system. Consult the documentation before using this option | All MySQL 5.7 based releases |
|
Don't start ndbd immediately; ndbd waits for command to start from ndb_mgmd | All MySQL 5.7 based releases |
|
Start ndbd as daemon (default); override with --nodaemon | All MySQL 5.7 based releases |
|
Do not start ndbd as daemon; provided for testing purposes | All MySQL 5.7 based releases |
|
Run ndbd in foreground, provided for debugging purposes (implies --nodaemon) | All MySQL 5.7 based releases |
|
Do not wait for these data nodes to start (takes comma-separated list of node IDs). Also requires --ndb-nodeid to be used. | All MySQL 5.7 based releases |
|
Perform partial initial start (requires --nowait-nodes) | All MySQL 5.7 based releases |
|
Local bind address | All MySQL 5.7 based releases |
|
Used to install the data node process as a Windows service. Does not apply on non-Windows platforms. | All MySQL 5.7 based releases |
|
Used to remove a data node process that was previously installed as a Windows service. Does not apply on non-Windows platforms. | All MySQL 5.7 based releases |
|
Set the number of times to retry a connection before giving up; 0 means 1 attempt only (and no retries) | All MySQL 5.7 based releases |
|
Time to wait between attempts to contact a management server, in seconds; 0 means do not wait between attempts | All MySQL 5.7 based releases |
|
Time to wait between attempts to contact a management server, in seconds; 0 means do not wait between attempts | All MySQL 5.7 based releases |
All of these options also apply to the multi-threaded version of this program (ndbmtd) and you may substitute “ndbmtd” for “ndbd” wherever the latter occurs in this section.
Command-Line Format | --bind-address=name | ||
Permitted Values | Type | string | |
Default |
|
Causes ndbd to bind to a specific network interface (host name or IP address). This option has no default value.
Command-Line Format | --daemon | ||
Permitted Values | Type | boolean | |
Default | TRUE |
Instructs ndbd or
ndbmtd to execute as a daemon process.
This is the default behavior.
--nodaemon
can be used to
prevent the process from running as a daemon.
This option has no effect when running ndbd or ndbmtd on Windows platforms.
Command-Line Format | --nodaemon | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Prevents ndbd or
ndbmtd from executing as a daemon
process. This option overrides the
--daemon
option. This is useful
for redirecting output to the screen when debugging the
binary.
The default behavior for ndbd and ndbmtd on Windows is to run in the foreground, making this option unnecessary on Windows platforms, where it has no effect.
Command-Line Format | --foreground | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Causes ndbd or ndbmtd
to execute as a foreground process, primarily for debugging
purposes. This option implies the
--nodaemon
option.
This option has no effect when running ndbd or ndbmtd on Windows platforms.
Command-Line Format | --initial | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Instructs ndbd to perform an initial start. An initial start erases any files created for recovery purposes by earlier instances of ndbd. It also re-creates recovery log files. On some operating systems, this process can take a substantial amount of time.
An --initial
start is to be
used only when starting the
ndbd process under very special
circumstances; this is because this option causes all files
to be removed from the MySQL Cluster file system and all
redo log files to be re-created. These circumstances are
listed here:
When performing a software upgrade which has changed the contents of any files.
When restarting the node with a new version of ndbd.
As a measure of last resort when for some reason the node restart or system restart repeatedly fails. In this case, be aware that this node can no longer be used to restore data due to the destruction of the data files.
Use of this option prevents the
StartPartialTimeout
and
StartPartitionedTimeout
configuration parameters from having any effect.
This option does not affect either of the following types of files:
Backup files that have already been created by the affected node
MySQL Cluster Disk Data files (see Section 19.5.13, “MySQL Cluster Disk Data Tables”).
This option also has no effect on recovery of data by a data node that is just starting (or restarting) from data nodes that are already running. This recovery of data occurs automatically, and requires no user intervention in a MySQL Cluster that is running normally.
It is permissible to use this option when starting the cluster for the very first time (that is, before any data node files have been created); however, it is not necessary to do so.
Command-Line Format | --initial-start | ||
Permitted Values | Type | boolean | |
Default | FALSE |
This option is used when performing a partial initial start
of the cluster. Each node should be started with this
option, as well as
--nowait-nodes
.
Suppose that you have a 4-node cluster whose data nodes have the IDs 2, 3, 4, and 5, and you wish to perform a partial initial start using only nodes 2, 4, and 5—that is, omitting node 3:
shell>ndbd --ndb-nodeid=2 --nowait-nodes=3 --initial-start
shell>ndbd --ndb-nodeid=4 --nowait-nodes=3 --initial-start
shell>ndbd --ndb-nodeid=5 --nowait-nodes=3 --initial-start
When using this option, you must also specify the node ID
for the data node being started with the
--ndb-nodeid
option.
Do not confuse this option with the
--nowait-nodes
option for
ndb_mgmd, which can be used to enable a
cluster configured with multiple management servers to be
started without all management servers being online.
--nowait-nodes=
node_id_1
[,
node_id_2
[, ...]]
Command-Line Format | --nowait-nodes=list | ||
Permitted Values | Type | string | |
Default |
|
This option takes a list of data nodes which for which the cluster will not wait for before starting.
This can be used to start the cluster in a partitioned
state. For example, to start the cluster with only half of
the data nodes (nodes 2, 3, 4, and 5) running in a 4-node
cluster, you can start each ndbd process
with --nowait-nodes=3,5
. In this case, the
cluster starts as soon as nodes 2 and 4 connect, and does
not wait
StartPartitionedTimeout
milliseconds for nodes 3 and 5 to connect as it would
otherwise.
If you wanted to start up the same cluster as in the
previous example without one ndbd (say,
for example, that the host machine for node 3 has suffered a
hardware failure) then start nodes 2, 4, and 5 with
--nowait-nodes=3
. Then the cluster will
start as soon as nodes 2, 4, and 5 connect and will not wait
for node 3 to start.
Command-Line Format | --nostart | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Instructs ndbd not to start
automatically. When this option is used,
ndbd connects to the management server,
obtains configuration data from it, and initializes
communication objects. However, it does not actually start
the execution engine until specifically requested to do so
by the management server. This can be accomplished by
issuing the proper START
command in the management client (see
Section 19.5.2, “Commands in the MySQL Cluster Management Client”).
Command-Line Format | --install[=name] | ||
Platform Specific | Windows | ||
Permitted Values | Type | string | |
Default | ndbd |
Causes ndbd to be installed as a Windows
service. Optionally, you can specify a name for the service;
if not set, the service name defaults to
ndbd
. Although it is preferable to
specify other ndbd program options in a
my.ini
or my.cnf
configuration file, it is possible to use together with
--install
. However, in such cases, the
--install
option must be specified first,
before any other options are given, for the Windows service
installation to succeed.
It is generally not advisable to use this option together
with the --initial
option,
since this causes the data node file system to be wiped and
rebuilt every time the service is stopped and started.
Extreme care should also be taken if you intend to use any
of the other ndbd options that affect the
starting of data nodes—including
--initial-start
,
--nostart
, and
--nowait-nodes
—together
with --install
, and you should
make absolutely certain you fully understand and allow for
any possible consequences of doing so.
The --install
option has no
effect on non-Windows platforms.
Command-Line Format | --remove[=name] | ||
Platform Specific | Windows | ||
Permitted Values | Type | string | |
Default | ndbd |
Causes an ndbd process that was
previously installed as a Windows service to be removed.
Optionally, you can specify a name for the service to be
uninstalled; if not set, the service name defaults to
ndbd
.
The --remove
option has no
effect on non-Windows platforms.
Command-Line Format | --connect-retries=# | ||
Permitted Values | Type | numeric | |
Default | 12 | ||
Min Value | 0 | ||
Max Value | 65535 |
Set the number of times to retry a connection before giving
up; 0 means 1 attempt only (and no retries). The default is
12 attempts. The time to wait between attempts is controlled
by the --connect-retry-delay
option.
Deprecated | 5.6.28-ndb-7.4.9 | ||
Command-Line Format | --connect-delay=# | ||
Permitted Values | Type | numeric | |
Default | 5 | ||
Min Value | 0 | ||
Max Value | 3600 |
Determines the time to wait between attempts to contact a
management server when starting (the number of attempts is
controlled by the
--connect-retries
option). The
default is 5 seconds.
This option is deprecated, and is subject to removal in a
future release of MySQL Cluster. Use
--connect-retry-delay
instead.
Command-Line Format | --connect-retry-delay=# | ||
Permitted Values | Type | numeric | |
Default | 5 | ||
Min Value | 0 | ||
Max Value | 4294967295 |
Determines the time to wait between attempts to contact a
management server when starting (the time between attempts
is controlled by the
--connect-retries
option). The
default is 5 seconds.
This option takes the place of the
--connect-delay
option, which
is now deprecated and subject to removal in a future release
of MySQL Cluster.
ndbd generates a set of log files which are
placed in the directory specified by
DataDir
in the
config.ini
configuration file.
These log files are listed below.
node_id
is and represents the node's
unique identifier. For example,
ndb_2_error.log
is the error log generated
by the data node whose node ID is 2
.
ndb_
is a file containing records of all crashes which the
referenced ndbd process has encountered.
Each record in this file contains a brief error string and a
reference to a trace file for this crash. A typical entry in
this file might appear as shown here:
node_id
_error.log
Date/Time: Saturday 30 July 2004 - 00:20:01 Type of error: error Message: Internal program error (failed ndbrequire) Fault ID: 2341 Problem data: DbtupFixAlloc.cpp Object of reference: DBTUP (Line: 173) ProgramName: NDB Kernel ProcessID: 14909 TraceFile: ndb_2_trace.log.2 ***EOM***
Listings of possible ndbd exit codes and messages generated when a data node process shuts down prematurely can be found in ndbd Error Messages.
The last entry in the error log file is not
necessarily the newest one (nor is it likely to
be). Entries in the error log are not
listed in chronological order; rather, they correspond to
the order of the trace files as determined in the
ndb_
file (see below). Error log entries are thus overwritten
in a cyclical and not sequential fashion.
node_id
_trace.log.next
ndb_
is a trace file describing exactly what happened just before
the error occurred. This information is useful for analysis
by the MySQL Cluster development team.
node_id
_trace.log.trace_id
It is possible to configure the number of these trace files
that will be created before old files are overwritten.
trace_id
is a number which is
incremented for each successive trace file.
ndb_
is the file that keeps track of the next trace file number
to be assigned.
node_id
_trace.log.next
ndb_
is a file containing any data output by the
ndbd process. This file is created only
if ndbd is started as a daemon, which is
the default behavior.
node_id
_out.log
ndb_
is a file containing the process ID of the
ndbd process when started as a daemon. It
also functions as a lock file to avoid the starting of nodes
with the same identifier.
node_id
.pid
ndb_
is a file used only in debug versions of
ndbd, where it is possible to trace all
incoming, outgoing, and internal messages with their data in
the ndbd process.
node_id
_signal.log
It is recommended not to use a directory mounted through NFS
because in some environments this can cause problems whereby the
lock on the .pid
file remains in effect
even after the process has terminated.
To start ndbd, it may also be necessary to specify the host name of the management server and the port on which it is listening. Optionally, one may also specify the node ID that the process is to use.
shell> ndbd --connect-string="nodeid=2;host=ndb_mgmd.mysql.com:1186"
See Section 19.3.3.3, “MySQL Cluster Connection Strings”, for additional information about this issue. Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”, describes other command-line options which can be used with ndbd. For information about data node configuration parameters, see Section 19.3.3.6, “Defining MySQL Cluster Data Nodes”.
When ndbd starts, it actually initiates two processes. The first of these is called the “angel process”; its only job is to discover when the execution process has been completed, and then to restart the ndbd process if it is configured to do so. Thus, if you attempt to kill ndbd using the Unix kill command, it is necessary to kill both processes, beginning with the angel process. The preferred method of terminating an ndbd process is to use the management client and stop the process from there.
The execution process uses one thread for reading, writing, and scanning data, as well as all other activities. This thread is implemented asynchronously so that it can easily handle thousands of concurrent actions. In addition, a watch-dog thread supervises the execution thread to make sure that it does not hang in an endless loop. A pool of threads handles file I/O, with each thread able to handle one open file. Threads can also be used for transporter connections by the transporters in the ndbd process. In a multi-processor system performing a large number of operations (including updates), the ndbd process can consume up to 2 CPUs if permitted to do so.
For a machine with many CPUs it is possible to use several ndbd processes which belong to different node groups; however, such a configuration is still considered experimental and is not supported for MySQL 5.7 in a production setting. See Section 19.1.6, “Known Limitations of MySQL Cluster”.
ndbinfo_select_all is a client program that
selects all rows and columns from one or more tables in the
ndbinfo
database
Not all ndbinfo
tables available in the
mysql client can be read by this program. In
addition, ndbinfo_select_all can show
information about some tables internal to
ndbinfo
which cannot be accessed using SQL,
including the tables
and
columns
metadata tables.
To select from one or more ndbinfo
tables
using ndbinfo_select_all, it is necessary to
supply the names of the tables when invoking the program as
shown here:
shell> ndbinfo_select_all table_name1
[table_name2
] [...]
For example:
shell> ndbinfo_select_all logbuffers logspaces
== logbuffers ==
node_id log_type log_id log_part total used high
5 0 0 0 33554432 262144 0
6 0 0 0 33554432 262144 0
7 0 0 0 33554432 262144 0
8 0 0 0 33554432 262144 0
== logspaces ==
node_id log_type log_id log_part total used high
5 0 0 0 268435456 0 0
5 0 0 1 268435456 0 0
5 0 0 2 268435456 0 0
5 0 0 3 268435456 0 0
6 0 0 0 268435456 0 0
6 0 0 1 268435456 0 0
6 0 0 2 268435456 0 0
6 0 0 3 268435456 0 0
7 0 0 0 268435456 0 0
7 0 0 1 268435456 0 0
7 0 0 2 268435456 0 0
7 0 0 3 268435456 0 0
8 0 0 0 268435456 0 0
8 0 0 1 268435456 0 0
8 0 0 2 268435456 0 0
8 0 0 3 268435456 0 0
shell>
The following table includes options that are specific to ndbinfo_select_all. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndbinfo_select_all), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.82 This table describes command-line options for the ndbinfo_select_all program
Format | Description | Added or Removed |
---|---|---|
Set the delay in seconds between loops. Default is 5. | All MySQL 5.7 based releases |
|
Set the number of times to perform the select. Default is 1. | All MySQL 5.7 based releases |
|
Name of the database where the table located. | All MySQL 5.7 based releases |
|
Set the degree of parallelism. | All MySQL 5.7 based releases |
Command-Line Format | --delay=# | ||
Permitted Values | Type | numeric | |
Default | 5 | ||
Min Value | 0 | ||
Max Value | MAX_INT |
This option sets the number of seconds to wait between
executing loops. Has no effect if
--loops
is set to
0 or 1.
Command-Line Format | --loops=# | ||
Permitted Values | Type | numeric | |
Default | 1 | ||
Min Value | 0 | ||
Max Value | MAX_INT |
This option sets the number of times to execute the select.
Use --delay
to
set the time between loops.
ndbmtd is a multi-threaded version of
ndbd, the process that is used to handle all
the data in tables using the
NDBCLUSTER
storage engine.
ndbmtd is intended for use on host computers
having multiple CPU cores. Except where otherwise noted,
ndbmtd functions in the same way as
ndbd; therefore, in this section, we
concentrate on the ways in which ndbmtd
differs from ndbd, and you should consult
Section 19.4.1, “ndbd — The MySQL Cluster Data Node Daemon”, for additional
information about running MySQL Cluster data nodes that apply to
both the single-threaded and multi-threaded versions of the data
node process.
Command-line options and configuration parameters used with ndbd also apply to ndbmtd. For more information about these options and parameters, see Section 19.4.1, “ndbd — The MySQL Cluster Data Node Daemon”, and Section 19.3.3.6, “Defining MySQL Cluster Data Nodes”, respectively.
ndbmtd is also file system-compatible with
ndbd. In other words, a data node running
ndbd can be stopped, the binary replaced with
ndbmtd, and then restarted without any loss
of data. (However, when doing this, you must make sure that
MaxNoOfExecutionThreads
is set to an apppriate value before restarting the node if you
wish for ndbmtd to run in multi-threaded
fashion.) Similarly, an ndbmtd binary can be
replaced with ndbd simply by stopping the
node and then starting ndbd in place of the
multi-threaded binary. It is not necessary when switching
between the two to start the data node binary using
--initial
.
Using ndbmtd differs from using ndbd in two key respects:
Because ndbmtd runs by default in
single-threaded mode (that is, it behaves like
ndbd), you must configure it to use
multiple threads. This can be done by setting an appropriate
value in the config.ini
file for the
MaxNoOfExecutionThreads
configuration parameter or the
ThreadConfig
configuration parameter. Using
MaxNoOfExecutionThreads
is simpler, but
ThreadConfig
offers more flexibility. For
more information about these configuration parameters and
their use, see
Multi-Threading Configuration Parameters (ndbmtd).
Trace files are generated by critical errors in ndbmtd processes in a somewhat different fashion from how these are generated by ndbd failures. These differences are discussed in more detail in the next few paragraphs.
Like ndbd, ndbmtd
generates a set of log files which are placed in the directory
specified by DataDir
in
the config.ini
configuration file. Except
for trace files, these are generated in the same way and have
the same names as those generated by ndbd.
In the event of a critical error, ndbmtd
generates trace files describing what happened just prior to the
error' occurrence. These files, which can be found in the
data node's
DataDir
, are useful for
analysis of problems by the MySQL Cluster Development and
Support teams. One trace file is generated for each
ndbmtd thread. The names of these files have
the following pattern:
ndb_node_id
_trace.log.trace_id
_tthread_id
,
In this pattern, node_id
stands for
the data node's unique node ID in the cluster,
trace_id
is a trace sequence number,
and thread_id
is the thread ID. For
example, in the event of the failure of an
ndbmtd process running as a MySQL Cluster
data node having the node ID 3 and with
MaxNoOfExecutionThreads
equal to 4, four trace files are generated in the data
node's data directory. If the is the first time this node
has failed, then these files are named
ndb_3_trace.log.1_t1
,
ndb_3_trace.log.1_t2
,
ndb_3_trace.log.1_t3
, and
ndb_3_trace.log.1_t4
. Internally, these
trace files follow the same format as ndbd
trace files.
The ndbd exit codes and messages that are generated when a data node process shuts down prematurely are also used by ndbmtd. See ndbd Error Messages, for a listing of these.
The management server is the process that reads the cluster configuration file and distributes this information to all nodes in the cluster that request it. It also maintains a log of cluster activities. Management clients can connect to the management server and check the cluster's status.
The following table includes options that are specific to the MySQL Cluster management server program ndb_mgmd. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndb_mgmd), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.83 This table describes command-line options for the ndb_mgmd program
Format | Description | Added or Removed |
---|---|---|
Specify the cluster configuration file; in NDB-6.4.0 and later, needs --reload or --initial to override configuration cache if present | All MySQL 5.7 based releases |
|
Specify the cluster management server's configuration cache directory | All MySQL 5.7 based releases |
|
Local bind address | All MySQL 5.7 based releases |
|
Print full configuration and exit | All MySQL 5.7 based releases |
|
Run ndb_mgmd in daemon mode (default) | All MySQL 5.7 based releases |
|
Do not run ndb_mgmd as a daemon | All MySQL 5.7 based releases |
|
Run ndb_mgmd in interactive mode (not officially supported in production; for testing purposes only) | All MySQL 5.7 based releases |
|
A name to use when writing messages applying to this node in the cluster log. | All MySQL 5.7 based releases |
|
Do not provide any node id checks | All MySQL 5.7 based releases |
|
Read cluster configuration data from the my.cnf file | All MySQL 5.7 based releases |
|
Causes the management server to compare the configuration file with its configuration cache | All MySQL 5.7 based releases |
|
Causes the management server reload its configuration data from the configuration file, bypassing the configuration cache | All MySQL 5.7 based releases |
|
Do not wait for these management nodes when starting this management server. Also requires --ndb-nodeid to be used. | All MySQL 5.7 based releases |
|
Enable the management server configuration cache; TRUE by default. | All MySQL 5.7 based releases |
|
Used to install the management server process as a Windows service. Does not apply on non-Windows platforms. | All MySQL 5.7 based releases |
|
Used to remove a management server process that was previously installed as a Windows service, optionally specifying the name of the service to be removed. Does not apply on non-Windows platforms. | All MySQL 5.7 based releases |
Command-Line Format | --bind-address=ip_address | ||
Permitted Values | Type | string | |
Default | [none] |
When specified, this option limits management server
connections by management clients to clients at the
specified host name or IP address (and possibly port, if
this is also specified). In such cases, a management client
attempting to connect to the management server from any
other address fails with the error Unable to
setup port:
host
:port
!
If the port
is not specified, the
management client attempts to use port 1186.
Command-Line Format | --no-nodeid-checks | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Do not perform any checks of node IDs.
Command-Line Format | --configdir=directory | ||
--config-dir=directory | |||
Permitted Values | Type | file name | |
Default | $INSTALLDIR/mysql-cluster |
Specifies the cluster management server's configuration
cache directory. --config-dir
is an alias
for this option.
Command-Line Format | --config-cache[=TRUE|FALSE] | ||
Permitted Values | Type | boolean | |
Default | TRUE |
This option, whose default value is 1
(or
TRUE
, or ON
), can be
used to disable the management server's configuration
cache, so that it reads its configuration from
config.ini
every time it starts (see
Section 19.3.3, “MySQL Cluster Configuration Files”). You can do
this by starting the ndb_mgmd process
with any one of the following options:
Using one of the options just listed is effective only if
the management server has no stored configuration at the
time it is started. If the management server finds any
configuration cache files, then the
--config-cache
option or the
--skip-config-cache
option is ignored.
Therefore, to disable configuration caching, the option
should be used the first time that the
management server is started. Otherwise—that is, if
you wish to disable configuration caching for a management
server that has already created a
configuration cache—you must stop the management
server, delete any existing configuration cache files
manually, then restart the management server with
--skip-config-cache
(or with
--config-cache
set equal to 0,
OFF
, or FALSE
).
Configuration cache files are normally created in a
directory named mysql-cluster
under the
installation directory (unless this location has been
overridden using the
--configdir
option). Each
time the management server updates its configuration data,
it writes a new cache file. The files are named sequentially
in order of creation using the following format:
ndb_node-id
_config.bin.seq-number
node-id
is the management
server's node ID; seq-number
is a sequence number, beginning with 1. For example, if the
management server's node ID is 5, then the first three
configuration cache files would, when they are created, be
named ndb_5_config.bin.1
,
ndb_5_config.bin.2
, and
ndb_5_config.bin.3
.
If your intent is to purge or reload the configuration cache
without actually disabling caching, you should start
ndb_mgmd with one of the options
--reload
or
--initial
instead of
--skip-config-cache
.
To re-enable the configuration cache, simply restart the
management server, but without the
--config-cache
or
--skip-config-cache
option that was used
previously to disable the configuration cache.
ndb_mgmd does not check for the
configuration directory
(--configdir
) or attempts
to create one when --skip-config-cache
is
used. (Bug #13428853)
--config-file=
,
filename
-f
filename
Command-Line Format | --config-file=file | ||
Permitted Values | Type | file name | |
Default | [none] |
Instructs the management server as to which file it should
use for its configuration file. By default, the management
server looks for a file named
config.ini
in the same directory as the
ndb_mgmd executable; otherwise the file
name and location must be specified explicitly.
This option has no default value, and is ignored unless the
management server is forced to read the configuration file,
either because ndb_mgmd was started with
the --reload
or
--initial
option, or
because the management server could not find any
configuration cache. This option is also read if
ndb_mgmd was started with
--config-cache=OFF
. See
Section 19.3.3, “MySQL Cluster Configuration Files”, for more
information.
Command-Line Format | --mycnf | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Read configuration data from the my.cnf
file.
Command-Line Format | --daemon | ||
Permitted Values | Type | boolean | |
Default | TRUE |
Instructs ndb_mgmd to start as a daemon process. This is the default behavior.
This option has no effect when running ndb_mgmd on Windows platforms.
Command-Line Format | --interactive | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Starts ndb_mgmd in interactive mode; that is, an ndb_mgm client session is started as soon as the management server is running. This option does not start any other MySQL Cluster nodes.
Command-Line Format | --initial | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Configuration data is cached internally, rather than being
read from the cluster global configuration file each time
the management server is started (see
Section 19.3.3, “MySQL Cluster Configuration Files”). Using the
--initial
option overrides this behavior,
by forcing the management server to delete any existing
cache files, and then to re-read the configuration data from
the cluster configuration file and to build a new cache.
This differs in two ways from the
--reload
option. First,
--reload
forces the server to check the
configuration file against the cache and reload its data
only if the contents of the file are different from the
cache. Second, --reload
does not delete any
existing cache files.
If ndb_mgmd is invoked with
--initial
but cannot find a global
configuration file, the management server cannot start.
When a management server starts, it checks for another
management server in the same MySQL Cluster and tries to use
the other management server's configuration data;
ndb_mgmd ignores
--initial
unless it is the
only management server running. This behavior also has
implications when performing a rolling restart of a MySQL
Cluster with multiple management nodes. See
Section 19.5.5, “Performing a Rolling Restart of a MySQL Cluster”, for more
information.
When used together with the
--config-file
option, the
cache is cleared only if the configuration file is actually
found.
Command-Line Format | --log-name=name | ||
Permitted Values | Type | string | |
Default | MgmtSrvr |
Provides a name to be used for this node in the cluster log.
Command-Line Format | --nodaemon | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Instructs ndb_mgmd not to start as a daemon process.
The default behavior for ndb_mgmd on Windows is to run in the foreground, making this option unnecessary on Windows platforms.
Command-Line Format | --print-full-config | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Shows extended information regarding the configuration of
the cluster. With this option on the command line the
ndb_mgmd process prints information about
the cluster setup including an extensive list of the cluster
configuration sections as well as parameters and their
values. Normally used together with the
--config-file
(-f
) option.
Command-Line Format | --reload | ||
Permitted Values | Type | boolean | |
Default | FALSE |
MySQL Cluster configuration data is stored internally rather than being read from the cluster global configuration file each time the management server is started (see Section 19.3.3, “MySQL Cluster Configuration Files”). Using this option forces the management server to check its internal data store against the cluster configuration file and to reload the configuration if it finds that the configuration file does not match the cache. Existing configuration cache files are preserved, but not used.
This differs in two ways from the
--initial
option. First,
--initial
causes all cache files to be
deleted. Second, --initial
forces the
management server to re-read the global configuration file
and construct a new cache.
If the management server cannot find a global configuration
file, then the --reload
option is ignored.
When a management server starts, it checks for another
management server in the same MySQL Cluster and tries to use
the other management server's configuration data;
ndb_mgmd ignores
--reload
unless it is the
only management server running. This behavior also has
implications when performing a rolling restart of a MySQL
Cluster with multiple management nodes. See
Section 19.5.5, “Performing a Rolling Restart of a MySQL Cluster”, for more
information.
Command-Line Format | --nowait-nodes=list | ||
Permitted Values | Type | numeric | |
Default |
| ||
Min Value | 1 | ||
Max Value | 255 |
When starting a MySQL Cluster is configured with two management nodes, each management server normally checks to see whether the other ndb_mgmd is also operational and whether the other management server's configuration is identical to its own. However, it is sometimes desirable to start the cluster with only one management node (and perhaps to allow the other ndb_mgmd to be started later). This option causes the management node to bypass any checks for any other management nodes whose node IDs are passed to this option, permitting the cluster to start as though configured to use only the management node that was started.
For purposes of illustration, consider the following portion
of a config.ini
file (where we have
omitted most of the configuration parameters that are not
relevant to this example):
[ndbd] NodeId = 1 HostName = 192.168.0.101 [ndbd] NodeId = 2 HostName = 192.168.0.102 [ndbd] NodeId = 3 HostName = 192.168.0.103 [ndbd] NodeId = 4 HostName = 192.168.0.104 [ndb_mgmd] NodeId = 10 HostName = 192.168.0.150 [ndb_mgmd] NodeId = 11 HostName = 192.168.0.151 [api] NodeId = 20 HostName = 192.168.0.200 [api] NodeId = 21 HostName = 192.168.0.201
Assume that you wish to start this cluster using only the
management server having node ID 10
and
running on the host having the IP address 192.168.0.150.
(Suppose, for example, that the host computer on which you
intend to the other management server is temporarily
unavailable due to a hardware failure, and you are waiting
for it to be repaired.) To start the cluster in this way,
use a command line on the machine at 192.168.0.150 to enter
the following command:
shell> ndb_mgmd --ndb-nodeid=10 --nowait-nodes=11
As shown in the preceding example, when using
--nowait-nodes
, you must
also use the --ndb-nodeid
option to specify the node ID of this
ndb_mgmd process.
You can then start each of the cluster's data nodes in the usual way. If you wish to start and use the second management server in addition to the first management server at a later time without restarting the data nodes, you must start each data node with a connection string that references both management servers, like this:
shell> ndbd -c 192.168.0.150,192.168.0.151
The same is true with regard to the connection string used with any mysqld processes that you wish to start as MySQL Cluster SQL nodes connected to this cluster. See Section 19.3.3.3, “MySQL Cluster Connection Strings”, for more information.
When used with ndb_mgmd, this option
affects the behavior of the management node with regard to
other management nodes only. Do not confuse it with the
--nowait-nodes
option used with
ndbd or ndbmtd to
permit a cluster to start with fewer than its full
complement of data nodes; when used with data nodes, this
option affects their behavior only with regard to other data
nodes.
Multiple management node IDs may be passed to this option as a comma-separated list. Each node ID must be no less than 1 and no greater than 255. In practice, it is quite rare to use more than two management servers for the same MySQL Cluster (or to have any need for doing so); in most cases you need to pass to this option only the single node ID for the one management server that you do not wish to use when starting the cluster.
When you later start the “missing” management server, its configuration must match that of the management server that is already in use by the cluster. Otherwise, it fails the configuration check performed by the existing management server, and does not start.
It is not strictly necessary to specify a connection string when starting the management server. However, if you are using more than one management server, a connection string should be provided and each node in the cluster should specify its node ID explicitly.
See Section 19.3.3.3, “MySQL Cluster Connection Strings”, for information about using connection strings. Section 19.4.4, “ndb_mgmd — The MySQL Cluster Management Server Daemon”, describes other options for ndb_mgmd.
The following files are created or used by
ndb_mgmd in its starting directory, and are
placed in the DataDir
as
specified in the config.ini
configuration
file. In the list that follows,
node_id
is the unique node
identifier.
config.ini
is the configuration file
for the cluster as a whole. This file is created by the user
and read by the management server.
Section 19.3, “Configuration of MySQL Cluster”, discusses how
to set up this file.
ndb_
is the cluster events log file. Examples of such events
include checkpoint startup and completion, node startup
events, node failures, and levels of memory usage. A
complete listing of cluster events with descriptions may be
found in Section 19.5, “Management of MySQL Cluster”.
node_id
_cluster.log
By default, when the size of the cluster log reaches one
million bytes, the file is renamed to
ndb_
,
where node_id
_cluster.log.seq_id
seq_id
is the sequence
number of the cluster log file. (For example: If files with
the sequence numbers 1, 2, and 3 already exist, the next log
file is named using the number 4
.) You
can change the size and number of files, and other
characteristics of the cluster log, using the
LogDestination
configuration parameter.
ndb_
is the file used for node_id
_out.logstdout
and
stderr
when running the management server
as a daemon.
ndb_
is the process ID file used when running the management
server as a daemon.
node_id
.pid
Command-Line Format | --install[=name] | ||
Platform Specific | Windows | ||
Permitted Values | Type | string | |
Default | ndb_mgmd |
Causes ndb_mgmd to be installed as a
Windows service. Optionally, you can specify a name for the
service; if not set, the service name defaults to
ndb_mgmd
. Although it is preferable to
specify other ndb_mgmd program options in
a my.ini
or my.cnf
configuration file, it is possible to use them together with
--install
. However, in such
cases, the --install
option
must be specified first, before any other options are given,
for the Windows service installation to succeed.
It is generally not advisable to use this option together
with the --initial
option,
since this causes the configuration cache to be wiped and
rebuilt every time the service is stopped and started. Care
should also be taken if you intend to use any other
ndb_mgmd options that affect the starting
of the management server, and you should make absolutely
certain you fully understand and allow for any possible
consequences of doing so.
The --install
option has no
effect on non-Windows platforms.
Command-Line Format | --remove[=name] | ||
Platform Specific | Windows | ||
Permitted Values | Type | string | |
Default | ndb_mgmd |
Causes an ndb_mgmd process that was
previously installed as a Windows service to be removed.
Optionally, you can specify a name for the service to be
uninstalled; if not set, the service name defaults to
ndb_mgmd
.
The --remove
option has no
effect on non-Windows platforms.
The ndb_mgm management client process is actually not needed to run the cluster. Its value lies in providing a set of commands for checking the cluster's status, starting backups, and performing other administrative functions. The management client accesses the management server using a C API. Advanced users can also employ this API for programming dedicated management processes to perform tasks similar to those performed by ndb_mgm.
To start the management client, it is necessary to supply the host name and port number of the management server:
shell> ndb_mgm [host_name
[port_num
]]
For example:
shell> ndb_mgm ndb_mgmd.mysql.com 1186
The default host name and port number are
localhost
and 1186, respectively.
The following table includes options that are specific to the MySQL Cluster management client program ndb_mgm. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndb_mgm), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.84 This table describes command-line options for the ndb_mgm program
Format | Description | Added or Removed |
---|---|---|
Set the number of times to retry a connection before giving up; synonym for --connect-retries | All MySQL 5.7 based releases |
|
Execute command and exit | All MySQL 5.7 based releases |
Command-Line Format | --connect-retries=# | ||
Permitted Values | Type | numeric | |
Default | 3 | ||
Min Value | 0 | ||
Max Value | 4294967295 |
This option specifies the number of times following the
first attempt to retry a connection before giving up (the
client always tries the connection at least once). The
length of time to wait per attempt is set using
--connect-retry-delay
.
This option is synonymous with the
--try-reconnect
option,
which is now deprecated.
The default for this option this option differs from its
default when used with other NDB
programs. See
Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”, for
more information.
Command-Line Format | --execute=name |
This option can be used to send a command to the MySQL
Cluster management client from the system shell. For
example, either of the following is equivalent to executing
SHOW
in the management
client:
shell>ndb_mgm -e "SHOW"
shell>ndb_mgm --execute="SHOW"
This is analogous to how the
--execute
or
-e
option works with the
mysql command-line client. See
Section 5.2.4, “Using Options on the Command Line”.
If the management client command to be passed using this option contains any space characters, then the command must be enclosed in quotation marks. Either single or double quotation marks may be used. If the management client command contains no space characters, the quotation marks are optional.
Deprecated | 5.6.28-ndb-7.4.9 | ||
Command-Line Format | --try-reconnect=# | ||
Permitted Values | Type | integer | |
Default | 3 | ||
Min Value | 0 | ||
Max Value | 4294967295 | ||
Permitted Values (>= 5.7.10-ndb-7.5.0) | Type | numeric | |
Default | 12 | ||
Min Value | 0 | ||
Max Value | 4294967295 |
If the connection to the management server is broken, the
node tries to reconnect to it every 5 seconds until it
succeeds. By using this option, it is possible to limit the
number of attempts to number
before giving up and reporting an error instead.
This option is deprecated and subject to removal in a future
release. Use
--connect-retries
, instead.
Additional information about using ndb_mgm can be found in Section 19.5.2, “Commands in the MySQL Cluster Management Client”.
This tool can be used to check for and remove orphaned BLOB
column parts from NDB
tables, as
well as to generate a file listing any orphaned parts. It is
sometimes useful in diagnosing and repairing corrupted or
damaged NDB
tables containing
BLOB
or
TEXT
columns.
The basic syntax for ndb_blob_tool is shown here:
ndb_blob_tool [options
]table
[column
, ...]
Unless you use the --help
option, you must specify an action to be performed by including
one or more of the options
--check-orphans
,
--delete-orphans
, or
--dump-file
. These options
cause ndb_blob_tool to check for orphaned
BLOB parts, remove any orphaned BLOB parts, and generate a dump
file listing orphaned BLOB parts, respectively, and are
described in more detail later in this section.
You must also specify the name of a table when invoking
ndb_blob_tool. In addition, you can
optionally follow the table name with the (comma-separated)
names of one or more BLOB
or
TEXT
columns from that table. If
no columns are listed, the tool works on all of the table's
BLOB
and
TEXT
columns. If you need to
specify a database, use the
--database
(-d
) option.
The --verbose
option
provides additional information in the output about the
tool's progress.
The following table includes options that are specific to ndb_blob_tool. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndb_blob_tool), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.85 This table describes command-line options for the ndb_blob_tool program
Format | Description | Added or Removed |
---|---|---|
Check for orphan blob parts | All MySQL 5.7 based releases |
|
Database to find the table in. | All MySQL 5.7 based releases |
|
Delete orphan blob parts | All MySQL 5.7 based releases |
|
Write orphan keys to specified file | All MySQL 5.7 based releases |
|
Verbose output | All MySQL 5.7 based releases |
Command-Line Format | --check-orphans | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Check for orphaned BLOB parts in MySQL Cluster tables.
Command-Line Format | --database=db_name | ||
Permitted Values | Type | string | |
Default | [none] |
Specify the database to find the table in.
Command-Line Format | --delete-orphans | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Remove orphaned BLOB parts from MySQL Cluster tables.
Command-Line Format | --dump-file=file | ||
Permitted Values | Type | file name | |
Default | [none] |
Writes a list of orphaned BLOB column parts to
file
. The information written to
the file includes the table key and BLOB part number for
each orphaned BLOB part.
Command-Line Format | --verbose | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Provide extra information in the tool's output regarding its progress.
First we create an NDB
table in the
test
database, using the
CREATE TABLE
statement shown
here:
USE test; CREATE TABLE btest ( c0 BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY, c1 TEXT, c2 BLOB ) ENGINE=NDB;
Then we insert a few rows into this table, using a series of statements similar to this one:
INSERT INTO btest VALUES (NULL, 'x', REPEAT('x', 1000));
When run with
--check-orphans
against
this table, ndb_blob_tool generates the
following output:
shell> ndb_blob_tool --check-orphans --verbose -d test btest
connected
processing 2 blobs
processing blob #0 c1 NDB$BLOB_19_1
NDB$BLOB_19_1: nextResult: res=1
total parts: 0
orphan parts: 0
processing blob #1 c2 NDB$BLOB_19_2
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=1
total parts: 10
orphan parts: 0
disconnected
NDBT_ProgramExit: 0 - OK
The tool reports that there are no NDB
BLOB
column parts associated with column c1
, even
though c1
is a
TEXT
column. This is due to the
fact that, in an NDB
table, only
the first 256 bytes of a BLOB
or
TEXT
column value are stored
inline, and only the excess, if any, is stored separately; thus,
if there are no values using more than 256 bytes in a given
column of one of these types, no BLOB
column
parts are created by NDB
for this column. See
Section 12.8, “Data Type Storage Requirements”, for more information.
This tool extracts current configuration information for data
nodes, SQL nodes, and API nodes from one of a number of sources:
a MySQL Cluster management node, or its
config.ini
or my.cnf
file. By default, the management node is the source for the
configuration data; to override the default, execute ndb_config
with the --config-file
or
--mycnf
option. It is also
possible to use a data node as the source by specifying its node
ID with
--config_from_node=
.
node_id
ndb_config can also provide an offline dump
of all configuration parameters which can be used, along with
their default, maximum, and minimum values and other
information. The dump can be produced in either text or XML
format; for more information, see the discussion of the
--configinfo
and
--xml
options later in this
section).
You can filter the results by section (DB
,
SYSTEM
, or CONNECTIONS
)
using one of the options
--nodes
,
--system
, or
--connections
.
The following table includes options that are specific to ndb_config. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndb_config), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.86 This table describes command-line options for the ndb_config program
Format | Description | Added or Removed |
---|---|---|
Print node information ([ndbd] or [ndbd default] section of cluster configuration file) only. Cannot be used with --system or --connections. | All MySQL 5.7 based releases |
|
Print connections information ([tcp], [tcp default], [sci], [sci default], [shm], or [shm default] sections of cluster configuration file) only. Cannot be used with --system or --nodes. | All MySQL 5.7 based releases |
|
One or more query options (attributes) | All MySQL 5.7 based releases |
|
Specify host | All MySQL 5.7 based releases |
|
Specify node type | All MySQL 5.7 based releases |
|
Get configuration of node with this ID | All MySQL 5.7 based releases |
|
Field separator | All MySQL 5.7 based releases |
|
Row separator | All MySQL 5.7 based releases |
|
Set the path to config.ini file | All MySQL 5.7 based releases |
|
Read configuration data from my.cnf file | All MySQL 5.7 based releases |
|
Short form for --ndb-connectstring | All MySQL 5.7 based releases |
|
Dumps information about all NDB configuration parameters in text format with default, maximum, and minimum values. Use with --xml to obtain XML output. | All MySQL 5.7 based releases |
|
Use --xml with --configinfo to obtain a dump of all NDB configuration parameters in XML format with default, maximum, and minimum values. | All MySQL 5.7 based releases |
|
Print SYSTEM section information only (see ndb_config --configinfo output). Cannot be used with --nodes or --connections. | All MySQL 5.7 based releases |
|
Obtain configuration data from the node having this ID (must be a data node). | All MySQL 5.7 based releases |
Command-Line Format | --help | ||
--usage |
Causes ndb_config to print a list of available options, and then exit.
Command-Line Format | --config_from_node=# | ||
Permitted Values | Type | numeric | |
Default | none | ||
Min Value | 1 | ||
Max Value | 48 |
Obtain the cluster's configuration data from the data node that has this ID.
If the node having this ID is not a data node, ndb_config fails with an error. (To obtain configuration data from the management node instead, simply omit this option.)
Command-Line Format | --version |
Causes ndb_config to print a version information string, and then exit.
--ndb-connectstring=
,
connection_string
-c
connection_string
Command-Line Format | --ndb-connectstring=connectstring | ||
--connect-string=connectstring | |||
Permitted Values | Type | string | |
Default | localhost:1186 |
Specifies the connection string to use in connecting to the
management server. The format for the connection string is
the same as described in
Section 19.3.3.3, “MySQL Cluster Connection Strings”, and
defaults to localhost:1186
.
Command-Line Format | --config-file=file_name | ||
Permitted Values | Type | file name | |
Default |
|
Gives the path to the management server's configuration file
(config.ini
). This may be a relative or
absolute path. If the management node resides on a different
host from the one on which ndb_config is
invoked, then an absolute path must be used.
Command-Line Format | --mycnf | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Read configuration data from the my.cnf
file.
--query=
,
query-options
-q
query-options
Command-Line Format | --query=string | ||
Permitted Values | Type | string | |
Default |
|
This is a comma-delimited list of
query
options—that is, a list of one or more node
attributes to be returned. These include
id
(node ID), type (node type—that
is, ndbd
, mysqld
, or
ndb_mgmd
), and any configuration
parameters whose values are to be obtained.
For example,
--query=id,type,indexmemory,datamemory
returns the node ID, node type,
DataMemory
, and
IndexMemory
for each
node.
If a given parameter is not applicable to a certain type of node, than an empty string is returned for the corresponding value. See the examples later in this section for more information.
Command-Line Format | --host=name | ||
Permitted Values | Type | string | |
Default |
|
Specifies the host name of the node for which configuration information is to be obtained.
While the hostname localhost
usually
resolves to the IP address 127.0.0.1
,
this may not necessarily be true for all operating
platforms and configurations. This means that it is
possible, when localhost
is used in
config.ini
, for ndb_config
--host=localhost
to fail if
ndb_config is run on a different host
where localhost
resolves to a different
address (for example, on some versions of SUSE Linux, this
is 127.0.0.2
). In general, for best
results, you should use numeric IP addresses for all MySQL
Cluster configuration values relating to hosts, or verify
that all MySQL Cluster hosts handle
localhost
in the same fashion.
Command-Line Format | --ndb-nodeid=# | ||
Permitted Values | Type | numeric | |
Default | 0 |
Either of these options can be used to specify the node ID
of the node for which configuration information is to be
obtained. --nodeid
is the preferred form.
Command-Line Format | --nodes | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Tells ndb_config to print information
relating only to parameters defined in an
[ndbd]
or [ndbd
default]
section of the cluster configuration file
(see Section 19.3.3.6, “Defining MySQL Cluster Data Nodes”).
This option is mutually exclusive with
--connections
and
--system
; only one of
these 3 options can be used.
Command-Line Format | --connections | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Tells ndb_config to print
CONNECTIONS
information only—that
is, information about parameters found in the
[tcp]
, [tcp default]
,
[sci]
, [sci default]
,
[shm]
, or [shm
default]
sections of the cluster configuration
file (see Section 19.3.3.9, “MySQL Cluster TCP/IP Connections”,
Section 19.3.3.12, “SCI Transport Connections in MySQL Cluster”, and
Section 19.3.3.11, “MySQL Cluster Shared-Memory Connections”, for more
information).
This option is mutually exclusive with
--nodes
and
--system
; only one of
these 3 options can be used.
Command-Line Format | --system | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Tells ndb_config to print
SYSTEM
information only. This consists of
system variables that cannot be changed at run time; thus,
there is no corresponding section of the cluster
configuration file for them. They can be seen (prefixed with
****** SYSTEM ******
) in the output of
ndb_config
--configinfo
.
This option is mutually exclusive with
--nodes
and
--connections
; only one
of these 3 options can be used.
Command-Line Format | --type=name | ||
Permitted Values | Type | enumeration | |
Default | [none] | ||
Valid Values | ndbd | ||
mysqld | |||
ndb_mgmd |
Filters results so that only configuration values applying
to nodes of the specified
node_type
(ndbd
, mysqld
, or
ndb_mgmd
) are returned.
--fields=
,
delimiter
-f
delimiter
Command-Line Format | --fields=string | ||
Permitted Values | Type | string | |
Default |
|
Specifies a delimiter
string used
to separate the fields in the result. The default is
“,
” (the comma character).
If the delimiter
contains
spaces or escapes (such as \n
for the
linefeed character), then it must be quoted.
--rows=
,
separator
-r
separator
Command-Line Format | --rows=string | ||
Permitted Values | Type | string | |
Default |
|
Specifies a separator
string used
to separate the rows in the result. The default is a space
character.
If the separator
contains
spaces or escapes (such as \n
for the
linefeed character), then it must be quoted.
The --configinfo
option causes
ndb_config to dump a list of each MySQL
Cluster configuration parameter supported by the MySQL
Cluster distribution of which ndb_config
is a part, including the following information:
A brief description of each parameter's purpose, effects, and usage
The section of the config.ini
file
where the parameter may be used
The parameter's data type or unit of measurement
Where applicable, the parameter's default, minimum, and maximum values
MySQL Cluster release version and build information
By default, this output is in text format. Part of this output is shown here:
shell> ndb_config --configinfo
****** SYSTEM ******
Name (String)
Name of system (NDB Cluster)
MANDATORY
PrimaryMGMNode (Non-negative Integer)
Node id of Primary ndb_mgmd(MGM) node
Default: 0 (Min: 0, Max: 4294967039)
ConfigGenerationNumber (Non-negative Integer)
Configuration generation number
Default: 0 (Min: 0, Max: 4294967039)
****** DB ******
MaxNoOfSubscriptions (Non-negative Integer)
Max no of subscriptions (default 0 == MaxNoOfTables)
Default: 0 (Min: 0, Max: 4294967039)
MaxNoOfSubscribers (Non-negative Integer)
Max no of subscribers (default 0 == 2 * MaxNoOfTables)
Default: 0 (Min: 0, Max: 4294967039)
…
Command-Line Format | --configinfo --xml | ||
Permitted Values | Type | boolean | |
Default | false |
You can obtain the output of ndb_config
--configinfo
as XML by
adding the --xml
option. A portion of the
resulting output is shown in this example:
shell> ndb_config --configinfo --xml
<configvariables protocolversion="1" ndbversionstring="5.7.13-ndb-7.5.3"
ndbversion="460032" ndbversionmajor="7" ndbversionminor="5"
ndbversionbuild="0">
<section name="SYSTEM">
<param name="Name" comment="Name of system (NDB Cluster)" type="string"
mandatory="true"/>
<param name="PrimaryMGMNode" comment="Node id of Primary ndb_mgmd(MGM) node"
type="unsigned" default="0" min="0" max="4294967039"/>
<param name="ConfigGenerationNumber" comment="Configuration generation number"
type="unsigned" default="0" min="0" max="4294967039"/>
</section>
<section name="MYSQLD" primarykeys="NodeId">
<param name="wan" comment="Use WAN TCP setting as default" type="bool"
default="false"/>
<param name="HostName" comment="Name of computer for this node"
type="string" default=""/>
<param name="Id" comment="NodeId" type="unsigned" mandatory="true"
min="1" max="255" deprecated="true"/>
<param name="NodeId" comment="Number identifying application node (mysqld(API))"
type="unsigned" mandatory="true" min="1" max="255"/>
<param name="ExecuteOnComputer" comment="HostName" type="string"
deprecated="true"/>
…
</section>
…
</configvariables>
Normally, the XML output produced by
ndb_config
--configinfo
--xml
is
formatted using one line per element; we have added extra
whitespace in the previous example, as well as the next
one, for reasons of legibility. This should not make any
difference to applications using this output, since most
XML processors either ignore nonessential whitespace as a
matter of course, or can be instructed to do so.
The XML output also indicates when changing a given
parameter requires that data nodes be restarted using the
--initial
option. This is shown
by the presence of an initial="true"
attribute in the corresponding
<param>
element. In addition, the
restart type (system
or
node
) is also shown; if a given parameter
requires a system restart, this is indicated by the presence
of a restart="system"
attribute in the
corresponding <param>
element. For
example, changing the value set for the
Diskless
parameter
requires a system initial restart, as shown here (with the
restart
and initial
attributes highlighted for visibility):
<param name="Diskless" comment="Run wo/ disk" type="bool" default="false"
restart="system" initial="true"/>
Currently, no initial
attribute is
included in the XML output for
<param>
elements corresponding to
parameters which do not require initial restarts; in other
words, initial="false"
is the default,
and the value false
should be assumed if
the attribute is not present. Similarly, the default restart
type is node
(that is, an online or
“rolling” restart of the cluster), but the
restart
attribute is included only if the
restart type is system
(meaning that all
cluster nodes must be shut down at the same time, then
restarted).
Deprecated parameters are indicated in the XML output by the
deprecated
attribute, as shown here:
<param name="NoOfDiskPagesToDiskAfterRestartACC" comment="DiskCheckpointSpeed"
type="unsigned" default="20" min="1" max="4294967039" deprecated="true"/>
In such cases, the comment
refers to one
or more parameters that supersede the deprecated parameter.
Similarly to initial
, the
deprecated
attribute is indicated only
when the parameter is deprecated, with
deprecated="true"
, and does not appear at
all for parameters which are not deprecated. (Bug #21127135)
Beginning with MySQL Cluster NDB 7.5.0, parameters that are
required are indicated with
mandatory="true"
. As with
initial
and
deprecated
, this attribute is included
only if the parameter is actually required.
The --xml
option can be used only with
the --configinfo
option. Using
--xml
without
--configinfo
fails with an error.
Unlike the options used with this program to obtain current
configuration data, --configinfo
and
--xml
use information obtained from the
MySQL Cluster sources when ndb_config was
compiled. For this reason, no connection to a running MySQL
Cluster or access to a config.ini
or
my.cnf
file is required for these two
options.
Combining other ndb_config options (such
as --query
or
--type
) with
--configinfo
or --xml
is
not supported. Currently, if you attempt to do so, the usual
result is that all other options besides
--configinfo
or --xml
are
simply ignored. However, this behavior is not
guaranteed and is subject to change at any time.
In addition, since ndb_config, when used
with the --configinfo
option, does not
access the MySQL Cluster or read any files, trying to
specify additional options such as
--ndb-connectstring
or
--config-file
with
--configinfo
serves no purpose.
To obtain the node ID and type of each node in the cluster:
shell> ./ndb_config --query=id,type --fields=':' --rows='\n'
1:ndbd
2:ndbd
3:ndbd
4:ndbd
5:ndb_mgmd
6:mysqld
7:mysqld
8:mysqld
9:mysqld
In this example, we used the
--fields
options to
separate the ID and type of each node with a colon character
(:
), and the
--rows
options to place
the values for each node on a new line in the output.
To produce a connection string that can be used by data, SQL, and API nodes to connect to the management server:
shell> ./ndb_config --config-file=usr/local/mysql/cluster-data/config.ini \
--query=hostname,portnumber --fields=: --rows=, --type=ndb_mgmd
192.168.0.179:1186
This invocation of ndb_config checks only
data nodes (using the
--type
option), and shows
the values for each node's ID and host name, as well as
the values set for its
DataMemory
,
IndexMemory
, and
DataDir
parameters:
shell> ./ndb_config --type=ndbd --query=id,host,datamemory,indexmemory,datadir -f ' : ' -r '\n'
1 : 192.168.0.193 : 83886080 : 18874368 : /usr/local/mysql/cluster-data
2 : 192.168.0.112 : 83886080 : 18874368 : /usr/local/mysql/cluster-data
3 : 192.168.0.176 : 83886080 : 18874368 : /usr/local/mysql/cluster-data
4 : 192.168.0.119 : 83886080 : 18874368 : /usr/local/mysql/cluster-data
In this example, we used the short options
-f
and -r
for setting the
field delimiter and row separator, respectively.
To exclude results from any host except one in particular,
use the --host
option:
shell> ./ndb_config --host=192.168.0.176 -f : -r '\n' -q id,type
3:ndbd
5:ndb_mgmd
In this example, we also used the short form
-q
to determine the attributes to be
queried.
Similarly, you can limit results to a node with a specific
ID using the --id
or
--nodeid
option.
A utility having this name was formerly part of an internal automated test framework used in testing and debugging MySQL Cluster. It is no longer included in MySQL Cluster distributions provided by Oracle.
ndb_delete_all deletes all rows from the
given NDB
table. In some cases,
this can be much faster than
DELETE
or even
TRUNCATE TABLE
.
ndb_delete_all -cconnection_string
tbl_name
-ddb_name
This deletes all rows from the table named
tbl_name
in the database named
db_name
. It is exactly equivalent to
executing TRUNCATE
in MySQL.
db_name
.tbl_name
The following table includes options that are specific to ndb_delete_all. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndb_delete_all), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.87 This table describes command-line options for the ndb_delete_all program
Format | Description | Added or Removed |
---|---|---|
|
Name of the database in which the table is found | All MySQL 5.7 based releases |
Perform the delete in a single transaction (may run out of operations) | All MySQL 5.7 based releases |
|
|
Run tup scan | All MySQL 5.7 based releases |
|
Run disk scan | All MySQL 5.7 based releases |
ndb_desc provides a detailed description of
one or more NDB
tables.
ndb_desc -cconnection_string
tbl_name
-ddb_name
[options
] ndb_desc -cconnection_string
index_name
-ddb_name
-ttbl_name
Additional options that can be used with ndb_desc are listed later in this section.
MySQL table creation and population statements:
USE test; CREATE TABLE fish ( id INT(11) NOT NULL AUTO_INCREMENT, name VARCHAR(20) NOT NULL, length_mm INT(11) NOT NULL, weight_gm INT(11) NOT NULL, PRIMARY KEY pk (id), UNIQUE KEY uk (name) ) ENGINE=NDB; INSERT INTO fish VALUES ('','guppy', 35, 2), ('','tuna', 2500, 150000), ('','shark', 3000, 110000), ('','manta ray', 1500, 50000), ('','grouper', 900, 125000), ('','puffer', 250, 2500);
Output from ndb_desc:
shell> ./ndb_desc -c localhost fish -d test -p
-- fish --
Version: 2
Fragment type: 9
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: no
Number of attributes: 4
Number of primary keys: 1
Length of frm data: 311
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
FragmentCount: 2
TableStatus: Retrieved
-- Attributes --
id Int PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
length_mm Int NOT NULL AT=FIXED ST=MEMORY
weight_gm Int NOT NULL AT=FIXED ST=MEMORY
-- Indexes --
PRIMARY KEY(id) - UniqueHashIndex
PRIMARY(id) - OrderedIndex
uk$unique(name) - UniqueHashIndex
uk(name) - OrderedIndex
-- Per partition info --
Partition Row count Commit count Frag fixed memory ...
0 2 2 32768 ...
1 4 4 32768 ...
... Frag varsized memory Extent_space Free extent_space
... 32768 0 0
... 32768 0 0
NDBT_ProgramExit: 0 - OK
Information about multiple tables can be obtained in a single invocation of ndb_desc by using their names, separated by spaces. All of the tables must be in the same database.
You can obtain additional information about a specific index
using the --table
(short form:
-t
) option and supplying the name of the index
as the first argument to ndb_desc, as shown
here:
shell> ./ndb_desc uk -d test -t fish
-- uk --
Version: 3
Base table: fish
Number of attributes: 1
Logging: 0
Index type: OrderedIndex
Index status: Retrieved
-- Attributes --
name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
-- IndexTable 10/uk --
Version: 3
Fragment type: FragUndefined
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: yes
Number of attributes: 2
Number of primary keys: 1
Length of frm data: 0
Row Checksum: 1
Row GCI: 1
SingleUserMode: 2
ForceVarPart: 0
FragmentCount: 4
ExtraRowGciBits: 0
ExtraRowAuthorBits: 0
TableStatus: Retrieved
-- Attributes --
name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
NDB$TNODE Unsigned [64] PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY
-- Indexes --
PRIMARY KEY(NDB$TNODE) - UniqueHashIndex
NDBT_ProgramExit: 0 - OK
When an index is specified in this way, the
--extra-partition-info
and
--extra-node-info
options have
no effect.
The Version
column in the output contains the
table's schema object version. For information about
interpreting this value, see
NDB Schema Object Versions.
The Extent_space
and Free
extent_space
columns are applicable only to
NDB
tables having columns on disk; for tables
having only in-memory columns, these columns always contain the
value 0
.
To illustrate their use, we modify the previous example. First, we must create the necessary Disk Data objects, as shown here:
CREATE LOGFILE GROUP lg_1 ADD UNDOFILE 'undo_1.log' INITIAL_SIZE 16M UNDO_BUFFER_SIZE 2M ENGINE NDB; ALTER LOGFILE GROUP lg_1 ADD UNDOFILE 'undo_2.log' INITIAL_SIZE 12M ENGINE NDB; CREATE TABLESPACE ts_1 ADD DATAFILE 'data_1.dat' USE LOGFILE GROUP lg_1 INITIAL_SIZE 32M ENGINE NDB; ALTER TABLESPACE ts_1 ADD DATAFILE 'data_2.dat' INITIAL_SIZE 48M ENGINE NDB;
(For more information on the statements just shown and the objects created by them, see Section 19.5.13.1, “MySQL Cluster Disk Data Objects”, as well as Section 14.1.15, “CREATE LOGFILE GROUP Syntax”, and Section 14.1.19, “CREATE TABLESPACE Syntax”.)
Now we can create and populate a version of the
fish
table that stores 2 of its columns on
disk (deleting the previous version of the table first, if it
already exists):
CREATE TABLE fish ( id INT(11) NOT NULL AUTO_INCREMENT, name VARCHAR(20) NOT NULL, length_mm INT(11) NOT NULL, weight_gm INT(11) NOT NULL, PRIMARY KEY pk (id), UNIQUE KEY uk (name) ) TABLESPACE ts_1 STORAGE DISK ENGINE=NDB; INSERT INTO fish VALUES ('','guppy', 35, 2), ('','tuna', 2500, 150000), ('','shark', 3000, 110000), ('','manta ray', 1500, 50000), ('','grouper', 900, 125000), ('','puffer', 250, 2500);
When run against this version of the table, ndb_desc displays the following output:
shell> ./ndb_desc -c localhost fish -d test -p
-- fish --
Version: 3
Fragment type: 9
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: no
Number of attributes: 4
Number of primary keys: 1
Length of frm data: 321
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
FragmentCount: 2
TableStatus: Retrieved
-- Attributes --
id Int PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
length_mm Int NOT NULL AT=FIXED ST=DISK
weight_gm Int NOT NULL AT=FIXED ST=DISK
-- Indexes --
PRIMARY KEY(id) - UniqueHashIndex
PRIMARY(id) - OrderedIndex
uk$unique(name) - UniqueHashIndex
uk(name) - OrderedIndex
-- Per partition info --
Partition Row count Commit count Frag fixed memory ...
0 2 2 32768 ...
1 4 4 32768 ...
... Frag varsized memory Extent_space Free extent_space
... 32768 0 0
... 32768 0 0
NDBT_ProgramExit: 0 - OK
This means that 1048576 bytes are allocated from the tablespace
for this table on each partition, of which 1044440 bytes remain
free for additional storage. In other words, 1048576 - 1044440 =
4136 bytes per partition is currently being used to store the
data from this table's disk-based columns. The number of
bytes shown as Free extent_space
is available
for storing on-disk column data from the fish
table only; for this reason, it is not visible when selecting
from the INFORMATION_SCHEMA.FILES
table.
The following table includes options that are specific to ndb_desc. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndb_desc), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.88 This table describes command-line options for the ndb_desc program
Format | Description | Added or Removed |
---|---|---|
Include partition information for BLOB tables in output. Requires that the -p option also be used | All MySQL 5.7 based releases |
|
Name of database containing table | All MySQL 5.7 based releases |
|
Include partition-to-data-node mappings in output. Requires that the -p option also be used | All MySQL 5.7 based releases |
|
Display information about partitions | All MySQL 5.7 based releases |
|
Number of times to retry the connection (once per second) | All MySQL 5.7 based releases |
|
Specify the table in which to find an index. When this option is used, -p and -n have no effect and are ignored. | All MySQL 5.7 based releases |
|
Use unqualified table names | All MySQL 5.7 based releases |
Include information about subordinate
BLOB
and
TEXT
columns.
Use of this option also requires the use of the
--extra-partition-info
(-p
) option.
Specify the database in which the table should be found.
Include information about the mappings between table partitions and the data nodes upon which they reside. This information can be useful for verifying distribution awareness mechanisms and supporting more efficient application access to the data stored in MySQL Cluster.
Use of this option also requires the use of the
--extra-partition-info
(-p
) option.
Print additional information about the table's partitions.
Try to connect this many times before giving up. One connect attempt is made per second.
Specify the table in which to look for an index.
Use unqualified table names.
ndb_drop_index drops the specified index from
an NDB
table. It is
recommended that you use this utility only as an example for
writing NDB API applications—see the Warning
later in this section for details.
ndb_drop_index -cconnection_string
table_name
index
-ddb_name
The statement shown above drops the index named
index
from the
table
in the
database
.
The following table includes options that are specific to ndb_drop_index. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndb_drop_index), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.89 This table describes command-line options for the ndb_drop_index program
Format | Description | Added or Removed |
---|---|---|
|
Name of the database in which the table is found | All MySQL 5.7 based releases |
Operations performed on Cluster table indexes using the NDB API are not visible to MySQL and make the table unusable by a MySQL server. If you use this program to drop an index, then try to access the table from an SQL node, an error results, as shown here:
shell>./ndb_drop_index -c localhost dogs ix -d ctest1
Dropping index dogs/idx...OK NDBT_ProgramExit: 0 - OK shell>./mysql -u jon -p ctest1
Enter password: ******* Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 7 to server version: 5.7.13-ndb-7.5.3 Type 'help;' or '\h' for help. Type '\c' to clear the buffer. mysql>SHOW TABLES;
+------------------+ | Tables_in_ctest1 | +------------------+ | a | | bt1 | | bt2 | | dogs | | employees | | fish | +------------------+ 6 rows in set (0.00 sec) mysql>SELECT * FROM dogs;
ERROR 1296 (HY000): Got error 4243 'Index not found' from NDBCLUSTER
In such a case, your only option for making
the table available to MySQL again is to drop the table and
re-create it. You can use either the SQL
statementDROP TABLE
or the
ndb_drop_table utility (see
Section 19.4.12, “ndb_drop_table — Drop an NDB Table”) to drop
the table.
ndb_drop_table drops the specified
NDB
table. (If you try to use this
on a table created with a storage engine other than
NDB
, the attempt fails with the
error 723: No such table exists.) This
operation is extremely fast; in some cases, it can be an order
of magnitude faster than using a MySQL DROP
TABLE
statement on an NDB
table.
ndb_drop_table -cconnection_string
tbl_name
-ddb_name
The following table includes options that are specific to ndb_drop_table. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndb_drop_table), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.90 This table describes command-line options for the ndb_drop_table program
Format | Description | Added or Removed |
---|---|---|
|
Name of the database in which the table is found | All MySQL 5.7 based releases |
ndb_error_reporter creates an archive from data node and management node log files that can be used to help diagnose bugs or other problems with a cluster. It is highly recommended that you make use of this utility when filing reports of bugs in MySQL Cluster.
The following table includes command options specific to the MySQL Cluster program ndb_error_reporter. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndb_error_reporter), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.91 This table describes command-line options for the ndb_error_reporter program
Format | Description | Added or Removed |
---|---|---|
Number of seconds to wait when connecting to nodes before timing out. | All MySQL 5.7 based releases |
|
Disable scp with remote hosts; used only for testing. | All MySQL 5.7 based releases |
|
Include file system data in error report; can use a large amount of disk space | All MySQL 5.7 based releases |
|
Skip all nodes in the node group having this ID. | All MySQL 5.7 based releases |
ndb_error_reporterpath/to/config-file
[username
] [options
]
This utility is intended for use on a management node host, and
requires the path to the management host configuration file
(usually named config.ini
). Optionally, you
can supply the name of a user that is able to access the
cluster's data nodes using SSH, to copy the data node log files.
ndb_error_reporter then includes all of these
files in archive that is created in the same directory in which
it is run. The archive is named
ndb_error_report_
,
where YYYYMMDDHHMMSS
.tar.bz2YYYYMMDDHHMMSS
is a datetime
string.
ndb_error_reporter also accepts the options listed here:
Command-Line Format | --connection-timeout=timeout | ||
Permitted Values | Type | integer | |
Default | 0 |
Wait this many seconds when trying to connect to nodes before timing out.
Command-Line Format | --dry-scp | ||
Permitted Values | Type | boolean | |
Default | TRUE |
Run ndb_error_reporter without using scp from remote hosts. Used for testing only.
Command-Line Format | --fs | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Copy the data node file systems to the management host and include them in the archive.
Because data node file systems can be extremely large, even after being compressed, we ask that you please do not send archives created using this option to Oracle unless you are specifically requested to do so.
Command-Line Format | --connection-timeout=timeout | ||
Permitted Values | Type | integer | |
Default | 0 |
Skip all nodes belong to the node group having the supplied node group ID.
ndb_index_stat provides per-fragment
statistical information about indexes on NDB
tables. This includes cache version and age, number of index
entries per partition, and memory consumption by indexes.
To obtain basic index statistics about a given
NDB
table, invoke
ndb_index_stat as shown here, with the name
of the table as the first argument and the name of the database
containing this table specified immediately following it, using
the --database
(-d
) option:
ndb_index_stattable
-ddatabase
In this example, we use ndb_index_stat to
obtain such information about an NDB
table
named mytable
in the test
database:
shell> ndb_index_stat -d test mytable
table:City index:PRIMARY fragCount:2
sampleVersion:3 loadTime:1399585986 sampleCount:1994 keyBytes:7976
query cache: valid:1 sampleCount:1994 totalBytes:27916
times in ms: save: 7.133 sort: 1.974 sort per sample: 0.000
NDBT_ProgramExit: 0 - OK
sampleVersion
is the version number of the
cache from which the statistics data is taken. Running
ndb_index_stat with the
--update
option causes
sampleVersion to be incremented.
loadTime
shows when the cache was last
updated. This is expressed as seconds since the Unix Epoch.
sampleCount
is the number of index entries
found per partition. You can estimate the total number of
entries by multiplying this by the number of fragments (shown as
fragCount
).
sampleCount
can be compared with the
cardinality of SHOW INDEX
or
INFORMATION_SCHEMA.STATISTICS
,
although the latter two provide a view of the table as a whole,
while ndb_index_stat provides a per-fragment
average.
keyBytes
is the number of bytes used by the
index. In this example, the primary key is an integer, which
requires four bytes for each index, so
keyBytes
can be calculated in this case as
shown here:
keyBytes = sampleCount * (4 bytes per index) = 1994 * 4 = 7976
This information can also be obtained using the corresponding
column definitions from
INFORMATION_SCHEMA.COLUMNS
(this
requires a MySQL Server and a MySQL client application).
totalBytes
is the total memory consumed by
all indexes on the table, in bytes.
Timings shown in the preceding examples are specific to each invocation of ndb_index_stat.
The --verbose
option
provides some additional output, as shown here:
shell> ndb_index_stat -d test mytable --verbose
random seed 1337010518
connected
loop 1 of 1
table:mytable index:PRIMARY fragCount:4
sampleVersion:2 loadTime:1336751773 sampleCount:0 keyBytes:0
read stats
query cache created
query cache: valid:1 sampleCount:0 totalBytes:0
times in ms: save: 20.766 sort: 0.001
disconnected
NDBT_ProgramExit: 0 - OK
shell>
The following table includes options that are specific to the MySQL Cluster ndb_index_stat utility. Additional descriptions are listed following the table. For options common to most MySQL Cluster programs (including ndb_index_stat), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.92 This table describes command-line options for the ndb_index_stat program
Format | Description | Added or Removed |
---|---|---|
Name of the database containing the table. | All MySQL 5.7 based releases |
|
Delete index statistics for the given table, stopping any auto-update previously configured. | All MySQL 5.7 based releases |
|
Update index statistics for the given table, restarting any auto-update previously configured. | All MySQL 5.7 based releases |
|
Print the query cache. | All MySQL 5.7 based releases |
|
Perform a number of random range queries on first key attr (must be int unsigned). | All MySQL 5.7 based releases |
|
Drop any statistics tables and events in NDB kernel (all statistics are lost) | All MySQL 5.7 based releases |
|
Create all statistics tables and events in NDB kernel, if none of them already exist | All MySQL 5.7 based releases |
|
Create any statistics tables and events in NDB kernel that do not already exist. | All MySQL 5.7 based releases |
|
Create any statistics tables or events that do not already exist in the NDB kernel. after dropping any that are invalid. | All MySQL 5.7 based releases |
|
Verify that NDB system index statistics and event tables exist. | All MySQL 5.7 based releases |
|
Do not apply sys-* options to tables. | All MySQL 5.7 based releases |
|
Do not apply sys-* options to events. | All MySQL 5.7 based releases |
|
Turn on verbose output | All MySQL 5.7 based releases |
|
Set the number of times to perform a given command. Default is 0. | All MySQL 5.7 based releases |
ndb_index_stat statistics options. The following options are used to generate index statistics. They work with a given table and database. They cannot be mixed with system options (see ndb_index_stat system options).
Command-Line Format | --database=name | ||
Permitted Values | Type | string | |
Default | [none] | ||
Min Value |
| ||
Max Value |
|
The name of the database that contains the table being queried.
Command-Line Format | --delete | ||
Permitted Values | Type | boolean | |
Default | false | ||
Min Value |
| ||
Max Value |
|
Delete the index statistics for the given table, stopping any auto-update that was previously configured.
Command-Line Format | --update | ||
Permitted Values | Type | boolean | |
Default | false | ||
Min Value |
| ||
Max Value |
|
Update the index statistics for the given table, and restart any auto-update that was previously configured.
Command-Line Format | --dump | ||
Permitted Values | Type | boolean | |
Default | false | ||
Min Value |
| ||
Max Value |
|
Dump the contents of the query cache.
Command-Line Format | --query=# | ||
Permitted Values | Type | numeric | |
Default | 0 | ||
Min Value | 0 | ||
Max Value | MAX_INT |
Perform random range queries on first key attribute (must be int unsigned).
ndb_index_stat system options. The following options are used to generate and update the statistics tables in the NDB kernel. None of these options can be mixed with statistics options (see ndb_index_stat statistics options).
Command-Line Format | --sys-drop | ||
Permitted Values | Type | boolean | |
Default | false | ||
Min Value |
| ||
Max Value |
|
Drop all statistics tables and events in the NDB kernel. This causes all statistics to be lost.
Command-Line Format | --sys-create | ||
Permitted Values | Type | boolean | |
Default | false | ||
Min Value |
| ||
Max Value |
|
Create all statistics tables and events in the NDB kernel. This works only if none of them exist previously.
Command-Line Format | --sys-create-if-not-exist | ||
Permitted Values | Type | boolean | |
Default | false | ||
Min Value |
| ||
Max Value |
|
Create any NDB system statistics tables or events (or both) that do not already exist when the program is invoked.
Command-Line Format | --sys-create-if-not-valid | ||
Permitted Values | Type | boolean | |
Default | false | ||
Min Value |
| ||
Max Value |
|
Create any NDB system statistics tables or events that do not already exist, after dropping any that are invalid.
Command-Line Format | --sys-check | ||
Permitted Values | Type | boolean | |
Default | false | ||
Min Value |
| ||
Max Value |
|
Verify that all required system statistics tables and events exist in the NDB kernel.
Command-Line Format | --sys-skip-tables | ||
Permitted Values | Type | boolean | |
Default | false | ||
Min Value |
| ||
Max Value |
|
Do not apply any --sys-*
options to any
statistics tables.
Command-Line Format | --sys-skip-events | ||
Permitted Values | Type | boolean | |
Default | false | ||
Min Value |
| ||
Max Value |
|
Do not apply any --sys-*
options to any
events.
Command-Line Format | --verbose | ||
Permitted Values | Type | boolean | |
Default | false | ||
Min Value |
| ||
Max Value |
|
Turn on verbose output.
Command-Line Format | --loops=# | ||
Permitted Values | Type | numeric | |
Default | 0 | ||
Min Value | 0 | ||
Max Value | MAX_INT |
Repeat commands this number of times (for use in testing).
ndb_print_backup_file obtains diagnostic information from a cluster backup file.
ndb_print_backup_file file_name
file_name
is the name of a cluster
backup file. This can be any of the files
(.Data
, .ctl
, or
.log
file) found in a cluster backup
directory. These files are found in the data node's backup
directory under the subdirectory
BACKUP-
, where
#
#
is the sequence number for the
backup. For more information about cluster backup files and
their contents, see
Section 19.5.3.1, “MySQL Cluster Backup Concepts”.
Like ndb_print_schema_file and
ndb_print_sys_file (and unlike most of the
other NDB
utilities that are
intended to be run on a management server host or to connect to
a management server) ndb_print_backup_file
must be run on a cluster data node, since it accesses the data
node file system directly. Because it does not make use of the
management server, this utility can be used when the management
server is not running, and even when the cluster has been
completely shut down.
None.
ndb_print_file obtains information from a MySQL Cluster Disk Data file.
ndb_print_file [-v] [-q] file_name
+
file_name
is the name of a MySQL
Cluster Disk Data file. Multiple filenames are accepted,
separated by spaces.
Like ndb_print_schema_file and
ndb_print_sys_file (and unlike most of the
other NDB
utilities that are
intended to be run on a management server host or to connect to
a management server) ndb_print_file must be
run on a MySQL Cluster data node, since it accesses the data
node file system directly. Because it does not make use of the
management server, this utility can be used when the management
server is not running, and even when the cluster has been
completely shut down.
ndb_print_file supports the following options:
-v
: Make output verbose.
-q
: Suppress output (quiet mode).
--help
, -h
,
-?
: Print help message.
For more information, see Section 19.5.13, “MySQL Cluster Disk Data Tables”.
ndb_print_schema_file obtains diagnostic information from a cluster schema file.
ndb_print_schema_file file_name
file_name
is the name of a cluster
schema file. For more information about cluster schema files,
see MySQL Cluster Data Node File System Directory Files.
Like ndb_print_backup_file and
ndb_print_sys_file (and unlike most of the
other NDB
utilities that are
intended to be run on a management server host or to connect to
a management server) ndb_schema_backup_file
must be run on a cluster data node, since it accesses the data
node file system directly. Because it does not make use of the
management server, this utility can be used when the management
server is not running, and even when the cluster has been
completely shut down.
None.
ndb_print_sys_file obtains diagnostic information from a MySQL Cluster system file.
ndb_print_sys_file file_name
file_name
is the name of a cluster
system file (sysfile). Cluster system files are located in a
data node's data directory
(DataDir
); the path
under this directory to system files matches the pattern
ndb_
.
In each case, the #
_fs/D#
/DBDIH/P#
.sysfile#
represents a
number (not necessarily the same number). For more information,
see MySQL Cluster Data Node File System Directory Files.
Like ndb_print_backup_file and
ndb_print_schema_file (and unlike most of the
other NDB
utilities that are
intended to be run on a management server host or to connect to
a management server) ndb_print_backup_file
must be run on a cluster data node, since it accesses the data
node file system directly. Because it does not make use of the
management server, this utility can be used when the management
server is not running, and even when the cluster has been
completely shut down.
None.
Reads a redo log file, checking it for errors, printing its contents in a human-readable format, or both. ndbd_redo_log_reader is intended for use primarily by MySQL Cluster developers and Support personnel in debugging and diagnosing problems.
This utility remains under development, and its syntax and behavior are subject to change in future MySQL Cluster releases.
The C++ source files for ndbd_redo_log_reader
can be found in the directory
/storage/ndb/src/kernel/blocks/dblqh/redoLogReader
.
The following table includes options that are specific to the MySQL Cluster program ndbd_redo_log_reader. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndbd_redo_log_reader), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
ndbd_redo_log_readerfile_name
[options
]
file_name
is the name of a cluster
redo log file. redo log files are located in the numbered
directories under the data node's data directory
(DataDir
); the path
under this directory to the redo log files matches the pattern
ndb_
.
In each case, the #
_fs/D#
/LCP/#
/T#
F#
.Data#
represents a
number (not necessarily the same number). For more information,
see MySQL Cluster Data Node File System Directory Files.
The name of the file to be read may be followed by one or more of the options listed here:
Like ndb_print_backup_file and
ndb_print_schema_file (and unlike most of the
NDB
utilities that are intended to
be run on a management server host or to connect to a management
server) ndbd_redo_log_reader must be run on a
cluster data node, since it accesses the data node file system
directly. Because it does not make use of the management server,
this utility can be used when the management server is not
running, and even when the cluster has been completely shut
down.
The cluster restoration program is implemented as a separate
command-line utility ndb_restore, which can
normally be found in the MySQL bin
directory. This program reads the files created as a result of
the backup and inserts the stored information into the database.
ndb_restore must be executed once for each of
the backup files that were created by the
START BACKUP
command used to
create the backup (see
Section 19.5.3.2, “Using The MySQL Cluster Management Client to Create a Backup”).
This is equal to the number of data nodes in the cluster at the
time that the backup was created.
Before using ndb_restore, it is recommended that the cluster be running in single user mode, unless you are restoring multiple data nodes in parallel. See Section 19.5.8, “MySQL Cluster Single User Mode”, for more information.
The following table includes options that are specific to the MySQL Cluster native backup restoration program ndb_restore. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndb_restore), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.94 This table describes command-line options for the ndb_restore program
Format | Description | Added or Removed |
---|---|---|
Alias for --connectstring. | All MySQL 5.7 based releases |
|
Restore backup files to node with this ID | All MySQL 5.7 based releases |
|
Restore from the backup with the given ID | All MySQL 5.7 based releases |
|
Restore table data and logs into NDB Cluster using the NDB API | All MySQL 5.7 based releases |
|
Restore metadata to NDB Cluster using the NDB API | All MySQL 5.7 based releases |
|
Do not upgrade array type for varsize attributes which do not already resize VAR data, and do not change column attributes | All MySQL 5.7 based releases |
|
Allow attributes to be promoted when restoring data from backup | All MySQL 5.7 based releases |
|
Allow preservation of trailing spaces (including padding) when promoting fixed-width string types to variable-width types | All MySQL 5.7 based releases |
|
Do not restore objects relating to Disk Data | All MySQL 5.7 based releases |
|
Restore epoch info into the status table. Convenient on a MySQL Cluster replication slave for starting replication. The row in mysql.ndb_apply_status with id 0 will be updated/inserted. | All MySQL 5.7 based releases |
|
Skip table structure check during restoring of data | All MySQL 5.7 based releases |
|
Number of parallel transactions to use while restoring data | All MySQL 5.7 based releases |
|
Print metadata, data and log to stdout (equivalent to --print_meta --print_data --print_log) | All MySQL 5.7 based releases |
|
Print metadata to stdout | All MySQL 5.7 based releases |
|
Print data to stdout | All MySQL 5.7 based releases |
|
Print to stdout | All MySQL 5.7 based releases |
|
Path to backup files directory | All MySQL 5.7 based releases |
|
Do not ignore system table during restore. Experimental only; not for production use | All MySQL 5.7 based releases |
|
Nodegroup map for NDBCLUSTER storage engine. Syntax: list of (source_nodegroup, destination_nodegroup) | All MySQL 5.7 based releases |
|
Fields are enclosed with the indicated character | All MySQL 5.7 based releases |
|
Fields are terminated by the indicated character | All MySQL 5.7 based releases |
|
Fields are optionally enclosed with the indicated character | All MySQL 5.7 based releases |
|
Lines are terminated by the indicated character | All MySQL 5.7 based releases |
|
Print binary types in hexadecimal format | All MySQL 5.7 based releases |
|
Creates a tab-separated .txt file for each table in the given path | All MySQL 5.7 based releases |
|
Append data to a tab-delimited file | All MySQL 5.7 based releases |
|
Print status of restoration each given number of seconds | All MySQL 5.7 based releases |
|
If a mysqld is connected and using binary logging, do not log the restored data | All MySQL 5.7 based releases |
|
Level of verbosity in output | All MySQL 5.7 based releases |
|
List of one or more databases to restore (excludes those not named) | All MySQL 5.7 based releases |
|
List of one or more databases to exclude (includes those not named) | All MySQL 5.7 based releases |
|
List of one or more tables to restore (excludes those in same database that are not named); each table reference must include the database name | All MySQL 5.7 based releases |
|
List of one or more tables to exclude (includes those in the same database that are not named); each table reference must include the database name | All MySQL 5.7 based releases |
|
Causes columns from the backup version of a table that are missing from the version of the table in the database to be ignored. | All MySQL 5.7 based releases |
|
Causes tables from the backup that are missing from the database to be ignored. | All MySQL 5.7 based releases |
|
Causes indexes from a backup to be ignored; may decrease time needed to restore data. | All MySQL 5.7 based releases |
|
Causes multi-threaded rebuilding of ordered indexes found in the backup. Number of threads used is determined by setting BuildIndexThreads parameter. | All MySQL 5.7 based releases |
|
Causes missing blob tables in the backup file to be ignored. | All MySQL 5.7 based releases |
|
Causes schema objects not recognized by ndb_restore to be ignored when restoring a backup made from a newer MySQL Cluster version to an older version. | All MySQL 5.7 based releases |
|
Restores to a database with a different name than the original | All MySQL 5.7 based releases |
|
Allow lossy conversions of column values (type demotions or changes in sign) when restoring data from backup | All MySQL 5.7 based releases |
|
Restore MySQL privilege tables that were previously moved to NDB. | All MySQL 5.7 based releases |
|
If TRUE (the default), do not restore any intermediate tables (having names prefixed with '#sql-') that were left over from copying ALTER TABLE operations. | All MySQL 5.7 based releases |
Typical options for this utility are shown here:
Normally, when restoring from a MySQL Cluster backup,
ndb_restore requires at a minimum the
--nodeid
(short form:
-n
),
--backupid
(short form:
-b
), and
--backup_path
options. In
addition, when ndb_restore is used to restore
any tables containing unique indexes, you must include
--disable-indexes
or
--rebuild-indexes
. (Bug
#57782, Bug #11764893)
ndb_restore [-cconnection_string
] -nnode_id
-bbackup_id
\ [-m] -r --backup_path=/path/to/backup/files
The -c
option is used to specify a connection
string which tells ndb_restore
where to
locate the cluster management server. (See
Section 19.3.3.3, “MySQL Cluster Connection Strings”, for
information on connection strings.) If this option is not used,
then ndb_restore attempts to connect to a
management server on localhost:1186
. This
utility acts as a cluster API node, and so requires a free
connection “slot” to connect to the cluster
management server. This means that there must be at least one
[api]
or [mysqld]
section
that can be used by it in the cluster
config.ini
file. It is a good idea to keep
at least one empty [api]
or
[mysqld]
section in
config.ini
that is not being used for a
MySQL server or other application for this reason (see
Section 19.3.3.7, “Defining SQL and Other API Nodes in a MySQL Cluster”).
You can verify that ndb_restore is connected to the cluster by using the SHOW command in the ndb_mgm management client. You can also accomplish this from a system shell, as shown here:
shell> ndb_mgm -e "SHOW"
The --nodeid
or -n
is used to
specify the node ID of the data node on which the backup should
be restored.
The first time you run the ndb_restore
restoration program, you also need to restore the metadata. In
other words, you must re-create the database tables—this
can be done by running it with the
--restore_meta
(-m
) option.
Restoring the metdata need be done only on a single data node;
this is sufficient to restore it to the entire cluster. Note
that the cluster should have an empty database when starting to
restore a backup. (In other words, you should start
ndbd with --initial
prior to
performing the restore.)
It is possible to restore data without restoring table metadata.
The default behavior when doing this is for
ndb_restore to fail with an error if table
data do not match the table schema; this can be overridden using
the --skip-table-check
or -s
option.
Some of the restrictions on mismatches in column definitions
when restoring data using ndb_restore are
relaxed; when one of these types of mismatches is encountered,
ndb_restore does not stop with an error as it
did previously, but rather accepts the data and inserts it into
the target table while issuing a warning to the user that this
is being done. This behavior occurs whether or not either of the
options --skip-table-check
or
--promote-attributes
is in
use. These differences in column definitions are of the
following types:
Different COLUMN_FORMAT
settings
(FIXED
, DYNAMIC
,
DEFAULT
)
Different STORAGE
settings
(MEMORY
, DISK
)
Different default values
Different distribution key settings
ndb_restore supports limited
attribute promotion in
much the same way that it is supported by MySQL replication;
that is, data backed up from a column of a given type can
generally be restored to a column using a “larger,
similar” type. For example, data from a
CHAR(20)
column can be restored to a column
declared as VARCHAR(20)
,
VARCHAR(30)
, or CHAR(30)
;
data from a MEDIUMINT
column can
be restored to a column of type
INT
or
BIGINT
. See
Section 18.4.1.10.2, “Replication of Columns Having Different Data Types”, for
a table of type conversions currently supported by attribute
promotion.
Attribute promotion by ndb_restore must be enabled explicitly, as follows:
Prepare the table to which the backup is to be restored.
ndb_restore cannot be used to re-create
the table with a different definition from the original;
this means that you must either create the table manually,
or alter the columns which you wish to promote using
ALTER TABLE
after restoring
the table metadata but before restoring the data.
Invoke ndb_restore with the
--promote-attributes
option (short form -A
) when restoring the
table data. Attribute promotion does not occur if this
option is not used; instead, the restore operation fails
with an error.
When converting between character data types and
TEXT
or BLOB
, only
conversions between character types
(CHAR
and
VARCHAR
) and binary types
(BINARY
and
VARBINARY
) can be performed at
the same time. For example, you cannot promote an
INT
column to
BIGINT
while promoting a
VARCHAR
column to TEXT
in
the same invocation of ndb_restore.
Converting between TEXT
columns
using different character sets is not supported, and is
expressly disallowed.
When performing conversions of character or binary types to
TEXT
or BLOB
with
ndb_restore, you may notice that it creates
and uses one or more staging tables named
.
These tables are not needed afterwards, and are normally deleted
by ndb_restore following a successful
restoration.
table_name
$STnode_id
Command-Line Format | --lossy-conversions | ||
Permitted Values | Type | boolean | |
Default | FALSE |
This option is intended to complement the
--promote-attributes
option.
Using --lossy-conversions
allows lossy
conversions of column values (type demotions or changes in sign)
when restoring data from backup. With some exceptions, the rules
governing demotion are the same as for MySQL replication; see
Section 18.4.1.10.2, “Replication of Columns Having Different Data Types”, for
information about specific type conversions currently supported
by attribute demotion.
ndb_restore reports any truncation of data that it performs during lossy conversions once per attribute and column.
The --preserve-trailing-spaces
option (short
form -R
) causes trailing spaces to be preserved
when promoting a fixed-width character data type to its
variable-width equivalent—that is, when promoting a
CHAR
column value to
VARCHAR
or a
BINARY
column value to
VARBINARY
. Otherwise, any
trailing spaces are dropped from such column values when they
are inserted into the new columns.
Although you can promote CHAR
columns to VARCHAR
and
BINARY
columns to
VARBINARY
, you cannot promote
VARCHAR
columns to
CHAR
or
VARBINARY
columns to
BINARY
.
The -b
option is used to specify the ID or
sequence number of the backup, and is the same number shown by
the management client in the Backup
message
displayed upon completion of a backup. (See
Section 19.5.3.2, “Using The MySQL Cluster Management Client to Create a Backup”.)
backup_id
completed
When restoring cluster backups, you must be sure to restore all data nodes from backups having the same backup ID. Using files from different backups will at best result in restoring the cluster to an inconsistent state, and may fail altogether.
--restore_epoch
(short form:
-e
) adds (or restores) epoch information to the
cluster replication status table. This is useful for starting
replication on a MySQL Cluster replication slave. When this
option is used, the row in the
mysql.ndb_apply_status
having
0
in the id
column is
updated if it already exists; such a row is inserted if it does
not already exist. (See
Section 19.6.9, “MySQL Cluster Backups With MySQL Cluster Replication”.)
This option causes ndb_restore to output
NDB
table data and logs.
This option causes ndb_restore to print
NDB
table metadata. Generally, you
need only use this option when restoring the first data node of
a cluster; additional data nodes can obtain the metadata from
the first one.
ndb_restore does not by default restore distributed MySQL privilege tables. This option causes ndb_restore to restore the privilege tables.
This works only if the privilege tables were converted to
NDB
before the backup was taken.
For more information, see
Section 19.5.15, “Distributed MySQL Privileges for MySQL Cluster”.
The path to the backup directory is required; this is supplied
to ndb_restore using the
--backup_path
option, and must include the
subdirectory corresponding to the ID backup of the backup to be
restored. For example, if the data node's
DataDir
is
/var/lib/mysql-cluster
, then the backup
directory is /var/lib/mysql-cluster/BACKUP
,
and the backup files for the backup with the ID 3 can be found
in /var/lib/mysql-cluster/BACKUP/BACKUP-3
.
The path may be absolute or relative to the directory in which
the ndb_restore executable is located, and
may be optionally prefixed with backup_path=
.
It is possible to restore a backup to a database with a
different configuration than it was created from. For example,
suppose that a backup with backup ID 12
,
created in a cluster with two database nodes having the node IDs
2
and 3
, is to be restored
to a cluster with four nodes. Then
ndb_restore must be run twice—once for
each database node in the cluster where the backup was taken.
However, ndb_restore cannot always restore
backups made from a cluster running one version of MySQL to a
cluster running a different MySQL version. See
Section 19.2.8, “Upgrading and Downgrading MySQL Cluster”, for more
information.
It is not possible to restore a backup made from a newer version of MySQL Cluster using an older version of ndb_restore. You can restore a backup made from a newer version of MySQL to an older cluster, but you must use a copy of ndb_restore from the newer MySQL Cluster version to do so.
For example, to restore a cluster backup taken from a cluster running MySQL Cluster NDB 7.4.5 to a cluster running MySQL Cluster NDB 7.3.8, you must use the ndb_restore that comes with the MySQL Cluster NDB 7.4.5 distribution.
For more rapid restoration, the data may be restored in
parallel, provided that there is a sufficient number of cluster
connections available. That is, when restoring to multiple nodes
in parallel, you must have an [api]
or
[mysqld]
section in the cluster
config.ini
file available for each
concurrent ndb_restore process. However, the
data files must always be applied before the logs.
When using ndb_restore to restore a backup,
VARCHAR
columns created using the
old fixed format are resized and recreated using the
variable-width format now employed. This behavior can be
overridden using the
--no-upgrade
option (short
form: -u
) when running
ndb_restore.
The --print_data
option causes
ndb_restore to direct its output to
stdout
.
TEXT
and
BLOB
column values are always
truncated. Such values are truncated to the first 256 bytes in
the output. This cannot currently be overridden when using
--print_data
.
Several additional options are available for use with the
--print_data
option in generating data dumps,
either to stdout
, or to a file. These are
similar to some of the options used with
mysqldump, and are shown in the following
list:
Command-Line Format | --tab=dir_name | ||
Permitted Values | Type | directory name |
This option causes
--print_data
to create
dump files, one per table, each named
.
It requires as its argument the path to the directory where
the files should be saved; use tbl_name
.txt.
for the
current directory.
Command-Line Format | --fields-enclosed-by=char | ||
Permitted Values | Type | string | |
Default |
|
Each column values are enclosed by the string passed to this option (regardless of data type; see next item).
--fields-optionally-enclosed-by=
string
Command-Line Format | --fields-optionally-enclosed-by | ||
Permitted Values | Type | string | |
Default |
|
The string passed to this option is used to enclose column
values containing character data (such as
CHAR
,
VARCHAR
,
BINARY
,
TEXT
, or
ENUM
).
Command-Line Format | --fields-terminated-by=char | ||
Permitted Values | Type | string | |
Default | \t (tab) |
The string passed to this option is used to separate column
values. The default value is a tab character
(\t
).
Command-Line Format | --hex |
If this option is used, all binary values are output in hexadecimal format.
Command-Line Format | --fields-terminated-by=char | ||
Permitted Values | Type | string | |
Default | \t (tab) |
This option specifies the string used to end each line of
output. The default is a linefeed character
(\n
).
Command-Line Format | --append |
When used with the --tab
and --print_data
options, this causes the data to be appended to any existing
files having the same names.
If a table has no explicit primary key, then the output
generated when using the
--print_data
option
includes the table's hidden primary key.
This option causes ndb_restore to print all
metadata to stdout
.
The --print_log
option causes
ndb_restore to output its log to
stdout
.
Causes ndb_restore to print all data,
metadata, and logs to stdout
. Equivalent to
using the --print_data
,
--print_meta
, and
--print_log
options
together.
Use of --print
or any of the
--print_*
options is in effect performing a
dry run. Including one or more of these options causes any
output to be redirected to stdout
; in such
cases, ndb_restore makes no attempt to
restore data or metadata to a MySQL Cluster.
Normally, when restoring table data and metadata,
ndb_restore ignores the copy of the
NDB
system table that is present in
the backup. --dont_ignore_systab_0
causes the
system table to be restored. This option is intended
for experimental and development use only, and is not
recommended in a production environment.
This option can be used to restore a backup taken from one node
group to a different node group. Its argument is a list of the
form
.
source_node_group
,
target_node_group
This option prevents any connected SQL nodes from writing data restored by ndb_restore to their binary logs.
This option stops ndb_restore from restoring any MySQL Cluster Disk Data objects, such as tablespaces and log file groups; see Section 19.5.13, “MySQL Cluster Disk Data Tables”, for more information about these.
ndb_restore uses single-row transactions to apply many rows concurrently. This parameter determines the number of parallel transactions (concurrent rows) that an instance of ndb_restore tries to use. By default, this is 128; the minimum is 1, and the maximum is 1024.
The work of performing the inserts is parallelized across the
threads in the data nodes involved. This mechanism is employed
for restoring bulk data from the .Data
file—that is, the fuzzy snapshot of the data; it is not
used for building or rebuilding indexes. The change log is
applied serially; index drops and builds are DDL operations and
handled separately. There is no thread-level parallelism on the
client side of the restore.
Print a status report each N
seconds
while the backup is in progress. 0 (the default) causes no
status reports to be printed. The maximum is 65535.
Sets the level for the verbosity of the output. The minimum is 0; the maximum is 255. The default value is 1.
It is possible to restore only selected databases, or selected tables from a single database, using the syntax shown here:
ndb_restoreother_options
db_name
,[db_name
[,...] |tbl_name
[,tbl_name
][,...]]
In other words, you can specify either of the following to be restored:
All tables from one or more databases
One or more tables from a single database
--include-databases=
db_name
[,db_name
][,...]
Command-Line Format | --include-databases=db-list | ||
Permitted Values | Type | string | |
Default |
|
--include-tables=
db_name.tbl_name
[,db_name.tbl_name
][,...]
Command-Line Format | --include-tables=table-list | ||
Permitted Values | Type | string | |
Default |
|
Use the --include-databases
option or the --include-tables
option for
restoring only specific databases or tables, respectively.
--include-databases
takes a comma-delimited
list of databases to be restored.
--include-tables
takes a comma-delimited list
of tables (in
format) to be restored.
database
.table
When --include-databases
or
--include-tables
is used, only those databases
or tables named by the option are restored; all other databases
and tables are excluded by ndb_restore, and
are not restored.
The following table shows several invocations of
ndb_restore using
--include-*
options (other options possibly
required have been omitted for clarity), and the effects these
have on restoring from a MySQL Cluster backup:
Option Used | Result |
---|---|
--include-databases=db1 | Only tables in database db1 are restored; all tables
in all other databases are ignored |
--include-databases=db1,db2 (or
--include-databases=db1
--include-databases=db2 ) | Only tables in databases db1 and
db2 are restored; all tables in all
other databases are ignored |
--include-tables=db1.t1 | Only table t1 in database db1 is
restored; no other tables in db1 or
in any other database are restored |
--include-tables=db1.t2,db2.t1 (or
--include-tables=db1.t2
--include-tables=db2.t1 ) | Only the table t2 in database db1
and the table t1 in database
db2 are restored; no other tables in
db1 , db2 , or any
other database are restored |
You can also use these two options together. For example, the
following causes all tables in databases db1
and db2
, together with the tables
t1
and t2
in database
db3
, to be restored (and no other databases
or tables):
shell> ndb_restore [...] --include-databases=db1,db2 --include-tables=db3.t1,db3.t2
(Again we have omitted other, possibly required, options in the example just shown.)
--exclude-databases=
db_name
[,db_name
][,...]
Command-Line Format | --exclude-databases=db-list | ||
Permitted Values | Type | string | |
Default |
|
--exclude-tables=
db_name.tbl_name
[,db_name.tbl_name
][,...]
Command-Line Format | --exclude-tables=table-list | ||
Permitted Values | Type | string | |
Default |
|
It is possible to prevent one or more databases or tables from
being restored using the ndb_restore options
--exclude-databases
and
--exclude-tables
.
--exclude-databases
takes a comma-delimited
list of one or more databases which should not be restored.
--exclude-tables
takes a comma-delimited list
of one or more tables (using
format) which should not be restored.
database
.table
When --exclude-databases
or
--exclude-tables
is used, only those databases
or tables named by the option are excluded; all other databases
and tables are restored by ndb_restore.
This table shows several invocations of
ndb_restore usng --exclude-*
options (other options possibly required have been omitted for
clarity), and the effects these options have on restoring from a
MySQL Cluster backup:
Option Used | Result |
---|---|
--exclude-databases=db1 | All tables in all databases except db1 are restored;
no tables in db1 are restored |
--exclude-databases=db1,db2 (or
--exclude-databases=db1
--exclude-databases=db2 ) | All tables in all databases except db1 and
db2 are restored; no tables in
db1 or db2 are
restored |
--exclude-tables=db1.t1 | All tables except t1 in database
db1 are restored; all other tables in
db1 are restored; all tables in all
other databases are restored |
--exclude-tables=db1.t2,db2.t1 (or
--exclude-tables=db1.t2
--exclude-tables=db2.t1) | All tables in database db1 except for
t2 and all tables in database
db2 except for table
t1 are restored; no other tables in
db1 or db2 are
restored; all tables in all other databases are restored |
You can use these two options together. For example, the
following causes all tables in all databases except
for databases db1
and
db2
, and tables t1
and
t2
in database db3
, to be
restored:
shell> ndb_restore [...] --exclude-databases=db1,db2 --exclude-tables=db3.t1,db3.t2
(Again, we have omitted other possibly necessary options in the interest of clarity and brevity from the example just shown.)
You can use --include-*
and
--exclude-*
options together, subject to the
following rules:
The actions of all --include-*
and
--exclude-*
options are cumulative.
All --include-*
and
--exclude-*
options are evaluated in the
order passed to ndb_restore, from right to left.
In the event of conflicting options, the first (rightmost) option takes precedence. In other words, the first option (going from right to left) that matches against a given database or table “wins”.
For example, the following set of options causes
ndb_restore to restore all tables from
database db1
except
db1.t1
, while restoring no other tables from
any other databases:
--include-databases=db1 --exclude-tables=db1.t1
However, reversing the order of the options just given simply
causes all tables from database db1
to be
restored (including db1.t1
, but no tables
from any other database), because the
--include-databases
option,
being farthest to the right, is the first match against database
db1
and thus takes precedence over any other
option that matches db1
or any tables in
db1
:
--exclude-tables=db1.t1 --include-databases=db1
Command-Line Format | --exclude-missing-columns |
It is also possible to restore only selected table columns using
the --exclude-missing-columns
option. When this
option is used, ndb_restore ignores any
columns missing from tables being restored as compared to the
versions of those tables found in the backup. This option
applies to all tables being restored. If you wish to apply this
option only to selected tables or databases, you can use it in
combination with one or more of the options described in the
previous paragraph to do so, then restore data to the remaining
tables using a complementary set of these options.
Command-Line Format | --exclude-missing-tables |
It is also possible to restore only selected tables columns using this option, which causes ndb_restore to ignore any tables from the backup that are not found in the target database.
Command-Line Format | --disable-indexes |
Disable restoration of indexes during restoration of the data
from a native NDB backup. Afterwards, you can restore indexes
for all tables at once with multi-threaded building of indexes
using --rebuild-indexes
,
which should be faster than rebuilding indexes concurrently for
very large tables.
Command-Line Format | --rebuild-indexes |
You can use this option with ndb_restore to
cause multi-threaded rebuilding of the ordered indexes while
restoring a native NDB
backup. The number of
threads used for building ordered indexes by
ndb_restore with this option is controlled by
the BuildIndexThreads
data node configuration parameter and the number of LDMs.
It is necessary to use this option only for the first run of
ndb_restore; this causes all ordered indexes
to be rebuilt without using --rebuild-indexes
again when restoring subsequent nodes. You should use this
option prior to inserting new rows into the database; otherwise,
it is possible for a row to be inserted that later causes a
unique constraint violation when trying to rebuild the indexes.
Building of ordered indices is parallelized with the number of
LDMs by default. Offline index builds performed during node and
system restarts can be made faster using the
BuildIndexThreads
data
node configuration parameter; this parameter has no effect on
dropping and rebuilding of indexes by
ndb_restore, which is performed online.
Rebuilding of unique indexes uses disk write bandwidth for redo
logging and local checkpointing. An insufficient amount of this
bandwith can lead to redo buffer overload or log overload
errors. In such cases you can run ndb_restore
--rebuild-indexes
again; the process resumes at
the point where the error occurred. You can also do this when
you have encountered temporarary errors. You can repeat
execution of ndb_restore
--rebuild-indexes
indefinitely; you may be able
to stop such errors by reducing the value of
DiskCheckpointSpeed
to
provide additional disk bandwidth to redo logging, or reducing
the --parallelism
. If the
problem is insufficient space, you can increase the size of the
redo log
(FragmentLogFileSize
node configuration parameter), or you can increase the speed at
which LCPs are performed
(DiskCheckpointSpeed
), in order to free space
more quickly.
Command-Line Format | --skip-broken-objects |
This option causes ndb_restore to ignore
corrupt tables while reading a native
NDB
backup, and to continue
restoring any remaining tables (that are not also corrupted).
Currently, the --skip-broken-objects
option
works only in the case of missing blob parts tables.
Command-Line Format | --skip-unknown-objects |
This option causes ndb_restore to ignore any
schema objects it does not recognize while reading a native
NDB
backup. This can be used for
restoring a backup made from a cluster running MySQL Cluster NDB
7.5 to a cluster running MySQL Cluster NDB 7.4.
--rewrite-database=
old_dbname
,new_dbname
Command-Line Format | --rewrite-database=olddb,newdb | ||
Permitted Values | Type | string | |
Default | none |
This option makes it possible to restore to a database having a
different name from that used in the backup. For example, if a
backup is made of a database named products
,
you can restore the data it contains to a database named
inventory
, use this option as shown here
(omitting any other options that might be required):
shell> ndb_restore --rewrite-database=product,inventory
The option can be employed multiple times in a single invocation
of ndb_restore. Thus it is possible to
restore simultaneously from a database named
db1
to a database named
db2
and from a database named
db3
to one named db4
using
--rewrite-database=db1,db2
--rewrite-database=db3,db4
. Other
ndb_restore options may be used between
multiple occurrences of --rewrite-database
.
In the event of conflicts between multiple
--rewrite-database
options, the last
--rewrite-database
option used, reading from
left to right, is the one that takes effect. For example, if
--rewrite-database=db1,db2
--rewrite-database=db1,db3
is used, only
--rewrite-database=db1,db3
is honored, and
--rewrite-database=db1,db2
is ignored. It is
also possible to restore from multiple databases to a single
database, so that --rewrite-database=db1,db3
--rewrite-database=db2,db3
restores all tables and data
from databases db1
and db2
into database db3
.
When restoring from multiple backup databases into a single
target database using --rewrite-database
, no
check is made for collisions between table or other object
names, and the order in which rows are restored is not
guaranteed. This means that it is possible in such cases for
rows to be overwritten and updates to be lost.
--exclude-intermediate-sql-tables[=TRUE|FALSE]
Command-Line Format | --exclude-intermediate-sql-tables[=TRUE|FALSE] | ||
Permitted Values | Type | boolean | |
Default | TRUE |
When performing copying ALTER
TABLE
operations, mysqld creates
intermediate tables (whose names are prefixed with
#sql-
). When TRUE
, the
--exclude-intermediate-sql-tables
option keeps
ndb_restore from restoring such tables that
may have been left over from such operations. This option is
TRUE
by default.
Error reporting.
ndb_restore reports both temporary and
permanent errors. In the case of temporary errors, it may able
to recover from them, and reports Restore successful,
but encountered temporary error, please look at
configuration
in such cases.
After using ndb_restore to initialize a
MySQL Cluster for use in circular replication, binary logs on
the SQL node acting as the replication slave are not
automatically created, and you must cause them to be created
manually. To cause the binary logs to be created, issue a
SHOW TABLES
statement on that
SQL node before running START
SLAVE
. This is a known issue in MySQL Cluster.
ndb_select_all prints all rows from an
NDB
table to
stdout
.
ndb_select_all -cconnection_string
tbl_name
-ddb_name
[>file_name
]
The following table includes options that are specific to the MySQL Cluster native backup restoration program ndb_select_all. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndb_select_all), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.95 This table describes command-line options for the ndb_select_all program
Format | Description | Added or Removed |
---|---|---|
Name of the database in which the table is found | All MySQL 5.7 based releases |
|
Degree of parallelism | All MySQL 5.7 based releases |
|
Lock type | All MySQL 5.7 based releases |
|
Sort resultset according to index whose name is supplied | All MySQL 5.7 based releases |
|
Sort resultset in descending order (requires order flag) | All MySQL 5.7 based releases |
|
Print header (set to 0|FALSE to disable headers in output) | All MySQL 5.7 based releases |
|
Output numbers in hexadecimal format | All MySQL 5.7 based releases |
|
Set a column delimiter | All MySQL 5.7 based releases |
|
Print disk references (useful only for Disk Data tables having nonindexed columns) | All MySQL 5.7 based releases |
|
Print rowid | All MySQL 5.7 based releases |
|
Include GCI in output | All MySQL 5.7 based releases |
|
Include GCI and row epoch in output | All MySQL 5.7 based releases |
|
Scan in tup order | All MySQL 5.7 based releases |
|
Do not print table column data | All MySQL 5.7 based releases |
Name of the database in which the table is found. The
default value is TEST_DB
.
Specifies the degree of parallelism.
--lock=
,
lock_type
-l
lock_type
Employs a lock when reading the table. Possible values for
lock_type
are:
0
: Read lock
1
: Read lock with hold
2
: Exclusive read lock
There is no default value for this option.
--order=
,
index_name
-o
index_name
Orders the output according to the index named
index_name
.
This is the name of an index, not of a column; the index must have been explicitly named when created.
Sorts the output in descending order. This option can be
used only in conjunction with the -o
(--order
) option.
Excludes column headers from the output.
Causes all numeric values to be displayed in hexadecimal format. This does not affect the output of numerals contained in strings or datetime values.
--delimiter=
,
character
-D
character
Causes the character
to be used
as a column delimiter. Only table data columns are separated
by this delimiter.
The default delimiter is the tab character.
Adds a disk reference column to the output. The column is nonempty only for Disk Data tables having nonindexed columns.
Adds a ROWID
column providing information
about the fragments in which rows are stored.
Adds a GCI
column to the output showing
the global checkpoint at which each row was last updated.
See Section 19.1, “MySQL Cluster Overview”, and
Section 19.5.6.2, “MySQL Cluster Log Events”, for more
information about checkpoints.
Adds a ROW$GCI64
column to the output
showing the global checkpoint at which each row was last
updated, as well as the number of the epoch in which this
update occurred.
Scan the table in the order of the tuples.
Causes any table data to be omitted.
Output from a MySQL SELECT
statement:
mysql> SELECT * FROM ctest1.fish;
+----+-----------+
| id | name |
+----+-----------+
| 3 | shark |
| 6 | puffer |
| 2 | tuna |
| 4 | manta ray |
| 5 | grouper |
| 1 | guppy |
+----+-----------+
6 rows in set (0.04 sec)
Output from the equivalent invocation of ndb_select_all:
shell> ./ndb_select_all -c localhost fish -d ctest1
id name
3 [shark]
6 [puffer]
2 [tuna]
4 [manta ray]
5 [grouper]
1 [guppy]
6 rows returned
NDBT_ProgramExit: 0 - OK
All string values are enclosed by square brackets
(“[
...]
”) in
the output of ndb_select_all. For another
example, consider the table created and populated as shown here:
CREATE TABLE dogs ( id INT(11) NOT NULL AUTO_INCREMENT, name VARCHAR(25) NOT NULL, breed VARCHAR(50) NOT NULL, PRIMARY KEY pk (id), KEY ix (name) ) TABLESPACE ts STORAGE DISK ENGINE=NDBCLUSTER; INSERT INTO dogs VALUES ('', 'Lassie', 'collie'), ('', 'Scooby-Doo', 'Great Dane'), ('', 'Rin-Tin-Tin', 'Alsatian'), ('', 'Rosscoe', 'Mutt');
This demonstrates the use of several additional ndb_select_all options:
shell> ./ndb_select_all -d ctest1 dogs -o ix -z --gci --disk
GCI id name breed DISK_REF
834461 2 [Scooby-Doo] [Great Dane] [ m_file_no: 0 m_page: 98 m_page_idx: 0 ]
834878 4 [Rosscoe] [Mutt] [ m_file_no: 0 m_page: 98 m_page_idx: 16 ]
834463 3 [Rin-Tin-Tin] [Alsatian] [ m_file_no: 0 m_page: 34 m_page_idx: 0 ]
835657 1 [Lassie] [Collie] [ m_file_no: 0 m_page: 66 m_page_idx: 0 ]
4 rows returned
NDBT_ProgramExit: 0 - OK
ndb_select_count prints the number of rows in
one or more NDB
tables. With a
single table, the result is equivalent to that obtained by using
the MySQL statement SELECT COUNT(*) FROM
.
tbl_name
ndb_select_count [-cconnection_string
] -ddb_name
tbl_name
[,tbl_name2
[, ...]]
The following table includes options that are specific to the MySQL Cluster native backup restoration program ndb_select_count. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndb_select_count), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.96 This table describes command-line options for the ndb_select_count program
Format | Description | Added or Removed |
---|---|---|
|
Name of the database in which the table is found | All MySQL 5.7 based releases |
|
Degree of parallelism | All MySQL 5.7 based releases |
|
Lock type | All MySQL 5.7 based releases |
You can obtain row counts from multiple tables in the same database by listing the table names separated by spaces when invoking this command, as shown under Sample Output.
shell> ./ndb_select_count -c localhost -d ctest1 fish dogs
6 records in table fish
4 records in table dogs
NDBT_ProgramExit: 0 - OK
ndb_setup.py starts the MySQL Cluster Auto-Installer and opens the installer's Start page in the default Web browser.
This section describes usage of and program options for the command-line tool only. For information about using the Auto-Installer GUI that is spawned when ndb_setup.py is invoked, see Section 19.2.1, “The MySQL Cluster Auto-Installer”.
All platforms:
ndb_setup.py [options
]
Additionally, on Windows platforms only:
setup.bat [options
]
The following table includes all options that are supported by the MySQL Cluster installation and configuration program ndb_setup.py. Additional descriptions follow the table.
Table 19.97 This table describes command-line options for the ndb_setup.py program
Format | Description | Added or Removed |
---|---|---|
Page that the web browser opens when starting. | All MySQL 5.7 based releases |
|
File containing list of client certificates allowed to connect to the server | All MySQL 5.7 based releases |
|
File containing X509 certificate that identifies the server. (Default: cfg.pem) | All MySQL 5.7 based releases |
|
Python logging module debug level. One of DEBUG, INFO, WARNING (default), ERROR, or CRITICAL. | All MySQL 5.7 based releases |
|
Print help message | All MySQL 5.7 based releases |
|
Specify file containing private key (if not included in --cert-file) | All MySQL 5.7 based releases |
|
Do not open the start page in a browser, merely start the tool | All MySQL 5.7 based releases |
|
Specify the port used by the web server | All MySQL 5.7 based releases |
|
|
Log requests to this file. Use '-' to force logging to stderr instead. | All MySQL 5.7 based releases |
The name of the server to connect with | All MySQL 5.7 based releases |
|
|
Use secure (HTTPS) client-server connection | All MySQL 5.7 based releases |
Command-Line Format | --browser-start-page=filename | ||
Permitted Values | Type | string | |
Default | index.html |
Specify the file to open in the browser as the installation
and configuration Start page. The default is
index.html
.
Command-Line Format | --ca-certs-file=filename | ||
Permitted Values | Type | file name | |
Default | [none] |
Specify a file containing a list of client certificates which are allowed to connect to the server. The default is an empty string, which means that no client authentication is used.
Command-Line Format | --cert-file=filename | ||
Permitted Values | Type | file name | |
Default | cfg.pem |
Specify a file containing an X509 certificate which
identifies the server. It is possible for the certificate to
be self-signed. The default is cfg.pem
.
Command-Line Format | --debug-level=level | ||
Permitted Values | Type | enumeration | |
Default | WARNING | ||
Valid Values | WARNING | ||
DEBUG | |||
INFO | |||
ERROR | |||
CRITICAL |
Set the Python logging module debug level. This is one of
DEBUG
, INFO
,
WARNING
, ERROR
, or
CRITICAL
. WARNING
is
the default.
Command-Line Format | --help |
Print a help message.
Command-Line Format | --key-file=file | ||
Permitted Values | Type | file name | |
Default | [none] |
Specify a file containing the private key if this is not
included in the X509 certificate file
(--cert-file
). The
default is an empty string, which means that no such file is
used.
Command-Line Format | --no-browser |
Start the installation and configuration tool, but do not open the Start page in a browser.
Command-Line Format | --port=# | ||
Permitted Values | Type | numeric | |
Default | 8081 | ||
Min Value | 1 | ||
Max Value | 65535 |
Set the port used by the web server. The default is 8081.
Command-Line Format | --server-log-file=file | ||
o | |||
Permitted Values | Type | file name | |
Default | ndb_setup.log | ||
Valid Values | ndb_setup.log | ||
- (Log to stderr) |
Log requests to this file. The default is
ndb_setup.log
. To specify logging to
stderr
, rather than to a file, use a
-
(dash character) for the file name.
Command-Line Format | --server-name=name | ||
Permitted Values | Type | string | |
Default | localhost |
Specify the host name or IP address for the browser to use
when connecting. The default is
localhost
.
Command-Line Format | --use-https |
Make the browser use a secure (HTTPS) connection with the server.
ndb_show_tables displays a list of all
NDB
database objects in the
cluster. By default, this includes not only both user-created
tables and NDB
system tables, but
NDB
-specific indexes, internal
triggers, and MySQL Cluster Disk Data objects as well.
The following table includes options that are specific to the MySQL Cluster native backup restoration program ndb_show_tables. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndb_show_tables), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.98 This table describes command-line options for the ndb_show_tables program
Format | Description | Added or Removed |
---|---|---|
Specifies the database in which the table is found | All MySQL 5.7 based releases |
|
Number of times to repeat output | All MySQL 5.7 based releases |
|
Limit output to objects of this type | All MySQL 5.7 based releases |
|
Do not qualify table names | All MySQL 5.7 based releases |
|
Return output suitable for MySQL LOAD DATA INFILE statement | All MySQL 5.7 based releases |
|
Show table temporary flag | All MySQL 5.7 based releases |
ndb_show_tables [-c connection_string
]
Specifies the name of the database in which the tables are
found. If this option has not been specified, and no tables
are found in the TEST_DB
database,
ndb_show_tables issues a warning.
Specifies the number of times the utility should execute. This is 1 when this option is not specified, but if you do use the option, you must supply an integer argument for it.
Using this option causes the output to be in a format
suitable for use with
LOAD DATA
INFILE
.
If specified, this causes temporary tables to be displayed.
Can be used to restrict the output to one type of object, specified by an integer type code as shown here:
1
: System table
2
: User-created table
3
: Unique hash index
Any other value causes all NDB
database objects to be listed (the default).
If specified, this causes unqualified object names to be displayed.
Only user-created MySQL Cluster tables may be accessed from
MySQL; system tables such as SYSTAB_0
are
not visible to mysqld. However, you can
examine the contents of system tables using
NDB
API applications such as
ndb_select_all (see
Section 19.4.21, “ndb_select_all — Print Rows from an NDB Table”).
This is a Perl script that can be used to estimate the amount of
space that would be required by a MySQL database if it were
converted to use the NDBCLUSTER
storage engine. Unlike the other utilities discussed in this
section, it does not require access to a MySQL Cluster (in fact,
there is no reason for it to do so). However, it does need to
access the MySQL server on which the database to be tested
resides.
A running MySQL server. The server instance does not have to provide support for MySQL Cluster.
A working installation of Perl.
The DBI
module, which can be obtained
from CPAN if it is not already part of your Perl
installation. (Many Linux and other operating system
distributions provide their own packages for this library.)
A MySQL user account having the necessary privileges. If you
do not wish to use an existing account, then creating one
using GRANT USAGE ON
—where
db_name
.*db_name
is the name of the
database to be examined—is sufficient for this
purpose.
ndb_size.pl
can also be found in the MySQL
sources in storage/ndb/tools
.
The following table includes options that are specific to the MySQL Cluster program ndb_size.pl. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndb_size.pl), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.99 This table describes command-line options for the ndb_size.pl program
Format | Description | Added or Removed |
---|---|---|
The database or databases to examine; accepts a comma-delimited list; the default is ALL (use all databases found on the server) | All MySQL 5.7 based releases |
|
Specify host and optional port as host[:port] | All MySQL 5.7 based releases |
|
Specify a socket to connect to | All MySQL 5.7 based releases |
|
Specify a MySQL user name | All MySQL 5.7 based releases |
|
Specify a MySQL user password | All MySQL 5.7 based releases |
|
Set output format (text or HTML) | All MySQL 5.7 based releases |
|
Skip any tables in a comma-separated list of tables | All MySQL 5.7 based releases |
|
Skip any databases in a comma-separated list of databases | All MySQL 5.7 based releases |
|
Saves all queries to the database into the file specified | All MySQL 5.7 based releases |
|
Loads all queries from the file specified; does not connect to a database | All MySQL 5.7 based releases |
|
Designates a table to handle unique index size calculations | All MySQL 5.7 based releases |
perl ndb_size.pl [--database={db_name
|ALL}] [--hostname=host
[:port
]] [--socket=socket
] \ [--user=user
] [--password=password
] \ [--help|-h] [--format={html|text}] \ [--loadqueries=file_name
] [--savequeries=file_name
]
By default, this utility attempts to analyze all databases on
the server. You can specify a single database using the
--database
option; the default behavior can be
made explicit by using ALL
for the name of
the database. You can also exclude one or more databases by
using the --excludedbs
option with a
comma-separated list of the names of the databases to be
skipped. Similarly, you can cause specific tables to be skipped
by listing their names, separated by commas, following the
optional --excludetables
option. A host name
can be specified using --hostname
; the default
is localhost
. You can specify a port in
addition to the host using
host
:port
format for the value of --hostname
. The default
port number is 3306. If necessary, you can also specify a
socket; the default is /var/lib/mysql.sock
.
A MySQL user name and password can be specified the
corresponding options shown. It also possible to control the
format of the output using the --format
option;
this can take either of the values html
or
text
, with text
being the
default. An example of the text output is shown here:
shell> ndb_size.pl --database=test --socket=/tmp/mysql.sock
ndb_size.pl report for database: 'test' (1 tables)
--------------------------------------------------
Connected to: DBI:mysql:host=localhost;mysql_socket=/tmp/mysql.sock
Including information for versions: 4.1, 5.0, 5.1
test.t1
-------
DataMemory for Columns (* means varsized DataMemory):
Column Name Type Varsized Key 4.1 5.0 5.1
HIDDEN_NDB_PKEY bigint PRI 8 8 8
c2 varchar(50) Y 52 52 4*
c1 int(11) 4 4 4
-- -- --
Fixed Size Columns DM/Row 64 64 12
Varsize Columns DM/Row 0 0 4
DataMemory for Indexes:
Index Name Type 4.1 5.0 5.1
PRIMARY BTREE 16 16 16
-- -- --
Total Index DM/Row 16 16 16
IndexMemory for Indexes:
Index Name 4.1 5.0 5.1
PRIMARY 33 16 16
-- -- --
Indexes IM/Row 33 16 16
Summary (for THIS table):
4.1 5.0 5.1
Fixed Overhead DM/Row 12 12 16
NULL Bytes/Row 4 4 4
DataMemory/Row 96 96 48
(Includes overhead, bitmap and indexes)
Varsize Overhead DM/Row 0 0 8
Varsize NULL Bytes/Row 0 0 4
Avg Varside DM/Row 0 0 16
No. Rows 0 0 0
Rows/32kb DM Page 340 340 680
Fixedsize DataMemory (KB) 0 0 0
Rows/32kb Varsize DM Page 0 0 2040
Varsize DataMemory (KB) 0 0 0
Rows/8kb IM Page 248 512 512
IndexMemory (KB) 0 0 0
Parameter Minimum Requirements
------------------------------
* indicates greater than default
Parameter Default 4.1 5.0 5.1
DataMemory (KB) 81920 0 0 0
NoOfOrderedIndexes 128 1 1 1
NoOfTables 128 1 1 1
IndexMemory (KB) 18432 0 0 0
NoOfUniqueHashIndexes 64 0 0 0
NoOfAttributes 1000 3 3 3
NoOfTriggers 768 5 5 5
For debugging purposes, the Perl arrays containing the queries
run by this script can be read from the file specified using can
be saved to a file using --savequeries
; a file
containing such arrays to be read in during script execution can
be specified using --loadqueries
. Neither of
these options has a default value.
To produce output in HTML format, use the
--format
option and redirect the output to a
file, as shown here:
shell> ndb_size.pl --database=test --socket=/tmp/mysql.sock --format=html > ndb_size.html
(Without the redirection, the output is sent to
stdout
.)
The output from this script includes the following information:
Minimum values for the
DataMemory
,
IndexMemory
,
MaxNoOfTables
,
MaxNoOfAttributes
,
MaxNoOfOrderedIndexes
,
MaxNoOfUniqueHashIndexes
,
and MaxNoOfTriggers
configuration parameters required to accommodate the tables
analyzed.
Memory requirements for all of the tables, attributes, ordered indexes, and unique hash indexes defined in the database.
The IndexMemory
and
DataMemory
required
per table and table row.
ndb_waiter repeatedly (each 100 milliseconds)
prints out the status of all cluster data nodes until either the
cluster reaches a given status or the
--timeout
limit is exceeded,
then exits. By default, it waits for the cluster to achieve
STARTED
status, in which all nodes have
started and connected to the cluster. This can be overridden
using the --no-contact
and
--not-started
options.
The node states reported by this utility are as follows:
NO_CONTACT
: The node cannot be contacted.
UNKNOWN
: The node can be contacted, but
its status is not yet known. Usually, this means that the
node has received a
START
or
RESTART
command from the
management server, but has not yet acted on it.
NOT_STARTED
: The node has stopped, but
remains in contact with the cluster. This is seen when
restarting the node using the management client's
RESTART
command.
STARTING
: The node's
ndbd process has started, but the node
has not yet joined the cluster.
STARTED
: The node is operational, and has
joined the cluster.
SHUTTING_DOWN
: The node is shutting down.
SINGLE USER MODE
: This is shown for all
cluster data nodes when the cluster is in single user mode.
The following table includes options that are specific to the MySQL Cluster native backup restoration program ndb_waiter. Additional descriptions follow the table. For options common to most MySQL Cluster programs (including ndb_waiter), see Section 19.4.27, “Options Common to MySQL Cluster Programs — Options Common to MySQL Cluster Programs”.
Table 19.100 This table describes command-line options for the ndb_waiter program
Format | Description | Added or Removed |
---|---|---|
Wait for cluster to reach NO CONTACT state | All MySQL 5.7 based releases |
|
Wait for cluster to reach NOT STARTED state | All MySQL 5.7 based releases |
|
Wait for cluster to enter single user mode | All MySQL 5.7 based releases |
|
Wait this many seconds, then exit whether or not cluster has reached desired state; default is 2 minutes (120 seconds) | All MySQL 5.7 based releases |
|
List of nodes not to be waited for. | All MySQL 5.7 based releases |
|
List of nodes to be waited for. | All MySQL 5.7 based releases |
ndb_waiter [-c connection_string
]
Instead of waiting for the STARTED
state,
ndb_waiter continues running until the
cluster reaches NO_CONTACT
status before
exiting.
Instead of waiting for the STARTED
state,
ndb_waiter continues running until the
cluster reaches NOT_STARTED
status before
exiting.
Time to wait. The program exits if the desired state is not achieved within this number of seconds. The default is 120 seconds (1200 reporting cycles).
The program waits for the cluster to enter single user mode.
When this option is used, ndb_waiter does not wait for the nodes whose IDs are listed. The list is comma-delimited; ranges can be indicated by dashes, as shown here:
shell> ndb_waiter --nowait-nodes=1,3,7-9
Do not use this option together with
the --wait-nodes
option.
When this option is used, ndb_waiter waits only for the nodes whose IDs are listed. The list is comma-delimited; ranges can be indicated by dashes, as shown here:
shell> ndb_waiter --wait-nodes=2,4-6,10
Do not use this option together with
the --nowait-nodes
option.
Sample Output.
Shown here is the output from ndb_waiter
when run against a 4-node cluster in which two nodes have been
shut down and then started again manually. Duplicate reports
(indicated by “...
”) are
omitted.
shell> ./ndb_waiter -c localhost
Connecting to mgmsrv at (localhost)
State node 1 STARTED
State node 2 NO_CONTACT
State node 3 STARTED
State node 4 NO_CONTACT
Waiting for cluster enter state STARTED
...
State node 1 STARTED
State node 2 UNKNOWN
State node 3 STARTED
State node 4 NO_CONTACT
Waiting for cluster enter state STARTED
...
State node 1 STARTED
State node 2 STARTING
State node 3 STARTED
State node 4 NO_CONTACT
Waiting for cluster enter state STARTED
...
State node 1 STARTED
State node 2 STARTING
State node 3 STARTED
State node 4 UNKNOWN
Waiting for cluster enter state STARTED
...
State node 1 STARTED
State node 2 STARTING
State node 3 STARTED
State node 4 STARTING
Waiting for cluster enter state STARTED
...
State node 1 STARTED
State node 2 STARTED
State node 3 STARTED
State node 4 STARTING
Waiting for cluster enter state STARTED
...
State node 1 STARTED
State node 2 STARTED
State node 3 STARTED
State node 4 STARTED
Waiting for cluster enter state STARTED
NDBT_ProgramExit: 0 - OK
If no connection string is specified, then
ndb_waiter tries to connect to a management
on localhost
, and reports
Connecting to mgmsrv at (null)
.
All MySQL Cluster programs accept the options described in this section, with the following exceptions:
Users of earlier MySQL Cluster versions should note that some
of these options have been changed to make them consistent
with one another, and also with mysqld. You
can use the --help
option with any MySQL
Cluster program—with the exception of
ndb_print_backup_file,
ndb_print_schema_file, and
ndb_print_sys_file—to view a list of
the options which the program supports.
The options in the following table are common to all MySQL Cluster executables (except those noted previously in this section).
Table 19.101 This table describes command-line options common to all MySQL Cluster programs
Format | Description | Added or Removed |
---|---|---|
Display help message and exit | All MySQL 5.7 based releases |
|
Directory where character sets are installed | All MySQL 5.7 based releases |
|
Set the number of times to retry a connection before giving up | All MySQL 5.7 based releases |
|
Time to wait between attempts to contact a management server, in seconds | All MySQL 5.7 based releases |
|
Write core on errors (defaults to TRUE in debug builds) | All MySQL 5.7 based releases |
|
Enable output from debug calls. Can be used only for versions compiled with debugging enabled | All MySQL 5.7 based releases |
|
|
Set connection string for connecting to ndb_mgmd. Syntax: [nodeid=<id>;][host=]<hostname>[:<port>]. Overrides entries specified in NDB_CONNECTSTRING or my.cnf. | All MySQL 5.7 based releases |
Set the host (and port, if desired) for connecting to management server | All MySQL 5.7 based releases |
|
Set node id for this node | All MySQL 5.7 based releases |
|
Select nodes for transactions in a more optimal way | All MySQL 5.7 based releases |
|
Output version information and exit | All MySQL 5.7 based releases |
For options specific to individual MySQL Cluster programs, see Section 19.4, “MySQL Cluster Programs”.
See Section 19.3.3.8.1, “MySQL Server Options for MySQL Cluster”, for mysqld options relating to MySQL Cluster.
Command-Line Format | --help | ||
--usage |
Prints a short list with descriptions of the available command options.
Command-Line Format | --character-sets-dir=dir_name | ||
Permitted Values | Type | directory name | |
Default |
|
Tells the program where to find character set information.
--ndb-connectstring=
,
connection_string
--connect-string=
,
connection_string
-c
connection_string
Command-Line Format | --ndb-connectstring=connectstring | ||
--connect-string=connectstring | |||
Permitted Values | Type | string | |
Default | localhost:1186 |
This option takes a MySQL Cluster connection string that specifies the management server for the application to connect to, as shown here:
shell> ndbd --ndb-connectstring="nodeid=2;host=ndb_mgmd.mysql.com:1186"
For more information, see Section 19.3.3.3, “MySQL Cluster Connection Strings”.
Command-Line Format | --connect-retries=# | ||
Permitted Values | Type | numeric | |
Default | 12 | ||
Min Value | 0 | ||
Max Value | 4294967295 |
This option specifies the number of times following the
first attempt to retry a connection before giving up (the
client always tries the connection at least once). The
length of time to wait per attempt is set using
--connect-retry-delay
.
When used with ndb_mgm, this option has 3 as its default. See Section 19.4.5, “ndb_mgm — The MySQL Cluster Management Client”, for more information.
Command-Line Format | --connect-retry-delay=# | ||
Permitted Values | Type | numeric | |
Default | 5 | ||
Min Value | 0 | ||
Max Value | 4294967295 | ||
Permitted Values (>= 5.7.10-ndb-7.5.0) | Type | numeric | |
Default | 5 | ||
Min Value | 1 | ||
Max Value | 4294967295 |
This option specifies the length of time to wait per attempt
a connection before giving up. The number of times to try
connecting is set by
--connect-retries
.
Command-Line Format | --core-file | ||
Permitted Values | Type | boolean | |
Default | FALSE |
Write a core file if the program dies. The name and location
of the core file are system-dependent. (For MySQL Cluster
programs nodes running on Linux, the default location is the
program's working directory—for a data node, this
is the node's
DataDir
.) For some
systems, there may be restrictions or limitations; for
example, it might be necessary to execute ulimit -c
unlimited before starting the server. Consult your
system documentation for detailed information.
If MySQL Cluster was built using the
--debug
option for
configure, then
--core-file
is enabled by default. For
regular builds, --core-file
is disabled by
default.
Command-Line Format | --debug=options | ||
Permitted Values | Type | string | |
Default | d:t:O,/tmp/ndb_restore.trace |
This option can be used only for versions compiled with debugging enabled. It is used to enable output from debug calls in the same manner as for the mysqld process.
Command-Line Format | --ndb-mgmd-host=host[:port] | ||
Permitted Values | Type | string | |
Default | localhost:1186 |
Can be used to set the host and port number of a single
management server for the program to connect to. If the
program requires node IDs or references to multiple
management servers (or both) in its connection information,
use the
--ndb-connectstring
option instead.
Command-Line Format | --ndb-nodeid=# | ||
Permitted Values | Type | numeric | |
Default | 0 |
Sets this node's MySQL Cluster node ID. The range of permitted values depends on the node's type (data, management, or API) and the MySQL Cluster software version. See Section 19.1.6.2, “Limits and Differences of MySQL Cluster from Standard MySQL Limits”, for more information.
--ndb-optimized-node-selection
Command-Line Format | --ndb-optimized-node-selection | ||
Permitted Values | Type | boolean | |
Default | TRUE |
Optimize selection of nodes for transactions. Enabled by default.
Command-Line Format | --version |
Prints the MySQL Cluster version number of the executable. The version number is relevant because not all versions can be used together, and the MySQL Cluster startup process verifies that the versions of the binaries being used can co-exist in the same cluster. This is also important when performing an online (rolling) software upgrade or downgrade of MySQL Cluster.
See Section 19.5.5, “Performing a Rolling Restart of a MySQL Cluster”), for more information.
Managing a MySQL Cluster involves a number of tasks, the first of which is to configure and start MySQL Cluster. This is covered in Section 19.3, “Configuration of MySQL Cluster”, and Section 19.4, “MySQL Cluster Programs”.
The next few sections cover the management of a running MySQL Cluster.
For information about security issues relating to management and deployment of a MySQL Cluster, see Section 19.5.12, “MySQL Cluster Security Issues”.
There are essentially two methods of actively managing a running
MySQL Cluster. The first of these is through the use of commands
entered into the management client whereby cluster status can be
checked, log levels changed, backups started and stopped, and nodes
stopped and started. The second method involves studying the
contents of the cluster log
ndb_
;
this is usually found in the management server's
node_id
_cluster.logDataDir
directory, but this
location can be overridden using the
LogDestination
option.
(Recall that node_id
represents the
unique identifier of the node whose activity is being logged.) The
cluster log contains event reports generated by
ndbd. It is also possible to send cluster log
entries to a Unix system log.
Some aspects of the cluster's operation can be also be monitored
from an SQL node using the
SHOW ENGINE NDB
STATUS
statement.
More detailed information about MySQL Cluster operations is
available in real time through an SQL interface using the
ndbinfo
database. For more
information, see Section 19.5.10, “The ndbinfo MySQL Cluster Information Database”.
NDB statistics counters provide improved monitoring using the
mysql client. These counters, implemented in the
NDB kernel, relate to operations performed by or affecting
Ndb
objects, such as starting,
closing, and aborting transactions; primary key and unique key
operations; table, range, and pruned scans; blocked threads waiting
for various operations to complete; and data and events sent and
received by MySQL Cluster. The counters are incremented by the NDB
kernel whenever NDB API calls are made or data is sent to or
received by the data nodes.
mysqld exposes the NDB API statistics counters as
system status variables, which can be identified from the prefix
common to all of their names (Ndb_api_
). The
values of these variables can be read in the
mysql client from the output of a
SHOW STATUS
statement, or by querying
either the
SESSION_STATUS
table
or the GLOBAL_STATUS
table (in the INFORMATION_SCHEMA
database). By
comparing the values of the status variables before and after the
execution of an SQL statement that acts on
NDB
tables, you can observe the actions
taken on the NDB API level that correspond to this statement, which
can be beneficial for monitoring and performance tuning of MySQL
Cluster.
MySQL Cluster Manager provides an advanced command-line interface that simplifies many otherwise complex MySQL Cluster management tasks, such as starting, stopping, or restarting a MySQL Cluster with a large number of nodes. The MySQL Cluster Manager client also supports commands for getting and setting the values of most node configuration parameters as well as mysqld server options and variables relating to MySQL Cluster. See MySQL™ Cluster Manager 1.4.0 User Manual, for more information.
This section provides a simplified outline of the steps involved
when MySQL Cluster data nodes are started. More complete
information can be found in
MySQL Cluster Start Phases, in the
NDB
Internals Guide.
These phases are the same as those reported in the output from the
command in the management client (see
Section 19.5.2, “Commands in the MySQL Cluster Management Client”). These start
phases are also reported in the node_id
STATUSstart_phase
column of the ndbinfo.nodes
table.
Start types. There are several different startup types and modes, as shown in the following list:
Initial start.
The cluster starts with a clean file system on all data
nodes. This occurs either when the cluster started for the
very first time, or when all data nodes are restarted using
the --initial
option.
Disk Data files are not removed when restarting a node using
--initial
.
System restart. The cluster starts and reads data stored in the data nodes. This occurs when the cluster has been shut down after having been in use, when it is desired for the cluster to resume operations from the point where it left off.
Node restart. This is the online restart of a cluster node while the cluster itself is running.
Initial node restart. This is the same as a node restart, except that the node is reinitialized and started with a clean file system.
Setup and initialization (phase -1). Prior to startup, each data node (ndbd process) must be initialized. Initialization consists of the following steps:
Obtain a node ID
Fetch configuration data
Allocate ports to be used for inter-node communications
Allocate memory according to settings obtained from the configuration file
When a data node or SQL node first connects to the management node, it reserves a cluster node ID. To make sure that no other node allocates the same node ID, this ID is retained until the node has managed to connect to the cluster and at least one ndbd reports that this node is connected. This retention of the node ID is guarded by the connection between the node in question and ndb_mgmd.
After each data node has been initialized, the cluster startup process can proceed. The stages which the cluster goes through during this process are listed here:
Phase 0.
The NDBFS
and NDBCNTR
blocks start (see
NDB Kernel Blocks). Data node
file systems are cleared on those data nodes that were
started with --initial
option.
Phase 1.
In this stage, all remaining
NDB
kernel blocks are started.
MySQL Cluster connections are set up, inter-block
communications are established, and heartbeats are started.
In the case of a node restart, API node connections are also
checked.
When one or more nodes hang in Phase 1 while the remaining node or nodes hang in Phase 2, this often indicates network problems. One possible cause of such issues is one or more cluster hosts having multiple network interfaces. Another common source of problems causing this condition is the blocking of TCP/IP ports needed for communications between cluster nodes. In the latter case, this is often due to a misconfigured firewall.
Phase 2.
The NDBCNTR
kernel block checks the
states of all existing nodes. The master node is chosen, and
the cluster schema file is initialized.
Phase 3.
The DBLQH
and DBTC
kernel blocks set up communications between them. The
startup type is determined; if this is a restart, the
DBDIH
block obtains permission to perform
the restart.
Phase 4.
For an initial start or initial node restart, the redo log
files are created. The number of these files is equal to
NoOfFragmentLogFiles
.
For a system restart:
Read schema or schemas.
Read data from the local checkpoint.
Apply all redo information until the latest restorable global checkpoint has been reached.
For a node restart, find the tail of the redo log.
Phase 5. Most of the database-related portion of a data node start is performed during this phase. For an initial start or system restart, a local checkpoint is executed, followed by a global checkpoint. Periodic checks of memory usage begin during this phase, and any required node takeovers are performed.
Phase 6. In this phase, node groups are defined and set up.
Phase 7.
The arbitrator node is selected and begins to function. The
next backup ID is set, as is the backup disk write speed.
Nodes reaching this start phase are marked as
Started
. It is now possible for API nodes
(including SQL nodes) to connect to the cluster.
Phase 8.
If this is a system restart, all indexes are rebuilt (by
DBDIH
).
Phase 9. The node internal startup variables are reset.
Phase 100 (OBSOLETE). Formerly, it was at this point during a node restart or initial node restart that API nodes could connect to the node and begin to receive events. Currently, this phase is empty.
Phase 101.
At this point in a node restart or initial node restart,
event delivery is handed over to the node joining the
cluster. The newly-joined node takes over responsibility for
delivering its primary data to subscribers. This phase is
also referred to as
SUMA
handover
phase.
After this process is completed for an initial start or system restart, transaction handling is enabled. For a node restart or initial node restart, completion of the startup process means that the node may now act as a transaction coordinator.
In addition to the central configuration file, a cluster may also be controlled through a command-line interface available through the management client ndb_mgm. This is the primary administrative interface to a running cluster.
Commands for the event logs are given in Section 19.5.6, “Event Reports Generated in MySQL Cluster”; commands for creating backups and restoring from them are provided in Section 19.5.3, “Online Backup of MySQL Cluster”.
Using ndb_mgm with MySQL Cluster Manager.
MySQL Cluster Manager handles starting and stopping processes and tracks their
states internally, so it is not necessary to use
ndb_mgm for these tasks for a MySQL Cluster
that is under MySQL Cluster Manager control. it is recommended
not to use the ndb_mgm
command-line client that comes with the MySQL Cluster
distribution to perform operations that involve starting or
stopping nodes. These include but are not limited to the
START
,
STOP
,
RESTART
, and
SHUTDOWN
commands. For more
information, see MySQL Cluster Manager Process Commands.
The management client has the following basic commands. In the
listing that follows, node_id
denotes
either a database node ID or the keyword ALL
,
which indicates that the command should be applied to all of the
cluster's data nodes.
Displays information on all available commands.
Connects to the management server indicated by the connection string. If the client is already connected to this server, the client reconnects.
Displays information on the cluster's status. Possible
node status values include UNKNOWN
,
NO_CONTACT
, NOT_STARTED
,
STARTING
, STARTED
,
SHUTTING_DOWN
, and
RESTARTING
. The output from this command
also indicates when the cluster is in single user mode (status
SINGLE USER MODE
).
Brings online the data node identified by
node_id
(or all data nodes).
ALL START
works on all data nodes only, and
does not affect management nodes.
To use this command to bring a data node online, the data
node must have been started using
--nostart
or
-n
.
Stops the data or management node identified by
node_id
.
ALL STOP
works to stop all data nodes
only, and does not affect management nodes.
A node affected by this command disconnects from the cluster, and its associated ndbd or ndb_mgmd process terminates.
The -a
option causes the node to be stopped
immediately, without waiting for the completion of any pending
transactions.
Normally, STOP
fails if the result would
cause an incomplete cluster. The -f
option
forces the node to shut down without checking for this. If
this option is used and the result is an incomplete cluster,
the cluster immediately shuts down.
Use of the -a
option also disables the
safety check otherwise performed when
STOP
is invoked to insure that stopping
the node does not cause an incomplete cluster. In other
words, you should exercise extreme care when using the
-a
option with the STOP
command, due to the fact that this option makes it possible
for the cluster to undergo a forced shutdown because it no
longer has a complete copy of all data stored in
NDB
.
node_id
RESTART [-n] [-i] [-a] [-f]
Restarts the data node identified by
node_id
(or all data nodes).
Using the -i
option with
RESTART
causes the data node to perform an
initial restart; that is, the node's file system is deleted
and recreated. The effect is the same as that obtained from
stopping the data node process and then starting it again
using ndbd
--initial
from the
system shell.
Backup files and Disk Data files are not removed when this option is used.
Using the -n
option causes the data node
process to be restarted, but the data node is not actually
brought online until the appropriate
START
command is issued.
The effect of this option is the same as that obtained from
stopping the data node and then starting it again using
ndbd --nostart
or ndbd -n
from the system
shell.
Using the -a
causes all current transactions
relying on this node to be aborted. No GCP check is done when
the node rejoins the cluster.
Normally, RESTART
fails if taking the node
offline would result in an incomplete cluster. The
-f
option forces the node to restart without
checking for this. If this option is used and the result is an
incomplete cluster, the entire cluster is restarted.
Displays status information for the data node identified by
node_id
(or for all data nodes).
The output from this command also indicates when the cluster is in single user mode.
Displays a report of type
report-type
for the data node
identified by node_id
, or for all
data nodes using ALL
.
Currently, there are three accepted values for
report-type
:
BackupStatus
provides a status report
on a cluster backup in progress
MemoryUsage
displays how much data
memory and index memory is being used by each data node as
shown in this example:
ndb_mgm> ALL REPORT MEMORY
Node 1: Data usage is 5%(177 32K pages of total 3200)
Node 1: Index usage is 0%(108 8K pages of total 12832)
Node 2: Data usage is 5%(177 32K pages of total 3200)
Node 2: Index usage is 0%(108 8K pages of total 12832)
This information is also available from the
ndbinfo.memoryusage
table.
EventLog
reports events from the event
log buffers of one or more data nodes.
report-type
is case-insensitive and
“fuzzy”; for MemoryUsage
, you
can use MEMORY
(as shown in the prior
example), memory
, or even simply
MEM
(or mem
). You can
abbreviate BackupStatus
in a similar
fashion.
ENTER SINGLE USER MODE
node_id
Enters single user mode, whereby only the MySQL server
identified by the node ID node_id
is permitted to access the database.
Currently, it is not possible for data nodes to join a MySQL Cluster while it is running in single user mode. (Bug #20395)
Exits single user mode, enabling all SQL nodes (that is, all running mysqld processes) to access the database.
It is possible to use EXIT SINGLE USER
MODE
even when not in single user mode, although
the command has no effect in this case.
Terminates the management client.
This command does not affect any nodes connected to the cluster.
Shuts down all cluster data nodes and management nodes. To
exit the management client after this has been done, use
EXIT
or
QUIT
.
This command does not shut down any SQL nodes or API nodes that are connected to the cluster.
CREATE NODEGROUP
nodeid
[,
nodeid
, ...]
Creates a new MySQL Cluster node group and causes data nodes to join it.
This command is used after adding new data nodes online to a MySQL Cluster, and causes them to join a new node group and thus to begin participating fully in the cluster. The command takes as its sole parameter a comma-separated list of node IDs—these are the IDs of the nodes just added and started that are to join the new node group. The number of nodes must be the same as the number of nodes in each node group that is already part of the cluster (each MySQL Cluster node group must have the same number of nodes). In other words, if the MySQL Cluster has 2 node groups of 2 data nodes each, then the new node group must also have 2 data nodes.
The node group ID of the new node group created by this command is determined automatically, and always the next highest unused node group ID in the cluster; it is not possible to set it manually.
For more information, see Section 19.5.14, “Adding MySQL Cluster Data Nodes Online”.
Drops the MySQL Cluster node group with the given
nodegroup_id
.
This command can be used to drop a node group from a MySQL
Cluster. DROP NODEGROUP
takes as its sole
argument the node group ID of the node group to be dropped.
DROP NODEGROUP
acts only to remove the data
nodes in the effected node group from that node group. It does
not stop data nodes, assign them to a different node group, or
remove them from the cluster's configuration. A data node
that does not belong to a node group is indicated in the
output of the management client
SHOW
command with
no nodegroup
in place of the node group ID,
like this (indicated using bold text):
id=3 @10.100.2.67 (5.7.13-ndb-7.5.3, no nodegroup)
DROP NODEGROUP
works only when all data
nodes in the node group to be dropped are completely empty of
any table data and table definitions. Since there is currently
no way using ndb_mgm or the
mysql client to remove all data from a
specific data node or node group, this means that the command
succeeds only in the two following cases:
After issuing CREATE
NODEGROUP
in the ndb_mgm
client, but before issuing any
ALTER TABLE
... REORGANIZE PARTITION
statements in the
mysql client.
After dropping all NDBCLUSTER
tables using DROP TABLE
.
TRUNCATE TABLE
does not
work for this purpose because this removes only the table
data; the data nodes continue to store an
NDBCLUSTER
table's
definition until a DROP
TABLE
statement is issued that causes the table
metadata to be dropped.
For more information about DROP NODEGROUP
,
see Section 19.5.14, “Adding MySQL Cluster Data Nodes Online”.
Changes the prompt shown by ndb_mgm to the
string literal prompt
.
prompt
should not be quoted (unless
you want the prompt to include the quotation marks). Unlike
the case with the mysql client, special
character sequences and escapes are not recognized. If called
without an argument, the command resets the prompt to the
default value (ndb_mgm>
).
Some examples are shown here:
jon@valhaj:~/bin>./ndb_mgm
-- NDB Cluster -- Management Client -- Connected to Management Server at: localhost:1186 ndb_mgm>PROMPT mgm#1:
mgm#1:SHOW
Cluster Configuration ... mgm#1:PROMPT mymgm >
mymgm >PROMPT 'mymgm:'
'mymgm:'PROMPT mymgm:
mymgm:PROMPT
ndb_mgm>EXIT
jon@valhaj:~/bin>
Note that leading spaces and spaces within the
prompt
string are not trimmed.
Trailing spaces are removed.
The PROMPT
command was added in MySQL
Cluster NDB 7.5.0.
Additional commands. A number of other commands available in the ndb_mgm client are described elsewhere, as shown in the following list:
START BACKUP
is used to
perform an online backup in the ndb_mgm
client; the ABORT BACKUP
command is used to cancel a backup already in progress. For
more information, see Section 19.5.3, “Online Backup of MySQL Cluster”.
The CLUSTERLOG
command is
used to perform various logging functions. See
Section 19.5.6, “Event Reports Generated in MySQL Cluster”, for more
information and examples.
For testing and diagnostics work, the client also supports a
DUMP
command which can be
used to execute internal commands on the cluster. It should
never be used in a production setting unless directed to do so
by MySQL Support. For more information, see
MySQL Cluster Internals.
The next few sections describe how to prepare for and then to create a MySQL Cluster backup using the functionality for this purpose found in the ndb_mgm management client. To distinguish this type of backup from a backup made using mysqldump, we sometimes refer to it as a “native” MySQL Cluster backup. (For information about the creation of backups with mysqldump, see Section 5.5.4, “mysqldump — A Database Backup Program”.) Restoration of MySQL Cluster backups is done using the ndb_restore utility provided with the MySQL Cluster distribution; for information about ndb_restore and its use in restoring MySQL Cluster backups, see Section 19.4.20, “ndb_restore — Restore a MySQL Cluster Backup”.
A backup is a snapshot of the database at a given time. The backup consists of three main parts:
Metadata. The names and definitions of all database tables
Table records. The data actually stored in the database tables at the time that the backup was made
Transaction log. A sequential record telling how and when data was stored in the database
Each of these parts is saved on all nodes participating in the backup. During backup, each node saves these three parts into three files on disk:
BACKUP-
backup_id
.node_id
.ctl
A control file containing control information and metadata. Each node saves the same table definitions (for all tables in the cluster) to its own version of this file.
BACKUP-
backup_id
-0.node_id
.data
A data file containing the table records, which are saved on a per-fragment basis. That is, different nodes save different fragments during the backup. The file saved by each node starts with a header that states the tables to which the records belong. Following the list of records there is a footer containing a checksum for all records.
BACKUP-
backup_id
.node_id
.log
A log file containing records of committed transactions. Only transactions on tables stored in the backup are stored in the log. Nodes involved in the backup save different records because different nodes host different database fragments.
In the listing above, backup_id
stands for the backup identifier and
node_id
is the unique identifier for
the node creating the file.
Before starting a backup, make sure that the cluster is properly configured for performing one. (See Section 19.5.3.3, “Configuration for MySQL Cluster Backups”.)
The START BACKUP
command is used to create a
backup:
START BACKUP [backup_id
] [wait_option
] [snapshot_option
]wait_option
: WAIT {STARTED | COMPLETED} | NOWAITsnapshot_option
: SNAPSHOTSTART | SNAPSHOTEND
Successive backups are automatically identified sequentially, so
the backup_id
, an integer greater
than or equal to 1, is optional; if it is omitted, the next
available value is used. If an existing
backup_id
value is used, the backup
fails with the error Backup failed: file already
exists. If used, the
backup_id
must follow START
BACKUP
immediately, before any other options are used.
The wait_option
can be used to
determine when control is returned to the management client
after a START BACKUP
command is issued, as
shown in the following list:
If NOWAIT
is specified, the management
client displays a prompt immediately, as seen here:
ndb_mgm> START BACKUP NOWAIT
ndb_mgm>
In this case, the management client can be used even while it prints progress information from the backup process.
With WAIT STARTED
the management client
waits until the backup has started before returning control
to the user, as shown here:
ndb_mgm> START BACKUP WAIT STARTED
Waiting for started, this may take several minutes
Node 2: Backup 3 started from node 1
ndb_mgm>
WAIT COMPLETED
causes the management
client to wait until the backup process is complete before
returning control to the user.
WAIT COMPLETED
is the default.
A snapshot_option
can be used to
determine whether the backup matches the state of the cluster
when START BACKUP
was issued, or when it was
completed. SNAPSHOTSTART
causes the backup to
match the state of the cluster when the backup began;
SNAPSHOTEND
causes the backup to reflect the
state of the cluster when the backup was finished.
SNAPSHOTEND
is the default, and matches the
behavior found in previous MySQL Cluster releases.
If you use the SNAPSHOTSTART
option with
START BACKUP
, and the
CompressedBackup
parameter is enabled, only the data and control files are
compressed—the log file is not compressed.
If both a wait_option
and a
snapshot_option
are used, they may be
specified in either order. For example, all of the following
commands are valid, assuming that there is no existing backup
having 4 as its ID:
START BACKUP WAIT STARTED SNAPSHOTSTART START BACKUP SNAPSHOTSTART WAIT STARTED START BACKUP 4 WAIT COMPLETED SNAPSHOTSTART START BACKUP SNAPSHOTEND WAIT COMPLETED START BACKUP 4 NOWAIT SNAPSHOTSTART
The procedure for creating a backup consists of the following steps:
Start the management client (ndb_mgm), if it not running already.
Execute the START BACKUP
command.
This produces several lines of output indicating the
progress of the backup, as shown here:
ndb_mgm> START BACKUP
Waiting for completed, this may take several minutes
Node 2: Backup 1 started from node 1
Node 2: Backup 1 started from node 1 completed
StartGCP: 177 StopGCP: 180
#Records: 7362 #LogRecords: 0
Data: 453648 bytes Log: 0 bytes
ndb_mgm>
When the backup has started the management client displays this message:
Backupbackup_id
started from nodenode_id
backup_id
is the unique
identifier for this particular backup. This identifier is
saved in the cluster log, if it has not been configured
otherwise. node_id
is the
identifier of the management server that is coordinating the
backup with the data nodes. At this point in the backup
process the cluster has received and processed the backup
request. It does not mean that the backup has finished. An
example of this statement is shown here:
Node 2: Backup 1 started from node 1
The management client indicates with a message like this one that the backup has started:
Backupbackup_id
started from nodenode_id
completed
As is the case for the notification that the backup has
started, backup_id
is the unique
identifier for this particular backup, and
node_id
is the node ID of the
management server that is coordinating the backup with the
data nodes. This output is accompanied by additional
information including relevant global checkpoints, the
number of records backed up, and the size of the data, as
shown here:
Node 2: Backup 1 started from node 1 completed StartGCP: 177 StopGCP: 180 #Records: 7362 #LogRecords: 0 Data: 453648 bytes Log: 0 bytes
It is also possible to perform a backup from the system shell by
invoking ndb_mgm with the -e
or --execute
option, as shown in
this example:
shell> ndb_mgm -e "START BACKUP 6 WAIT COMPLETED SNAPSHOTSTART"
When using START BACKUP
in this way, you must
specify the backup ID.
Cluster backups are created by default in the
BACKUP
subdirectory of the
DataDir
on each data
node. This can be overridden for one or more data nodes
individually, or for all cluster data nodes in the
config.ini
file using the
BackupDataDir
configuration parameter. The backup files created for a backup
with a given backup_id
are stored in
a subdirectory named
BACKUP-
in the backup directory.
backup_id
Cancelling backups. To cancel or abort a backup that is already in progress, perform the following steps:
Start the management client.
Execute this command:
ndb_mgm> ABORT BACKUP backup_id
The number backup_id
is the
identifier of the backup that was included in the response
of the management client when the backup was started (in the
message Backup
).
backup_id
started from node
management_node_id
The management client will acknowledge the abort request
with Abort of backup
.
backup_id
ordered
At this point, the management client has not yet received a response from the cluster data nodes to this request, and the backup has not yet actually been aborted.
After the backup has been aborted, the management client will report this fact in a manner similar to what is shown here:
Node 1: Backup 3 started from 5 has been aborted. Error: 1321 - Backup aborted by user request: Permanent error: User defined error Node 3: Backup 3 started from 5 has been aborted. Error: 1323 - 1323: Permanent error: Internal error Node 2: Backup 3 started from 5 has been aborted. Error: 1323 - 1323: Permanent error: Internal error Node 4: Backup 3 started from 5 has been aborted. Error: 1323 - 1323: Permanent error: Internal error
In this example, we have shown sample output for a cluster
with 4 data nodes, where the sequence number of the backup
to be aborted is 3
, and the management
node to which the cluster management client is connected has
the node ID 5
. The first node to complete
its part in aborting the backup reports that the reason for
the abort was due to a request by the user. (The remaining
nodes report that the backup was aborted due to an
unspecified internal error.)
There is no guarantee that the cluster nodes respond to an
ABORT BACKUP
command in any particular
order.
The Backup
messages mean that the backup has been
terminated and that all files relating to this backup have
been removed from the cluster file system.
backup_id
started from node
management_node_id
has been
aborted
It is also possible to abort a backup in progress from a system shell using this command:
shell> ndb_mgm -e "ABORT BACKUP backup_id
"
If there is no backup having the ID
backup_id
running when an
ABORT BACKUP
is issued, the management
client makes no response, nor is it indicated in the cluster
log that an invalid abort command was sent.
Five configuration parameters are essential for backup:
The amount of memory used to buffer data before it is written to disk.
The amount of memory used to buffer log records before these are written to disk.
The total memory allocated in a data node for backups. This should be the sum of the memory allocated for the backup data buffer and the backup log buffer.
The default size of blocks written to disk. This applies for both the backup data buffer and the backup log buffer.
The maximum size of blocks written to disk. This applies for both the backup data buffer and the backup log buffer.
More detailed information about these parameters can be found in Backup Parameters.
If an error code is returned when issuing a backup request, the most likely cause is insufficient memory or disk space. You should check that there is enough memory allocated for the backup.
If you have set
BackupDataBufferSize
and
BackupLogBufferSize
and their sum is greater than 4MB, then you must also set
BackupMemory
as well.
You should also make sure that there is sufficient space on the hard drive partition of the backup target.
NDB
does not support repeatable
reads, which can cause problems with the restoration process.
Although the backup process is “hot”, restoring a
MySQL Cluster from backup is not a 100% “hot”
process. This is due to the fact that, for the duration of the
restore process, running transactions get nonrepeatable reads
from the restored data. This means that the state of the data is
inconsistent while the restore is in progress.
mysqld is the traditional MySQL server process.
To be used with MySQL Cluster, mysqld needs to
be built with support for the NDB
storage engine, as it is in the precompiled binaries available
from http://dev.mysql.com/downloads/. If you build MySQL from
source, you must invoke CMake with the
-DWITH_NDBCLUSTER=1
option to
include support for NDB
.
For more information about compiling MySQL Cluster from source, see Section 19.2.2.4, “Building MySQL Cluster from Source on Linux”, and Section 19.2.3.2, “Compiling and Installing MySQL Cluster from Source on Windows”.
(For information about mysqld options and variables, in addition to those discussed in this section, which are relevant to MySQL Cluster, see Section 19.3.3.8, “MySQL Server Options and Variables for MySQL Cluster”.)
If the mysqld binary has been built with
Cluster support, the NDBCLUSTER
storage engine is still disabled by default. You can use either of
two possible options to enable this engine:
Use --ndbcluster
as a startup
option on the command line when starting
mysqld.
Insert a line containing ndbcluster
in the
[mysqld]
section of your
my.cnf
file.
An easy way to verify that your server is running with the
NDBCLUSTER
storage engine enabled is
to issue the SHOW ENGINES
statement
in the MySQL Monitor (mysql). You should see
the value YES
as the Support
value in the row for NDBCLUSTER
. If
you see NO
in this row or if there is no such
row displayed in the output, you are not running an
NDB
-enabled version of MySQL. If you
see DISABLED
in this row, you need to enable it
in either one of the two ways just described.
To read cluster configuration data, the MySQL server requires at a minimum three pieces of information:
The MySQL server's own cluster node ID
The host name or IP address for the management server (MGM node)
The number of the TCP/IP port on which it can connect to the management server
Node IDs can be allocated dynamically, so it is not strictly necessary to specify them explicitly.
The mysqld parameter
ndb-connectstring
is used to specify the
connection string either on the command line when starting
mysqld or in my.cnf
. The
connection string contains the host name or IP address where the
management server can be found, as well as the TCP/IP port it
uses.
In the following example, ndb_mgmd.mysql.com
is
the host where the management server resides, and the management
server listens for cluster messages on port 1186:
shell> mysqld --ndbcluster --ndb-connectstring=ndb_mgmd.mysql.com:1186
See Section 19.3.3.3, “MySQL Cluster Connection Strings”, for more information on connection strings.
Given this information, the MySQL server will be a full participant in the cluster. (We often refer to a mysqld process running in this manner as an SQL node.) It will be fully aware of all cluster data nodes as well as their status, and will establish connections to all data nodes. In this case, it is able to use any data node as a transaction coordinator and to read and update node data.
You can see in the mysql client whether a MySQL
server is connected to the cluster using SHOW
PROCESSLIST
. If the MySQL server is connected to the
cluster, and you have the PROCESS
privilege, then the first row of the output is as shown here:
mysql> SHOW PROCESSLIST \G *************************** 1. row *************************** Id: 1 User: system user Host: db: Command: Daemon Time: 1 State: Waiting for event from ndbcluster Info: NULL
To participate in a MySQL Cluster, the mysqld
process must be started with both the
options --ndbcluster
and
--ndb-connectstring
(or their
equivalents in my.cnf
). If
mysqld is started with only the
--ndbcluster
option, or if it is
unable to contact the cluster, it is not possible to work with
NDB
tables, nor is it
possible to create any new tables regardless of storage
engine. The latter restriction is a safety measure
intended to prevent the creation of tables having the same names
as NDB
tables while the SQL node is
not connected to the cluster. If you wish to create tables using
a different storage engine while the mysqld
process is not participating in a MySQL Cluster, you must
restart the server without the
--ndbcluster
option.
This section discusses how to perform a rolling restart of a MySQL Cluster installation, so called because it involves stopping and starting (or restarting) each node in turn, so that the cluster itself remains operational. This is often done as part of a rolling upgrade or rolling downgrade, where high availability of the cluster is mandatory and no downtime of the cluster as a whole is permissible. Where we refer to upgrades, the information provided here also generally applies to downgrades as well.
There are a number of reasons why a rolling restart might be desirable. These are described in the next few paragraphs.
Configuration change. To make a change in the cluster's configuration, such as adding an SQL node to the cluster, or setting a configuration parameter to a new value.
MySQL Cluster software upgrade or downgrade. To upgrade the cluster to a newer version of the MySQL Cluster software (or to downgrade it to an older version). This is usually referred to as a “rolling upgrade” (or “rolling downgrade”, when reverting to an older version of MySQL Cluster).
Change on node host. To make changes in the hardware or operating system on which one or more MySQL Cluster node processes are running.
System reset (cluster reset). To reset the cluster because it has reached an undesirable state. In such cases it is often desirable to reload the data and metadata of one or more data nodes. This can be done in any of three ways:
Start each data node process (ndbd or
possibly ndbmtd) with the
--initial
option, which forces
the data node to clear its file system and to reload all MySQL
Cluster data and metadata from the other data nodes.
Create a backup using the ndb_mgm client
START BACKUP
command prior
to performing the restart. Following the upgrade, restore the
node or nodes using ndb_restore.
See Section 19.5.3, “Online Backup of MySQL Cluster”, and Section 19.4.20, “ndb_restore — Restore a MySQL Cluster Backup”, for more information.
Use mysqldump to create a backup prior to
the upgrade; afterward, restore the dump using
LOAD DATA
INFILE
.
Resource Recovery.
To free memory previously allocated to a table by successive
INSERT
and
DELETE
operations, for re-use by
other MySQL Cluster tables.
The process for performing a rolling restart may be generalized as follows:
Stop all cluster management nodes (ndb_mgmd processes), reconfigure them, then restart them. (See Rolling restarts with multiple management servers.)
Stop, reconfigure, then restart each cluster data node (ndbd process) in turn.
Stop, reconfigure, then restart each cluster SQL node (mysqld process) in turn.
The specifics for implementing a given rolling upgrade depend upon the changes being made. A more detailed view of the process is presented here:
In the previous diagram, the Stop
and Start steps indicate that the
process must be stopped completely using a shell command (such as
kill on most Unix systems) or the management
client STOP
command, then
started again from a system shell by invoking the
ndbd or ndb_mgmd executable
as appropriate. On Windows, you can also use the system
NET START
and NET STOP
commands or the Windows Service Manager to start and stop nodes
which have been installed as Windows services (see
Section 19.2.3.4, “Installing MySQL Cluster Processes as Windows Services”).
Restart indicates that the
process may be restarted using the ndb_mgm
management client RESTART
command.
MySQL Cluster supports a flexible order for upgrading nodes. When upgrading a MySQL Cluster, you may upgrade API nodes (including SQL nodes) before upgrading the management nodes, data nodes, or both. In other words, you are permitted to upgrade the API and SQL nodes in any order. This is subject to the following provisions:
This functionality is intended for use as part of an online upgrade only. A mix of node binaries from different MySQL Cluster releases is neither intended nor supported for continuous, long-term use in a production setting.
All management nodes must be upgraded before any data nodes are upgraded. This remains true regardless of the order in which you upgrade the cluster's API and SQL nodes.
Features specific to the “new” version must not be used until all management nodes and data nodes have been upgraded.
This also applies to any MySQL Server version change that may apply, in addition to the NDB engine version change, so do not forget to take this into account when planning the upgrade. (This is true for online upgrades of MySQL Cluster in general.)
See also Bug #48528 and Bug #49163.
Rolling restarts with multiple management servers. When performing a rolling restart of a MySQL Cluster with multiple management nodes, you should keep in mind that ndb_mgmd checks to see if any other management node is running, and, if so, tries to use that node's configuration data. To keep this from occurring, and to force ndb_mgmd to reread its configuration file, perform the following steps:
Stop all MySQL Cluster ndb_mgmd processes.
Update all config.ini
files.
Start a single ndb_mgmd with
--reload
,
--initial
, or both options as
desired.
If you started the first ndb_mgmd with the
--initial
option, you must
also start any remaining ndb_mgmd processes
using --initial
.
Regardless of any other options used when starting the first
ndb_mgmd, you should not start any
remaining ndb_mgmd processes after the
first one using --reload
.
Complete the rolling restarts of the data nodes and API nodes as normal.
When performing a rolling restart to update the cluster's
configuration, you can use the
config_generation
column of the
ndbinfo.nodes
table to keep
track of which data nodes have been successfully restarted with
the new configuration. See
Section 19.5.10.25, “The ndbinfo nodes Table”.
In this section, we discuss the types of event logs provided by MySQL Cluster, and the types of events that are logged.
MySQL Cluster provides two types of event log:
The cluster log, which includes events generated by all cluster nodes. The cluster log is the log recommended for most uses because it provides logging information for an entire cluster in a single location.
By default, the cluster log is saved to a file named
ndb_
,
(where node_id
_cluster.lognode_id
is the node ID of
the management server) in the management server's
DataDir
.
Cluster logging information can also be sent to
stdout
or a syslog
facility in addition to or instead of being saved to a file,
as determined by the values set for the
DataDir
and
LogDestination
configuration parameters. See
Section 19.3.3.5, “Defining a MySQL Cluster Management Server”, for more
information about these parameters.
Node logs are local to each node.
Output generated by node event logging is written to the file
ndb_
(where node_id
_out.lognode_id
is the node's node
ID) in the node's
DataDir
. Node event
logs are generated for both management nodes and data nodes.
Node logs are intended to be used only during application development, or for debugging application code.
Both types of event logs can be set to log different subsets of events.
Each reportable event can be distinguished according to three different criteria:
Category: This can be any one of the
following values: STARTUP
,
SHUTDOWN
, STATISTICS
,
CHECKPOINT
, NODERESTART
,
CONNECTION
, ERROR
, or
INFO
.
Priority: This is represented by one of the numbers from 0 to 15 inclusive, where 0 indicates “most important” and 15 “least important.”
Severity Level: This can be any one of
the following values: ALERT
,
CRITICAL
, ERROR
,
WARNING
, INFO
, or
DEBUG
.
Both the cluster log and the node log can be filtered on these properties.
The format used in the cluster log is as shown here:
2007-01-26 19:35:55 [MgmSrvr] INFO -- Node 1: Data usage is 2%(60 32K pages of total 2560) 2007-01-26 19:35:55 [MgmSrvr] INFO -- Node 1: Index usage is 1%(24 8K pages of total 2336) 2007-01-26 19:35:55 [MgmSrvr] INFO -- Node 1: Resource 0 min: 0 max: 639 curr: 0 2007-01-26 19:35:55 [MgmSrvr] INFO -- Node 2: Data usage is 2%(76 32K pages of total 2560) 2007-01-26 19:35:55 [MgmSrvr] INFO -- Node 2: Index usage is 1%(24 8K pages of total 2336) 2007-01-26 19:35:55 [MgmSrvr] INFO -- Node 2: Resource 0 min: 0 max: 639 curr: 0 2007-01-26 19:35:55 [MgmSrvr] INFO -- Node 3: Data usage is 2%(58 32K pages of total 2560) 2007-01-26 19:35:55 [MgmSrvr] INFO -- Node 3: Index usage is 1%(25 8K pages of total 2336) 2007-01-26 19:35:55 [MgmSrvr] INFO -- Node 3: Resource 0 min: 0 max: 639 curr: 0 2007-01-26 19:35:55 [MgmSrvr] INFO -- Node 4: Data usage is 2%(74 32K pages of total 2560) 2007-01-26 19:35:55 [MgmSrvr] INFO -- Node 4: Index usage is 1%(25 8K pages of total 2336) 2007-01-26 19:35:55 [MgmSrvr] INFO -- Node 4: Resource 0 min: 0 max: 639 curr: 0 2007-01-26 19:39:42 [MgmSrvr] INFO -- Node 4: Node 9 Connected 2007-01-26 19:39:42 [MgmSrvr] INFO -- Node 1: Node 9 Connected 2007-01-26 19:39:42 [MgmSrvr] INFO -- Node 1: Node 9: API 5.7.13-ndb-7.5.3 2007-01-26 19:39:42 [MgmSrvr] INFO -- Node 2: Node 9 Connected 2007-01-26 19:39:42 [MgmSrvr] INFO -- Node 2: Node 9: API 5.7.13-ndb-7.5.3 2007-01-26 19:39:42 [MgmSrvr] INFO -- Node 3: Node 9 Connected 2007-01-26 19:39:42 [MgmSrvr] INFO -- Node 3: Node 9: API 5.7.13-ndb-7.5.3 2007-01-26 19:39:42 [MgmSrvr] INFO -- Node 4: Node 9: API 5.7.13-ndb-7.5.3 2007-01-26 19:59:22 [MgmSrvr] ALERT -- Node 2: Node 7 Disconnected 2007-01-26 19:59:22 [MgmSrvr] ALERT -- Node 2: Node 7 Disconnected
Each line in the cluster log contains the following information:
A timestamp in
format.
YYYY
-MM
-DD
HH
:MM
:SS
The type of node which is performing the logging. In the
cluster log, this is always [MgmSrvr]
.
The severity of the event.
The ID of the node reporting the event.
A description of the event. The most common types of events to appear in the log are connections and disconnections between different nodes in the cluster, and when checkpoints occur. In some cases, the description may contain status information.
ndb_mgm supports a number of management
commands related to the cluster log. In the listing that
follows, node_id
denotes either a
database node ID or the keyword ALL
, which
indicates that the command should be applied to all of the
cluster's data nodes.
CLUSTERLOG ON
Turns the cluster log on.
CLUSTERLOG OFF
Turns the cluster log off.
CLUSTERLOG INFO
Provides information about cluster log settings.
node_id
CLUSTERLOG
category
=threshold
Logs category
events with
priority less than or equal to
threshold
in the cluster log.
CLUSTERLOG FILTER
severity_level
Toggles cluster logging of events of the specified
severity_level
.
The following table describes the default setting (for all data nodes) of the cluster log category threshold. If an event has a priority with a value lower than or equal to the priority threshold, it is reported in the cluster log.
Events are reported per data node, and that the threshold can be set to different values on different nodes.
Category | Default threshold (All data nodes) |
---|---|
STARTUP | 7 |
SHUTDOWN | 7 |
STATISTICS | 7 |
CHECKPOINT | 7 |
NODERESTART | 7 |
CONNECTION | 7 |
ERROR | 15 |
INFO | 7 |
The STATISTICS
category can provide a great
deal of useful data. See
Section 19.5.6.3, “Using CLUSTERLOG STATISTICS in the MySQL Cluster Management Client”, for more
information.
Thresholds are used to filter events within each category. For
example, a STARTUP
event with a priority of 3
is not logged unless the threshold for
STARTUP
is set to 3 or higher. Only events
with priority 3 or lower are sent if the threshold is 3.
The following table shows the event severity levels.
These correspond to Unix syslog
levels,
except for LOG_EMERG
and
LOG_NOTICE
, which are not used or mapped.
Severity Level Value | Severity | Description |
---|---|---|
1 |
| A condition that should be corrected immediately, such as a corrupted system database |
2 |
| Critical conditions, such as device errors or insufficient resources |
3 |
| Conditions that should be corrected, such as configuration errors |
4 | WARNING | Conditions that are not errors, but that might require special handling |
5 | INFO | Informational messages |
6 | DEBUG | Debugging messages used for NDBCLUSTER
development |
Event severity levels can be turned on or off (using
CLUSTERLOG FILTER
—see above). If a
severity level is turned on, then all events with a priority
less than or equal to the category thresholds are logged. If the
severity level is turned off then no events belonging to that
severity level are logged.
Cluster log levels are set on a per
ndb_mgmd, per subscriber basis. This means
that, in a MySQL Cluster with multiple management servers,
using a CLUSTERLOG
command in an instance
of ndb_mgm connected to one management
server affects only logs generated by that management server
but not by any of the others. This also means that, should one
of the management servers be restarted, only logs generated by
that management server are affected by the resetting of log
levels caused by the restart.
An event report reported in the event logs has the following format:
datetime
[string
]severity
--message
For example:
09:19:30 2005-07-24 [NDB] INFO -- Node 4 Start phase 4 completed
This section discusses all reportable events, ordered by category and severity level within each category.
In the event descriptions, GCP and LCP mean “Global Checkpoint” and “Local Checkpoint”, respectively.
These events are associated with connections between Cluster nodes.
Event | Priority | Severity Level | Description |
---|---|---|---|
Connected | 8 | INFO | Data nodes connected |
Disconnected | 8 | ALERT | Data nodes disconnected |
CommunicationClosed | 8 | INFO | SQL node or data node connection closed |
CommunicationOpened | 8 | INFO | SQL node or data node connection open |
ConnectedApiVersion | 8 | INFO | Connection using API version |
The logging messages shown here are associated with checkpoints.
Event | Priority | Severity Level | Description |
---|---|---|---|
GlobalCheckpointStarted | 9 | INFO | Start of GCP: REDO log is written to disk |
GlobalCheckpointCompleted | 10 | INFO | GCP finished |
LocalCheckpointStarted | 7 | INFO | Start of LCP: data written to disk |
LocalCheckpointCompleted | 7 | INFO | LCP completed normally |
LCPStoppedInCalcKeepGci | 0 | ALERT | LCP stopped |
LCPFragmentCompleted | 11 | INFO | LCP on a fragment has been completed |
UndoLogBlocked | 7 | INFO | UNDO logging blocked; buffer near overflow |
RedoStatus | 7 | INFO | Redo status |
The following events are generated in response to the startup of a node or of the cluster and of its success or failure. They also provide information relating to the progress of the startup process, including information concerning logging activities.
Event | Priority | Severity Level | Description |
---|---|---|---|
NDBStartStarted | 1 | INFO | Data node start phases initiated (all nodes starting) |
NDBStartCompleted | 1 | INFO | Start phases completed, all data nodes |
STTORRYRecieved | 15 | INFO | Blocks received after completion of restart |
StartPhaseCompleted | 4 | INFO | Data node start phase X completed |
CM_REGCONF | 3 | INFO | Node has been successfully included into the cluster; shows the node, managing node, and dynamic ID |
CM_REGREF | 8 | INFO | Node has been refused for inclusion in the cluster; cannot be included in cluster due to misconfiguration, inability to establish communication, or other problem |
FIND_NEIGHBOURS | 8 | INFO | Shows neighboring data nodes |
NDBStopStarted | 1 | INFO | Data node shutdown initiated |
NDBStopCompleted | 1 | INFO | Data node shutdown complete |
NDBStopForced | 1 | ALERT | Forced shutdown of data node |
NDBStopAborted | 1 | INFO | Unable to shut down data node normally |
StartREDOLog | 4 | INFO | New redo log started; GCI keep X , newest
restorable GCI Y |
StartLog | 10 | INFO | New log started; log part X , start MB
Y , stop MB
Z |
UNDORecordsExecuted | 15 | INFO | Undo records executed |
StartReport | 4 | INFO | Report started |
LogFileInitStatus | 7 | INFO | Log file initialization status |
LogFileInitCompStatus | 7 | INFO | Log file completion status |
StartReadLCP | 10 | INFO | Start read for local checkpoint |
ReadLCPComplete | 10 | INFO | Read for local checkpoint completed |
RunRedo | 8 | INFO | Running the redo log |
RebuildIndex | 10 | INFO | Rebuilding indexes |
The following events are generated when restarting a node and relate to the success or failure of the node restart process.
Event | Priority | Severity Level | Description |
---|---|---|---|
NR_CopyDict | 7 | INFO | Completed copying of dictionary information |
NR_CopyDistr | 7 | INFO | Completed copying distribution information |
NR_CopyFragsStarted | 7 | INFO | Starting to copy fragments |
NR_CopyFragDone | 10 | INFO | Completed copying a fragment |
NR_CopyFragsCompleted | 7 | INFO | Completed copying all fragments |
NodeFailCompleted | 8 | ALERT | Node failure phase completed |
NODE_FAILREP | 8 | ALERT | Reports that a node has failed |
ArbitState | 6 | INFO | Report whether an arbitrator is found or not; there are seven different
possible outcomes when seeking an arbitrator, listed
here:
|
ArbitResult | 2 | ALERT | Report arbitrator results; there are eight different possible results
for arbitration attempts, listed here:
|
GCP_TakeoverStarted | 7 | INFO | GCP takeover started |
GCP_TakeoverCompleted | 7 | INFO | GCP takeover complete |
LCP_TakeoverStarted | 7 | INFO | LCP takeover started |
LCP_TakeoverCompleted | 7 | INFO | LCP takeover complete (state = X ) |
ConnectCheckStarted | 6 | INFO | Connection check started |
ConnectCheckCompleted | 6 | INFO | Connection check completed |
NodeFailRejected | 6 | ALERT | Node failure phase failed |
The following events are of a statistical nature. They provide information such as numbers of transactions and other operations, amount of data sent or received by individual nodes, and memory usage.
Event | Priority | Severity Level | Description |
---|---|---|---|
TransReportCounters | 8 | INFO | Report transaction statistics, including numbers of transactions, commits, reads, simple reads, writes, concurrent operations, attribute information, and aborts |
OperationReportCounters | 8 | INFO | Number of operations |
TableCreated | 7 | INFO | Report number of tables created |
JobStatistic | 9 | INFO | Mean internal job scheduling statistics |
ThreadConfigLoop | 9 | INFO | Number of thread configuration loops |
SendBytesStatistic | 9 | INFO | Mean number of bytes sent to node X |
ReceiveBytesStatistic | 9 | INFO | Mean number of bytes received from node X |
MemoryUsage | 5 | INFO | Data and index memory usage (80%, 90%, and 100%) |
MTSignalStatistics | 9 | INFO | Multi-threaded signals |
These events relate to MySQL Cluster schema operations.
Event | Priority | Severity | Description |
---|---|---|---|
CreateSchemaObject | 8 | INFO | Schema objected created |
AlterSchemaObject | 8 | INFO | Schema object updated |
DropSchemaObject | 8 | INFO | Schema object dropped |
These events relate to Cluster errors and warnings. The presence of one or more of these generally indicates that a major malfunction or failure has occurred.
Event | Priority | Severity | Description |
---|---|---|---|
TransporterError | 2 | ERROR | Transporter error |
TransporterWarning | 8 | WARNING | Transporter warning |
MissedHeartbeat | 8 | WARNING | Node X missed heartbeat number
Y |
DeadDueToHeartbeat | 8 | ALERT | Node X declared “dead” due to
missed heartbeat |
WarningEvent | 2 | WARNING | General warning event |
SubscriptionStatus | 4 | WARNING | Change in subscription status |
These events provide general information about the state of the cluster and activities associated with Cluster maintenance, such as logging and heartbeat transmission.
Event | Priority | Severity | Description |
---|---|---|---|
SentHeartbeat | 12 | INFO | Sent heartbeat |
CreateLogBytes | 11 | INFO | Create log: Log part, log file, size in MB |
InfoEvent | 2 | INFO | General informational event |
EventBufferStatus | 7 | INFO | Event buffer status |
EventBufferStatus2 | 7 | INFO | Improved event buffer status information; added in MySQL Cluster NDB 7.5.1 |
SentHeartbeat
events are available only if
MySQL Cluster was compiled with VM_TRACE
enabled.
Node node_id: Event buffer status: used=bytes_used (used as a percent of alloc) alloc=bytes_allocated (alloc as a % of max. If max is 0 (unlimited) the % will not be printed) max=bytes_available (if not configured, max will be 0, meaning unlimited, i.e. no limit on event buffer memory usage) latest_consumed_epoch=epoch that was consumed completely (using nextEvent()) latest_buffered_epoch=epoch which is buffered completely in the event buffer ndb_reference=the object id of the Ndb that originates the report report_reason=the reason for reporting this log event Note: latest_consumed_epoch is the same as apply_gci of the old EventBufferStatus and latest_buffered_epoch is the same as latest_gci of the old EventBufferStatus. Remember to chagnge the explanations of apply_gci and latest_gci in the old EventBufferStatus.
These events are associated with entering and exiting single user mode.
Event | Priority | Severity | Description |
---|---|---|---|
SingleUser | 7 | INFO | Entering or exiting single user mode |
These events provide information about backups being created or restored.
Event | Priority | Severity | Description |
---|---|---|---|
BackupStarted | 7 | INFO | Backup started |
BackupStatus | 7 | INFO | Backup status |
BackupCompleted | 7 | INFO | Backup completed |
BackupFailedToStart | 7 | ALERT | Backup failed to start |
BackupAborted | 7 | ALERT | Backup aborted by user |
RestoreStarted | 7 | INFO | Started restoring from backup |
RestoreMetaData | 7 | INFO | Restoring metadata |
RestoreData | 7 | INFO | Restoring data |
RestoreLog | 7 | INFO | Restoring log files |
RestoreCompleted | 7 | INFO | Completed restoring from backup |
SavedEvent | 7 | INFO | Event saved |
The NDB
management client's
CLUSTERLOG STATISTICS
command can provide a number of useful statistics in its output.
Counters providing information about the state of the cluster
are updated at 5-second reporting intervals by the transaction
coordinator (TC) and the local query handler (LQH), and written
to the cluster log.
Transaction coordinator statistics. Each transaction has one transaction coordinator, which is chosen by one of the following methods:
In a round-robin fashion
By communication proximity
(Beginning with MySQL Cluster NDB 6.3.4:) By supplying a data placement hint when the transaction is started
You can determine which TC selection method is used for
transactions started from a given SQL node using the
ndb_optimized_node_selection
system variable.
All operations within the same transaction use the same transaction coordinator, which reports the following statistics:
Trans count. This is the number transactions started in the last interval using this TC as the transaction coordinator. Any of these transactions may have committed, have been aborted, or remain uncommitted at the end of the reporting interval.
Transactions do not migrate between TCs.
Commit count.
This is the number of transactions using this TC as the
transaction coordinator that were committed in the last
reporting interval. Because some transactions committed in
this reporting interval may have started in a previous
reporting interval, it is possible for Commit
count
to be greater than Trans
count
.
Read count. This is the number of primary key read operations using this TC as the transaction coordinator that were started in the last reporting interval, including simple reads. This count also includes reads performed as part of unique index operations. A unique index read operation generates 2 primary key read operations—1 for the hidden unique index table, and 1 for the table on which the read takes place.
Simple read count. This is the number of simple read operations using this TC as the transaction coordinator that were started in the last reporting interval.
Write count. This is the number of primary key write operations using this TC as the transaction coordinator that were started in the last reporting interval. This includes all inserts, updates, writes and deletes, as well as writes performed as part of unique index operations.
A unique index update operation can generate multiple PK read and write operations on the index table and on the base table.
AttrInfoCount. This is the number of 32-bit data words received in the last reporting interval for primary key operations using this TC as the transaction coordinator. For reads, this is proportional to the number of columns requested. For inserts and updates, this is proportional to the number of columns written, and the size of their data. For delete operations, this is usually zero.
Unique index operations generate multiple PK operations and
so increase this count. However, data words sent to describe
the PK operation itself, and the key information sent, are
not counted here. Attribute information
sent to describe columns to read for scans, or to describe
ScanFilters, is also not counted in
AttrInfoCount
.
Concurrent Operations. This is the number of primary key or scan operations using this TC as the transaction coordinator that were started during the last reporting interval but that were not completed. Operations increment this counter when they are started and decrement it when they are completed; this occurs after the transaction commits. Dirty reads and writes—as well as failed operations—decrement this counter.
The maximum value that Concurrent
Operations
can have is the maximum number of
operations that a TC block can support; currently, this is
(2 * MaxNoOfConcurrentOperations) + 16 +
MaxNoOfConcurrentTransactions
. (For more
information about these configuration parameters, see the
Transaction Parameters section of
Section 19.3.3.6, “Defining MySQL Cluster Data Nodes”.)
Abort count.
This is the number of transactions using this TC as the
transaction coordinator that were aborted during the last
reporting interval. Because some transactions that were
aborted in the last reporting interval may have started in
a previous reporting interval, Abort
count
can sometimes be greater than
Trans count
.
Scans. This is the number of table scans using this TC as the transaction coordinator that were started during the last reporting interval. This does not include range scans (that is, ordered index scans).
Range scans. This is the number of ordered index scans using this TC as the transaction coordinator that were started in the last reporting interval.
Local query handler statistics (Operations). There is 1 cluster event per local query handler block (that is, 1 per data node process). Operations are recorded in the LQH where the data they are operating on resides.
A single transaction may operate on data stored in multiple LQH blocks.
The Operations
statistic provides the number
of local operations performed by this LQH block in the last
reporting interval, and includes all types of read and write
operations (insert, update, write, and delete operations). This
also includes operations used to replicate writes. For example,
in a 2-replica cluster, the write to the primary replica is
recorded in the primary LQH, and the write to the backup will be
recorded in the backup LQH. Unique key operations may result in
multiple local operations; however, this does
not include local operations generated as a
result of a table scan or ordered index scan, which are not
counted.
Process scheduler statistics. In addition to the statistics reported by the transaction coordinator and local query handler, each ndbd process has a scheduler which also provides useful metrics relating to the performance of a MySQL Cluster. This scheduler runs in an infinite loop; during each loop the scheduler performs the following tasks:
Read any incoming messages from sockets into a job buffer.
Check whether there are any timed messages to be executed; if so, put these into the job buffer as well.
Execute (in a loop) any messages in the job buffer.
Send any distributed messages that were generated by executing the messages in the job buffer.
Wait for any new incoming messages.
Process scheduler statistics include the following:
Mean Loop Counter. This is the number of loops executed in the third step from the preceding list. This statistic increases in size as the utilization of the TCP/IP buffer improves. You can use this to monitor changes in performance as you add new data node processes.
Mean send size and Mean receive size. These statistics enable you to gauge the efficiency of, respectively writes and reads between nodes. The values are given in bytes. Higher values mean a lower cost per byte sent or received; the maximum value is 64K.
To cause all cluster log statistics to be logged, you can use
the following command in the NDB
management client:
ndb_mgm> ALL CLUSTERLOG STATISTICS=15
Setting the threshold for STATISTICS
to 15
causes the cluster log to become very verbose, and to grow
quite rapidly in size, in direct proportion to the number of
cluster nodes and the amount of activity in the MySQL Cluster.
For more information about MySQL Cluster management client commands relating to logging and reporting, see Section 19.5.6.1, “MySQL Cluster Logging Management Commands”.
This section contains information about the messages written to
the cluster log in response to different cluster log events. It
provides additional, more specific information on
NDB
transporter errors.
The following table lists the most common
NDB
cluster log messages. For
information about the cluster log, log events, and event types,
see Section 19.5.6, “Event Reports Generated in MySQL Cluster”. These log
messages also correspond to log event types in the MGM API; see
The Ndb_logevent_type Type, for related information
of interest to Cluster API developers.
Log Message | Description | Event Name | Event Type | Priority | Severity |
---|---|---|---|---|---|
Node | The data node having node ID node_id has
connected to the management server (node
mgm_node_id ). | Connected | Connection | 8 | INFO |
Node | The data node having node ID data_node_id has
disconnected from the management server (node
mgm_node_id ). | Disconnected | Connection | 8 | ALERT |
Node | The API node or SQL node having node ID
api_node_id is no longer
communicating with data node
data_node_id . | CommunicationClosed | Connection | 8 | INFO |
Node | The API node or SQL node having node ID
api_node_id is now
communicating with data node
data_node_id . | CommunicationOpened | Connection | 8 | INFO |
Node | The API node having node ID api_node_id has
connected to management node
mgm_node_id using
NDB API version
version (generally the same
as the MySQL version number). | ConnectedApiVersion | Connection | 8 | INFO |
Node | A global checkpoint with the ID gci has been
started; node node_id is the
master responsible for this global checkpoint. | GlobalCheckpointStarted | Checkpoint | 9 | INFO |
Node | The global checkpoint having the ID gci has
been completed; node node_id
was the master responsible for this global checkpoint. | GlobalCheckpointCompleted | Checkpoint | 10 | INFO |
Node | The local checkpoint having sequence ID lcp
has been started on node
node_id . The most recent GCI
that can be used has the index
current_gci , and the oldest
GCI from which the cluster can be restored has the index
old_gci . | LocalCheckpointStarted | Checkpoint | 7 | INFO |
Node | The local checkpoint having sequence ID lcp
on node node_id has been
completed. | LocalCheckpointCompleted | Checkpoint | 8 | INFO |
Node | The node was unable to determine the most recent usable GCI. | LCPStoppedInCalcKeepGci | Checkpoint | 0 | ALERT |
Node | A table fragment has been checkpointed to disk on node
node_id . The GCI in progress
has the index started_gci ,
and the most recent GCI to have been completed has the
index completed_gci . | LCPFragmentCompleted | Checkpoint | 11 | INFO |
Node | Undo logging is blocked because the log buffer is close to overflowing. | UndoLogBlocked | Checkpoint | 7 | INFO |
Node | Data node node_id , running
NDB version
version , is beginning its
startup process. | NDBStartStarted | StartUp | 1 | INFO |
Node | Data node node_id , running
NDB version
version , has started
successfully. | NDBStartCompleted | StartUp | 1 | INFO |
Node | The node has received a signal indicating that a cluster restart has completed. | STTORRYRecieved | StartUp | 15 | INFO |
Node | The node has completed start phase phase of a
type start. For a listing of
start phases, see
Section 19.5.1, “Summary of MySQL Cluster Start Phases”.
(type is one of
initial , system ,
node , initial
node , or <Unknown> .) | StartPhaseCompleted | StartUp | 4 | INFO |
Node | Node president_id has been selected as
“president”.
own_id and
dynamic_id should always be
the same as the ID (node_id )
of the reporting node. | CM_REGCONF | StartUp | 3 | INFO |
Node | The reporting node (ID node_id ) was unable to
accept node president_id as
president. The cause of the
problem is given as one of Busy ,
Election with wait = false ,
Not president , Election
without selecting new candidate , or
No such cause . | CM_REGREF | StartUp | 8 | INFO |
Node | The node has discovered its neighboring nodes in the cluster (node
id_1 and node
id_2 ).
node_id ,
own_id , and
dynamic_id should always be
the same; if they are not, this indicates a serious
misconfiguration of the cluster nodes. | FIND_NEIGHBOURS | StartUp | 8 | INFO |
Node | The node has received a shutdown signal. The
type of shutdown is either
Cluster or Node . | NDBStopStarted | StartUp | 1 | INFO |
Node [,
]
[Initiated by signal
] | The node has been shut down. This report may include an
action , which if present is
one of restarting , no
start , or initial . The
report may also include a reference to an
NDB Protocol
signal ; for possible signals,
refer to
Operations and Signals. | NDBStopCompleted | StartUp | 1 | INFO |
Node [,
action ]. [Occured
during startphase
]
[ Initiated by
]
[Caused by error
[(extra info
]] | The node has been forcibly shut down. The
action (one of
restarting , no
start , or initial )
subsequently being taken, if any, is also reported. If
the shutdown occurred while the node was starting, the
report includes the
start_phase during which the
node failed. If this was a result of a
signal sent to the node, this
information is also provided (see
Operations and Signals,
for more information). If the error causing the failure
is known, this is also included; for more information
about NDB error messages
and classifications, see MySQL Cluster API Errors. | NDBStopForced | StartUp | 1 | ALERT |
Node | The node shutdown process was aborted by the user. | NDBStopAborted | StartUp | 1 | INFO |
Node | This reports global checkpoints referenced during a node start. The redo
log prior to keep_pos is
dropped. last_pos is the last
global checkpoint in which data node the participated;
restore_pos is the global
checkpoint which is actually used to restore all data
nodes. | StartREDOLog | StartUp | 4 | INFO |
startup_message [Listed separately;
see below.] | There are a number of possible startup messages that can be logged under different circumstances. These are listed separately; see Section 19.5.7.2, “MySQL Cluster Log Startup Messages”. | StartReport | StartUp | 4 | INFO |
Node | Copying of data dictionary information to the restarted node has been completed. | NR_CopyDict | NodeRestart | 8 | INFO |
Node | Copying of data distribution information to the restarted node has been completed. | NR_CopyDistr | NodeRestart | 8 | INFO |
Node | Copy of fragments to starting data node
node_id has begun | NR_CopyFragsStarted | NodeRestart | 8 | INFO |
Node | Fragment fragment_id from table
table_id has been copied to
data node node_id | NR_CopyFragDone | NodeRestart | 10 | INFO |
Node | Copying of all table fragments to restarting data node
node_id has been completed | NR_CopyFragsCompleted | NodeRestart | 8 | INFO |
Node | Data node node1_id has detected the failure
of data node node2_id | NodeFailCompleted | NodeRestart | 8 | ALERT |
All nodes completed failure of Node
| All (remaining) data nodes have detected the failure of data node
node_id | NodeFailCompleted | NodeRestart | 8 | ALERT |
Node failure of
| The failure of data node node_id has been
detected in the
block NDB
kernel block, where block is 1 of
DBTC , DBDICT ,
DBDIH , or DBLQH ;
for more information, see
NDB Kernel Blocks | NodeFailCompleted | NodeRestart | 8 | ALERT |
Node | A data node has failed. Its state at the time of failure is described by
an arbitration state code
state_code : possible state
code values can be found in the file
include/kernel/signaldata/ArbitSignalData.hpp . | NODE_FAILREP | NodeRestart | 8 | ALERT |
President restarts arbitration thread
[state=
or Prepare arbitrator node
or Receive arbitrator node
or Started arbitrator node
or Lost arbitrator node
or Lost arbitrator node
or Lost arbitrator node
| This is a report on the current state and progress of arbitration in the
cluster. node_id is the node
ID of the management node or SQL node selected as the
arbitrator. state_code is an
arbitration state code, as found in
include/kernel/signaldata/ArbitSignalData.hpp .
When an error has occurred, an
error_message , also defined
in ArbitSignalData.hpp , is
provided. ticket_id is a
unique identifier handed out by the arbitrator when it
is selected to all the nodes that participated in its
selection; this is used to ensure that each node
requesting arbitration was one of the nodes that took
part in the selection process. | ArbitState | NodeRestart | 6 | INFO |
Arbitration check lost - less than 1/2 nodes left or
Arbitration check won - all node groups and
more than 1/2 nodes left or
Arbitration check won - node group
majority or Arbitration check lost -
missing node group or Network
partitioning - arbitration required or
Arbitration won - positive reply from node
or
Arbitration lost - negative reply from node
or
Network partitioning - no arbitrator
available or Network partitioning -
no arbitrator configured or
Arbitration failure -
| This message reports on the result of arbitration. In the event of
arbitration failure, an
error_message and an
arbitration state_code are
provided; definitions for both of these are found in
include/kernel/signaldata/ArbitSignalData.hpp . | ArbitResult | NodeRestart | 2 | ALERT |
Node | This node is attempting to assume responsibility for the next global checkpoint (that is, it is becoming the master node) | GCP_TakeoverStarted | NodeRestart | 7 | INFO |
Node | This node has become the master, and has assumed responsibility for the next global checkpoint | GCP_TakeoverCompleted | NodeRestart | 7 | INFO |
Node | This node is attempting to assume responsibility for the next set of local checkpoints (that is, it is becoming the master node) | LCP_TakeoverStarted | NodeRestart | 7 | INFO |
Node | This node has become the master, and has assumed responsibility for the next set of local checkpoints | LCP_TakeoverCompleted | NodeRestart | 7 | INFO |
Node | This report of transaction activity is given approximately once every 10 seconds | TransReportCounters | Statistic | 8 | INFO |
Node | Number of operations performed by this node, provided approximately once every 10 seconds | OperationReportCounters | Statistic | 8 | INFO |
Node | A table having the table ID shown has been created | TableCreated | Statistic | 7 | INFO |
Node | JobStatistic | Statistic | 9 | INFO | |
Mean send size to Node = | This node is sending an average of bytes
bytes per send to node
node_id | SendBytesStatistic | Statistic | 9 | INFO |
Mean receive size to Node = | This node is receiving an average of bytes of
data each time it receives data from node
node_id | ReceiveBytesStatistic | Statistic | 9 | INFO |
Node /
Node | This report is generated when a DUMP
1000 command is issued in the cluster
management client; for more information, see
DUMP 1000, in
MySQL Cluster Internals | MemoryUsage | Statistic | 5 | INFO |
Node | A transporter error occurred while communicating with node
node2_id ; for a listing of
transporter error codes and messages, see
NDB Transporter Errors, in
MySQL Cluster Internals | TransporterError | Error | 2 | ERROR |
Node | A warning of a potential transporter problem while communicating with
node node2_id ; for a listing
of transporter error codes and messages, see
NDB Transporter Errors, for more
information | TransporterWarning | Error | 8 | WARNING |
Node | This node missed a heartbeat from node
node2_id | MissedHeartbeat | Error | 8 | WARNING |
Node | This node has missed at least 3 heartbeats from node
node2_id , and so has declared
that node “dead” | DeadDueToHeartbeat | Error | 8 | ALERT |
Node | This node has sent a heartbeat to node
node2_id | SentHeartbeat | Info | 12 | INFO |
(NDB 7.5.0 and earlier:) Node
| This report is seen during heavy event buffer usage, for example, when many updates are being applied in a relatively short period of time; the report shows the number of bytes and the percentage of event buffer memory used, the bytes allocated and percentage still available, and the latest and latest restorable global checkpoints | EventBufferStatus | Info | 7 | INFO |
(NDB 7.5.1 and later:) Node
| This report is seen during heavy event buffer usage, for example, when many updates are being applied in a relatively short period of time; the report shows the number of bytes and the percentage of event buffer memory used, the bytes allocated and percentage still available, and the latest buffered and consumed epochs; for more information, see Section 19.5.7.3, “Event Buffer Reporting in the Cluster Log” | EventBufferStatus2 | Info | 7 | INFO |
Node , Node
, Node
| These reports are written to the cluster log when entering and exiting
single user mode; API_node_id
is the node ID of the API or SQL having exclusive access
to the cluster (for more information, see
Section 19.5.8, “MySQL Cluster Single User Mode”); the
message Unknown single user report
indicates an error has taken place and should never be
seen in normal operation | SingleUser | Info | 7 | INFO |
Node | A backup has been started using the management node having
mgm_node_id ; this message is
also displayed in the cluster management client when the
START BACKUP command
is issued; for more information, see
Section 19.5.3.2, “Using The MySQL Cluster Management Client to Create a Backup” | BackupStarted | Backup | 7 | INFO |
Node | The backup having the ID backup_id has been
completed; for more information, see
Section 19.5.3.2, “Using The MySQL Cluster Management Client to Create a Backup” | BackupCompleted | Backup | 7 | INFO |
Node | The backup failed to start; for error codes, see MGM API Errors | BackupFailedToStart | Backup | 7 | ALERT |
Node | The backup was terminated after starting, possibly due to user intervention | BackupAborted | Backup | 7 | ALERT |
Possible startup messages with descriptions are provided in the following list:
Initial start, waiting for %s to connect, nodes [
all: %s connected: %s no-wait: %s ]
Waiting until nodes: %s connects, nodes [ all: %s
connected: %s no-wait: %s ]
Waiting %u sec for nodes %s to connect, nodes [
all: %s connected: %s no-wait: %s ]
Waiting for non partitioned start, nodes [ all: %s
connected: %s missing: %s no-wait: %s ]
Waiting %u sec for non partitioned start, nodes [
all: %s connected: %s missing: %s no-wait: %s ]
Initial start with nodes %s [ missing: %s no-wait:
%s ]
Start with all nodes %s
Start with nodes %s [ missing: %s no-wait: %s
]
Start potentially partitioned with nodes %s [
missing: %s no-wait: %s ]
Unknown startreport: 0x%x [ %s %s %s %s ]
NDB
uses one or more memory buffers for
events received from the data nodes. There is one such buffer
for each Ndb
object subscribing
to table events, which means that there are usually two buffers
for each mysqld performing binary logging
(one buffer for schema events, and one for data events). Each
buffer contains epochs made up of events. These events consist
of operation types (insert, update, delete) and row data (before
and after images plus metadata).
NDB
generates messages in the cluster log to
describe the state of these buffers. Although these reports
appear in the cluster log, they refer to buffers on API nodes
(unlike most other cluster log messages, which are generated by
data nodes). These messages and the data structures underlying
them were changed significantly in MySQL Cluster NDB 7.5.1, with
the addition of the NDB_LE_EventBufferStatus2
event type and the
ndb_logevent_EventBufferStatus2
data
structure (see The Ndb_logevent_type Type). The
remainder of this discussion focuses on the implementation based
on NDB_LE_EventBufferStatus2
.
Event buffer logging reports in the cluster log use the format shown here:
Nodenode_id
: Event buffer status (object_id
): used=bytes_used
(percent_used
% of alloc) alloc=bytes_allocated
(percent_alloc
% of max) max=bytes_available
latest_consumed_epoch=latest_consumed_epoch
latest_buffered_epoch=latest_buffered_epoch
report_reason=report_reason
The fields making up this report are listed here, with descriptions:
node_id
: ID of the node where the
report originated.
object_id
: ID of the
Ndb
object where the report
originated.
bytes_used
: Number of bytes used
by the buffer.
percent_used
: Percentage of
allocated bytes used; not printed if
ndb_eventbuffer_max_alloc
is equal to 0 (unlimited).
bytes_allocated
: Number of bytes
allocated to this buffer.
percent_alloc
: Percentage of
available bytes used; not printed if
ndb_eventbuffer_max_alloc
is equal to 0
(unlimited).
bytes_available
: Number of bytes
available; this is 0 if
ndb_eventbuffer_max_alloc
is 0
(unlimited).
latest_consumed_epoch
: The epoch
most recently consumed to completion. (In NDB API
applications, this is done by calling
nextEvent()
.)
latest_buffered_epoch
: The epoch
most recently buffered (completely) in the event buffer.
report_reason
: The reason for
making the report. Possible reasons are shown later in this
section.
The latest_consumed_epoch
and
latest_buffered_epoch
fields correspond,
respectively, to the apply_gci
and
latest_gci
fields of the old-style event
buffer logging messages used prior to MySQL Cluster NDB 7.5.1.
Possible reasons for reporting are described in the following list:
ENOUGH_FREE_EVENTBUFFER
: The event buffer
has sufficient space.
LOW_FREE_EVENTBUFFER
: The event buffer is
running low on free space.
The threshold free percentage level triggering these reports
can be adjusted by setting the
ndb_report_thresh_binlog_mem_usage
server variable.
BUFFERED_EPOCHS_OVER_THRESHOLD
: Whether
the number of buffered epochs has exceeded the configured
threshold. This number is the difference between the latest
epoch that has been received in its entirety and the epoch
that has most recently been consumed (in NDB API
applications, this is done by calling
nextEvent()
). The
report is generated every second until the number of
buffered epochs goes below the threshold, which can be
adjusted by setting the
ndb_report_thresh_binlog_epoch_slip
server variable.
PARTIALLY_DISCARDING
: Event buffer memory
is exhausted—that is, 100% of
ndb_eventbuffer_max_alloc
has been used. Any partially buffered epoch is buffered to
completion even is usage exceeds 100%, but any new epochs
received are discarded. This means that a gap has occurred
in the event stream.
COMPLETELY_DISCARDING
: No epochs are
buffered.
PARTIALLY_BUFFERING
: The buffer free
percentage following the gap has risen to the threshold,
which can be set in the mysql client
using the
ndb_eventbuffer_free_percent
server system variable or in NDB API applications by calling
set_eventbuffer_free_percent()
.
New epochs are buffered. Epochs that could not be completed
due to the gap are discarded.
COMPLETELY_BUFFERING
: All epochs received
are being buffered, which means that there is sufficient
event buffer memory. The gap in the event stream has been
closed.
This section lists error codes, names, and messages that are written to the cluster log in the event of transporter errors.
Error Code | Error Name | Error Text |
---|---|---|
0x00 | TE_NO_ERROR | No error |
0x01 | TE_ERROR_CLOSING_SOCKET | Error found during closing of socket |
0x02 | TE_ERROR_IN_SELECT_BEFORE_ACCEPT | Error found before accept. The transporter will retry |
0x03 | TE_INVALID_MESSAGE_LENGTH | Error found in message (invalid message length) |
0x04 | TE_INVALID_CHECKSUM | Error found in message (checksum) |
0x05 | TE_COULD_NOT_CREATE_SOCKET | Error found while creating socket(can't create socket) |
0x06 | TE_COULD_NOT_BIND_SOCKET | Error found while binding server socket |
0x07 | TE_LISTEN_FAILED | Error found while listening to server socket |
0x08 | TE_ACCEPT_RETURN_ERROR | Error found during accept(accept return error) |
0x0b | TE_SHM_DISCONNECT | The remote node has disconnected |
0x0c | TE_SHM_IPC_STAT | Unable to check shm segment |
0x0d | TE_SHM_UNABLE_TO_CREATE_SEGMENT | Unable to create shm segment |
0x0e | TE_SHM_UNABLE_TO_ATTACH_SEGMENT | Unable to attach shm segment |
0x0f | TE_SHM_UNABLE_TO_REMOVE_SEGMENT | Unable to remove shm segment |
0x10 | TE_TOO_SMALL_SIGID | Sig ID too small |
0x11 | TE_TOO_LARGE_SIGID | Sig ID too large |
0x12 | TE_WAIT_STACK_FULL | Wait stack was full |
0x13 | TE_RECEIVE_BUFFER_FULL | Receive buffer was full |
0x14 | TE_SIGNAL_LOST_SEND_BUFFER_FULL | Send buffer was full,and trying to force send fails |
0x15 | TE_SIGNAL_LOST | Send failed for unknown reason(signal lost) |
0x16 | TE_SEND_BUFFER_FULL | The send buffer was full, but sleeping for a while solved |
0x0017 | TE_SCI_LINK_ERROR | There is no link from this node to the switch |
0x18 | TE_SCI_UNABLE_TO_START_SEQUENCE | Could not start a sequence, because system resources are exumed or no sequence has been created |
0x19 | TE_SCI_UNABLE_TO_REMOVE_SEQUENCE | Could not remove a sequence |
0x1a | TE_SCI_UNABLE_TO_CREATE_SEQUENCE | Could not create a sequence, because system resources are exempted. Must reboot |
0x1b | TE_SCI_UNRECOVERABLE_DATA_TFX_ERROR | Tried to send data on redundant link but failed |
0x1c | TE_SCI_CANNOT_INIT_LOCALSEGMENT | Cannot initialize local segment |
0x1d | TE_SCI_CANNOT_MAP_REMOTESEGMENT | Cannot map remote segment |
0x1e | TE_SCI_UNABLE_TO_UNMAP_SEGMENT | Cannot free the resources used by this segment (step 1) |
0x1f | TE_SCI_UNABLE_TO_REMOVE_SEGMENT | Cannot free the resources used by this segment (step 2) |
0x20 | TE_SCI_UNABLE_TO_DISCONNECT_SEGMENT | Cannot disconnect from a remote segment |
0x21 | TE_SHM_IPC_PERMANENT | Shm ipc Permanent error |
0x22 | TE_SCI_UNABLE_TO_CLOSE_CHANNEL | Unable to close the sci channel and the resources allocated |
Single user mode enables the database administrator to restrict access to the database system to a single API node, such as a MySQL server (SQL node) or an instance of ndb_restore. When entering single user mode, connections to all other API nodes are closed gracefully and all running transactions are aborted. No new transactions are permitted to start.
Once the cluster has entered single user mode, only the designated API node is granted access to the database.
You can use the ALL STATUS command in the
ndb_mgm client to see when the cluster has
entered single user mode. You can also check the
status
column of the
ndbinfo.nodes
table (see
Section 19.5.10.25, “The ndbinfo nodes Table”, for more
information).
Example:
ndb_mgm> ENTER SINGLE USER MODE 5
After this command has executed and the cluster has entered single
user mode, the API node whose node ID is 5
becomes the cluster's only permitted user.
The node specified in the preceding command must be an API node; attempting to specify any other type of node will be rejected.
When the preceding command is invoked, all transactions running on the designated node are aborted, the connection is closed, and the server must be restarted.
The command EXIT SINGLE USER MODE changes the state of the cluster's data nodes from single user mode to normal mode. API nodes—such as MySQL Servers—waiting for a connection (that is, waiting for the cluster to become ready and available), are again permitted to connect. The API node denoted as the single-user node continues to run (if still connected) during and after the state change.
Example:
ndb_mgm> EXIT SINGLE USER MODE
There are two recommended ways to handle a node failure when running in single user mode:
Method 1:
Finish all single user mode transactions
Issue the EXIT SINGLE USER MODE command
Restart the cluster's data nodes
Method 2:
Restart database nodes prior to entering single user mode.
This section discusses several SQL statements that can prove useful in managing and monitoring a MySQL server that is connected to a MySQL Cluster, and in some cases provide information about the cluster itself.
SHOW ENGINE NDB
STATUS
,
SHOW ENGINE
NDBCLUSTER STATUS
The output of this statement contains information about the server's connection to the cluster, creation and usage of MySQL Cluster objects, and binary logging for MySQL Cluster replication.
See Section 14.7.5.15, “SHOW ENGINE Syntax”, for a usage example and more detailed information.
This statement can be used to determine whether or not clustering support is enabled in the MySQL server, and if so, whether it is active.
See Section 14.7.5.16, “SHOW ENGINES Syntax”, for more detailed information.
This statement does not support a
LIKE
clause. However, you can
use LIKE
to filter queries
against the
INFORMATION_SCHEMA.ENGINES
table, as discussed in the next item.
SELECT * FROM INFORMATION_SCHEMA.ENGINES [WHERE
ENGINE LIKE 'NDB%']
This is the equivalent of SHOW
ENGINES
, but uses the
ENGINES
table of the
INFORMATION_SCHEMA
database. Unlike the
case with the SHOW ENGINES
statement, it is possible to filter the results using a
LIKE
clause, and to select
specific columns to obtain information that may be of use in
scripts. For example, the following query shows whether the
server was built with NDB
support
and, if so, whether it is enabled:
mysql>SELECT SUPPORT FROM INFORMATION_SCHEMA.ENGINES
->WHERE ENGINE LIKE 'NDB%';
+---------+ | support | +---------+ | ENABLED | +---------+
See Section 22.6, “The INFORMATION_SCHEMA ENGINES Table”, for more information.
This statement provides a list of most server system variables
relating to the NDB
storage
engine, and their values, as shown here:
mysql> SHOW VARIABLES LIKE 'NDB%';
+-------------------------------------+-------+
| Variable_name | Value |
+-------------------------------------+-------+
| ndb_autoincrement_prefetch_sz | 32 |
| ndb_cache_check_time | 0 |
| ndb_extra_logging | 0 |
| ndb_force_send | ON |
| ndb_index_stat_cache_entries | 32 |
| ndb_index_stat_enable | OFF |
| ndb_index_stat_update_freq | 20 |
| ndb_report_thresh_binlog_epoch_slip | 3 |
| ndb_report_thresh_binlog_mem_usage | 10 |
| ndb_use_copying_alter_table | OFF |
| ndb_use_exact_count | ON |
| ndb_use_transactions | ON |
+-------------------------------------+-------+
See Section 6.1.4, “Server System Variables”, for more information.
SELECT * FROM INFORMATION_SCHEMA.GLOBAL_VARIABLES
WHERE VARIABLE_NAME LIKE 'NDB%';
This statement is the equivalent of the
SHOW
command described in
the previous item, and provides almost identical output, as
shown here:
mysql>SELECT * FROM INFORMATION_SCHEMA.GLOBAL_VARIABLES
->WHERE VARIABLE_NAME LIKE 'NDB%';
+-------------------------------------+----------------+ | VARIABLE_NAME | VARIABLE_VALUE | +-------------------------------------+----------------+ | NDB_AUTOINCREMENT_PREFETCH_SZ | 32 | | NDB_CACHE_CHECK_TIME | 0 | | NDB_EXTRA_LOGGING | 0 | | NDB_FORCE_SEND | ON | | NDB_INDEX_STAT_CACHE_ENTRIES | 32 | | NDB_INDEX_STAT_ENABLE | OFF | | NDB_INDEX_STAT_UPDATE_FREQ | 20 | | NDB_REPORT_THRESH_BINLOG_EPOCH_SLIP | 3 | | NDB_REPORT_THRESH_BINLOG_MEM_USAGE | 10 | | NDB_USE_COPYING_ALTER_TABLE | OFF | | NDB_USE_EXACT_COUNT | ON | | NDB_USE_TRANSACTIONS | ON | +-------------------------------------+----------------+
Unlike the case with the
SHOW
command, it is
possible to select individual columns. For example:
mysql>SELECT VARIABLE_VALUE
->FROM INFORMATION_SCHEMA.GLOBAL_VARIABLES
->WHERE VARIABLE_NAME = 'ndb_force_send';
+----------------+ | VARIABLE_VALUE | +----------------+ | ON | +----------------+
See Section 22.10, “The INFORMATION_SCHEMA GLOBAL_VARIABLES and SESSION_VARIABLES Tables”, and Section 6.1.4, “Server System Variables”, for more information.
This statement shows at a glance whether or not the MySQL server is acting as a cluster SQL node, and if so, it provides the MySQL server's cluster node ID, the host name and port for the cluster management server to which it is connected, and the number of data nodes in the cluster, as shown here:
mysql> SHOW STATUS LIKE 'NDB%';
+--------------------------+---------------+
| Variable_name | Value |
+--------------------------+---------------+
| Ndb_cluster_node_id | 10 |
| Ndb_config_from_host | 192.168.0.103 |
| Ndb_config_from_port | 1186 |
| Ndb_number_of_data_nodes | 4 |
+--------------------------+---------------+
If the MySQL server was built with clustering support, but it is not connected to a cluster, all rows in the output of this statement contain a zero or an empty string:
mysql> SHOW STATUS LIKE 'NDB%';
+--------------------------+-------+
| Variable_name | Value |
+--------------------------+-------+
| Ndb_cluster_node_id | 0 |
| Ndb_config_from_host | |
| Ndb_config_from_port | 0 |
| Ndb_number_of_data_nodes | 0 |
+--------------------------+-------+
See also Section 14.7.5.35, “SHOW STATUS Syntax”.
SELECT * FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE
VARIABLE_NAME LIKE 'NDB%';
This statement provides similar output to the
SHOW
command discussed in
the previous item. However, unlike the case with
SHOW STATUS
, it is possible
using the SELECT
to extract
values in SQL for use in scripts for monitoring and automation
purposes.
See Section 22.9, “The INFORMATION_SCHEMA GLOBAL_STATUS and SESSION_STATUS Tables”, for more information.
You can also query the tables in the
ndbinfo
information database for
real-time data about many MySQL Cluster operations. See
Section 19.5.10, “The ndbinfo MySQL Cluster Information Database”.
ndbinfo
is a database storing containing
information specific to MySQL Cluster.
This database contains a number of tables, each providing a different sort of data about MySQL Cluster node status, resource usage, and operations. You can find more detailed information about each of these tables in the next several sections.
ndbinfo
is included with MySQL Cluster support
in the MySQL Server; no special compilation or configuration steps
are required; the tables are created by the MySQL Server when it
connects to the cluster. You can verify that
ndbinfo
support is active in a given MySQL
Server instance using SHOW PLUGINS
;
if ndbinfo
support is enabled, you should see a
row containing ndbinfo
in the
Name
column and ACTIVE
in
the Status
column, as shown here (emphasized
text):
mysql> SHOW PLUGINS;
+----------------------------------+--------+--------------------+---------+---------+
| Name | Status | Type | Library | License |
+----------------------------------+--------+--------------------+---------+---------+
| binlog | ACTIVE | STORAGE ENGINE | NULL | GPL |
| mysql_native_password | ACTIVE | AUTHENTICATION | NULL | GPL |
| sha256_password | ACTIVE | AUTHENTICATION | NULL | GPL |
| MRG_MYISAM | ACTIVE | STORAGE ENGINE | NULL | GPL |
| MEMORY | ACTIVE | STORAGE ENGINE | NULL | GPL |
| CSV | ACTIVE | STORAGE ENGINE | NULL | GPL |
| MyISAM | ACTIVE | STORAGE ENGINE | NULL | GPL |
| InnoDB | ACTIVE | STORAGE ENGINE | NULL | GPL |
| INNODB_TRX | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_LOCKS | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_LOCK_WAITS | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_CMP | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_CMP_RESET | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_CMPMEM | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_CMPMEM_RESET | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_CMP_PER_INDEX | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_CMP_PER_INDEX_RESET | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_BUFFER_PAGE | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_BUFFER_PAGE_LRU | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_BUFFER_POOL_STATS | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_TEMP_TABLE_INFO | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_METRICS | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_FT_DEFAULT_STOPWORD | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_FT_DELETED | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_FT_BEING_DELETED | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_FT_CONFIG | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_FT_INDEX_CACHE | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_FT_INDEX_TABLE | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_SYS_TABLES | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_SYS_TABLESTATS | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_SYS_INDEXES | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_SYS_COLUMNS | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_SYS_FIELDS | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_SYS_FOREIGN | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_SYS_FOREIGN_COLS | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_SYS_TABLESPACES | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_SYS_DATAFILES | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| INNODB_SYS_VIRTUAL | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| PERFORMANCE_SCHEMA | ACTIVE | STORAGE ENGINE | NULL | GPL |
| ndbcluster | ACTIVE | STORAGE ENGINE | NULL | GPL |
| ndbinfo | ACTIVE | STORAGE ENGINE | NULL | GPL |
| ndb_transid_mysql_connection_map | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
| BLACKHOLE | ACTIVE | STORAGE ENGINE | NULL | GPL |
| ARCHIVE | ACTIVE | STORAGE ENGINE | NULL | GPL |
| partition | ACTIVE | STORAGE ENGINE | NULL | GPL |
| ngram | ACTIVE | FTPARSER | NULL | GPL |
+----------------------------------+--------+--------------------+---------+---------+
46 rows in set (0.00 sec)
You can also do this by checking the output of
SHOW ENGINES
for a line including
ndbinfo
in the Engine
column
and YES
in the Support
column, as shown here (emphasized text):
*************************** 1. row *************************** Engine: ndbcluster Support: YES Comment: Clustered, fault-tolerant tables Transactions: YES XA: NO Savepoints: NO *************************** 2. row *************************** Engine: CSV Support: YES Comment: CSV storage engine Transactions: NO XA: NO Savepoints: NO *************************** 3. row *************************** Engine: InnoDB Support: DEFAULT Comment: Supports transactions, row-level locking, and foreign keys Transactions: YES XA: YES Savepoints: YES *************************** 4. row *************************** Engine: BLACKHOLE Support: YES Comment: /dev/null storage engine (anything you write to it disappears) Transactions: NO XA: NO Savepoints: NO *************************** 5. row *************************** Engine: MyISAM Support: YES Comment: MyISAM storage engine Transactions: NO XA: NO Savepoints: NO *************************** 6. row *************************** Engine: MRG_MYISAM Support: YES Comment: Collection of identical MyISAM tables Transactions: NO XA: NO Savepoints: NO *************************** 7. row *************************** Engine: ARCHIVE Support: YES Comment: Archive storage engine Transactions: NO XA: NO Savepoints: NO *************************** 8. row *************************** Engine: ndbinfo Support: YES Comment: MySQL Cluster system information storage engine Transactions: NO XA: NO Savepoints: NO *************************** 9. row *************************** Engine: PERFORMANCE_SCHEMA Support: YES Comment: Performance Schema Transactions: NO XA: NO Savepoints: NO *************************** 10. row *************************** Engine: MEMORY Support: YES Comment: Hash based, stored in memory, useful for temporary tables Transactions: NO XA: NO Savepoints: NO 10 rows in set (0.00 sec)
If ndbinfo
support is enabled, then you can
access ndbinfo
using SQL statements in
mysql or another MySQL client. For example, you
can see ndbinfo
listed in the output of
SHOW DATABASES
, as shown here:
mysql> SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| ndbinfo |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.04 sec)
If the mysqld process was not started with the
--ndbcluster
option,
ndbinfo
is not available and is not displayed
by SHOW DATABASES
. If
mysqld was formerly connected to a MySQL
Cluster but the cluster becomes unavailable (due to events such as
cluster shutdown, loss of network connectivity, and so forth),
ndbinfo
and its tables remain visible, but an
attempt to access any tables (other than blocks
or config_params
) fails with Got
error 157 'Connection to NDB failed' from NDBINFO.
With the exception of the blocks
and
config_params
tables, what we refer to as
ndbinfo
“tables” are actually
views generated from internal NDB
tables not normally visible to the MySQL Server.
All ndbinfo
tables are read-only, and are
generated on demand when queried. Because many of them are
generated in parallel by the data nodes while other are specific
to a given SQL node, they are not guaranteed to provide a
consistent snapshot.
In addition, pushing down of joins is not supported on
ndbinfo
tables; so joining large
ndbinfo
tables can require transfer of a large
amount of data to the requesting API node, even when the query
makes use of a WHERE
clause.
ndbinfo
tables are not included in the query
cache. (Bug #59831)
You can select the ndbinfo
database with a
USE
statement, and then issue a
SHOW TABLES
statement to obtain a
list of tables, just as for any other database, like this:
mysql>USE ndbinfo;
Database changed mysql>SHOW TABLES;
+---------------------------------+ | Tables_in_ndbinfo | +---------------------------------+ | arbitrator_validity_detail | | arbitrator_validity_summary | | blocks | | cluster_locks | | cluster_operations | | cluster_transactions | | config_params | | config_values | | counters | | cpustat | | cpustat_1sec | | cpustat_20sec | | cpustat_50ms | | dict_obj_types | | disk_write_speed_aggregate | | disk_write_speed_aggregate_node | | disk_write_speed_base | | diskpagebuffer | | locks_per_fragment | | logbuffers | | logspaces | | membership | | memory_per_fragment | | memoryusage | | nodes | | operations_per_fragment | | resources | | restart_info | | server_locks | | server_operations | | server_transactions | | tc_time_track_stats | | threadblocks | | threads | | threadstat | | transporters | +---------------------------------+ 36 rows in set (0.00 sec)
In MySQL Cluster NDB 7.5.0 (and later), all
ndbinfo
tables use the NDB
storage engine.
The config_values
table was
added in MySQL Cluster NDB 7.5.0.
The cpustat
,
cpustat_50ms
,
cpustat_1sec
,
cpustat_20sec
, and
threads
tables were added in
MySQL Cluster NDB 7.5.2.
The cluster_locks
,
locks_per_fragment
, and
server_locks
tables were added
in MySQL Cluster NDB 7.5.3.
You can execute SELECT
statements
against these tables, just as you would normally expect:
mysql> SELECT * FROM memoryusage;
+---------+---------------------+--------+------------+------------+-------------+
| node_id | memory_type | used | used_pages | total | total_pages |
+---------+---------------------+--------+------------+------------+-------------+
| 5 | Data memory | 753664 | 23 | 1073741824 | 32768 |
| 5 | Index memory | 163840 | 20 | 1074003968 | 131104 |
| 5 | Long message buffer | 2304 | 9 | 67108864 | 262144 |
| 6 | Data memory | 753664 | 23 | 1073741824 | 32768 |
| 6 | Index memory | 163840 | 20 | 1074003968 | 131104 |
| 6 | Long message buffer | 2304 | 9 | 67108864 | 262144 |
+---------+---------------------+--------+------------+------------+-------------+
6 rows in set (0.02 sec)
More complex queries, such as the two following
SELECT
statements using the
memoryusage
table, are possible:
mysql>SELECT SUM(used) as 'Data Memory Used, All Nodes'
>FROM memoryusage
>WHERE memory_type = 'Data memory';
+-----------------------------+ | Data Memory Used, All Nodes | +-----------------------------+ | 6460 | +-----------------------------+ 1 row in set (0.37 sec) mysql>SELECT SUM(max) as 'Total IndexMemory Available'
>FROM memoryusage
>WHERE memory_type = 'Index memory';
+-----------------------------+ | Total IndexMemory Available | +-----------------------------+ | 25664 | +-----------------------------+ 1 row in set (0.33 sec)
ndbinfo
table and column names are case
sensitive (as is the name of the ndbinfo
database itself). These identifiers are in lowercase. Trying to
use the wrong lettercase results in an error, as shown in this
example:
mysql>SELECT * FROM nodes;
+---------+--------+---------+-------------+ | node_id | uptime | status | start_phase | +---------+--------+---------+-------------+ | 1 | 13602 | STARTED | 0 | | 2 | 16 | STARTED | 0 | +---------+--------+---------+-------------+ 2 rows in set (0.04 sec) mysql>SELECT * FROM Nodes;
ERROR 1146 (42S02): Table 'ndbinfo.Nodes' doesn't exist
mysqldump ignores the
ndbinfo
database entirely, and excludes it from
any output. This is true even when using the
--databases
or
--all-databases
option.
MySQL Cluster also maintains tables in the
INFORMATION_SCHEMA
information database,
including the FILES
table which
contains information about files used for MySQL Cluster Disk Data
storage, and the
ndb_transid_mysql_connection_map
table, which shows the relationships between transactions,
transaction coordinators, and MySQL Cluster API nodes. For more
information, see the descriptions of the tables or
Section 19.5.11, “INFORMATION_SCHEMA Tables for MySQL Cluster”.
The arbitrator_validity_detail
table shows
the view that each data node in the cluster of the arbitrator.
It is a subset of the
membership
table.
The following table provides information about the columns in
the arbitrator_validity_detail
table. For
each column, the table shows the name, data type, and a brief
description. Additional information can be found in the notes
following the table.
Column Name | Type | Description |
---|---|---|
node_id | integer | This node's node ID |
arbitrator | integer | Node ID of arbitrator |
arb_ticket | string | Internal identifier used to track arbitration |
arb_connected | Yes or No | Whether this node is connected to the arbitrator |
arb_state | Enumeration (see text) | Arbitration state |
The node ID is the same as that reported by ndb_mgm -e "SHOW".
All nodes should show the same arbitrator
and
arb_ticket
values as well as the same
arb_state
value. Possible
arb_state
values are
ARBIT_NULL
, ARBIT_INIT
,
ARBIT_FIND
, ARBIT_PREP1
,
ARBIT_PREP2
, ARBIT_START
,
ARBIT_RUN
, ARBIT_CHOOSE
,
ARBIT_CRASH
, and UNKNOWN
.
arb_connected
shows whether the current node
is connected to the arbitrator
.
The arbitrator_validity_summary
table
provides a composite view of the arbitrator with regard to the
cluster's data nodes.
The following table provides information about the columns in
the arbitrator_validity_summary
table. For
each column, the table shows the name, data type, and a brief
description. Additional information can be found in the notes
following the table.
Column Name | Type | Description |
---|---|---|
arbitrator | integer | Node ID of arbitrator |
arb_ticket | string | Internal identifier used to track arbitration |
arb_connected | Yes or No | Whether this arbitrator is connected to the cluster |
consensus_count | integer | Number of data nodes that see this node as arbitrator |
In normal operations, this table should have only 1 row for any appreciable length of time. If it has more than 1 row for longer than a few moments, then either not all nodes are connected to the arbitrator, or all nodes are connected, but do not agree on the same arbitrator.
The arbitrator
column shows the
arbitrator's node ID.
arb_ticket
is the internal identifier used by
this arbitrator.
arb_connected
shows whether this node is
connected to the cluster as an arbitrator.
The blocks
table is a static table which
simply contains the names and internal IDs of all NDB kernel
blocks (see NDB Kernel Blocks). It
is for use by the other
ndbinfo
tables (most of which
are actually views) in mapping block numbers to block names for
producing human-readable output.
The following table provides information about the columns in
the blocks
table. For each column, the table
shows the name, data type, and a brief description. Additional
information can be found in the notes following the table.
Column Name | Type | Description |
---|---|---|
block_number | integer | Block number |
block_name | string | Block name |
To obtain a list of all block names, simply execute
SELECT block_name FROM ndbinfo.blocks
.
Although this is a static table, its content can vary between
different MySQL Cluster releases.
The cluster_locks
table provides information
about current lock requests holding and waiting for locks on
NDB
tables in a MySQL Cluster, and is
intended as a companion table to
cluster_operations
.
Information obtain from the cluster_locks
table may be useful in investigating stalls and deadlocks.
The following table provides information about the columns in
the cluster_locks
table. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Column Name | Type | Description |
---|---|---|
node_id | integer | ID of reporting node |
block_instance | integer | ID of reporting LDM instance |
tableid | integer | ID of table containing this row |
fragmentid | integer | ID of fragment containing locked row |
rowid | integer | ID of locked row |
transid | integer | Transaction ID |
mode | string | Lock request mode |
state | string | Lock state |
detail | string | Whether this is first holding lock in row lock queue |
op | string | Operation type |
duration_millis | integer | Milliseconds spent waiting or holding lock |
lock_num | integer | ID of lock object |
waiting_for | integer | Waiting for lock with this ID |
The table ID (tableid
column) is assigned
internally, and is the same as that used in other
ndbinfo
tables. It is also shown in the
output of ndb_show_tables.
The transaction ID (transid
column) is the
identifier generated by the NDB API for the transaction
requestiong or holding the current lock.
The mode
column shows the lock mode; this is
always one of S
(indicating a shared lock) or
X
(an exclusive lock). If a transaction holds
an exclusive lock on a given row, all other locks on that row
have the same transaction ID.
The state
column shows the lock state. Its
value is always one of H
(holding) or
W
(waiting). A waiting lock request waits for
a lock held by a different transaction.
When the detail
column contains a
*
(asterisk character), this means that this
lock is the first holding lock in the affected row's lock
queue; otherwise, this column is empty. This information can be
used to help identify the unique entries in a list of lock
requests.
The op
column shows the type of operation
requesting the lock. This is always one of the values
READ
, INSERT
,
UPDATE
, DELETE
,
SCAN
, or REFRESH
.
The duration_millis
column shows the number
of milliseconds for which this lock request has been waiting or
holding the lock. This is reset to 0 when a lock is granted for
a waiting request.
The lock ID (lockid
column) is unique to this
node and block instance.
The lock state is shown in the lock_state
column; if this is W
, the lock is waiting to
be granted, and the waiting_for
column shows
the lock ID of the lock object this request is waiting for.
Otherwise, the waiting_for
column is empty.
waiting_for
can refer only to locks on the
same row, as identified by node_id
,
block_instance
, tableid
,
fragmentid
, and rowid
.
The cluster_locks
table was added in MySQL
Cluster NDB 7.5.3.
The cluster_operations
table provides a
per-operation (stateful primary key op) view of all activity in
the MySQL Cluster from the point of view of the local data
management (LQH) blocks (see
The DBLQH Block).
The following table provides information about the columns in
the cluster_operations
table. For each
column, the table shows the name, data type, and a brief
description. Additional information can be found in the notes
following the table.
Column Name | Type | Description |
---|---|---|
node_id | integer | Node ID of reporting LQH block |
block_instance | integer | LQH block instance |
transid | integer | Transaction ID |
operation_type | string | Operation type (see text for possible values) |
state | string | Operation state (see text for possible values) |
tableid | integer | Table ID |
fragmentid | integer | Fragment ID |
client_node_id | integer | Client node ID |
client_block_ref | integer | Client block reference |
tc_node_id | integer | Transaction coordinator node ID |
tc_block_no | integer | Transaction coordinator block number |
tc_block_instance | integer | Transaction coordinator block instance |
The transaction ID is a unique 64-bit number which can be
obtained using the NDB API's
getTransactionId()
method. (Currently, the MySQL Server does not expose the NDB API
transaction ID of an ongoing transaction.)
The operation_type
column can take any one of
the values READ
, READ-SH
,
READ-EX
, INSERT
,
UPDATE
, DELETE
,
WRITE
, UNLOCK
,
REFRESH
, SCAN
,
SCAN-SH
, SCAN-EX
, or
<unknown>
.
The state
column can have any one of the
values ABORT_QUEUED
,
ABORT_STOPPED
, COMMITTED
,
COMMIT_QUEUED
,
COMMIT_STOPPED
,
COPY_CLOSE_STOPPED
,
COPY_FIRST_STOPPED
,
COPY_STOPPED
, COPY_TUPKEY
,
IDLE
, LOG_ABORT_QUEUED
,
LOG_COMMIT_QUEUED
,
LOG_COMMIT_QUEUED_WAIT_SIGNAL
,
LOG_COMMIT_WRITTEN
,
LOG_COMMIT_WRITTEN_WAIT_SIGNAL
,
LOG_QUEUED
, PREPARED
,
PREPARED_RECEIVED_COMMIT
,
SCAN_CHECK_STOPPED
,
SCAN_CLOSE_STOPPED
,
SCAN_FIRST_STOPPED
,
SCAN_RELEASE_STOPPED
,
SCAN_STATE_USED
,
SCAN_STOPPED
, SCAN_TUPKEY
,
STOPPED
, TC_NOT_CONNECTED
,
WAIT_ACC
, WAIT_ACC_ABORT
,
WAIT_AI_AFTER_ABORT
,
WAIT_ATTR
, WAIT_SCAN_AI
,
WAIT_TUP
, WAIT_TUPKEYINFO
,
WAIT_TUP_COMMIT
, or
WAIT_TUP_TO_ABORT
. (If the MySQL Server is
running with
ndbinfo_show_hidden
enabled,
you can view this list of states by selecting from the
ndb$dblqh_tcconnect_state
table, which is
normally hidden.)
You can obtain the name of an NDB
table from
its table ID by checking the output of
ndb_show_tables.
The fragid
is the same as the partition
number seen in the output of ndb_desc
--extra-partition-info
(short
form -p
).
In client_node_id
and
client_block_ref
, client
refers to a MySQL Cluster API or SQL node (that is, an NDB API
client or a MySQL Server attached to the cluster).
The cluster_transactions
table shows
information about all ongoing transactions in a MySQL Cluster.
The following table provides information about the columns in
the cluster_transactions
table. For each
column, the table shows the name, data type, and a brief
description. Additional information can be found in the notes
following the table.
Column Name | Type | Description |
---|---|---|
node_id | integer | Node ID of transaction coordinator |
block_instance | integer | TC block instance |
transid | integer | Transaction ID |
state | string | Operation state (see text for possible values) |
count_operations | integer | Number of stateful primary key operations in transaction (includes reads with locks, as well as DML operations) |
outstanding_operations | integer | Operations still being executed in local data management blocks |
inactive_seconds | integer | Time spent waiting for API |
client_node_id | integer | Client node ID |
client_block_ref | integer | Client block reference |
The transaction ID is a unique 64-bit number which can be
obtained using the NDB API's
getTransactionId()
method. (Currently, the MySQL Server does not expose the NDB API
transaction ID of an ongoing transaction.)
The state
column can have any one of the
values CS_ABORTING
,
CS_COMMITTING
,
CS_COMMIT_SENT
,
CS_COMPLETE_SENT
,
CS_COMPLETING
,
CS_CONNECTED
,
CS_DISCONNECTED
,
CS_FAIL_ABORTED
,
CS_FAIL_ABORTING
,
CS_FAIL_COMMITTED
,
CS_FAIL_COMMITTING
,
CS_FAIL_COMPLETED
,
CS_FAIL_PREPARED
,
CS_PREPARE_TO_COMMIT
,
CS_RECEIVING
,
CS_REC_COMMITTING
,
CS_RESTART
,
CS_SEND_FIRE_TRIG_REQ
,
CS_STARTED
,
CS_START_COMMITTING
,
CS_START_SCAN
,
CS_WAIT_ABORT_CONF
,
CS_WAIT_COMMIT_CONF
,
CS_WAIT_COMPLETE_CONF
,
CS_WAIT_FIRE_TRIG_REQ
. (If the MySQL Server
is running with
ndbinfo_show_hidden
enabled,
you can view this list of states by selecting from the
ndb$dbtc_apiconnect_state
table, which is
normally hidden.)
In client_node_id
and
client_block_ref
, client
refers to a MySQL Cluster API or SQL node (that is, an NDB API
client or a MySQL Server attached to the cluster).
The config_params
table is a static table
which provides the names and internal ID numbers of and other
information about MySQL Cluster configuration parameters.
The following table provides information about the columns in
the config_params
table. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table. This table can also be used in conjunction with the
config_values
table for
obtaining realtime information about node configuration
parameters.
Column Name | Type | Description |
---|---|---|
param_number | integer | The parameter's internal ID number |
param_name | string | The name of the parameter |
param_description | string | A brief description of the parameter |
param_type | string | The parameter's data type |
param_default | string | The parameter's default value, if any |
param_min | string | The parameter's maximum value, if any |
param_max | string | The parameter's minimum value, if any |
param_mandatory | integer | This is 1 if the parameter is required, otherwise 0 |
param_status | string | Currently unused |
In MySQL Cluster NDB 7.5 (and later), this table is read-only.
The param_description
,
param_type
, param_default
,
param_min
, param_max
,
param_mandatory
, and
param_status
columns were all added in MySQL
Cluster NDB 7.5.0.
Although this is a static table, its content can vary between MySQL Cluster installations, since supported parameters can vary due to differences between software releases, cluster hardware configurations, and other factors.
The config_values
table, implemented in MySQL
Cluster NDB 7.5.0, provides information about the current state
of node configuration parameter values. Each row in the table
corresponds to the current value of a parameter on a given node.
Column Name | Type | Description |
---|---|---|
node_id | integer | ID of the node in the cluster |
config_param | integer | The parameter's internal ID number |
config_value | string | Current value of the parameter |
This table's config_param
column and the
config_params
table's
param_number
column use the same parameter
identifiers. By joining the two tables on these columns, you can
obtain detailed information about desired node configuration
parameters by name, as shown in the following example:
SELECT p.param_name AS Name, v.node_id AS Node, p.param_type AS Type, p.param_default AS 'Default', p.param_min AS Minimum, p.param_max AS Maximum, CASE p.param_mandatory WHEN 1 THEN 'Y' ELSE 'N' END AS 'Required', v.config_value AS Current FROM config_params p JOIN config_values v ON p.param_number = v.config_param WHERE p. param_name IN ('NodeId', 'NoOfReplicas', 'HostName', 'DataMemory', 'IndexMemory', 'TotalSendBufferMemory');
The counters
table provides running totals of
events such as reads and writes for specific kernel blocks and
data nodes. Counts are kept from the most recent node start or
restart; a node start or restart resets all counters on that
node. Not all kernel blocks have all types of counters.
The following table provides information about the columns in
the counters
table. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Column Name | Type | Description |
---|---|---|
node_id | integer | The data node ID |
block_name | string | Name of the associated NDB kernel block (see NDB Kernel Blocks). |
block_instance | integer | Block instance |
counter_id | integer | The counter's internal ID number; normally an integer between 1 and 10, inclusive. |
counter_name | string | The name of the counter. See text for names of individual counters and the NDB kernel block with which each counter is associated. |
val | integer | The counter's value |
Each counter is associated with a particular NDB kernel block.
The OPERATIONS
counter is associated with the
DBLQH
(local query handler) kernel block (see
The DBLQH Block). A
primary-key read counts as one operation, as does a primary-key
update. For reads, there is one operation in
DBLQH
per operation in
DBTC
. For writes, there is one operation
counted per replica.
The ATTRINFO
,
TRANSACTIONS
, COMMITS
,
READS
, LOCAL_READS
,
SIMPLE_READS
, WRITES
,
LOCAL_WRITES
, ABORTS
,
TABLE_SCANS
, and
RANGE_SCANS
counters are associated with the
DBTC (transaction co-ordinator) kernel block (see
The DBTC Block).
LOCAL_WRITES
and
LOCAL_READS
are primary-key operations using
a transaction coordinator in a node that also holds the primary
replica of the record.
The READS
counter includes all reads.
LOCAL_READS
includes only those reads of the
primary replica on the same node as this transaction
coordinator. SIMPLE_READS
includes only those
reads in which the read operation is the beginning and ending
operation for a given transaction. Simple reads do not hold
locks but are part of a transaction, in that they observe
uncommitted changes made by the transaction containing them but
not of any other uncommitted transactions. Such reads are
“simple” from the point of view of the TC block;
since they hold no locks they are not durable, and once
DBTC
has routed them to the relevant LQH
block, it holds no state for them.
ATTRINFO
keeps a count of the number of times
an interpreted program is sent to the data node. See
NDB Protocol Messages, for more
information about ATTRINFO
messages in the
NDB
kernel.
The LOCAL_TABLE_SCANS_SENT
,
READS_RECEIVED
,
PRUNED_RANGE_SCANS_RECEIVED
,
RANGE_SCANS_RECEIVED
,
LOCAL_READS_SENT
,
CONST_PRUNED_RANGE_SCANS_RECEIVED
,
LOCAL_RANGE_SCANS_SENT
,
REMOTE_READS_SENT
,
REMOTE_RANGE_SCANS_SENT
,
READS_NOT_FOUND
,
SCAN_BATCHES_RETURNED
,
TABLE_SCANS_RECEIVED
, and
SCAN_ROWS_RETURNED
counters are associated
with the DBSPJ
(select push-down join) kernel
block (see The DBSPJ Block).
A number of counters provide information about transporter overload and send buffer sizing when troubleshooting such issues. For each LQH instance, there is one instance of each counter in the following list:
LQHKEY_OVERLOAD
: Number of primary key
requests rejected at the LQH block instance due to
transporter overload
LQHKEY_OVERLOAD_TC
: Count of instances of
LQHKEY_OVERLOAD
where the TC node
transporter was overloaded
LQHKEY_OVERLOAD_READER
: Count of
instances of LQHKEY_OVERLOAD
where the
API reader (reads only) node was overloaded.
LQHKEY_OVERLOAD_NODE_PEER
: Count of
instances of LQHKEY_OVERLOAD
where the
next backup data node (writes only) was overloaded
LQHKEY_OVERLOAD_SUBSCRIBER
: Count of
instances of LQHKEY_OVERLOAD
where a
event subscriber (writes only) was overloaded.
LQHSCAN_SLOWDOWNS
: Count of instances
where a fragment scan batch size was reduced due to scanning
API transporter overload.
The cpustat
table provides per-thread CPU
statistics gathered each second, for each thread running in the
NDB
kernel.
The following table provides information about the columns in
the cpustat
table. For each column, the table
shows the name, data type, and a brief description. Additional
information can be found in the notes following the table.
Column Name | Type | Description |
---|---|---|
node_id | integer | ID of the node where the the thread is running |
thr_no | integer | Thread ID (specific to this node) |
OS_user | integer | OS user time |
OS_system | integer | OS system time |
OS_idle | integer | OS idle time |
thread_exec | integer | Thread execution time |
thread_sleeping | integer | Thread sleep time |
thread_send | integer | Thread send time |
thread_buffer_full | integer | Thread buffer full time |
elapsed_time | integer | Elapsed time |
This table was added in MySQL Cluster NDB 7.5.2.
The cpustat_50ms
table provides raw,
per-thread CPU data obtained each 50 milliseconds for each
thread running in the NDB
kernel.
Like cpustat_1sec
and
cpustat_20sec
, this table
shows 20 measurement sets per thread, each referencing a period
of the named duration. Thus, cpsustat_50ms
provides 1 second of history.
The following table provides information about the columns in
the cpustat_50ms
table. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Column Name | Type | Description |
---|---|---|
node_id | integer | ID of the node where the the thread is running |
thr_no | integer | Thread ID (specific to this node) |
OS_user_time | integer | OS user time |
OS_system_time | integer | OS system time |
OS_idle_time | integer | OS idle time |
exec_time | integer | Thread execution time |
sleep_time | integer | Thread sleep time |
send_time | integer | Thread send time |
buffer_full_time | integer | Thread buffer full time |
elapsed_time | integer | Elapsed time |
This table was added in MySQL Cluster NDB 7.5.2.
The cpustat-1sec
table provides raw,
per-thread CPU data obtained each second for each thread running
in the NDB
kernel.
Like cpustat_50ms
and
cpustat_20sec
, this table
shows 20 measurement sets per thread, each referencing a period
of the named duration. Thus, cpsustat_1sec
provides 20 seconds of history.
The following table provides information about the columns in
the cpustat_1sec
table. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Column Name | Type | Description |
---|---|---|
node_id | integer | ID of the node where the the thread is running |
thr_no | integer | Thread ID (specific to this node) |
OS_user_time | integer | OS user time |
OS_system_time | integer | OS system time |
OS_idle_time | integer | OS idle time |
exec_time | integer | Thread execution time |
sleep_time | integer | Thread sleep time |
send_time | integer | Thread send time |
buffer_full_time | integer | Thread buffer full time |
elapsed_time | integer | Elapsed time |
This table was added in MySQL Cluster NDB 7.5.2.
The cpustat_20sec
table provides raw,
per-thread CPU data obtained each 20 seconds, for each thread
running in the NDB
kernel.
Like cpustat_50ms
and
cpustat_1sec
, this table shows
20 measurement sets per thread, each referencing a period of the
named duration. Thus, cpsustat_20sec
provides
400 seconds of history.
The following table provides information about the columns in
the cpustat_20sec
table. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Column Name | Type | Description |
---|---|---|
node_id | integer | ID of the node where the the thread is running |
thr_no | integer | Thread ID (specific to this node) |
OS_user_time | integer | OS user time |
OS_system_time | integer | OS system time |
OS_idle_time | integer | OS idle time |
exec_time | integer | Thread execution time |
sleep_time | integer | Thread sleep time |
send_time | integer | Thread send time |
buffer_full_time | integer | Thread buffer full time |
elapsed_time | integer | Elapsed time |
This table was added in MySQL Cluster NDB 7.5.2.
The dict_obj_types
table is a static table
listing possible dictionary object types used in the NDB kernel.
These are the same types defined by
Object::Type
in the NDB API.
The following table provides information about the columns in
the dict_obj_types
table. For each column,
the table shows the name, data type, and a brief description.
Column Name | Type | Description |
---|---|---|
type_id | integer | The type ID for this type |
type_name | string | The name of this type |
The disk_write_speed_base
table provides base
information about the speed of disk writes during LCP, backup,
and restore operations.
The following table provides information about the columns in
the disk_write_speed_base
table. For each
column, the table shows the name, data type, and a brief
description. Additional information can be found in the notes
following the table.
Column Name | Type | Description |
---|---|---|
node_id | integer | Node ID of this node |
thr_no | integer | Thread ID of this LDM thread |
millis_ago | integer | Milliseconds since this reporting period ended |
millis_passed | integer | Milliseconds elapsed in this reporting period |
backup_lcp_bytes_written | integer | Number of bytes written to disk by local checkpoints and backup processes during this period |
redo_bytes_written | integer | Number of bytes written to REDO log during this period |
target_disk_write_speed | integer | Actual speed of disk writes per LDM thread (base data) |
The disk_write_speed_aggregate
table provides
aggregated information about the speed of disk writes during
LCP, backup, and restore operations.
The following table provides information about the columns in
the disk_write_speed_aggregate
table. For
each column, the table shows the name, data type, and a brief
description. Additional information can be found in the notes
following the table.
Column Name | Type | Description |
---|---|---|
node_id | integer | Node ID of this node |
thr_no | integer | Thread ID of this LDM thread |
backup_lcp_speed_last_sec | integer | Number of bytes written to disk by backup and LCP processes in the last second |
redo_speed_last_sec | integer | Number of bytes written to REDO log in the last second |
backup_lcp_speed_last_10sec | integer | Number of bytes written to disk by backup and LCP processes per second, averaged over the last 10 seconds |
redo_speed_last_10sec | integer | Number of bytes written to REDO log per second, averaged over the last 10 seconds |
std_dev_backup_lcp_speed_last_10sec | integer | Standard deviation in number of bytes written to disk by backup and LCP processes per second, averaged over the last 10 seconds |
std_dev_redo_speed_last_10sec | integer | Standard deviation in number of bytes written to REDO log per second, averaged over the last 10 seconds |
backup_lcp_speed_last_60sec | integer | Number of bytes written to disk by backup and LCP processes per second, averaged over the last 60 seconds |
redo_speed_last_60sec | integer | Number of bytes written to REDO log per second, averaged over the last 10 seconds |
std_dev_backup_lcp_speed_last_60sec | integer | Standard deviation in number of bytes written to disk by backup and LCP processes per second, averaged over the last 60 seconds |
std_dev_redo_speed_last_60sec | integer | Standard deviation in number of bytes written to REDO log per second, averaged over the last 60 seconds |
slowdowns_due_to_io_lag | integer | Number of seconds since last node start that disk writes were slowed due to REDO log I/O lag |
slowdowns_due_to_high_cpu | integer | Number of seconds since last node start that disk writes were slowed due to high CPU usage |
disk_write_speed_set_to_min | integer | Number of seconds since last node start that disk write speed was set to minimum |
current_target_disk_write_speed | integer | Actual speed of disk writes per LDM thread (aggregated) |
The disk_write_speed_aggregate_node
table
provides aggregated information per node about the speed of disk
writes during LCP, backup, and restore operations.
The following table provides information about the columns in
the disk_write_speed_aggregate_node
table.
For each column, the table shows the name, data type, and a
brief description. Additional information can be found in the
notes following the table.
Column Name | Type | Description |
---|---|---|
node_id | integer | Node ID of this node |
backup_lcp_speed_last_sec | numeric | Number of bytes written to disk by backup and LCP processes in the last second |
redo_speed_last_sec | numeric | Number of bytes written to REDO log in the last second |
backup_lcp_speed_last_10sec | numeric | Number of bytes written to disk by backup and LCP processes per second, averaged over the last 10 seconds |
redo_speed_last_10sec | numeric | Number of bytes written to REDO log per second, averaged over the last 10 seconds |
backup_lcp_speed_last_60sec | numeric | Number of bytes written to disk by backup and LCP processes per second, averaged over the last 60 seconds |
redo_speed_last_60sec | numeric | Number of bytes written to disk by backup and LCP processes per second, averaged over the last 60 seconds |
The diskpagebuffer
table provides statistics
about disk page buffer usage by MySQL Cluster Disk Data tables.
The following table provides information about the columns in
the diskpagebuffer
table. For each column,
the table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Column Name | Type | Description |
---|---|---|
node_id | integer | The data node ID |
block_instance | integer | Block instance |
pages_written | integer | Number of pages written to disk. |
pages_written_lcp | integer | Number of pages written by local checkpoints. |
pages_read | integer | Number of pages read from disk |
log_waits | integer | Number of page writes waiting for log to be written to disk |
page_requests_direct_return | integer | Number of requests for pages that were available in buffer |
page_requests_wait_queue | integer | Number of requests that had to wait for pages to become available in buffer |
page_requests_wait_io | integer | Number of requests that had to be read from pages on disk (pages were unavailable in buffer) |
You can use this table with MySQL Cluster Disk Data tables to
determine whether
DiskPageBufferMemory
is
sufficiently large to allow data to be read from the buffer
rather from disk; minimizing disk seeks can help improve
performance of such tables.
You can determine the proportion of reads from
DiskPageBufferMemory
to
the total number of reads using a query such as this one, which
obtains this ratio as a percentage:
SELECT node_id, 100 * page_requests_direct_return / (page_requests_direct_return + page_requests_wait_io) AS hit_ratio FROM ndbinfo.diskpagebuffer;
The result from this query should be similar to what is shown here, with one row for each data node in the cluster (in this example, the cluster has 4 data nodes):
+---------+-----------+ | node_id | hit_ratio | +---------+-----------+ | 5 | 97.6744 | | 6 | 97.6879 | | 7 | 98.1776 | | 8 | 98.1343 | +---------+-----------+ 4 rows in set (0.00 sec)
hit_ratio
values approaching 100% indicate
that only a very small number of reads are being made from disk
rather than from the buffer, which means that Disk Data read
performance is approaching an optimum level. If any of these
values are less than 95%, this is a strong indicator that the
setting for
DiskPageBufferMemory
needs to be increased in the config.ini
file.
A change in
DiskPageBufferMemory
requires a rolling restart of all of the cluster's data
nodes before it takes effect.
The locks_per_fragment
table provides
information about counts of lock claim requests, and the
outcomes of these requests on a per-fragment basis, serving as a
companion table to
operations_per_fragment
and
memory_per_fragment
. This
table also shows the total time spent waiting for locks
successfully and unsuccessfully since fragment or table
creation, or since the most recent restart.
The following table provides information about the columns in
the locks_per_fragment
table. For each
column, the table shows the name, data type, and a brief
description. Additional information can be found in the notes
following the table.
Column Name | Type | Description |
---|---|---|
fq_name | string | Fully qualified table name |
parent_fq_name | string | Fully qualified name of parent object |
type | string | Table type; see text for possible values |
table_id | integer | Table ID |
node_id | integer | Reporting node ID |
block_instance | integer | LDM instance ID |
fragment_num | integer | Fragment identifier |
ex_req | integer | Exclusive lock requests started |
ex_imm_ok | integer | Exclusive lock requests immediately granted |
ex_wait_ok | integer | Exclusive lock requests granted following wait |
ex_wait_fail | integer | Exclusive lock requests not granted |
sh_req | integer | Shared lock requests started |
sh_imm_ok | integer | Shared lock requests immediately granted |
sh_wait_ok | integer | Shared lock requests granted following wait |
sh_wait_fail | integer | Shared lock requests not granted |
wait_ok_millis | integer | Time spent waiting for lock requests that were granted, in milliseconds |
wait_fail_millis | integer | Time spent waiting for lock requests that failed, in milliseconds |
fq_name
is a fully qualified database object
name in
database
/schema
/name
format, such as test/def/t1
or
sys/def/10/b$unique
.
parent_fq_name
is the fully qualified name of
this object's parent object (table).
table_id
is the table's internal ID
generated by NDB
. This is the same internal
table ID shown in other ndbinfo
tables; it is
also visible in the output of
ndb_show_tables.
The type
column shows the type of table. This
is always one of System table
, User
table
, Unique hash index
,
Hash index
, Unique ordered
index
, Ordered index
, Hash
index trigger
, Subscription
trigger
, Read only constraint
,
Index trigger
, Reorganize
trigger
, Tablespace
, Log
file group
, Data file
,
Undo file
, Hash map
,
Foreign key definition
, Foreign key
parent trigger
, Foreign key child
trigger
, or Schema transaction
.
The values shown in all of the columns
ex_req
, ex_req_imm_ok
,
ex_wait_ok
, ex_wait_fail
,
sh_req
, sh_req_imm_ok
,
sh_wait_ok
, and
sh_wait_fail
represent cumulative numbers of
requests since the table or fragment was created, or since the
last restart of this node, whichever of these occurred later.
This is also true for the time values shown in the
wait_ok_millis
and
wait_fail_millis
columns.
Every lock request is considered either to be in progress, or to have completed in some way (that is, to have succeeded or failed). This means that the following relationships are true:
ex_req >= (ex_req_imm_ok + ex_wait_ok + ex_wait_fail) sh_req >= (sh_req_imm_ok + sh_wait_ok + sh_wait_fail)
The number of requests currently in progress is the current number of incomplete requests, which can be found as shown here:
[exclusive lock requests in progress] = ex_req - (ex_req_imm_ok + ex_wait_ok + ex_wait_fail) [shared lock requests in progress] = sh_req - (sh_req_imm_ok + sh_wait_ok + sh_wait_fail)
A failed wait indicates an aborted transaction, but the abort may or may not be caused by a lock wait timeout. You can obtain the total number of aborts while waiting for locks as shown here:
[aborts while waiting for locks] = ex_wait_fail + sh_wait_fail
The locks_per_fragment
table was added in
MySQL Cluster NDB 7.5.3.
The logbuffer
table provides information on
MySQL Cluster log buffer usage.
The following table provides information about the columns in
the logbuffers
table. For each column, the
table shows the name, data type, and a brief description.
Column Name | Type | Description |
---|---|---|
node_id | integer | The ID of this data node. |
log_type | string | Type of log; one of: REDO or
DD-UNDO . |
log_id | integer | The log ID. |
log_part | integer | The log part number. |
total | integer | Total space available for this log. |
used | integer | Space used by this log. |
This table provides information about MySQL Cluster log space usage.
The following table provides information about the columns in
the logspaces
table. For each column, the
table shows the name, data type, and a brief description.
Column Name | Type | Description |
---|---|---|
node_id | integer | The ID of this data node. |
log_type | string | Type of log; one of: REDO or
DD-UNDO . |
log_id | integer | The log ID. |
log_part | integer | The log part number. |
total | integer | Total space available for this log. |
used | integer | Space used by this log. |
The membership
table describes the view that
each data node has of all the others in the cluster, including
node group membership, president node, arbitrator, arbitrator
successor, arbitrator connection states, and other information.
The following table provides information about the columns in
the membership
table. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Column Name | Type | Description |
---|---|---|
node_id | integer | This node's node ID |
group_id | integer | Node group to which this node belongs |
left node | integer | Node ID of the previous node |
right_node | integer | Node ID of the next node |
president | integer | President's node ID |
successor | integer | Node ID of successor to president |
succession_order | integer | Order in which this node succeeds to presidency |
Conf_HB_order | integer | - |
arbitrator | integer | Node ID of arbitrator |
arb_ticket | string | Internal identifier used to track arbitration |
arb_state | Enumeration (see text) | Arbitration state |
arb_connected | Yes or No | Whether this node is connected to the arbitrator |
connected_rank1_arbs | List of node IDs | Connected arbitrators of rank 1 |
connected_rank2_arbs | List of node IDs | Connected arbitrators of rank 1 |
The node ID and node group ID are the same as reported by ndb_mgm -e "SHOW".
left_node
and right_node
are defined in terms of a model that connects all data nodes in
a circle, in order of their node IDs, similar to the ordering of
the numbers on a clock dial, as shown here:
In this example, we have 8 data nodes, numbered 5, 6, 7, 8, 12, 13, 14, and 15, ordered clockwise in a circle. We determine “left” and “right” from the interior of the circle. The node to the left of node 5 is node 15, and the node to the right of node 5 is node 6. You can see all these relationships by running the following query and observing the output:
mysql>SELECT node_id,left_node,right_node
->FROM ndbinfo.membership;
+---------+-----------+------------+ | node_id | left_node | right_node | +---------+-----------+------------+ | 5 | 15 | 6 | | 6 | 5 | 7 | | 7 | 6 | 8 | | 8 | 7 | 12 | | 12 | 8 | 13 | | 13 | 12 | 14 | | 14 | 13 | 15 | | 15 | 14 | 5 | +---------+-----------+------------+ 8 rows in set (0.00 sec)
The designations “left” and “right” are used in the event log in the same way.
The president
node is the node viewed by the
current node as responsible for setting an arbitrator (see
MySQL Cluster Start Phases). If the president
fails or becomes disconnected, the current node expects the node
whose ID is shown in the successor
column to
become the new president. The
succession_order
column shows the place in
the succession queue that the current node views itself as
having.
In a normal MySQL Cluster, all data nodes should see the same
node as president
, and the same node (other
than the president) as its successor
. In
addition, the current president should see itself as
1
in the order of succession, the
successor
node should see itself as
2
, and so on.
All nodes should show the same arb_ticket
values as well as the same arb_state
values.
Possible arb_state
values are
ARBIT_NULL
, ARBIT_INIT
,
ARBIT_FIND
, ARBIT_PREP1
,
ARBIT_PREP2
, ARBIT_START
,
ARBIT_RUN
, ARBIT_CHOOSE
,
ARBIT_CRASH
, and UNKNOWN
.
arb_connected
shows whether this node is
connected to the node shown as this node's
arbitrator
.
The connected_rank1_arbs
and
connected_rank2_arbs
columns each display a
list of 0 or more arbitrators having an
ArbitrationRank
equal to
1, or to 2, respectively.
Both management nodes and API nodes are eligible to become arbitrators.
Querying this table provides information similar to that
provided by the ALL REPORT
MemoryUsage
command in the ndb_mgm
client, or logged by ALL DUMP
1000
.
The following table provides information about the columns in
the memoryusage
table. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Column Name | Type | Description |
---|---|---|
node_id | integer | The node ID of this data node. |
memory_type | string | One of Data memory , Index memory ,
or Long message buffer . |
used | integer | Number of bytes currently used for data memory or index memory by this data node. |
used_pages | integer | Number of pages currently used for data memory or index memory by this data node; see text. |
total | integer | Total number of bytes of data memory or index memory available for this data node; see text. |
total_pages | integer | Total number of memory pages available for data memory or index memory on this data node; see text. |
The total
column represents the total amount
of memory in bytes available for the given resource (data memory
or index memory) on a particular data node. This number should
be approximately equal to the setting of the corresponding
configuration parameter in the config.ini
file.
Suppose that the cluster has 2 data nodes having node IDs
5
and 6
, and the
config.ini
file contains the following:
[ndbd default] DataMemory = 1G IndexMemory = 1G
Suppose also that the value of the
LongMessageBuffer
configuration parameter is allowed to assume its default (64
MB).
The following query shows approximately the same values:
mysql> SELECT node_id, memory_type, total > FROM ndbinfo.memoryusage; +---------+---------------------+------------+ | node_id | memory_type | total | +---------+---------------------+------------+ | 5 | Data memory | 1073741824 | | 5 | Index memory | 1074003968 | | 5 | Long message buffer | 67108864 | | 6 | Data memory | 1073741824 | | 6 | Index memory | 1074003968 | | 6 | Long message buffer | 67108864 | +---------+---------------------+------------+ 6 rows in set (0.00 sec)
In this case, the total
column values for
index memory are slightly higher than the value set of
IndexMemory
due to
internal rounding.
For the used_pages
and
total_pages
columns, resources are measured
in pages, which are 32K in size for
DataMemory
and 8K for
IndexMemory
. For long
message buffer memory, the page size is 256 bytes.
The memory_per_fragment
table provides
information about the usage of memory by indidivual fragments.
The following table provides information about the columns in
the memory_per_fragment
table. For each
column, the table shows the name, data type, and a brief
description. Additional information can be found in the notes
following the table.
Column Name | Type | Description |
---|---|---|
fq_name | string | Name of this fragment |
parent_fq_name | string | Name of this fragment's parent |
type | string | Type of object; see text for possible values |
table_id | integer | Table ID for this table |
node_id | integer | Node ID for this node |
block_instance | integer | Kernel block instance ID |
fragment_num | integer | Fragment ID (number) |
fixed_elem_alloc_bytes | integer | Number of bytes allocated for fixed-sized elements |
fixed_elem_free_bytes | integer | Free bytes remaining in pages allocated to fixed-size elements |
fixed_elem_size_bytes | integer | Length of each fixed-size element in bytes |
fixed_elem_count | integer | Number of fixed-size elements |
fixed_elem_free_rows | decimal | Number of free rows for fixed-size elements |
var_elem_alloc_bytes | integer | Number of bytes allocated for variable-size elements |
var_elem_free_bytes | integer | Free bytes remaining in pages allocated to variable-size elements |
var_elem_count | integer | Number of variable-size elements |
hash_index_alloc_bytes | integer | Number of bytes allocated to hash indexes |
The type
column from this table shows the
dictionary object type used for this fragment
(Object::Type
, in the NDB API),
and can take any one of the values shown in the following list:
System table
User table
Unique hash index
Hash index
Unique ordered index
Ordered index
Hash index trigger
Subscription trigger
Read only constraint
Index trigger
Reorganize trigger
Tablespace
Log file group
Data file
Undo file
Hash map
Foreign key definition
Foreign key parent trigger
Foreign key child trigger
Schema transaction
You can also obtain this list by executing
SELECT * FROM
ndbinfo.dict_obj_types
in the
mysql client.
This table contains information on the status of data nodes. For each data node that is running in the cluster, a corresponding row in this table provides the node's node ID, status, and uptime. For nodes that are starting, it also shows the current start phase.
The following table provides information about the columns in
the nodes
table. For each column, the table
shows the name, data type, and a brief description. Additional
information can be found in the notes following the table.
Column Name | Type | Description |
---|---|---|
node_id | integer | The data node's unique node ID in the cluster. |
uptime | integer | Time since the node was last started, in seconds. |
status | string | Current status of the data node; see text for possible values. |
start_phase | integer | If the data node is starting, the current start phase. |
config_generation | integer | The version of the cluster configuration file in use on this data node. |
The uptime
column shows the time in seconds
that this node has been running since it was last started or
restarted. This is a BIGINT
value. This figure includes the time actually needed to start
the node; in other words, this counter starts running the moment
that ndbd or ndbmtd is
first invoked; thus, even for a node that has not yet finished
starting, uptime
may show a non-zero value.
The status
column shows the node's
current status. This is one of: NOTHING
,
CMVMI
, STARTING
,
STARTED
, SINGLEUSER
,
STOPPING_1
, STOPPING_2
,
STOPPING_3
, or STOPPING_4
.
When the status is STARTING
, you can see the
current start phase in the start_phase
column
(see later in this section). SINGLEUSER
is
displayed in the status
column for all data
nodes when the cluster is in single user mode (see
Section 19.5.8, “MySQL Cluster Single User Mode”). Seeing one of
the STOPPING
states does not necessarily mean
that the node is shutting down but can mean rather that it is
entering a new state; for example, if you put the cluster in
single user mode, you can sometimes see data nodes report their
state briefly as STOPPING_2
before the status
changes to SINGLEUSER
.
The start_phase
column uses the same range of
values as those used in the output of the
ndb_mgm client
command (see
Section 19.5.2, “Commands in the MySQL Cluster Management Client”). If the
node is not currently starting, then this column shows
node_id
STATUS0
. For a listing of MySQL Cluster start
phases with descriptions, see
Section 19.5.1, “Summary of MySQL Cluster Start Phases”.
The config_generation
column shows which
version of the cluster configuration is in effect on each data
node. This can be useful when performing a rolling restart of
the cluster in order to make changes in configuration
parameters. For example, from the output of the following
SELECT
statement, you can see
that node 3 is not yet using the latest version of the cluster
configuration (6
) although nodes 1, 2, and 4
are doing so:
mysql>USE ndbinfo;
Database changed mysql>SELECT * FROM nodes;
+---------+--------+---------+-------------+-------------------+ | node_id | uptime | status | start_phase | config_generation | +---------+--------+---------+-------------+-------------------+ | 1 | 10462 | STARTED | 0 | 6 | | 2 | 10460 | STARTED | 0 | 6 | | 3 | 10457 | STARTED | 0 | 5 | | 4 | 10455 | STARTED | 0 | 6 | +---------+--------+---------+-------------+-------------------+ 2 rows in set (0.04 sec)
Therefore, for the case just shown, you should restart node 3 to complete the rolling restart of the cluster.
Nodes that are stopped are not accounted for in this table. Suppose that you have a MySQL Cluster with 4 data nodes (node IDs 1, 2, 3 and 4), and all nodes are running normally, then this table contains 4 rows, 1 for each data node:
mysql>USE ndbinfo;
Database changed mysql>SELECT * FROM nodes;
+---------+--------+---------+-------------+-------------------+ | node_id | uptime | status | start_phase | config_generation | +---------+--------+---------+-------------+-------------------+ | 1 | 11776 | STARTED | 0 | 6 | | 2 | 11774 | STARTED | 0 | 6 | | 3 | 11771 | STARTED | 0 | 6 | | 4 | 11769 | STARTED | 0 | 6 | +---------+--------+---------+-------------+-------------------+ 4 rows in set (0.04 sec)
If you shut down one of the nodes, only the nodes that are still
running are represented in the output of this
SELECT
statement, as shown here:
ndb_mgm> 2 STOP
Node 2: Node shutdown initiated
Node 2: Node shutdown completed.
Node 2 has shutdown.
mysql> SELECT * FROM nodes;
+---------+--------+---------+-------------+-------------------+
| node_id | uptime | status | start_phase | config_generation |
+---------+--------+---------+-------------+-------------------+
| 1 | 11807 | STARTED | 0 | 6 |
| 3 | 11802 | STARTED | 0 | 6 |
| 4 | 11800 | STARTED | 0 | 6 |
+---------+--------+---------+-------------+-------------------+
3 rows in set (0.02 sec)
The operations_per_fragment
table provides
information about the operations performed on indidivual
fragments and fragment replicas, as well as about some of the
results from these operations.
The following table provides information about the columns in
the operations_per_fragment
table. For each
column, the table shows the name, data type, and a brief
description. Additional information can be found in the notes
following the table.
Column Name | Type | Description |
---|---|---|
fq_name | string | Name of this fragment |
parent_fq_name | string | Name of this fragment's parent |
type | string | Type of object; see text for possible values |
table_id | integer | Table ID for this table |
node_id | integer | Node ID for this node |
block_instance | integer | Kernel block instance ID |
fragment_num | integer | Fragment ID (number) |
tot_key_reads | integer | Total number of key reads for this fragment replica |
tot_key_inserts | integer | Total number of key inserts for this fragment replica |
tot_key_updates | integer | total number of key updates for this fragment replica |
tot_key_writes | integer | Total number of key writes for this fragment replica |
tot_key_deletes | integer | Total number of key deletes for this fragment replica |
tot_key_refs | integer | Number of key operations refused |
tot_key_attrinfo_bytes | integer | Total size of all attrinfo attributes |
tot_key_keyinfo_bytes | integer | Total size of all keyinfo attributes |
tot_key_prog_bytes | integer | Total size of all interpreted programs carried by
attrinfo attributes |
tot_key_inst_exec | integer | Total number of instructions executed by interpeted programs for key operations |
tot_key_bytes_returned | integer | Total size of all data and metadata returned from key read operations |
tot_frag_scans | integer | Total number of scans performed on this fragment replica |
tot_scan_rows_examined | integer | Total number of rows examined by scans |
tot_scan_rows_returned | integer | Total number of rows returned to client |
tot_scan_bytes_returned | ineteger | Total size of data and metadata returned to the client |
tot_scan_prog_bytes | integer | Total size of interpreted programs for scan operations |
tot_scan_bound_bytes | integer | Total size of all bounds used in ordered index scans |
tot_scan_inst_exec | integer | Total number of instructions executed for scans |
tot_qd_frag_scans | integer | Number of times that scans of this fragment replica have been queued |
conc_frag_scans | integer | Number of scans currently active on this fragment replica (excluding queued scans) |
conc_qd_frag_scans | integer | Number of scans currently queued for this fragment replica |
tot_commits | integer | Total number of row changes committed to this fragment replica |
The fq_name
contains the fully qualified name
of the schema object to which this fragment replica belongs.
This currently has the following formats:
Base table: -
DbName
/def/TblName
BLOB
table: -
DbName
/def/NDB$BLOB_BaseTblId
_ColNo
Ordered index: -
sys/def/
BaseTblId
/IndexName
Unique index: -
sys/def/
BaseTblId
/IndexName
$unique
The $unique
suffix shown for unique indexes
is added by mysqld; for an index created by a
different NDB API client application, this may differ, or not be
present.
The syntax just shown for fully qualified object names is an internal interface which is subject to change in future releases.
Consider a table t1
created and modified by
the following SQL statements:
CREATE DATABASE mydb; USE mydb; CREATE TABLE t1 ( a INT NOT NULL, b INT NOT NULL, t TEXT NOT NULL, PRIMARY KEY (b) ) ENGINE=ndbcluster; CREATE UNIQUE INDEX ix1 ON t1(b) USING HASH;
If t1
is assigned table ID 11, this yields
the fq_name
values shown here:
Base table: mydb/def/t1
BLOB
table:
mydb/def/NDB$BLOB_11_2
Ordered index (primary key):
sys/def/11/PRIMARY
Unique index: sys/def/11/ix1$unique
For indexes or BLOB
tables, the
parent_fq_name
column contains the
fq_name
of the corresponding base table. For
base tables, this column is always NULL
.
The type
column shows the schema object type
used for this fragment, which can take any one of the values
System table
, User table
,
Unique hash index
, or Ordered
index
. BLOB
tables are shown as
User table
.
The table_id
column value is unique at any
given time, but can be reused if the corresponding object has
been deleted. The same ID can be seen using the
ndb_show_tables utility.
The block_instance
column shows which LDM
instance this fragment replica belongs to. The first such
instance is always numbered 0.
Since there are typically two replicas, and assuming that this
is so, each fragment_num
value should appear
twice in the table, on two different data nodes from the same
node group.
Since NDB
does not use single-key access for
ordered indexes, the counts for
tot_key_reads
,
tot_key_inserts
,
tot_key_updates
,
tot_key_writes
, and
tot_key_deletes
are not incremented by
ordered index operations.
When using tot_key_writes
, you should keep
in mind that a write operation in this context updates the row
if the key exists, and inserts a new row otherwise. (One use
of this is in the NDB
implementation of the
REPLACE
SQL statement.)
The tot_key_refs
column shows the number of
key operations refused by the LDM. Generally, such a refusal is
due to duplicate keys (inserts), Key not
found errors (updates, deletes, and reads), or the
operation was rejected by an interpreted program used as a
predicate on the row matching the key.
The attrinfo
and keyinfo
attributes counted by the
tot_key_attrinfo_bytes
and
tot_key_keyinfo_bytes
columns are attributes
of an LQHKEYREQ
signal (see
The NDB Communication Protocol) used to initiate a
key operation by the LDM. An attrinfo
typically contains tuple field values (inserts and updates) or
projection specifications (for reads);
keyinfo
contains the primary or unique key
needed to locate a given tuple in this schema object.
The value shown by tot_frag_scans
includes
both full scans (that examine every row) and scans of subsets.
Unique indexes and BLOB
tables are never
scanned, so this value, like other scan-related counts, is 0 for
fragment replicas of these.
tot_scan_rows_examined
may display less than
the total number of rows in a given fragment replica, since
ordered index scans can limited by bounds. In addition, a client
may choose to end a scan before all potentially matching rows
have been examined; this occurs when using an SQL statement
containing a LIMIT
or
EXISTS
clause, for example.
tot_scan_rows_returned
is always less than or
equal to tot_scan_rows_examined
.
tot_scan_bytes_returned
includes, in the case
of pushed joins, projections returned to the
DBSPJ
block in the NDB kernel.
tot_qd_frag_scans
can be effected by the
setting for the
MaxParallelScansPerFragment
data node configuration parameter, which limits the number of
scans that may execute concurrently on a single fragment
replica.
This table provides information about data node resource availability and usage.
These resources are sometimes known as super-pools.
The following table provides information about the columns in
the resources
table. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Column Name | Type | Description |
---|---|---|
node_id | integer | The unique node ID of this data node. |
resource_name | string | Name of the resource; see text. |
reserved | integer | The amount reserved for this resource. |
used | integer | The amount actually used by this resource. |
max | integer | The maximum amount of this resource used, since the node was last started. |
The resource_name
can be one of the names
shown in the following table:
Resource name | Description |
---|---|
RESERVED | Reserved by the system; cannot be overridden. |
DISK_OPERATIONS | If a log file group is allocated, the size of the undo log buffer is
used to set the size of this resource. This resource is
used only to allocate the undo log buffer for an undo
log file group; there can only be one such group.
Overallocation occurs as needed by
CREATE LOGFILE GROUP . |
DISK_RECORDS | Records allocated for Disk Data operations. |
DATA_MEMORY | Used for main memory tuples, indexes, and hash indexes. Sum of DataMemory and IndexMemory, plus 8 pages of 32 KB each if IndexMemory has been set. Cannot be overallocated. |
JOBBUFFER | Used for allocating job buffers by the NDB scheduler; cannot be overallocated. This is approximately 2 MB per thread plus a 1 MB buffer in both directions for all threads that can communicate. For large configurations this consume several GB. |
FILE_BUFFERS | Used by the redo log handler in the DBLQH kernel
block; cannot be overallocated. Size is
NoOfFragmentLogParts
* RedoBuffer ,
plus 1 MB per log file part. |
TRANSPORTER_BUFFERS | Used for send buffers by ndbmtd; the sum of
TotalSendBufferMemory
and
ExtraSendBufferMemory .
This resource that can be overallocated by up to 25
percent. TotalSendBufferMemory is
calculated by summing the send buffer memory per node,
the default value of which is 2 MB. Thus, in a system
having four data nodes and eight API nodes, the data
nodes have 12 * 2 MB send buffer memory.
ExtraSendBufferMemory is used by
ndbmtd and amounts to 2 MB extra
memory per thread. Thus, with 4 LDM threads, 2 TC
threads, 1 main thread, 1 replication thread, and 2
receive threads,
ExtraSendBufferMemory is 10 * 2 MB.
Overallocation of this resource can be performed by
setting the
SharedGlobalMemory
data node configuration parameter. |
DISK_PAGE_BUFFER | Used for the disk page buffer; determined by the
DiskPageBufferMemory
configuration parameter. Cannot be overallocated. |
QUERY_MEMORY | Used by the DBSPJ kernel block. |
SCHEMA_TRANS_MEMORY | Minimum is 2 MB; can be overallocated to use any remaining available memory. |
The restart_info
table contains information
about node restart operations. Each entry in the table
corresponds to a node restart status report in real time from a
data node with the given node ID. Only the most recent report
for any given node is shown.
The following table provides information about the columns in
the restart_info
table. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Column Name | Type | Description |
---|---|---|
node_id | integer | Node ID in the cluster |
node_restart_status | VARCHAR(256) | Node status; see text for values. Each of these corresponds to a
possible value of
node_restart_status_int . |
node_restart_status_int | integer | Node status code; see text for values. |
secs_to_complete_node_failure | integer | Time in seconds to complete node failure handling |
secs_to_allocate_node_id | integer | Time in seconds from node failure completion to allocation of node ID |
secs_to_include_in_heartbeat_protocol | integer | Time in seconds from allocation of node ID to inclusion in heartbeat protocol |
secs_until_wait_for_ndbcntr_master | integer | Time in seconds from being included in heartbeat protocol until waiting
for NDBCNTR master began |
secs_wait_for_ndbcntr_master | integer | Time in seconds spent waiting to be accepted by
NDBCNTR master for starting |
secs_to_get_start_permitted | integer | Time in seconds elapsed from receiving of permission for start from master until all nodes have accepted start of this node |
secs_to_wait_for_lcp_for_copy_meta_data | integer | Time in seconds spent waiting for LCP completion before copying meta data |
secs_to_copy_meta_data | integer | Time in seconds required to copy metadata from master to newly starting node |
secs_to_include_node | integer | Time in seconds waited for GCP and inclusion of all nodes into protocols |
secs_starting_node_to_request_local_recovery | integer | Time in seconds that the node just starting spent waiting to request local recovery |
secs_for_local_recovery | integer | Time in seconds required for local recovery by node just starting |
secs_restore_fragments | integer | Time in seconds required to restore fragments from LCP files |
secs_undo_disk_data | integer | Time in seconds required to execute undo log on disk data part of records |
secs_exec_redo_log | integer | Time in seconds required to execute redo log on all restored fragments |
secs_index_rebuild | integer | Time in seconds required to rebuild indexes on restored fragments |
secs_to_synchronize_starting_node | integer | Time in seconds required to synchronize starting node from live nodes |
secs_wait_lcp_for_restart | integer | Time in seconds required for LCP start and completion before restart was completed |
secs_wait_subscription_handover | integer | Time in seconds spent waiting for handover of replication subscriptions |
total_restart_secs | integer | Total number of seconds from node failure until node is started again |
Defined values for node_restart_status_int
and corresponding status names and messages
(node_restart_status
) are shown in the
following table:
node_restart_status_int value | Status | Message (node_restart_status) |
---|---|---|
0 | ALLOCATED_NODE_ID | Allocated node id |
1 | INCLUDED_IN_HB_PROTOCOL | Included in heartbeat protocol |
2 | NDBCNTR_START_WAIT | Wait for NDBCNTR master to permit us to start |
3 | NDBCNTR_STARTED | NDBCNTR master permitted us to start |
4 | START_PERMITTED | All nodes permitted us to start |
5 | WAIT_LCP_TO_COPY_DICT | Wait for LCP completion to start copying metadata |
6 | COPY_DICT_TO_STARTING_NODE | Copying metadata to starting node |
7 | INCLUDE_NODE_IN_LCP_AND_GCP | Include node in LCP and GCP protocols |
8 | LOCAL_RECOVERY_STARTED | Restore fragments ongoing |
9 | COPY_FRAGMENTS_STARTED | Synchronizing starting node with live nodes |
10 | WAIT_LCP_FOR_RESTART | Wait for LCP to ensure durability |
11 | WAIT_SUMA_HANDOVER | Wait for handover of subscriptions |
12 | RESTART_COMPLETED | Restart completed |
13 | NODE_FAILED | Node failed, failure handling in progress |
14 | NODE_FAILURE_COMPLETED | Node failure handling completed |
15 | NODE_GETTING_PERMIT | All nodes permitted us to start |
16 | NODE_GETTING_INCLUDED | Include node in LCP and GCP protocols |
17 | NODE_GETTING_SYNCHED | Synchronizing starting node with live nodes |
18 | NODE_GETTING_LCP_WAITED | [none] |
19 | NODE_ACTIVE | Restart completed |
20 | NOT_DEFINED_IN_CLUSTER | [none] |
21 | NODE_NOT_RESTARTED_YET | Initial state |
Status numbers 0 through 12 apply on master nodes only; the remainder of those shown in the table apply to all restarting data nodes. Status numbers 13 and 14 define node failure states; 20 and 21 occur when no information about the restart of a given node is available.
See also Section 19.5.1, “Summary of MySQL Cluster Start Phases”.
The server_locks
table is similar in
structure to the cluster_locks
table, and
provides a subset of the information found in the latter table,
but which is specific to the SQL node (MySQL server) where it
resides. (The cluster_locks
table provides
information about all locks in the cluster.) More precisely,
server_locks
contains information about locks
requested by threads belonging to the current
mysqld instance, and serves as a companion
table to server_operations
.
This may be useful for correlating locking patterns with
specific MySQL user sessions, queries, or use cases.
The following table provides information about the columns in
the server_locks
table. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Column Name | Type | Description |
---|---|---|
mysql_connection_id | insteger | MySQL connection ID |
node_id | integer | ID of reporting node |
block_instance | integer | ID of reporting LDM instance |
tableid | integer | ID of table containing this row |
fragmentid | integer | ID of fragment containing locked row |
rowid | integer | ID of locked row |
transid | integer | Transaction ID |
mode | string | Lock request mode |
state | string | Lock state |
detail | string | Whether this is first holding lock in row lock queue |
op | string | Operation type |
duration_millis | integer | Milliseconds spent waiting or holding lock |
lock_num | integer | ID of lock object |
waiting_for | integer | Waiting for lock with this ID |
The mysql_connection_id
column shows the
MySQL connection or thread ID as shown by
SHOW PROCESSLIST
.
The tableid
is assigned to the table by
NDB
; the same ID is used for this table in
other ndbinfo
tables, as well as in the
output of ndb_show_tables.
The transaction ID shown in the transid
column is the identifier generated by the NDB API for the
transaction requesting or holding the current lock.
The mode
column shows the lock mode, which is
always one of S
(shared lock) or
X
(exclusive lock). If a transaction has an
exclusive lock on a given row, all other locks on that row have
the same transaction ID.
The state
column shows the lock state. Its
value is always one of H
(holding) or
W
(waiting). A waiting lock request waits for
a lock held by a different transaction.
The detail
column indicates whether this lock
is the first holding lock in the affected row's lock queue,
in which case it contains a *
(asterisk
character); otherwise, this column is empty. This information
can be used to help identify the unique entries in a list of
lock requests.
The op
column shows the type of operation
requesting the lock. This is always one of the values
READ
, INSERT
,
UPDATE
, DELETE
,
SCAN
, or REFRESH
.
The duration_millis
column shows the number
of milliseconds for which this lock request has been waiting or
holding the lock. This is reset to 0 when a lock is granted for
a waiting request.
The lock ID (lockid
column) is unique to this
node and block instance.
If the lock_state
column's value is
W
, this lock is waiting to be granted, and
the waiting_for
column shows the lock ID of
the lock object this request is waiting for. Otherwise,
waiting_for
is empty.
waiting_for
can refer only to locks on the
same row (as identified by node_id
,
block_instance
, tableid
,
fragmentid
, and rowid
).
The server_locks
table was added in MySQL
Cluster NDB 7.5.3.
The server_operations
table contains entries
for all ongoing NDB
operations that
the current SQL node (MySQL Server) is currently involved in. It
effectively is a subset of the
cluster_operations
table, in
which operations for other SQL and API nodes are not shown.
The following table provides information about the columns in
the server_operations
table. For each column,
the table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Column Name | Type | Description |
---|---|---|
mysql_connection_id | integer | MySQL Server connection ID |
node_id | integer | Node ID |
block_instance | integer | Block instance |
transid | integer | Transaction ID |
operation_type | string | Operation type (see text for possible values) |
state | string | Operation state (see text for possible values) |
tableid | integer | Table ID |
fragmentid | integer | Fragment ID |
client_node_id | integer | Client node ID |
client_block_ref | integer | Client block reference |
tc_node_id | integer | Transaction coordinator node ID |
tc_block_no | integer | Transaction coordinator block number |
tc_block_instance | integer | Transaction coordinator block instance |
The mysql_connection_id
is the same as the
connection or session ID shown in the output of
SHOW PROCESSLIST
. It is obtained
from the INFORMATION_SCHEMA
table
NDB_TRANSID_MYSQL_CONNECTION_MAP
.
The transaction ID is a unique 64-bit number which can be
obtained using the NDB API's
getTransactionId()
method. (Currently, the MySQL Server does not expose the NDB API
transaction ID of an ongoing transaction.)
The operation_type
column can take any one of
the values READ
, READ-SH
,
READ-EX
, INSERT
,
UPDATE
, DELETE
,
WRITE
, UNLOCK
,
REFRESH
, SCAN
,
SCAN-SH
, SCAN-EX
, or
<unknown>
.
The state
column can have any one of the
values ABORT_QUEUED
,
ABORT_STOPPED
, COMMITTED
,
COMMIT_QUEUED
,
COMMIT_STOPPED
,
COPY_CLOSE_STOPPED
,
COPY_FIRST_STOPPED
,
COPY_STOPPED
, COPY_TUPKEY
,
IDLE
, LOG_ABORT_QUEUED
,
LOG_COMMIT_QUEUED
,
LOG_COMMIT_QUEUED_WAIT_SIGNAL
,
LOG_COMMIT_WRITTEN
,
LOG_COMMIT_WRITTEN_WAIT_SIGNAL
,
LOG_QUEUED
, PREPARED
,
PREPARED_RECEIVED_COMMIT
,
SCAN_CHECK_STOPPED
,
SCAN_CLOSE_STOPPED
,
SCAN_FIRST_STOPPED
,
SCAN_RELEASE_STOPPED
,
SCAN_STATE_USED
,
SCAN_STOPPED
, SCAN_TUPKEY
,
STOPPED
, TC_NOT_CONNECTED
,
WAIT_ACC
, WAIT_ACC_ABORT
,
WAIT_AI_AFTER_ABORT
,
WAIT_ATTR
, WAIT_SCAN_AI
,
WAIT_TUP
, WAIT_TUPKEYINFO
,
WAIT_TUP_COMMIT
, or
WAIT_TUP_TO_ABORT
. (If the MySQL Server is
running with
ndbinfo_show_hidden
enabled,
you can view this list of states by selecting from the
ndb$dblqh_tcconnect_state
table, which is
normally hidden.)
You can obtain the name of an NDB
table from
its table ID by checking the output of
ndb_show_tables.
The fragid
is the same as the partition
number seen in the output of ndb_desc
--extra-partition-info
(short
form -p
).
In client_node_id
and
client_block_ref
, client
refers to a MySQL Cluster API or SQL node (that is, an NDB API
client or a MySQL Server attached to the cluster).
The server_transactions
table is subset of
the cluster_transactions
table, but includes only those transactions in which the current
SQL node (MySQL Server) is a participant, while including the
relevant connection IDs.
The following table provides information about the columns in
the server_transactions
table. For each
column, the table shows the name, data type, and a brief
description. Additional information can be found in the notes
following the table.
Column Name | Type | Description |
---|---|---|
mysql_connection_id | integer | MySQL Server connection ID |
node_id | integer | Transaction coordinator node ID |
block_instance | integer | Transaction coordinator block instance |
transid | integer | Transaction ID |
state | string | Operation state (see text for possible values) |
count_operations | integer | Number of stateful operations in the transaction |
outstanding_operations | integer | Operations still being executed by local data management layer (LQH blocks) |
inactive_seconds | integer | Time spent waiting for API |
client_node_id | integer | Client node ID |
client_block_ref | integer | Client block reference |
The mysql_connection_id
is the same as the
connection or session ID shown in the output of
SHOW PROCESSLIST
. It is obtained
from the INFORMATION_SCHEMA
table
NDB_TRANSID_MYSQL_CONNECTION_MAP
.
The transaction ID is a unique 64-bit number which can be
obtained using the NDB API's
getTransactionId()
method. (Currently, the MySQL Server does not expose the NDB API
transaction ID of an ongoing transaction.)
The state
column can have any one of the
values CS_ABORTING
,
CS_COMMITTING
,
CS_COMMIT_SENT
,
CS_COMPLETE_SENT
,
CS_COMPLETING
,
CS_CONNECTED
,
CS_DISCONNECTED
,
CS_FAIL_ABORTED
,
CS_FAIL_ABORTING
,
CS_FAIL_COMMITTED
,
CS_FAIL_COMMITTING
,
CS_FAIL_COMPLETED
,
CS_FAIL_PREPARED
,
CS_PREPARE_TO_COMMIT
,
CS_RECEIVING
,
CS_REC_COMMITTING
,
CS_RESTART
,
CS_SEND_FIRE_TRIG_REQ
,
CS_STARTED
,
CS_START_COMMITTING
,
CS_START_SCAN
,
CS_WAIT_ABORT_CONF
,
CS_WAIT_COMMIT_CONF
,
CS_WAIT_COMPLETE_CONF
,
CS_WAIT_FIRE_TRIG_REQ
. (If the MySQL Server
is running with
ndbinfo_show_hidden
enabled,
you can view this list of states by selecting from the
ndb$dbtc_apiconnect_state
table, which is
normally hidden.)
In client_node_id
and
client_block_ref
, client
refers to a MySQL Cluster API or SQL node (that is, an NDB API
client or a MySQL Server attached to the cluster).
The tc_time_track_stats
table provides
time-tracking information relating to transactions, key
operations, and scan operations performed by
NDB
.
The following table provides information about the columns in
tc_time_track_stats
. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Column Name | Type | Description |
---|---|---|
node_id | integer | Node ID |
block_number | integer | Block number |
block_instance | integer | Block instance |
comm_node_id | integer | Node ID of API or data node |
upper_bound | integer | Upper bound of interval (in microseconds) |
scans | integer | Scan histogram interval |
scan_errors | integer | Scan error histogram interval |
scan_fragments | integer | Scan fragment histogram interval |
scan_fragment_errors | integer | Scan fragment error histogram interval |
transactions | integer | Transaction histogram interval |
transaction_errors | integer | Transaction error histogram interval |
read_key_ops | integer | Read key operation histogram interval |
write_key_ops | integer | Write key operation histogram interval |
index_key_ops | integer | Index key operation histogram interval |
key_op_errors | integer | Key operation error histogram interval |
The threadblocks
table associates data nodes,
threads, and instances of NDB
kernel blocks.
The following table provides information about the columns in
the threadblocks
table. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Column Name | Type | Description |
---|---|---|
node_id | integer | Node ID |
thr_no | integer | Thread ID |
block_name | string | Block name |
block_instance | integer | Block instance number |
The block_name
is one of the values found in
the block_name
column when selecting from the
ndbinfo.blocks
table. Although
the list of possible values is static for a given MySQL Cluster
release, the list may vary between releases.
The threads
table provides information about
threads running in the NDB
kernel.
The following table provides information about the columns in
the threads
table. For each column, the table
shows the name, data type, and a brief description. Additional
information can be found in the notes following the table.
Column Name | Type | Description |
---|---|---|
node_id | integer | ID of the node where the the thread is running |
thr_no | integer | Thread ID (specific to this node) |
thread_name | string | Thread name (type of thread) |
thread_description | string | Thread (type) description |
Sample output from a 2-node example cluster, including thread descriptions, is shown here:
mysql> SELECT * FROM threads;
+---------+--------+-------------+------------------------------------------------------------------+
| node_id | thr_no | thread_name | thread_description |
+---------+--------+-------------+------------------------------------------------------------------+
| 5 | 0 | main | main thread, schema and distribution handling |
| 5 | 1 | rep | rep thread, asynch replication and proxy block handling |
| 5 | 2 | ldm | ldm thread, handling a set of data partitions |
| 5 | 3 | recv | receive thread, performing receieve and polling for new receives |
| 6 | 0 | main | main thread, schema and distribution handling |
| 6 | 1 | rep | rep thread, asynch replication and proxy block handling |
| 6 | 2 | ldm | ldm thread, handling a set of data partitions |
| 6 | 3 | recv | receive thread, performing receieve and polling for new receives |
+---------+--------+-------------+------------------------------------------------------------------+
8 rows in set (0.01 sec)
This table was added in MySQL Cluster NDB 7.5.2.
The threadstat
table provides a rough
snapshot of statistics for threads running in the
NDB
kernel.
The following table provides information about the columns in
the threadstat
table. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Column Name | Type | Description |
---|---|---|
node_id | integer | Node ID |
thr_no | integer | Thread ID |
thr_nm | string | Thread name |
c_loop | string | Number of loops in main loop |
c_exec | string | Number of signals executed |
c_wait | string | Number of times waiting for additional input |
c_l_sent_prioa | integer | Number of priority A signals sent to own node |
c_l_sent_priob | integer | Number of priority B signals sent to own node |
c_r_sent_prioa | integer | Number of priority A signals sent to remote node |
c_r_sent_priob | integer | Number of priority B signals sent to remote node |
os_tid | integer | OS thread ID |
os_now | integer | OS time (ms) |
os_ru_utime | integer | OS user CPU time (µs) |
os_ru_stime | integer | OS system CPU time (µs) |
os_ru_minflt | integer | OS page reclaims (soft page faults) |
os_ru_majflt | integer | OS page faults (hard page faults) |
os_ru_nvcsw | integer | OS voluntary context switches |
os_ru_nivcsw | integer | OS involuntary context switches |
os_time
uses the system
gettimeofday()
call.
The values of the os_ru_utime
,
os_ru_stime
, os_ru_minflt
,
os_ru_majflt
, os_ru_nvcsw
,
and os_ru_nivcsw
columns are obtained using
the system getrusage()
call, or the
equivalent.
Since this table contains counts taken at a given point in time, for best results it is necessary to query this table periodically and store the results in an intermediate table or tables. The MySQL Server's Event Scheduler can be employed to automate such monitoring. For more information, see Section 21.4, “Using the Event Scheduler”.
This table contains information about NDB transporters.
The following table provides information about the columns in
the transporters
table. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Column Name | Type | Description |
---|---|---|
node_id | integer | This data node's unique node ID in the cluster. |
remote_node_id | integer | The remote data node's node ID. |
status | string | Status of the connection. |
remote_address | string | Name or IP address of the remote host |
bytes_sent | integer | Number of bytes sent using this connection |
bytes_received | Number of bytes received using this connection | |
connect_count | Number of times connection established on this transporter | |
overloaded | 1 if this transporter is currently overloaded, otherwise 0 | |
overload_count | Number of times this transporter has entered overload state since connecting | |
slowdown | 1 if this transporter is in scan slowdown state, otherwise 0 | |
slowdown_count | Number of times this transporter has entered scan slowdown state since connecting |
For each running data node in the cluster, the
transporters
table displays a row showing the
status of each of that node's connections with all nodes in
the cluster, including itself. This
information is shown in the table's
status column, which can have any one of
the following values: CONNECTING
,
CONNECTED
, DISCONNECTING
,
or DISCONNECTED
.
Connections to API and management nodes which are configured but
not currently connected to the cluster are shown with status
DISCONNECTED
. Rows where the
node_id
is that of a data nodes which is not
currently connected are not shown in this table. (This is
similar omission of disconnected nodes in the
ndbinfo.nodes
table.
The remote_address
is the host name or
address for the node whose ID is shown in the
remote_node_id
column. The
bytes_sent
from this node and
bytes_received
by this node are the numbers,
respectively, of bytes sent and received by the node using this
connection since it was established. For nodes whose status is
CONNECTING
or
DISCONNECTED
, these columns always display
0
.
The connect_count
,
overloaded
, overload_count
,slowdown
, and
slowdown_count
counters are reset on
connection, and retain their values after the remote node
disconnects. The bytes_send
and
bytes_received
counters are also reset on
connection, and so retain their values following disconnection
(until the next connection resets them).
Assume you have a 5-node cluster consisting of 2 data nodes, 2
SQL nodes, and 1 management node, as shown in the output of the
SHOW
command in the
ndb_mgm client:
ndb_mgm> SHOW
Connected to Management Server at: localhost:1186
Cluster Configuration
---------------------
[ndbd(NDB)] 2 node(s)
id=1 @10.100.10.1 (5.7.13-ndb-7.5.3, Nodegroup: 0, *)
id=2 @10.100.10.2 (5.7.13-ndb-7.5.3, Nodegroup: 0)
[ndb_mgmd(MGM)] 1 node(s)
id=10 @10.100.10.10 (5.7.13-ndb-7.5.3)
[mysqld(API)] 2 node(s)
id=20 @10.100.10.20 (5.7.13-ndb-7.5.3)
id=21 @10.100.10.21 (5.7.13-ndb-7.5.3)
There are 10 rows in the transporters
table—5 for the first data node, and 5 for the
second—assuming that all data nodes are running, as shown
here:
mysql>SELECT node_id, remote_node_id, status
->FROM ndbinfo.transporters;
+---------+----------------+---------------+ | node_id | remote_node_id | status | +---------+----------------+---------------+ | 1 | 1 | DISCONNECTED | | 1 | 2 | CONNECTED | | 1 | 10 | CONNECTED | | 1 | 20 | CONNECTED | | 1 | 21 | CONNECTED | | 2 | 1 | CONNECTED | | 2 | 2 | DISCONNECTED | | 2 | 10 | CONNECTED | | 2 | 20 | CONNECTED | | 2 | 21 | CONNECTED | +---------+----------------+---------------+ 10 rows in set (0.04 sec)
If you shut down one of the data nodes in this cluster using the
command 2 STOP
in the
ndb_mgm client, then repeat the previous
query (again using the mysql client), this
table now shows only 5 rows—1 row for each connection from
the remaining management node to another node, including both
itself and the data node that is currently offline—and
displays CONNECTING
for the status of each
remaining connection to the data node that is currently offline,
as shown here:
mysql>SELECT node_id, remote_node_id, status
->FROM ndbinfo.transporters;
+---------+----------------+---------------+ | node_id | remote_node_id | status | +---------+----------------+---------------+ | 1 | 1 | DISCONNECTED | | 1 | 2 | CONNECTING | | 1 | 10 | CONNECTED | | 1 | 20 | CONNECTED | | 1 | 21 | CONNECTED | +---------+----------------+---------------+ 5 rows in set (0.02 sec)
Two INFORMATION_SCHEMA
tables provide
information that is of particular use when managing a MySQL
Cluster. The FILES
table provides
information about MySQL Cluster Disk Data files. The
ndb_transid_mysql_connection_map
table provides a mapping between transactions, transaction
coordinators, and API nodes.
Additional statistical and other data about MySQL Cluster
transactions, operations, threads, blocks, and other aspects of
performance can be obtained from the tables in the
ndbinfo
database. For
information about these tables, see
Section 19.5.10, “The ndbinfo MySQL Cluster Information Database”.
This section discusses security considerations to take into account when setting up and running MySQL Cluster.
Topics covered in this section include the following:
MySQL Cluster and network security issues
Configuration issues relating to running MySQL Cluster securely
MySQL Cluster and the MySQL privilege system
MySQL standard security procedures as applicable to MySQL Cluster
In this section, we discuss basic network security issues as they relate to MySQL Cluster. It is extremely important to remember that MySQL Cluster “out of the box” is not secure; you or your network administrator must take the proper steps to ensure that your cluster cannot be compromised over the network.
Cluster communication protocols are inherently insecure, and no encryption or similar security measures are used in communications between nodes in the cluster. Because network speed and latency have a direct impact on the cluster's efficiency, it is also not advisable to employ SSL or other encryption to network connections between nodes, as such schemes will effectively slow communications.
It is also true that no authentication is used for controlling API node access to a MySQL Cluster. As with encryption, the overhead of imposing authentication requirements would have an adverse impact on Cluster performance.
In addition, there is no checking of the source IP address for either of the following when accessing the cluster:
SQL or API nodes using “free slots” created by
empty [mysqld]
or
[api]
sections in the
config.ini
file
This means that, if there are any empty
[mysqld]
or [api]
sections in the config.ini
file, then
any API nodes (including SQL nodes) that know the management
server's host name (or IP address) and port can connect to
the cluster and access its data without restriction. (See
Section 19.5.12.2, “MySQL Cluster and MySQL Privileges”,
for more information about this and related issues.)
You can exercise some control over SQL and API node access
to the cluster by specifying a HostName
parameter for all [mysqld]
and
[api]
sections in the
config.ini
file. However, this also
means that, should you wish to connect an API node to the
cluster from a previously unused host, you need to add an
[api]
section containing its host name
to the config.ini
file.
More information is available
elsewhere in this
chapter about the HostName
parameter. Also see Section 19.3.1, “Quick Test Setup of MySQL Cluster”,
for configuration examples using
HostName
with API nodes.
Any ndb_mgm client
This means that any cluster management client that is given
the management server's host name (or IP address) and port
(if not the standard port) can connect to the cluster and
execute any management client command. This includes
commands such as ALL
STOP
and
SHUTDOWN
.
For these reasons, it is necessary to protect the cluster on the network level. The safest network configuration for Cluster is one which isolates connections between Cluster nodes from any other network communications. This can be accomplished by any of the following methods:
Keeping Cluster nodes on a network that is physically separate from any public networks. This option is the most dependable; however, it is the most expensive to implement.
We show an example of a MySQL Cluster setup using such a physically segregated network here:
This setup has two networks, one private (solid box) for the Cluster management servers and data nodes, and one public (dotted box) where the SQL nodes reside. (We show the management and data nodes connected using a gigabit switch since this provides the best performance.) Both networks are protected from the outside by a hardware firewall, sometimes also known as a network-based firewall.
This network setup is safest because no packets can reach the cluster's management or data nodes from outside the network—and none of the cluster's internal communications can reach the outside—without going through the SQL nodes, as long as the SQL nodes do not permit any packets to be forwarded. This means, of course, that all SQL nodes must be secured against hacking attempts.
With regard to potential security vulnerabilities, an SQL node is no different from any other MySQL server. See Section 7.1.3, “Making MySQL Secure Against Attackers”, for a description of techniques you can use to secure MySQL servers.
Using one or more software firewalls (also known as host-based firewalls) to control which packets pass through to the cluster from portions of the network that do not require access to it. In this type of setup, a software firewall must be installed on every host in the cluster which might otherwise be accessible from outside the local network.
The host-based option is the least expensive to implement, but relies purely on software to provide protection and so is the most difficult to keep secure.
This type of network setup for MySQL Cluster is illustrated here:
Using this type of network setup means that there are two zones of MySQL Cluster hosts. Each cluster host must be able to communicate with all of the other machines in the cluster, but only those hosting SQL nodes (dotted box) can be permitted to have any contact with the outside, while those in the zone containing the data nodes and management nodes (solid box) must be isolated from any machines that are not part of the cluster. Applications using the cluster and user of those applications must not be permitted to have direct access to the management and data node hosts.
To accomplish this, you must set up software firewalls that limit the traffic to the type or types shown in the following table, according to the type of node that is running on each cluster host computer:
Type of Node to be Accessed | Traffic to Permit |
---|---|
SQL or API node |
|
Data node or Management node |
|
Any traffic other than that shown in the table for a given node type should be denied.
The specifics of configuring a firewall vary from firewall application to firewall application, and are beyond the scope of this Manual. iptables is a very common and reliable firewall application, which is often used with APF as a front end to make configuration easier. You can (and should) consult the documentation for the software firewall that you employ, should you choose to implement a MySQL Cluster network setup of this type, or of a “mixed” type as discussed under the next item.
It is also possible to employ a combination of the first two methods, using both hardware and software to secure the cluster—that is, using both network-based and host-based firewalls. This is between the first two schemes in terms of both security level and cost. This type of network setup keeps the cluster behind the hardware firewall, but permits incoming packets to travel beyond the router connecting all cluster hosts to reach the SQL nodes.
One possible network deployment of a MySQL Cluster using hardware and software firewalls in combination is shown here:
In this case, you can set the rules in the hardware firewall to deny any external traffic except to SQL nodes and API nodes, and then permit traffic to them only on the ports required by your application.
Whatever network configuration you use, remember that your objective from the viewpoint of keeping the cluster secure remains the same—to prevent any unessential traffic from reaching the cluster while ensuring the most efficient communication between the nodes in the cluster.
Because MySQL Cluster requires large numbers of ports to be open for communications between nodes, the recommended option is to use a segregated network. This represents the simplest way to prevent unwanted traffic from reaching the cluster.
If you wish to administer a MySQL Cluster remotely (that is, from outside the local network), the recommended way to do this is to use ssh or another secure login shell to access an SQL node host. From this host, you can then run the management client to access the management server safely, from within the Cluster's own local network.
Even though it is possible to do so in theory, it is not recommended to use ndb_mgm to manage a Cluster directly from outside the local network on which the Cluster is running. Since neither authentication nor encryption takes place between the management client and the management server, this represents an extremely insecure means of managing the cluster, and is almost certain to be compromised sooner or later.
In this section, we discuss how the MySQL privilege system works in relation to MySQL Cluster and the implications of this for keeping a MySQL Cluster secure.
Standard MySQL privileges apply to MySQL Cluster tables. This
includes all MySQL privilege types
(SELECT
privilege,
UPDATE
privilege,
DELETE
privilege, and so on)
granted on the database, table, and column level. As with any
other MySQL Server, user and privilege information is stored in
the mysql
system database. The SQL statements
used to grant and revoke privileges on
NDB
tables, databases containing
such tables, and columns within such tables are identical in all
respects with the GRANT
and
REVOKE
statements used in
connection with database objects involving any (other) MySQL
storage engine. The same thing is true with respect to the
CREATE USER
and
DROP USER
statements.
It is important to keep in mind that, by default, the MySQL
grant tables use the MyISAM
storage
engine. Because of this, those tables are not normally
duplicated or shared among MySQL servers acting as SQL nodes in
a MySQL Cluster. In other words, changes in users and their
privileges do not automatically propagate between SQL nodes by
default. If you wish, you can enable automatic distribution of
MySQL users and privileges across MySQL Cluster SQL nodes; see
Section 19.5.15, “Distributed MySQL Privileges for MySQL Cluster”, for
details.
Conversely, because there is no way in MySQL to deny privileges
(privileges can either be revoked or not granted in the first
place, but not denied as such), there is no special protection
for NDB
tables on one SQL node from
users that have privileges on another SQL node; (This is true
even if you are not using automatic distribution of user
privileges. The definitive example of this is the MySQL
root
account, which can perform any action on
any database object. In combination with empty
[mysqld]
or [api]
sections
of the config.ini
file, this account can be
especially dangerous. To understand why, consider the following
scenario:
The config.ini
file contains at least
one empty [mysqld]
or
[api]
section. This means that the MySQL
Cluster management server performs no checking of the host
from which a MySQL Server (or other API node) accesses the
MySQL Cluster.
There is no firewall, or the firewall fails to protect against access to the MySQL Cluster from hosts external to the network.
The host name or IP address of the MySQL Cluster's management server is known or can be determined from outside the network.
If these conditions are true, then anyone, anywhere can start a
MySQL Server with --ndbcluster
--ndb-connectstring=
and access this MySQL Cluster. Using the MySQL
management_host
root
account, this person can then perform
the following actions:
Execute metadata statements such as
SHOW DATABASES
statement (to
obtain a list of all NDB
databases on the server) or
SHOW TABLES
FROM
statement to obtain a list of all
some_ndb_database
NDB
tables in a given database
Run any legal MySQL statements on any of the discovered tables, such as:
SELECT * FROM
to read
all the data from any table
some_table
DELETE FROM
to
delete all the data from a table
some_table
DESCRIBE
or
some_table
SHOW CREATE TABLE
to
determine the table schema
some_table
UPDATE
to fill
a table column with “garbage” data; this
could actually cause much greater damage than simply
deleting all the data
some_table
SET column1
=
some_value
More insidious variations might include statements like these:
UPDATEsome_table
SETan_int_column
=an_int_column
+ 1
or
UPDATEsome_table
SETa_varchar_column
= REVERSE(a_varchar_column
)
Such malicious statements are limited only by the imagination of the attacker.
The only tables that would be safe from this sort of mayhem
would be those tables that were created using storage
engines other than NDB
, and so
not visible to a “rogue” SQL node.
A user who can log in as root
can also
access the INFORMATION_SCHEMA
database
and its tables, and so obtain information about databases,
tables, stored routines, scheduled events, and any other
database objects for which metadata is stored in
INFORMATION_SCHEMA
.
It is also a very good idea to use different passwords for
the root
accounts on different MySQL
Cluster SQL nodes unless you are using distributed
privileges.
In sum, you cannot have a safe MySQL Cluster if it is directly accessible from outside your local network.
Never leave the MySQL root account password empty. This is just as true when running MySQL as a MySQL Cluster SQL node as it is when running it as a standalone (non-Cluster) MySQL Server, and should be done as part of the MySQL installation process before configuring the MySQL Server as an SQL node in a MySQL Cluster.
If you wish to employ MySQL Cluster's distributed privilege
capabilities, you should not simply convert the system tables in
the mysql
database to use the
NDB
storage engine manually. Use
the stored procedure provided for this purpose instead; see
Section 19.5.15, “Distributed MySQL Privileges for MySQL Cluster”.
Otherwise, if you need to synchronize mysql
system tables between SQL nodes, you can use standard MySQL
replication to do so, or employ a script to copy table entries
between the MySQL servers.
Summary. The most important points to remember regarding the MySQL privilege system with regard to MySQL Cluster are listed here:
Users and privileges established on one SQL node do not automatically exist or take effect on other SQL nodes in the cluster. Conversely, removing a user or privilege on one SQL node in the cluster does not remove the user or privilege from any other SQL nodes.
You can distribute MySQL users and privileges among SQL nodes using the SQL script, and the stored procedures it contains, that are supplied for this purpose in the MySQL Cluster distribution.
Once a MySQL user is granted privileges on an
NDB
table from one SQL node in
a MySQL Cluster, that user can “see” any data
in that table regardless of the SQL node from which the data
originated, even if you are not using privilege
distribution.
In this section, we discuss MySQL standard security procedures as they apply to running MySQL Cluster.
In general, any standard procedure for running MySQL securely
also applies to running a MySQL Server as part of a MySQL
Cluster. First and foremost, you should always run a MySQL
Server as the mysql
system user; this is no
different from running MySQL in a standard (non-Cluster)
environment. The mysql
system account should
be uniquely and clearly defined. Fortunately, this is the
default behavior for a new MySQL installation. You can verify
that the mysqld process is running as the
system user mysql
by using the system command
such as the one shown here:
shell> ps aux | grep mysql
root 10467 0.0 0.1 3616 1380 pts/3 S 11:53 0:00 \
/bin/sh ./mysqld_safe --ndbcluster --ndb-connectstring=localhost:1186
mysql 10512 0.2 2.5 58528 26636 pts/3 Sl 11:53 0:00 \
/usr/local/mysql/libexec/mysqld --basedir=/usr/local/mysql \
--datadir=/usr/local/mysql/var --user=mysql --ndbcluster \
--ndb-connectstring=localhost:1186 --pid-file=/usr/local/mysql/var/mothra.pid \
--log-error=/usr/local/mysql/var/mothra.err
jon 10579 0.0 0.0 2736 688 pts/0 S+ 11:54 0:00 grep mysql
If the mysqld process is running as any other
user than mysql
, you should immediately shut
it down and restart it as the mysql
user. If
this user does not exist on the system, the
mysql
user account should be created, and
this user should be part of the mysql
user
group; in this case, you should also make sure that the MySQL
data directory on this system (as set using the
--datadir
option for
mysqld) is owned by the
mysql
user, and that the SQL node's
my.cnf
file includes
user=mysql
in the [mysqld]
section. Alternatively, you can start the MySQL server process
with --user=mysql
on the command
line, but it is preferable to use the
my.cnf
option, since you might forget to
use the command-line option and so have
mysqld running as another user
unintentionally. The mysqld_safe startup
script forces MySQL to run as the mysql
user.
Never run mysqld as the system root user. Doing so means that potentially any file on the system can be read by MySQL, and thus—should MySQL be compromised—by an attacker.
As mentioned in the previous section (see Section 19.5.12.2, “MySQL Cluster and MySQL Privileges”), you should always set a root password for the MySQL Server as soon as you have it running. You should also delete the anonymous user account that is installed by default. You can accomplish these tasks using the following statements:
shell>mysql -u root
mysql>UPDATE mysql.user
->SET Password=PASSWORD('
->secure_password
')WHERE User='root';
mysql>DELETE FROM mysql.user
->WHERE User='';
mysql>FLUSH PRIVILEGES;
Be very careful when executing the
DELETE
statement not to omit the
WHERE
clause, or you risk deleting
all MySQL users. Be sure to run the
FLUSH
PRIVILEGES
statement as soon as you have modified the
mysql.user
table, so that the changes take
immediate effect. Without
FLUSH
PRIVILEGES
, the changes do not take effect until the
next time that the server is restarted.
Many of the MySQL Cluster utilities such as
ndb_show_tables,
ndb_desc, and
ndb_select_all also work without
authentication and can reveal table names, schemas, and data.
By default these are installed on Unix-style systems with the
permissions wxr-xr-x
(755), which means
they can be executed by any user that can access the
mysql/bin
directory.
See Section 19.4, “MySQL Cluster Programs”, for more information about these utilities.
It is possible to store the nonindexed columns of
NDB
tables on disk, rather than in
RAM.
As part of implementing MySQL Cluster Disk Data work, a number of improvements were made in MySQL Cluster for the efficient handling of very large amounts (terabytes) of data during node recovery and restart. These include a “no-steal” algorithm for synchronizing a starting node with very large data sets. For more information, see the paper Recovery Principles of MySQL Cluster 5.1, by MySQL Cluster developers Mikael Ronström and Jonas Oreland.
MySQL Cluster Disk Data performance can be influenced by a number of configuration parameters. For information about these parameters and their effects, see MySQL Cluster Disk Data configuration parameters and MySQL Cluster Disk Data storage and GCP Stop errors
The performance of a MySQL Cluster that uses Disk Data storage can also be greatly improved by separating data node file systems from undo log files and tablespace data files, which can be done using symbolic links. For more information, see Section 19.5.13.2, “Using Symbolic Links with Disk Data Objects”.
MySQL Cluster Disk Data storage is implemented using a number of Disk Data objects. These include the following:
Tablespaces act as containers for other Disk Data objects.
Undo log files undo information required for rolling back transactions.
One or more undo log files are assigned to a log file group, which is then assigned to a tablespace.
Data files store Disk Data table data. A data file is assigned directly to a tablespace.
Undo log files and data files are actual files in the file
system of each data node; by default they are placed in
ndb_
in
the node_id
_fsDataDir
specified in the MySQL
Cluster config.ini
file, and where
node_id
is the data node's node
ID. It is possible to place these elsewhere by specifying either
an absolute or relative path as part of the filename when
creating the undo log or data file. Statements that create these
files are shown later in this section.
MySQL Cluster tablespaces and log file groups are not implemented as files.
Although not all Disk Data objects are implemented as files,
they all share the same namespace. This means that
each Disk Data object must be uniquely
named (and not merely each Disk Data object of a given type).
For example, you cannot have a tablespace and a log file group
both named dd1
.
Assuming that you have already set up a MySQL Cluster with all nodes (including management and SQL nodes), the basic steps for creating a MySQL Cluster table on disk are as follows:
Create a log file group, and assign one or more undo log files to it (an undo log file is also sometimes referred to as an undofile).
Undo log files are necessary only for Disk Data tables;
they are not used for
NDBCLUSTER
tables that are
stored only in memory.
Create a tablespace; assign the log file group, as well as one or more data files, to the tablespace.
Create a Disk Data table that uses this tablespace for data storage.
Each of these tasks can be accomplished using SQL statements in the mysql client or other MySQL client application, as shown in the example that follows.
We create a log file group named lg_1
using CREATE LOGFILE GROUP
.
This log file group is to be made up of two undo log files,
which we name undo_1.log
and
undo_2.log
, whose initial sizes are 16
MB and 12 MB, respectively. (The default initial size for an
undo log file is 128 MB.) Optionally, you can also specify a
size for the log file group's undo buffer, or permit it to
assume the default value of 8 MB. In this example, we set
the UNDO buffer's size at 2 MB. A log file group must be
created with an undo log file; so we add
undo_1.log
to lg_1
in this CREATE LOGFILE GROUP
statement:
CREATE LOGFILE GROUP lg_1 ADD UNDOFILE 'undo_1.log' INITIAL_SIZE 16M UNDO_BUFFER_SIZE 2M ENGINE NDBCLUSTER;
To add undo_2.log
to the log file
group, use the following ALTER LOGFILE
GROUP
statement:
ALTER LOGFILE GROUP lg_1 ADD UNDOFILE 'undo_2.log' INITIAL_SIZE 12M ENGINE NDBCLUSTER;
Some items of note:
The .log
file extension used here
is not required. We use it merely to make the log files
easily recognisable.
Every CREATE LOGFILE
GROUP
and ALTER LOGFILE
GROUP
statement must include an
ENGINE
option. The only permitted
values for this option are
NDBCLUSTER
and
NDB
.
There can exist at most one log file group in the same MySQL Cluster at any given time.
When you add an undo log file to a log file group using
ADD UNDOFILE
'
, a file
with the name filename
'filename
is
created in the
ndb_
directory within the
node_id
_fsDataDir
of each
data node in the cluster, where
node_id
is the node ID of the
data node. Each undo log file is of the size specified
in the SQL statement. For example, if a MySQL Cluster
has 4 data nodes, then the ALTER
LOGFILE GROUP
statement just shown creates 4
undo log files, 1 each on in the data directory of each
of the 4 data nodes; each of these files is named
undo_2.log
and each file is 12 MB
in size.
UNDO_BUFFER_SIZE
is limited by the
amount of system memory available.
For more information about the
CREATE LOGFILE GROUP
statement, see Section 14.1.15, “CREATE LOGFILE GROUP Syntax”.
For more information about ALTER
LOGFILE GROUP
, see
Section 14.1.3, “ALTER LOGFILE GROUP Syntax”.
Now we can create a tablespace, which contains files to be used by MySQL Cluster Disk Data tables for storing their data. A tablespace is also associated with a particular log file group. When creating a new tablespace, you must specify the log file group which it is to use for undo logging; you must also specify a data file. You can add more data files to the tablespace after the tablespace is created; it is also possible to drop data files from a tablespace (an example of dropping data files is provided later in this section).
Assume that we wish to create a tablespace named
ts_1
which uses lg_1
as its log file group. This tablespace is to contain two
data files named data_1.dat
and
data_2.dat
, whose initial sizes are 32
MB and 48 MB, respectively. (The default value for
INITIAL_SIZE
is 128 MB.) We can do this
using two SQL statements, as shown here:
CREATE TABLESPACE ts_1 ADD DATAFILE 'data_1.dat' USE LOGFILE GROUP lg_1 INITIAL_SIZE 32M ENGINE NDBCLUSTER; ALTER TABLESPACE ts_1 ADD DATAFILE 'data_2.dat' INITIAL_SIZE 48M ENGINE NDBCLUSTER;
The CREATE TABLESPACE
statement creates a tablespace ts_1
with
the data file data_1.dat
, and
associates ts_1
with log file group
lg_1
. The ALTER
TABLESPACE
adds the second data file
(data_2.dat
).
Some items of note:
As is the case with the .log
file
extension used in this example for undo log files, there
is no special significance for the
.dat
file extension; it is used
merely for easy recognition of data files.
When you add a data file to a tablespace using
ADD DATAFILE
'
, a file
with the name filename
'filename
is
created in the
ndb_
directory within the
node_id
_fsDataDir
of each
data node in the cluster, where
node_id
is the node ID of the
data node. Each data file is of the size specified in
the SQL statement. For example, if a MySQL Cluster has 4
data nodes, then the ALTER
TABLESPACE
statement just shown creates 4 data
files, 1 each in the data directory of each of the 4
data nodes; each of these files is named
data_2.dat
and each file is 48 MB
in size.
All CREATE TABLESPACE
and
ALTER TABLESPACE
statements must contain an ENGINE
clause; only tables using the same storage engine as the
tablespace can be created in the tablespace. For MySQL
Cluster tablespaces, the only permitted values for this
option are NDBCLUSTER
and
NDB
.
For more information about the
CREATE TABLESPACE
and
ALTER TABLESPACE
statements, see Section 14.1.19, “CREATE TABLESPACE Syntax”, and
Section 14.1.9, “ALTER TABLESPACE Syntax”.
Now it is possible to create a table whose nonindexed
columns are stored on disk in the tablespace
ts_1
:
CREATE TABLE dt_1 ( member_id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY, last_name VARCHAR(50) NOT NULL, first_name VARCHAR(50) NOT NULL, dob DATE NOT NULL, joined DATE NOT NULL, INDEX(last_name, first_name) ) TABLESPACE ts_1 STORAGE DISK ENGINE NDBCLUSTER;
The TABLESPACE ... STORAGE DISK
option
tells the NDBCLUSTER
storage
engine to use tablespace ts_1
for disk
data storage.
It is also possible to specify whether an individual
column is stored on disk or in memory by using a
STORAGE
clause as part of the column's
definition in a CREATE
TABLE
or ALTER
TABLE
statement. STORAGE DISK
causes the column to be stored on disk, and
STORAGE MEMORY
causes in-memory storage
to be used. See Section 14.1.18, “CREATE TABLE Syntax”, for more
information.
Once table ts_1
has been created as
shown, you can perform
INSERT
,
SELECT
,
UPDATE
, and
DELETE
statements on it just
as you would with any other MySQL table.
For table dt_1
as it has been defined
here, only the dob
and
joined
columns are stored on disk. This
is because there are indexes on the id
,
last_name
, and
first_name
columns, and so data belonging
to these columns is stored in RAM. Only nonindexed columns
can be held on disk; indexes and indexed column data
continue to be stored in memory. This tradeoff between the
use of indexes and conservation of RAM is something you must
keep in mind as you design Disk Data tables.
Performance note. The performance of a cluster using Disk Data storage is greatly improved if Disk Data files are kept on a separate physical disk from the data node file system. This must be done for each data node in the cluster to derive any noticeable benefit.
You may use absolute and relative file system paths with
ADD UNDOFILE
and ADD
DATAFILE
. Relative paths are calculated relative to
the data node's data directory. You may also use symbolic links;
see Section 19.5.13.2, “Using Symbolic Links with Disk Data Objects”, for more
information and examples.
A log file group, a tablespace, and any Disk Data tables using these must be created in a particular order. The same is true for dropping any of these objects:
A log file group cannot be dropped as long as any tablespaces are using it.
A tablespace cannot be dropped as long as it contains any data files.
You cannot drop any data files from a tablespace as long as there remain any tables which are using the tablespace.
It is not possible to drop files created in association with a different tablespace than the one with which the files were created. (Bug #20053)
For example, to drop all the objects created so far in this section, you would use the following statements:
mysql>DROP TABLE dt_1;
mysql>ALTER TABLESPACE ts_1
->DROP DATAFILE 'data_2.dat'
->ENGINE NDBCLUSTER;
mysql>ALTER TABLESPACE ts_1
->DROP DATAFILE 'data_1.dat'
->ENGINE NDBCLUSTER;
mysql>DROP TABLESPACE ts_1
->ENGINE NDBCLUSTER;
mysql>DROP LOGFILE GROUP lg_1
->ENGINE NDBCLUSTER;
These statements must be performed in the order shown, except
that the two ALTER TABLESPACE ... DROP
DATAFILE
statements may be executed in either order.
You can obtain information about data files used by Disk Data
tables by querying the FILES
table
in the INFORMATION_SCHEMA
database. An extra
“NULL
row” provides additional
information about undo log files. For more information and
examples, see Section 22.8, “The INFORMATION_SCHEMA FILES Table”.
It is also possible to view information about allocated and free disk space for each Disk Data table or table partition using the ndb_desc utility. For more information, see Section 19.4.10, “ndb_desc — Describe NDB Tables”.
The performance of a MySQL Cluster that uses Disk Data storage
can be greatly improved by separating data node file systems
from undo log files and tablespace data files and placing these
on different disks. In early versions of MySQL Cluster, there
was no direct support for this in MySQL Cluster, but it was
possible to achieve this separation using symbolic links as
described in this section. MySQL Cluster supports the data node
configuration parameters
FileSystemPathDD
,
FileSystemPathDataFiles
,
and
FileSystemPathUndoFiles
,
which make the use of symbolic links for this purpose
unnecessary. For more information about these parameters, see
Disk Data file system parameters.
Each data node in the cluster creates a file system in the
directory named
ndb_
under the data node's
node_id
_fsDataDir
as defined in
the config.ini
file. In this example, we
assume that each data node host has 3 disks, aliased as
/data0
, /data1
, and
/data2
, and that the cluster's
config.ini
includes the following:
[ndbd default] DataDir= /data0
Our objective is to place all Disk Data log files in
/data1
, and all Disk Data data files in
/data2
, on each data node host.
In this example, we assume that the cluster's data node hosts are all using Linux operating systems. For other platforms, you may need to substitute you operating system's commands for those shown here.
To accomplish this, perform the following steps:
Under the data node file system create symbolic links pointing to the other drives:
shell>cd /data0/ndb_2_fs
shell>ls
D1 D10 D11 D2 D8 D9 LCP shell>ln -s /data0 dnlogs
shell>ln -s /data1 dndata
You should now have two symbolic links:
shell> ls -l --hide=D*
lrwxrwxrwx 1 user group 30 2007-03-19 13:58 dndata -> /data1
lrwxrwxrwx 1 user group 30 2007-03-19 13:59 dnlogs -> /data2
We show this only for the data node with node ID 2; however, you must do this for each data node.
Now, in the mysql client, create a log file group and tablespace using the symbolic links, as shown here:
mysql>CREATE LOGFILE GROUP lg1
->ADD UNDOFILE 'dnlogs/undo1.log'
->INITIAL_SIZE 150M
->UNDO_BUFFER_SIZE = 1M
->ENGINE=NDBCLUSTER;
mysql>CREATE TABLESPACE ts1
->ADD DATAFILE 'dndata/data1.log'
->USE LOGFILE GROUP lg1
->INITIAL_SIZE 1G
->ENGINE=NDBCLUSTER;
Verify that the files were created and placed correctly as shown here:
shell>cd /data1
shell>ls -l
total 2099304 -rw-rw-r-- 1 user group 157286400 2007-03-19 14:02 undo1.dat shell>cd /data2
shell>ls -l
total 2099304 -rw-rw-r-- 1 user group 1073741824 2007-03-19 14:02 data1.dat
If you are running multiple data nodes on one host, you must
take care to avoid having them try to use the same space for
Disk Data files. You can make this easier by creating a
symbolic link in each data node file system. Suppose you are
using /data0
for both data node file
systems, but you wish to have the Disk Data files for both
nodes on /data1
. In this case, you can
do something similar to what is shown here:
shell>cd /data0
shell>ln -s /data1/dn2 ndb_2_fs/dd
shell>ln -s /data1/dn3 ndb_3_fs/dd
shell>ls -l --hide=D* ndb_2_fs
lrwxrwxrwx 1 user group 30 2007-03-19 14:22 dd -> /data1/dn2 shell>ls -l --hide=D* ndb_3_fs
lrwxrwxrwx 1 user group 30 2007-03-19 14:22 dd -> /data1/dn3
Now you can create a logfile group and tablespace using the symbolic link, like this:
mysql>CREATE LOGFILE GROUP lg1
->ADD UNDOFILE 'dd/undo1.log'
->INITIAL_SIZE 150M
->UNDO_BUFFER_SIZE = 1M
->ENGINE=NDBCLUSTER;
mysql>CREATE TABLESPACE ts1
->ADD DATAFILE 'dd/data1.log'
->USE LOGFILE GROUP lg1
->INITIAL_SIZE 1G
->ENGINE=NDBCLUSTER;
Verify that the files were created and placed correctly as shown here:
shell>cd /data1
shell>ls
dn2 dn3 shell>ls dn2
undo1.log data1.log shell>ls dn3
undo1.log data1.log
The following items apply to Disk Data storage requirements:
Variable-length columns of Disk Data tables take up a fixed amount of space. For each row, this is equal to the space required to store the largest possible value for that column.
For general information about calculating these values, see Section 12.8, “Data Type Storage Requirements”.
You can obtain an estimate the amount of space available in
data files and undo log files by querying the
INFORMATION_SCHEMA.FILES
table.
For more information and examples, see
Section 22.8, “The INFORMATION_SCHEMA FILES Table”.
The OPTIMIZE TABLE
statement does not have any effect on Disk Data tables.
In a Disk Data table, the first 256 bytes of a
TEXT
or
BLOB
column are stored in
memory; only the remainder is stored on disk.
Each row in a Disk Data table uses 8 bytes in memory to
point to the data stored on disk. This means that, in some
cases, converting an in-memory column to the disk-based
format can actually result in greater memory usage. For
example, converting a CHAR(4)
column from
memory-based to disk-based format increases the amount of
DataMemory
used per
row from 4 to 8 bytes.
Starting the cluster with the --initial
option does not remove Disk Data files.
You must remove these manually prior to performing an initial
restart of the cluster.
Performance of Disk Data tables can be improved by minimizing
the number of disk seeks by making sure that
DiskPageBufferMemory
is
of sufficient size. You can query the
diskpagebuffer
table to help
determine whether the value for this parameter needs to be
increased.
This section describes how to add MySQL Cluster data nodes “online”—that is, without needing to shut down the cluster completely and restart it as part of the process.
Currently, you must add new data nodes to a MySQL Cluster as part of a new node group. In addition, it is not possible to change the number of replicas (or the number of nodes per node group) online.
This section provides general information about the behavior of and current limitations in adding MySQL Cluster nodes online.
Redistribution of Data.
The ability to add new nodes online includes a means to
reorganize NDBCLUSTER
table data
and indexes so that they are distributed across all data
nodes, including the new ones, by means of the
ALTER
TABLE ... REORGANIZE PARTITION
statement. Table
reorganization of both in-memory and Disk Data tables is
supported. This redistribution does not currently include
unique indexes (only ordered indexes are redistributed).
The redistribution for NDBCLUSTER
tables already existing before the new data nodes were added is
not automatic, but can be accomplished using simple SQL
statements in mysql or another MySQL client
application. However, all data and indexes added to tables
created after a new node group has been added are distributed
automatically among all cluster data nodes, including those
added as part of the new node group.
Partial starts. It is possible to add a new node group without all of the new data nodes being started. It is also possible to add a new node group to a degraded cluster—that is, a cluster that is only partially started, or where one or more data nodes are not running. In the latter case, the cluster must have enough nodes running to be viable before the new node group can be added.
Effects on ongoing operations.
Normal DML operations using MySQL Cluster data are not
prevented by the creation or addition of a new node group, or
by table reorganization. However, it is not possible to
perform DDL concurrently with table reorganization—that
is, no other DDL statements can be issued while an
ALTER TABLE ...
REORGANIZE PARTITION
statement is executing. In
addition, during the execution of ALTER TABLE ...
REORGANIZE PARTITION
(or the execution of any other
DDL statement), it is not possible to restart cluster data
nodes.
Failure handling. Failures of data nodes during node group creation and table reorganization are handled as hown in the following table:
Failure occurs during: | Failure occurs in: | ||
---|---|---|---|
“Old” data nodes | “New” data nodes | System | |
Node group creation |
|
|
|
Table reorganization |
|
|
|
Dropping node groups.
The ndb_mgm client supports a
DROP NODEGROUP
command,
but it is possible to drop a node group only when no data
nodes in the node group contain any data. Since there is
currently no way to “empty” a specific data node
or node group, this command works only the following two
cases:
After issuing CREATE
NODEGROUP
in the ndb_mgm
client, but before issuing any
ALTER TABLE ...
REORGANIZE PARTITION
statements in the
mysql client.
After dropping all NDBCLUSTER
tables using DROP TABLE
.
TRUNCATE TABLE
does not work
for this purpose because the data nodes continue to store
the table definitions.
In this section, we list the basic steps required to add new data nodes to a MySQL Cluster. This procedure applies whether you are using ndbd or ndbmtd binaries for the data node processes. For a more detailed example, see Section 19.5.14.3, “Adding MySQL Cluster Data Nodes Online: Detailed Example”.
Assuming that you already have a running MySQL Cluster, adding data nodes online requires the following steps:
Edit the cluster configuration
config.ini
file, adding new
[ndbd]
sections corresponding to the
nodes to be added. In the case where the cluster uses
multiple management servers, these changes need to be made
to all config.ini
files used by the
management servers.
You must be careful that node IDs for any new data nodes
added in the config.ini
file do not
overlap node IDs used by existing nodes. In the event that
you have API nodes using dynamically allocated node IDs and
these IDs match node IDs that you want to use for new data
nodes, it is possible to force any such API nodes to
“migrate”, as described later in this
procedure.
Perform a rolling restart of all MySQL Cluster management servers.
Perform a rolling restart of all existing MySQL Cluster data
nodes. It is not necessary (or usually even desirable) to
use --initial
when restarting
the existing data nodes.
If you are using API nodes with dynamically allocated IDs matching any node IDs that you wish to assign to new data nodes, you must restart all API nodes (including SQL nodes) before restarting any of the data nodes processes in this step. This causes any API nodes with node IDs that were previously not explicitly assigned to relinquish those node IDs and acquire new ones.
Perform a rolling restart of any SQL or API nodes connected to the MySQL Cluster.
Start the new data nodes.
The new data nodes may be started in any order. They can also be started concurrently, as long as they are started after the rolling restarts of all existing data nodes have been completed, and before proceeding to the next step.
Execute one or more CREATE
NODEGROUP
commands in the MySQL Cluster management
client to create the new node group or node groups to which
the new data nodes will belong.
Redistribute the cluster's data among all data nodes,
including the new ones. Normally this is done by issuing an
ALTER TABLE ...
ALGORITHM=INPLACE REORGANIZE PARTITION
statement
in the mysql client for each
NDBCLUSTER
table.
Exception: For tables created using the
MAX_ROWS
option, this statement does not
work; instead, use ALTER TABLE ...
ALGORITHM=INPLACE MAX_ROWS=...
to reorganize such
tables.
This needs to be done only for tables already existing at
the time the new node group is added. Data in tables
created after the new node group is added is distributed
automatically; however, data added to any given table
tbl
that existed before the new nodes
were added is not distributed using the new nodes until
that table has been reorganized.
Reclaim the space freed on the “old” nodes by
issuing, for each NDBCLUSTER
table, an OPTIMIZE TABLE
statement in the mysql client.
You can add all the nodes desired, then issue several
CREATE NODEGROUP
commands in
succession to add the new node groups to the cluster.
In this section we provide a detailed example illustrating how to add new MySQL Cluster data nodes online, starting with a MySQL Cluster having 2 data nodes in a single node group and concluding with a cluster having 4 data nodes in 2 node groups.
Starting configuration.
For purposes of illustration, we assume a minimal
configuration, and that the cluster uses a
config.ini
file containing only the
following information:
[ndbd default] DataMemory = 100M IndexMemory = 100M NoOfReplicas = 2 DataDir = /usr/local/mysql/var/mysql-cluster [ndbd] Id = 1 HostName = 192.168.0.1 [ndbd] Id = 2 HostName = 192.168.0.2 [mgm] HostName = 192.168.0.10 Id = 10 [api] Id=20 HostName = 192.168.0.20 [api] Id=21 HostName = 192.168.0.21
We have left a gap in the sequence between data node IDs and other nodes. This make it easier later to assign node IDs that are not already in use to data nodes which are newly added.
We also assume that you have already started the cluster using
the appropriate command line or my.cnf
options, and that running
SHOW
in the management
client produces output similar to what is shown here:
-- NDB Cluster -- Management Client --
ndb_mgm> SHOW
Connected to Management Server at: 192.168.0.10:1186
Cluster Configuration
---------------------
[ndbd(NDB)] 2 node(s)
id=1 @192.168.0.1 (5.7.13-ndb-7.5.3, Nodegroup: 0, *)
id=2 @192.168.0.2 (5.7.13-ndb-7.5.3, Nodegroup: 0)
[ndb_mgmd(MGM)] 1 node(s)
id=10 @192.168.0.10 (5.7.13-ndb-7.5.3)
[mysqld(API)] 2 node(s)
id=20 @192.168.0.20 (5.7.13-ndb-7.5.3)
id=21 @192.168.0.21 (5.7.13-ndb-7.5.3)
Finally, we assume that the cluster contains a single
NDBCLUSTER
table created as shown
here:
USE n; CREATE TABLE ips ( id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY, country_code CHAR(2) NOT NULL, type CHAR(4) NOT NULL, ip_address varchar(15) NOT NULL, addresses BIGINT UNSIGNED DEFAULT NULL, date BIGINT UNSIGNED DEFAULT NULL ) ENGINE NDBCLUSTER;
The memory usage and related information shown later in this section was generated after inserting approximately 50000 rows into this table.
In this example, we show the single-threaded ndbd being used for the data node processes. You can also apply this example, if you are using the multi-threaded ndbmtd by substituting ndbmtd for ndbd wherever it appears in the steps that follow.
Step 1: Update configuration file.
Open the cluster global configuration file in a text editor
and add [ndbd]
sections corresponding to
the 2 new data nodes. (We give these data nodes IDs 3 and 4,
and assume that they are to be run on host machines at
addresses 192.168.0.3 and 192.168.0.4, respectively.) After
you have added the new sections, the contents of the
config.ini
file should look like what is
shown here, where the additions to the file are shown in bold
type:
[ndbd default]
DataMemory = 100M
IndexMemory = 100M
NoOfReplicas = 2
DataDir = /usr/local/mysql/var/mysql-cluster
[ndbd]
Id = 1
HostName = 192.168.0.1
[ndbd]
Id = 2
HostName = 192.168.0.2
[ndbd]
Id = 3
HostName = 192.168.0.3
[ndbd]
Id = 4
HostName = 192.168.0.4
[mgm]
HostName = 192.168.0.10
Id = 10
[api]
Id=20
HostName = 192.168.0.20
[api]
Id=21
HostName = 192.168.0.21
Once you have made the necessary changes, save the file.
Step 2: Restart the management server. Restarting the cluster management server requires that you issue separate commands to stop the management server and then to start it again, as follows:
Stop the management server using the management client
STOP
command, as shown
here:
ndb_mgm> 10 STOP
Node 10 has shut down.
Disconnecting to allow Management Server to shutdown
shell>
Because shutting down the management server causes the
management client to terminate, you must start the
management server from the system shell. For simplicity, we
assume that config.ini
is in the same
directory as the management server binary, but in practice,
you must supply the correct path to the configuration file.
You must also supply the
--reload
or
--initial
option so that
the management server reads the new configuration from the
file rather than its configuration cache. If your
shell's current directory is also the same as the
directory where the management server binary is located,
then you can invoke the management server as shown here:
shell> ndb_mgmd -f config.ini --reload
2008-12-08 17:29:23 [MgmSrvr] INFO -- NDB Cluster Management Server. 5.7.13-ndb-7.5.3
2008-12-08 17:29:23 [MgmSrvr] INFO -- Reading cluster configuration from 'config.ini'
If you check the output of
SHOW
in the management
client after restarting the ndb_mgm process,
you should now see something like this:
-- NDB Cluster -- Management Client --
ndb_mgm> SHOW
Connected to Management Server at: 192.168.0.10:1186
Cluster Configuration
---------------------
[ndbd(NDB)] 2 node(s)
id=1 @192.168.0.1 (5.7.13-ndb-7.5.3, Nodegroup: 0, *)
id=2 @192.168.0.2 (5.7.13-ndb-7.5.3, Nodegroup: 0)
id=3 (not connected, accepting connect from 192.168.0.3)
id=4 (not connected, accepting connect from 192.168.0.4)
[ndb_mgmd(MGM)] 1 node(s)
id=10 @192.168.0.10 (5.7.13-ndb-7.5.3)
[mysqld(API)] 2 node(s)
id=20 @192.168.0.20 (5.7.13-ndb-7.5.3)
id=21 @192.168.0.21 (5.7.13-ndb-7.5.3)
Step 3: Perform a rolling restart of the existing data nodes.
This step can be accomplished entirely within the cluster
management client using the
RESTART
command, as shown
here:
ndb_mgm>1 RESTART
Node 1: Node shutdown initiated Node 1: Node shutdown completed, restarting, no start. Node 1 is being restarted ndb_mgm> Node 1: Start initiated (version 7.5.3) Node 1: Started (version 7.5.3) ndb_mgm>2 RESTART
Node 2: Node shutdown initiated Node 2: Node shutdown completed, restarting, no start. Node 2 is being restarted ndb_mgm> Node 2: Start initiated (version 7.5.3) ndb_mgm> Node 2: Started (version 7.5.3)
After issuing each
command, wait until the management client
reports X
RESTARTNode
before proceeding
any further.
X
: Started
(version ...)
You can verify that all existing data nodes were restarted using
the updated configuration by checking the
ndbinfo.nodes
table in the
mysql client.
Step 4: Perform a rolling restart of all cluster API nodes.
Shut down and restart each MySQL server acting as an SQL node
in the cluster using mysqladmin shutdown
followed by mysqld_safe (or another startup
script). This should be similar to what is shown here, where
password
is the MySQL
root
password for a given MySQL server
instance:
shell>mysqladmin -uroot -p
081208 20:19:56 mysqld_safe mysqld from pid file /usr/local/mysql/var/tonfisk.pid ended shell>password
shutdownmysqld_safe --ndbcluster --ndb-connectstring=192.168.0.10 &
081208 20:20:06 mysqld_safe Logging to '/usr/local/mysql/var/tonfisk.err'. 081208 20:20:06 mysqld_safe Starting mysqld daemon with databases from /usr/local/mysql/var
Of course, the exact input and output depend on how and where
MySQL is installed on the system, as well as which options you
choose to start it (and whether or not some or all of these
options are specified in a my.cnf
file).
Step 5: Perform an initial start of the new data nodes.
From a system shell on each of the hosts for the new data
nodes, start the data nodes as shown here, using the
--initial
option:
shell> ndbd -c 192.168.0.10 --initial
Unlike the case with restarting the existing data nodes, you can start the new data nodes concurrently; you do not need to wait for one to finish starting before starting the other.
Wait until both of the new data nodes have started
before proceeding with the next step. Once the new
data nodes have started, you can see in the output of the
management client SHOW
command that they do not yet belong to any node group (as
indicated with bold type here):
ndb_mgm> SHOW
Connected to Management Server at: 192.168.0.10:1186
Cluster Configuration
---------------------
[ndbd(NDB)] 2 node(s)
id=1 @192.168.0.1 (5.7.13-ndb-7.5.3, Nodegroup: 0, *)
id=2 @192.168.0.2 (5.7.13-ndb-7.5.3, Nodegroup: 0)
id=3 @192.168.0.3 (5.7.13-ndb-7.5.3, no nodegroup)
id=4 @192.168.0.4 (5.7.13-ndb-7.5.3, no nodegroup)
[ndb_mgmd(MGM)] 1 node(s)
id=10 @192.168.0.10 (5.7.13-ndb-7.5.3)
[mysqld(API)] 2 node(s)
id=20 @192.168.0.20 (5.7.13-ndb-7.5.3)
id=21 @192.168.0.21 (5.7.13-ndb-7.5.3)
Step 6: Create a new node group.
You can do this by issuing a CREATE
NODEGROUP
command in the cluster management client.
This command takes as its argument a comma-separated list of
the node IDs of the data nodes to be included in the new node
group, as shown here:
ndb_mgm> CREATE NODEGROUP 3,4
Nodegroup 1 created
By issuing SHOW
again, you
can verify that data nodes 3 and 4 have joined the new node
group (again indicated in bold type):
ndb_mgm> SHOW
Connected to Management Server at: 192.168.0.10:1186
Cluster Configuration
---------------------
[ndbd(NDB)] 2 node(s)
id=1 @192.168.0.1 (5.7.13-ndb-7.5.3, Nodegroup: 0, *)
id=2 @192.168.0.2 (5.7.13-ndb-7.5.3, Nodegroup: 0)
id=3 @192.168.0.3 (5.7.13-ndb-7.5.3, Nodegroup: 1)
id=4 @192.168.0.4 (5.7.13-ndb-7.5.3, Nodegroup: 1)
[ndb_mgmd(MGM)] 1 node(s)
id=10 @192.168.0.10 (5.7.13-ndb-7.5.3)
[mysqld(API)] 2 node(s)
id=20 @192.168.0.20 (5.7.13-ndb-7.5.3)
id=21 @192.168.0.21 (5.7.13-ndb-7.5.3)
Step 7: Redistribute cluster data.
When a node group is created, existing data and indexes are
not automatically distributed to the new node group's
data nodes, as you can see by issuing the appropriate
REPORT
command in the
management client:
ndb_mgm> ALL REPORT MEMORY
Node 1: Data usage is 5%(177 32K pages of total 3200)
Node 1: Index usage is 0%(108 8K pages of total 12832)
Node 2: Data usage is 5%(177 32K pages of total 3200)
Node 2: Index usage is 0%(108 8K pages of total 12832)
Node 3: Data usage is 0%(0 32K pages of total 3200)
Node 3: Index usage is 0%(0 8K pages of total 12832)
Node 4: Data usage is 0%(0 32K pages of total 3200)
Node 4: Index usage is 0%(0 8K pages of total 12832)
By using ndb_desc with the
-p
option, which causes the output to include
partitioning information, you can see that the table still uses
only 2 partitions (in the Per partition info
section of the output, shown here in bold text):
shell> ndb_desc -c 192.168.0.10 -d n ips -p
-- ips --
Version: 1
Fragment type: 9
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: no
Number of attributes: 6
Number of primary keys: 1
Length of frm data: 340
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
FragmentCount: 2
TableStatus: Retrieved
-- Attributes --
id Bigint PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
country_code Char(2;latin1_swedish_ci) NOT NULL AT=FIXED ST=MEMORY
type Char(4;latin1_swedish_ci) NOT NULL AT=FIXED ST=MEMORY
ip_address Varchar(15;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
addresses Bigunsigned NULL AT=FIXED ST=MEMORY
date Bigunsigned NULL AT=FIXED ST=MEMORY
-- Indexes --
PRIMARY KEY(id) - UniqueHashIndex
PRIMARY(id) - OrderedIndex
-- Per partition info --
Partition Row count Commit count Frag fixed memory Frag varsized memory
0 26086 26086 1572864 557056
1 26329 26329 1605632 557056
NDBT_ProgramExit: 0 - OK
You can cause the data to be redistributed among all of the data
nodes by performing, for each NDB
table, an ALTER
TABLE ... ALGORITHM=INPLACE REORGANIZE PARTITION
statement in the mysql client.
ALTER TABLE ... ALGORITHM=INPLACE REORGANIZE
PARTITION
does not work on tables that were created
with the MAX_ROWS
option. Instead, use
ALTER TABLE ... ALGORITHM=INPLACE
MAX_ROWS=...
to reorganize such tables.
After issuing the statement ALTER TABLE ips
ALGORITHM=INPLACE REORGANIZE PARTITION
, you can see
using ndb_desc that the data for this table
is now stored using 4 partitions, as shown here (with the
relevant portions of the output in bold type):
shell> ndb_desc -c 192.168.0.10 -d n ips -p
-- ips --
Version: 16777217
Fragment type: 9
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: no
Number of attributes: 6
Number of primary keys: 1
Length of frm data: 341
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
FragmentCount: 4
TableStatus: Retrieved
-- Attributes --
id Bigint PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
country_code Char(2;latin1_swedish_ci) NOT NULL AT=FIXED ST=MEMORY
type Char(4;latin1_swedish_ci) NOT NULL AT=FIXED ST=MEMORY
ip_address Varchar(15;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
addresses Bigunsigned NULL AT=FIXED ST=MEMORY
date Bigunsigned NULL AT=FIXED ST=MEMORY
-- Indexes --
PRIMARY KEY(id) - UniqueHashIndex
PRIMARY(id) - OrderedIndex
-- Per partition info --
Partition Row count Commit count Frag fixed memory Frag varsized memory
0 12981 52296 1572864 557056
1 13236 52515 1605632 557056
2 13105 13105 819200 294912
3 13093 13093 819200 294912
NDBT_ProgramExit: 0 - OK
Normally, ALTER
TABLE
is used
with a list of partition identifiers and a set of partition
definitions to create a new partitioning scheme for a table
that has already been explicitly partitioned. Its use here to
redistribute data onto a new MySQL Cluster node group is an
exception in this regard; when used in this way, only the name
of the table is used following the table_name
[ALGORITHM=INPLACE] REORGANIZE PARTITIONTABLE
keyword, and no other keywords or identifiers follow
REORGANIZE PARTITION
.
For more information, see Section 14.1.8, “ALTER TABLE Syntax”.
In addition, for each table, the
ALTER
TABLE
statement should be followed by an
OPTIMIZE TABLE
to reclaim wasted
space. You can obtain a list of all
NDBCLUSTER
tables using the
following query against the
INFORMATION_SCHEMA.TABLES
table:
SELECT TABLE_SCHEMA, TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE ENGINE = 'NDBCLUSTER';
The INFORMATION_SCHEMA.TABLES.ENGINE
value
for a MySQL Cluster table is always
NDBCLUSTER
, regardless of whether
the CREATE TABLE
statement used to create
the table (or ALTER TABLE
statement used to convert an existing table from a different
storage engine) used NDB
or
NDBCLUSTER
in its
ENGINE
option.
You can see after performing these statements in the output of
ALL REPORT MEMORY
that the
data and indexes are now redistributed between all cluster data
nodes, as shown here:
ndb_mgm> ALL REPORT MEMORY
Node 1: Data usage is 5%(176 32K pages of total 3200)
Node 1: Index usage is 0%(76 8K pages of total 12832)
Node 2: Data usage is 5%(176 32K pages of total 3200)
Node 2: Index usage is 0%(76 8K pages of total 12832)
Node 3: Data usage is 2%(80 32K pages of total 3200)
Node 3: Index usage is 0%(51 8K pages of total 12832)
Node 4: Data usage is 2%(80 32K pages of total 3200)
Node 4: Index usage is 0%(50 8K pages of total 12832)
Since only one DDL operation on
NDBCLUSTER
tables can be executed
at a time, you must wait for each
ALTER TABLE ...
REORGANIZE PARTITION
statement to finish before
issuing the next one.
It is not necessary to issue
ALTER TABLE ...
REORGANIZE PARTITION
statements for
NDBCLUSTER
tables created
after the new data nodes have been added;
data added to such tables is distributed among all data nodes
automatically. However, in
NDBCLUSTER
tables that existed
prior to the addition of the new nodes,
neither existing nor new data is distributed using the new nodes
until these tables have been reorganized using
ALTER TABLE ...
REORGANIZE PARTITION
.
Alternative procedure, without rolling restart. It is possible to avoid the need for a rolling restart by configuring the extra data nodes, but not starting them, when first starting the cluster. We assume, as before, that you wish to start with two data nodes—nodes 1 and 2—in one node group and later to expand the cluster to four data nodes, by adding a second node group consisting of nodes 3 and 4:
[ndbd default] DataMemory = 100M IndexMemory = 100M NoOfReplicas = 2 DataDir = /usr/local/mysql/var/mysql-cluster [ndbd] Id = 1 HostName = 192.168.0.1 [ndbd] Id = 2 HostName = 192.168.0.2 [ndbd] Id = 3 HostName = 192.168.0.3 Nodegroup = 65536 [ndbd] Id = 4 HostName = 192.168.0.4 Nodegroup = 65536 [mgm] HostName = 192.168.0.10 Id = 10 [api] Id=20 HostName = 192.168.0.20 [api] Id=21 HostName = 192.168.0.21
The data nodes to be brought online at a later time (nodes 3 and
4) can be configured with
NodeGroup = 65536
, in
which case nodes 1 and 2 can each be started as shown here:
shell> ndbd -c 192.168.0.10 --initial
The data nodes configured with
NodeGroup = 65536
are
treated by the management server as though you had started nodes
1 and 2 using --nowait-nodes=3,4
after waiting for a period of time determined by the setting for
the
StartNoNodeGroupTimeout
data node configuration parameter. By default, this is 15
seconds (15000 milliseconds).
StartNoNodegroupTimeout
must be the same for all data nodes in the cluster; for this
reason, you should always set it in the [ndbd
default]
section of the
config.ini
file, rather than for
individual data nodes.
When you are ready to add the second node group, you need only perform the following additional steps:
Start data nodes 3 and 4, invoking the data node process once for each new node:
shell> ndbd -c 192.168.0.10 --initial
Issue the appropriate CREATE
NODEGROUP
command in the management client:
ndb_mgm> CREATE NODEGROUP 3,4
In the mysql client, issue
ALTER TABLE ...
REORGANIZE PARTITION
and
OPTIMIZE TABLE
statements for
each existing NDBCLUSTER
table.
(As noted elsewhere in this section, existing MySQL Cluster
tables cannot use the new nodes for data distribution until
this has been done.)
MySQL Cluster supports distribution of MySQL users and privileges across all SQL nodes in a MySQL Cluster. This support is not enabled by default; you should follow the procedure outlined in this section in order to do so.
Normally, each MySQL server's user privilege tables in the
mysql
database must use the
MyISAM
storage engine, which means
that a user account and its associated privileges created on one
SQL node are not available on the cluster's other SQL nodes.
An SQL file ndb_dist_priv.sql
provided with
the MySQL Cluster distribution can be found in the
share
directory in the MySQL installation
directory.
The first step in enabling distributed privileges is to load this
script into a MySQL Server that functions as an SQL node (which we
refer to after this as the
target SQL node or MySQL
Server). You can do this by executing the following command from
the system shell on the target SQL node after changing to its
MySQL installation directory (where
options
stands for any additional
options needed to connect to this SQL node):
shell> mysql options
-uroot < share/ndb_dist_priv.sql
Importing ndb_dist_priv.sql
creates a number
of stored routines (six stored procedures and one stored function)
in the mysql
database on the target SQL node.
After connecting to the SQL node in the mysql
client (as the MySQL root
user), you can verify
that these were created as shown here:
mysql>SELECT ROUTINE_NAME, ROUTINE_SCHEMA, ROUTINE_TYPE
->FROM INFORMATION_SCHEMA.ROUTINES
->WHERE ROUTINE_NAME LIKE 'mysql_cluster%'
->ORDER BY ROUTINE_TYPE
; +---------------------------------------------+----------------+--------------+ | ROUTINE_NAME | ROUTINE_SCHEMA | ROUTINE_TYPE | +---------------------------------------------+----------------+--------------+ | mysql_cluster_privileges_are_distributed | mysql | FUNCTION | | mysql_cluster_backup_privileges | mysql | PROCEDURE | | mysql_cluster_move_grant_tables | mysql | PROCEDURE | | mysql_cluster_move_privileges | mysql | PROCEDURE | | mysql_cluster_restore_local_privileges | mysql | PROCEDURE | | mysql_cluster_restore_privileges | mysql | PROCEDURE | | mysql_cluster_restore_privileges_from_local | mysql | PROCEDURE | +---------------------------------------------+----------------+--------------+ 7 rows in set (0.01 sec)
The stored procedure named
mysql_cluster_move_privileges
creates backup
copies of the existing privilege tables, then converts them to
NDB
.
mysql_cluster_move_privileges
performs the
backup and conversion in two steps. The first step is to call
mysql_cluster_backup_privileges
, which creates
two sets of copies in the mysql
database:
A set of local copies that use the
MyISAM
storage engine. Their
names are generated by adding the suffix
_backup
to the original privilege table
names.
A set of distributed copies that use the
NDBCLUSTER
storage engine. These
tables are named by prefixing ndb_
and
appending _backup
to the names of the
original tables.
After the copies are created,
mysql_cluster_move_privileges
invokes
mysql_cluster_move_grant_tables
, which contains
the ALTER TABLE ...
ENGINE = NDB
statements that convert the mysql system
tables to NDB
.
Normally, you should not invoke either
mysql_cluster_backup_privileges
or
mysql_cluster_move_grant_tables
manually; these
stored procedures are intended only for use by
mysql_cluster_move_privileges
.
Although the original privilege tables are backed up automatically, it is always a good idea to create backups manually of the existing privilege tables on all affected SQL nodes before proceeding. You can do this using mysqldump in a manner similar to what is shown here:
shell> mysqldumpoptions
-uroot \ mysql user db tables_priv columns_priv procs_priv proxies_priv >backup_file
To perform the conversion, you must be connected to the target SQL
node using the mysql client (again, as the
MySQL root
user). Invoke the stored procedure
like this:
mysql> CALL mysql.mysql_cluster_move_privileges();
Query OK, 0 rows affected (22.32 sec)
Depending on the number of rows in the privilege tables, this
procedure may take some time to execute. If some of the privilege
tables are empty, you may see one or more No data -
zero rows fetched, selected, or processed warnings
when mysql_cluster_move_privileges
returns. In
such cases, the warnings may be safely ignored. To verify that the
conversion was successful, you can use the stored function
mysql_cluster_privileges_are_distributed
as
shown here:
mysql>SELECT CONCAT(
->'Conversion ',
->IF(mysql.mysql_cluster_privileges_are_distributed(), 'succeeded', 'failed'),
->'.')
->AS Result;
+-----------------------+ | Result | +-----------------------+ | Conversion succeeded. | +-----------------------+ 1 row in set (0.00 sec)
mysql_cluster_privileges_are_distributed
checks
for the existence of the distributed privilege tables and returns
1
if all of the privilege tables are
distributed; otherwise, it returns 0
.
You can verify that the backups have been created using a query such as this one:
mysql>SELECT TABLE_NAME, ENGINE FROM INFORMATION_SCHEMA.TABLES
->WHERE TABLE_SCHEMA = 'mysql' AND TABLE_NAME LIKE '%backup'
->ORDER BY ENGINE;
+-------------------------+------------+ | TABLE_NAME | ENGINE | +-------------------------+------------+ | host_backup | MyISAM | | db_backup | MyISAM | | columns_priv_backup | MyISAM | | user_backup | MyISAM | | tables_priv_backup | MyISAM | | proxies_priv_backup | MyISAM | | procs_priv_backup | MyISAM | | ndb_user_backup | ndbcluster | | ndb_tables_priv_backup | ndbcluster | | ndb_proxies_priv_backup | ndbcluster | | ndb_procs_priv_backup | ndbcluster | | ndb_host_backup | ndbcluster | | ndb_db_backup | ndbcluster | | ndb_columns_priv_backup | ndbcluster | +-------------------------+------------+ 14 rows in set (0.00 sec)
Once the conversion to distributed privileges has been made, any time a MySQL user account is created, dropped, or has its privileges updated on any SQL node, the changes take effect immediately on all other MySQL servers attached to the cluster. Once privileges are distributed, any new MySQL Servers that connect to the cluster automatically participate in the distribution.
For clients connected to SQL nodes at the time that
mysql_cluster_move_privileges
is executed,
you may need to execute
FLUSH
PRIVILEGES
on those SQL nodes, or to disconnect and
then reconnect the clients, in order for those clients to be
able to see the changes in privileges.
All MySQL user privileges are distributed across all connected MySQL Servers. This includes any privileges associated with views and stored routines, even though distribution of views and stored routines themselves is not currently supported.
In the event that an SQL node becomes disconnected from the
cluster while mysql_cluster_move_privileges
is
running, you must drop its privilege tables after reconnecting to
the cluster, using a statement such as
DROP TABLE IF EXISTS
mysql.user mysql.db mysql.tables_priv mysql.columns_priv
mysql.procs_priv
. This causes the SQL node to use the
shared privilege tables rather than its own local versions of
them. This is not needed when connecting a new SQL node to the
cluster for the first time.
In the event of an initial restart of the entire cluster (all data
nodes shut down, then started again with
--initial
), the shared privilege
tables are lost. If this happens, you can restore them using the
original target SQL node either from the backups made by
mysql_cluster_move_privileges
or from a dump
file created with mysqldump. If you need to use
a new MySQL Server to perform the restoration, you should start it
with --skip-grant-tables
when
connecting to the cluster for the first time; after this, you can
restore the privilege tables locally, then distribute them again
using mysql_cluster_move_privileges
. After
restoring and distributing the tables, you should restart this
MySQL Server without the
--skip-grant-tables
option.
You can also restore the distributed tables using
ndb_restore
--restore-privilege-tables
from a backup made using START
BACKUP
in the ndb_mgm client. (The
MyISAM
tables created by
mysql_cluster_move_privileges
are not backed up
by the START BACKUP
command.)
ndb_restore does not restore the privilege
tables by default; the
--restore-privilege-tables
option causes it to do so.
You can restore the SQL node's local privileges using either
of two procedures.
mysql_cluster_restore_privileges
works as
follows:
If copies of the mysql.ndb_*_backup
tables
are available, attempt to restore the system tables from
these.
Otherwise, attempt to restore the system tables from the local
backups named *_backup
(without the
ndb_
prefix).
The other procedure, named
mysql_cluster_restore_local_privileges
,
restores the system tables from the local backups only, without
checking the ndb_*
backups.
The system tables re-created by
mysql_cluster_restore_privileges
or
mysql_cluster_restore_local_privileges
use the
MySQL server default storage engine; they are not shared or
distributed in any way, and do not use MySQL Cluster's
NDB
storage engine.
The additional stored procedure
mysql_cluster_restore_privileges_from_local
is
intended for the use of
mysql_cluster_restore_privileges
and
mysql_cluster_restore_local_privileges
. It
should not be invoked directly.
Applications that access MySQL Cluster data directly, including
NDB API and ClusterJ applications, are not subject to the MySQL
privilege system. This means that, once you have distributed the
grant tables, they can be freely accessed by such applications,
just as they can any other NDB
tables. In particular, you should keep in mind that
NDB API and ClusterJ applications can read and write
user names, host names, password hashes, and any other contents
of the distributed grant tables without any
restrictions.
A number of types of statistical counters relating to actions
performed by or affecting Ndb
objects are available. Such actions include starting and closing
(or aborting) transactions; primary key and unique key operations;
table, range, and pruned scans; threads blocked while waiting for
the completion of various operations; and data and events sent and
received by NDBCLUSTER
. The counters are
incremented inside the NDB kernel whenever NDB API calls are made
or data is sent to or received by the data nodes.
mysqld exposes these counters as system status
variables; their values can be read in the output of
SHOW STATUS
, or by querying the
INFORMATION_SCHEMA.SESSION_STATUS
or
INFORMATION_SCHEMA.GLOBAL_STATUS
table. By comparing the values before and after statements
operating on NDB
tables, you can
observe the corresponding actions taken on the API level, and thus
the cost of performing the statement.
You can list all of these status variables using the following
SHOW STATUS
statement:
mysql> SHOW STATUS LIKE 'ndb_api%';
+--------------------------------------------+----------+
| Variable_name | Value |
+--------------------------------------------+----------+
| Ndb_api_wait_exec_complete_count_session | 0 |
| Ndb_api_wait_scan_result_count_session | 0 |
| Ndb_api_wait_meta_request_count_session | 0 |
| Ndb_api_wait_nanos_count_session | 0 |
| Ndb_api_bytes_sent_count_session | 0 |
| Ndb_api_bytes_received_count_session | 0 |
| Ndb_api_trans_start_count_session | 0 |
| Ndb_api_trans_commit_count_session | 0 |
| Ndb_api_trans_abort_count_session | 0 |
| Ndb_api_trans_close_count_session | 0 |
| Ndb_api_pk_op_count_session | 0 |
| Ndb_api_uk_op_count_session | 0 |
| Ndb_api_table_scan_count_session | 0 |
| Ndb_api_range_scan_count_session | 0 |
| Ndb_api_pruned_scan_count_session | 0 |
| Ndb_api_scan_batch_count_session | 0 |
| Ndb_api_read_row_count_session | 0 |
| Ndb_api_trans_local_read_row_count_session | 0 |
| Ndb_api_event_data_count_injector | 0 |
| Ndb_api_event_nondata_count_injector | 0 |
| Ndb_api_event_bytes_count_injector | 0 |
| Ndb_api_wait_exec_complete_count_slave | 0 |
| Ndb_api_wait_scan_result_count_slave | 0 |
| Ndb_api_wait_meta_request_count_slave | 0 |
| Ndb_api_wait_nanos_count_slave | 0 |
| Ndb_api_bytes_sent_count_slave | 0 |
| Ndb_api_bytes_received_count_slave | 0 |
| Ndb_api_trans_start_count_slave | 0 |
| Ndb_api_trans_commit_count_slave | 0 |
| Ndb_api_trans_abort_count_slave | 0 |
| Ndb_api_trans_close_count_slave | 0 |
| Ndb_api_pk_op_count_slave | 0 |
| Ndb_api_uk_op_count_slave | 0 |
| Ndb_api_table_scan_count_slave | 0 |
| Ndb_api_range_scan_count_slave | 0 |
| Ndb_api_pruned_scan_count_slave | 0 |
| Ndb_api_scan_batch_count_slave | 0 |
| Ndb_api_read_row_count_slave | 0 |
| Ndb_api_trans_local_read_row_count_slave | 0 |
| Ndb_api_wait_exec_complete_count | 2 |
| Ndb_api_wait_scan_result_count | 3 |
| Ndb_api_wait_meta_request_count | 27 |
| Ndb_api_wait_nanos_count | 45612023 |
| Ndb_api_bytes_sent_count | 992 |
| Ndb_api_bytes_received_count | 9640 |
| Ndb_api_trans_start_count | 2 |
| Ndb_api_trans_commit_count | 1 |
| Ndb_api_trans_abort_count | 0 |
| Ndb_api_trans_close_count | 2 |
| Ndb_api_pk_op_count | 1 |
| Ndb_api_uk_op_count | 0 |
| Ndb_api_table_scan_count | 1 |
| Ndb_api_range_scan_count | 0 |
| Ndb_api_pruned_scan_count | 0 |
| Ndb_api_scan_batch_count | 0 |
| Ndb_api_read_row_count | 1 |
| Ndb_api_trans_local_read_row_count | 1 |
| Ndb_api_event_data_count | 0 |
| Ndb_api_event_nondata_count | 0 |
| Ndb_api_event_bytes_count | 0 |
+--------------------------------------------+----------+
60 rows in set (0.02 sec)
These status variables are also available from the
SESSION_STATUS
and
GLOBAL_STATUS
tables of the INFORMATION_SCHEMA
database, as
shown here:
mysql>SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS
->WHERE VARIABLE_NAME LIKE 'ndb_api%';
+--------------------------------------------+----------------+ | VARIABLE_NAME | VARIABLE_VALUE | +--------------------------------------------+----------------+ | NDB_API_WAIT_EXEC_COMPLETE_COUNT_SESSION | 2 | | NDB_API_WAIT_SCAN_RESULT_COUNT_SESSION | 0 | | NDB_API_WAIT_META_REQUEST_COUNT_SESSION | 1 | | NDB_API_WAIT_NANOS_COUNT_SESSION | 8144375 | | NDB_API_BYTES_SENT_COUNT_SESSION | 68 | | NDB_API_BYTES_RECEIVED_COUNT_SESSION | 84 | | NDB_API_TRANS_START_COUNT_SESSION | 1 | | NDB_API_TRANS_COMMIT_COUNT_SESSION | 1 | | NDB_API_TRANS_ABORT_COUNT_SESSION | 0 | | NDB_API_TRANS_CLOSE_COUNT_SESSION | 1 | | NDB_API_PK_OP_COUNT_SESSION | 1 | | NDB_API_UK_OP_COUNT_SESSION | 0 | | NDB_API_TABLE_SCAN_COUNT_SESSION | 0 | | NDB_API_RANGE_SCAN_COUNT_SESSION | 0 | | NDB_API_PRUNED_SCAN_COUNT_SESSION | 0 | | NDB_API_SCAN_BATCH_COUNT_SESSION | 0 | | NDB_API_READ_ROW_COUNT_SESSION | 1 | | NDB_API_TRANS_LOCAL_READ_ROW_COUNT_SESSION | 1 | | NDB_API_EVENT_DATA_COUNT_INJECTOR | 0 | | NDB_API_EVENT_NONDATA_COUNT_INJECTOR | 0 | | NDB_API_EVENT_BYTES_COUNT_INJECTOR | 0 | | NDB_API_WAIT_EXEC_COMPLETE_COUNT_SLAVE | 0 | | NDB_API_WAIT_SCAN_RESULT_COUNT_SLAVE | 0 | | NDB_API_WAIT_META_REQUEST_COUNT_SLAVE | 0 | | NDB_API_WAIT_NANOS_COUNT_SLAVE | 0 | | NDB_API_BYTES_SENT_COUNT_SLAVE | 0 | | NDB_API_BYTES_RECEIVED_COUNT_SLAVE | 0 | | NDB_API_TRANS_START_COUNT_SLAVE | 0 | | NDB_API_TRANS_COMMIT_COUNT_SLAVE | 0 | | NDB_API_TRANS_ABORT_COUNT_SLAVE | 0 | | NDB_API_TRANS_CLOSE_COUNT_SLAVE | 0 | | NDB_API_PK_OP_COUNT_SLAVE | 0 | | NDB_API_UK_OP_COUNT_SLAVE | 0 | | NDB_API_TABLE_SCAN_COUNT_SLAVE | 0 | | NDB_API_RANGE_SCAN_COUNT_SLAVE | 0 | | NDB_API_PRUNED_SCAN_COUNT_SLAVE | 0 | | NDB_API_SCAN_BATCH_COUNT_SLAVE | 0 | | NDB_API_READ_ROW_COUNT_SLAVE | 0 | | NDB_API_TRANS_LOCAL_READ_ROW_COUNT_SLAVE | 0 | | NDB_API_WAIT_EXEC_COMPLETE_COUNT | 4 | | NDB_API_WAIT_SCAN_RESULT_COUNT | 3 | | NDB_API_WAIT_META_REQUEST_COUNT | 28 | | NDB_API_WAIT_NANOS_COUNT | 53756398 | | NDB_API_BYTES_SENT_COUNT | 1060 | | NDB_API_BYTES_RECEIVED_COUNT | 9724 | | NDB_API_TRANS_START_COUNT | 3 | | NDB_API_TRANS_COMMIT_COUNT | 2 | | NDB_API_TRANS_ABORT_COUNT | 0 | | NDB_API_TRANS_CLOSE_COUNT | 3 | | NDB_API_PK_OP_COUNT | 2 | | NDB_API_UK_OP_COUNT | 0 | | NDB_API_TABLE_SCAN_COUNT | 1 | | NDB_API_RANGE_SCAN_COUNT | 0 | | NDB_API_PRUNED_SCAN_COUNT | 0 | | NDB_API_SCAN_BATCH_COUNT | 0 | | NDB_API_READ_ROW_COUNT | 2 | | NDB_API_TRANS_LOCAL_READ_ROW_COUNT | 2 | | NDB_API_EVENT_DATA_COUNT | 0 | | NDB_API_EVENT_NONDATA_COUNT | 0 | | NDB_API_EVENT_BYTES_COUNT | 0 | +--------------------------------------------+----------------+ 60 rows in set (0.00 sec) mysql>SELECT * FROM INFORMATION_SCHEMA.GLOBAL_STATUS
->WHERE VARIABLE_NAME LIKE 'ndb_api%';
+--------------------------------------------+----------------+ | VARIABLE_NAME | VARIABLE_VALUE | +--------------------------------------------+----------------+ | NDB_API_WAIT_EXEC_COMPLETE_COUNT_SESSION | 2 | | NDB_API_WAIT_SCAN_RESULT_COUNT_SESSION | 0 | | NDB_API_WAIT_META_REQUEST_COUNT_SESSION | 1 | | NDB_API_WAIT_NANOS_COUNT_SESSION | 8144375 | | NDB_API_BYTES_SENT_COUNT_SESSION | 68 | | NDB_API_BYTES_RECEIVED_COUNT_SESSION | 84 | | NDB_API_TRANS_START_COUNT_SESSION | 1 | | NDB_API_TRANS_COMMIT_COUNT_SESSION | 1 | | NDB_API_TRANS_ABORT_COUNT_SESSION | 0 | | NDB_API_TRANS_CLOSE_COUNT_SESSION | 1 | | NDB_API_PK_OP_COUNT_SESSION | 1 | | NDB_API_UK_OP_COUNT_SESSION | 0 | | NDB_API_TABLE_SCAN_COUNT_SESSION | 0 | | NDB_API_RANGE_SCAN_COUNT_SESSION | 0 | | NDB_API_PRUNED_SCAN_COUNT_SESSION | 0 | | NDB_API_SCAN_BATCH_COUNT_SESSION | 0 | | NDB_API_READ_ROW_COUNT_SESSION | 1 | | NDB_API_TRANS_LOCAL_READ_ROW_COUNT_SESSION | 1 | | NDB_API_EVENT_DATA_COUNT_INJECTOR | 0 | | NDB_API_EVENT_NONDATA_COUNT_INJECTOR | 0 | | NDB_API_EVENT_BYTES_COUNT_INJECTOR | 0 | | NDB_API_WAIT_EXEC_COMPLETE_COUNT_SLAVE | 0 | | NDB_API_WAIT_SCAN_RESULT_COUNT_SLAVE | 0 | | NDB_API_WAIT_META_REQUEST_COUNT_SLAVE | 0 | | NDB_API_WAIT_NANOS_COUNT_SLAVE | 0 | | NDB_API_BYTES_SENT_COUNT_SLAVE | 0 | | NDB_API_BYTES_RECEIVED_COUNT_SLAVE | 0 | | NDB_API_TRANS_START_COUNT_SLAVE | 0 | | NDB_API_TRANS_COMMIT_COUNT_SLAVE | 0 | | NDB_API_TRANS_ABORT_COUNT_SLAVE | 0 | | NDB_API_TRANS_CLOSE_COUNT_SLAVE | 0 | | NDB_API_PK_OP_COUNT_SLAVE | 0 | | NDB_API_UK_OP_COUNT_SLAVE | 0 | | NDB_API_TABLE_SCAN_COUNT_SLAVE | 0 | | NDB_API_RANGE_SCAN_COUNT_SLAVE | 0 | | NDB_API_PRUNED_SCAN_COUNT_SLAVE | 0 | | NDB_API_SCAN_BATCH_COUNT_SLAVE | 0 | | NDB_API_READ_ROW_COUNT_SLAVE | 0 | | NDB_API_TRANS_LOCAL_READ_ROW_COUNT_SLAVE | 0 | | NDB_API_WAIT_EXEC_COMPLETE_COUNT | 4 | | NDB_API_WAIT_SCAN_RESULT_COUNT | 3 | | NDB_API_WAIT_META_REQUEST_COUNT | 28 | | NDB_API_WAIT_NANOS_COUNT | 53756398 | | NDB_API_BYTES_SENT_COUNT | 1060 | | NDB_API_BYTES_RECEIVED_COUNT | 9724 | | NDB_API_TRANS_START_COUNT | 3 | | NDB_API_TRANS_COMMIT_COUNT | 2 | | NDB_API_TRANS_ABORT_COUNT | 0 | | NDB_API_TRANS_CLOSE_COUNT | 3 | | NDB_API_PK_OP_COUNT | 2 | | NDB_API_UK_OP_COUNT | 0 | | NDB_API_TABLE_SCAN_COUNT | 1 | | NDB_API_RANGE_SCAN_COUNT | 0 | | NDB_API_PRUNED_SCAN_COUNT | 0 | | NDB_API_SCAN_BATCH_COUNT | 0 | | NDB_API_READ_ROW_COUNT | 2 | | NDB_API_TRANS_LOCAL_READ_ROW_COUNT | 2 | | NDB_API_EVENT_DATA_COUNT | 0 | | NDB_API_EVENT_NONDATA_COUNT | 0 | | NDB_API_EVENT_BYTES_COUNT | 0 | +--------------------------------------------+----------------+ 60 rows in set (0.00 sec)
Each Ndb
object has its own
counters. NDB API applications can read the values of the counters
for use in optimization or monitoring. For multi-threaded clients
which use more than one Ndb
object concurrently, it is also possible to obtain a summed view
of counters from all Ndb
objects
belonging to a given
Ndb_cluster_connection
.
Four sets of these counters are exposed. One set applies to the
current session only; the other 3 are global. This is in
spite of the fact that their values can be obtained as either
session or global status variables in the mysql
client. This means that specifying the
SESSION
or GLOBAL
keyword
with SHOW STATUS
has no effect on
the values reported for NDB API statistics status variables, and
the value for each of these variables is the same whether the
value is obtained from the equivalent column of the
SESSION_STATUS
or
the GLOBAL_STATUS
table.
Session counters (session specific)
Session counters relate to the
Ndb
objects in use by (only)
the current session. Use of such objects by other MySQL
clients does not influence these counts.
In order to minimize confusion with standard MySQL session
variables, we refer to the variables that correspond to these
NDB API session counters as “_session
variables”, with a leading underscore.
Slave counters (global)
This set of counters relates to the
Ndb
objects used by the
replication slave SQL thread, if any. If this
mysqld does not act as a replication slave,
or does not use NDB
tables, then
all of these counts are 0.
We refer to the related status variables as
“_slave
variables” (with a
leading underscore).
Injector counters (global)
Injector counters relate to the
Ndb
object used to listen to
cluster events by the binary log injector thread. Even when
not writing a binary log, mysqld processes
attached to a MySQL Cluster continue to listen for some
events, such as schema changes.
We refer to the status variables that correspond to NDB API
injector counters as “_injector
variables” (with a leading underscore).
Server (Global) counters (global)
This set of counters relates to all
Ndb
objects currently used by
this mysqld. This includes all MySQL client
applications, the slave SQL thread (if any), the binlog
injector, and the NDB
utility
thread.
We refer to the status variables that correspond to these counters as “global variables” or “mysqld-level variables”.
You can obtain values for a particular set of variables by
additionally filtering for the substring
session
, slave
, or
injector
in the variable name (along with the
common prefix Ndb_api
). For
_session
variables, this can be done as shown
here:
mysql> SHOW STATUS LIKE 'ndb_api%session';
+--------------------------------------------+---------+
| Variable_name | Value |
+--------------------------------------------+---------+
| Ndb_api_wait_exec_complete_count_session | 2 |
| Ndb_api_wait_scan_result_count_session | 0 |
| Ndb_api_wait_meta_request_count_session | 1 |
| Ndb_api_wait_nanos_count_session | 8144375 |
| Ndb_api_bytes_sent_count_session | 68 |
| Ndb_api_bytes_received_count_session | 84 |
| Ndb_api_trans_start_count_session | 1 |
| Ndb_api_trans_commit_count_session | 1 |
| Ndb_api_trans_abort_count_session | 0 |
| Ndb_api_trans_close_count_session | 1 |
| Ndb_api_pk_op_count_session | 1 |
| Ndb_api_uk_op_count_session | 0 |
| Ndb_api_table_scan_count_session | 0 |
| Ndb_api_range_scan_count_session | 0 |
| Ndb_api_pruned_scan_count_session | 0 |
| Ndb_api_scan_batch_count_session | 0 |
| Ndb_api_read_row_count_session | 1 |
| Ndb_api_trans_local_read_row_count_session | 1 |
+--------------------------------------------+---------+
18 rows in set (0.50 sec)
To obtain a listing of the NDB API mysqld-level
status variables, filter for variable names beginning with
ndb_api
and ending in
_count
, like this:
mysql>SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS
->WHERE VARIABLE_NAME LIKE 'ndb_api%count';
+------------------------------------+----------------+ | VARIABLE_NAME | VARIABLE_VALUE | +------------------------------------+----------------+ | NDB_API_WAIT_EXEC_COMPLETE_COUNT | 4 | | NDB_API_WAIT_SCAN_RESULT_COUNT | 3 | | NDB_API_WAIT_META_REQUEST_COUNT | 28 | | NDB_API_WAIT_NANOS_COUNT | 53756398 | | NDB_API_BYTES_SENT_COUNT | 1060 | | NDB_API_BYTES_RECEIVED_COUNT | 9724 | | NDB_API_TRANS_START_COUNT | 3 | | NDB_API_TRANS_COMMIT_COUNT | 2 | | NDB_API_TRANS_ABORT_COUNT | 0 | | NDB_API_TRANS_CLOSE_COUNT | 3 | | NDB_API_PK_OP_COUNT | 2 | | NDB_API_UK_OP_COUNT | 0 | | NDB_API_TABLE_SCAN_COUNT | 1 | | NDB_API_RANGE_SCAN_COUNT | 0 | | NDB_API_PRUNED_SCAN_COUNT | 0 | | NDB_API_SCAN_BATCH_COUNT | 0 | | NDB_API_READ_ROW_COUNT | 2 | | NDB_API_TRANS_LOCAL_READ_ROW_COUNT | 2 | | NDB_API_EVENT_DATA_COUNT | 0 | | NDB_API_EVENT_NONDATA_COUNT | 0 | | NDB_API_EVENT_BYTES_COUNT | 0 | +------------------------------------+----------------+ 21 rows in set (0.09 sec)
Not all counters are reflected in all 4 sets of status variables.
For the event counters DataEventsRecvdCount
,
NondataEventsRecvdCount
, and
EventBytesRecvdCount
, only
_injector
and mysqld-level
NDB API status variables are available:
mysql> SHOW STATUS LIKE 'ndb_api%event%';
+--------------------------------------+-------+
| Variable_name | Value |
+--------------------------------------+-------+
| Ndb_api_event_data_count_injector | 0 |
| Ndb_api_event_nondata_count_injector | 0 |
| Ndb_api_event_bytes_count_injector | 0 |
| Ndb_api_event_data_count | 0 |
| Ndb_api_event_nondata_count | 0 |
| Ndb_api_event_bytes_count | 0 |
+--------------------------------------+-------+
6 rows in set (0.00 sec)
_injector
status variables are not implemented
for any other NDB API counters, as shown here:
mysql> SHOW STATUS LIKE 'ndb_api%injector%';
+--------------------------------------+-------+
| Variable_name | Value |
+--------------------------------------+-------+
| Ndb_api_event_data_count_injector | 0 |
| Ndb_api_event_nondata_count_injector | 0 |
| Ndb_api_event_bytes_count_injector | 0 |
+--------------------------------------+-------+
3 rows in set (0.00 sec)
The names of the status variables can easily be associated with the names of the corresponding counters. Each NDB API statistics counter is listed in the following table with a description as well as the names of any MySQL server status variables corresponding to this counter.
Counter Name | Description |
---|---|
Status Variables (by statistic type):
| |
WaitExecCompleteCount | Number of times thread has been blocked while waiting for execution of
an operation to complete. Includes all
execute()
calls as well as implicit executes for blob operations and
auto-increment not visible to clients. |
WaitScanResultCount | Number of times thread has been blocked while waiting for a scan-based signal, such waiting for additional results, or for a scan to close. |
WaitMetaRequestCount | Number of times thread has been blocked waiting for a metadata-based signal; this can occur when waiting for a DDL operation or for an epoch to be started (or ended). |
WaitNanosCount | Total time (in nanoseconds) spent waiting for some type of signal from the data nodes. |
BytesSentCount | Amount of data (in bytes) sent to the data nodes |
BytesRecvdCount | Amount of data (in bytes) received from the data nodes |
TransStartCount | Number of transactions started. |
TransCommitCount | Number of transactions committed. |
TransAbortCount | Number of transactions aborted. |
TransCloseCount | Number of transactions aborted. (This value may be greater than the sum
of TransCommitCount and
TransAbortCount .) |
PkOpCount | Number of operations based on or using primary keys. This count includes blob-part table operations, implicit unlocking operations, and auto-increment operations, as well as primary key operations normally visible to MySQL clients. |
UkOpCount | Number of operations based on or using unique keys. |
TableScanCount | Number of table scans that have been started. This includes scans of internal tables. |
RangeScanCount | Number of range scans that have been started. |
PrunedScanCount | Number of scans that have been pruned to a single partition. |
ScanBatchCount | Number of batches of rows received. (A batch in this context is a set of scan results from a single fragment.) |
ReadRowCount | Total number of rows that have been read. Includes rows read using primary key, unique key, and scan operations. |
TransLocalReadRowCount | Number of rows read from the data same node on which the transaction was being run. |
DataEventsRecvdCount | Number of row change events received. |
| |
NondataEventsRecvdCount | Number of events received, other than row change events. |
EventBytesRecvdCount | Number of bytes of events received. |
|
To see all counts of committed transactions—that is, all
TransCommitCount
counter status
variables—you can filter the results of
SHOW STATUS
for the substring
trans_commit_count
, like this:
mysql> SHOW STATUS LIKE '%trans_commit_count%';
+------------------------------------+-------+
| Variable_name | Value |
+------------------------------------+-------+
| Ndb_api_trans_commit_count_session | 1 |
| Ndb_api_trans_commit_count_slave | 0 |
| Ndb_api_trans_commit_count | 2 |
+------------------------------------+-------+
3 rows in set (0.00 sec)
From this you can determine that 1 transaction has been committed in the current mysql client session, and 2 transactions have been committed on this mysqld since it was last restarted.
You can see how various NDB API counters are incremented by a
given SQL statement by comparing the values of the corresponding
_session
status variables immediately before
and after performing the statement. In this example, after getting
the initial values from SHOW
STATUS
, we create in the test
database an NDB
table, named
t
, that has a single column:
mysql>SHOW STATUS LIKE 'ndb_api%session%';
+--------------------------------------------+--------+ | Variable_name | Value | +--------------------------------------------+--------+ | Ndb_api_wait_exec_complete_count_session | 2 | | Ndb_api_wait_scan_result_count_session | 0 | | Ndb_api_wait_meta_request_count_session | 3 | | Ndb_api_wait_nanos_count_session | 820705 | | Ndb_api_bytes_sent_count_session | 132 | | Ndb_api_bytes_received_count_session | 372 | | Ndb_api_trans_start_count_session | 1 | | Ndb_api_trans_commit_count_session | 1 | | Ndb_api_trans_abort_count_session | 0 | | Ndb_api_trans_close_count_session | 1 | | Ndb_api_pk_op_count_session | 1 | | Ndb_api_uk_op_count_session | 0 | | Ndb_api_table_scan_count_session | 0 | | Ndb_api_range_scan_count_session | 0 | | Ndb_api_pruned_scan_count_session | 0 | | Ndb_api_scan_batch_count_session | 0 | | Ndb_api_read_row_count_session | 1 | | Ndb_api_trans_local_read_row_count_session | 1 | +--------------------------------------------+--------+ 18 rows in set (0.00 sec) mysql>USE test;
Database changed mysql>CREATE TABLE t (c INT) ENGINE NDBCLUSTER;
Query OK, 0 rows affected (0.85 sec)
Now you can execute a new SHOW
STATUS
statement and observe the changes, as shown here
(with the changed rows highlighted in the output):
mysql> SHOW STATUS LIKE 'ndb_api%session%'; +--------------------------------------------+-----------+ | Variable_name | Value | +--------------------------------------------+-----------+ | Ndb_api_wait_exec_complete_count_session | 8 | | Ndb_api_wait_scan_result_count_session | 0 | | Ndb_api_wait_meta_request_count_session | 17 | | Ndb_api_wait_nanos_count_session | 706871709 | | Ndb_api_bytes_sent_count_session | 2376 | | Ndb_api_bytes_received_count_session | 3844 | | Ndb_api_trans_start_count_session | 4 | | Ndb_api_trans_commit_count_session | 4 | | Ndb_api_trans_abort_count_session | 0 | | Ndb_api_trans_close_count_session | 4 | | Ndb_api_pk_op_count_session | 6 | | Ndb_api_uk_op_count_session | 0 | | Ndb_api_table_scan_count_session | 0 | | Ndb_api_range_scan_count_session | 0 | | Ndb_api_pruned_scan_count_session | 0 | | Ndb_api_scan_batch_count_session | 0 | | Ndb_api_read_row_count_session | 2 | | Ndb_api_trans_local_read_row_count_session | 1 | +--------------------------------------------+-----------+ 18 rows in set (0.00 sec)
Similarly, you can see the changes in the NDB API statistics
counters caused by inserting a row into t
:
Insert the row, then run the same SHOW
STATUS
statement used in the previous example, as shown
here:
mysql>INSERT INTO t VALUES (100);
Query OK, 1 row affected (0.00 sec) mysql>SHOW STATUS LIKE 'ndb_api%session%';
+--------------------------------------------+-----------+ | Variable_name | Value | +--------------------------------------------+-----------+ | Ndb_api_wait_exec_complete_count_session | 11 | | Ndb_api_wait_scan_result_count_session | 6 | | Ndb_api_wait_meta_request_count_session | 20 | | Ndb_api_wait_nanos_count_session | 707370418 | | Ndb_api_bytes_sent_count_session | 2724 | | Ndb_api_bytes_received_count_session | 4116 | | Ndb_api_trans_start_count_session | 7 | | Ndb_api_trans_commit_count_session | 6 | | Ndb_api_trans_abort_count_session | 0 | | Ndb_api_trans_close_count_session | 7 | | Ndb_api_pk_op_count_session | 8 | | Ndb_api_uk_op_count_session | 0 | | Ndb_api_table_scan_count_session | 1 | | Ndb_api_range_scan_count_session | 0 | | Ndb_api_pruned_scan_count_session | 0 | | Ndb_api_scan_batch_count_session | 0 | | Ndb_api_read_row_count_session | 3 | | Ndb_api_trans_local_read_row_count_session | 2 | +--------------------------------------------+-----------+ 18 rows in set (0.00 sec)
We can make a number of observations from these results:
Although we created t
with no explicit
primary key, 5 primary key operations were performed in doing
so (the difference in the “before” and
“after” values of
Ndb_api_pk_op_count_session
,
or 6 minus 1). This reflects the creation of the hidden
primary key that is a feature of all tables using the
NDB
storage engine.
By comparing successive values for
Ndb_api_wait_nanos_count_session
,
we can see that the NDB API operations implementing the
CREATE TABLE
statement waited
much longer (706871709 - 820705 = 706051004 nanoseconds, or
approximately 0.7 second) for responses from the data nodes
than those executed by the
INSERT
(707370418 - 706871709 =
498709 ns or roughly .0005 second). The execution times
reported for these statements in the mysql
client correlate roughly with these figures.
On platforms without sufficient (nanosecond) time resolution,
small changes in the value of the
WaitNanosCount
NDB API counter due to SQL
statements that execute very quickly may not always be visible
in the values of
Ndb_api_wait_nanos_count_session
,
Ndb_api_wait_nanos_count_slave
,
or Ndb_api_wait_nanos_count
.
The INSERT
statement
incremented both the ReadRowCount
and
TransLocalReadRowCount
NDB API statistics
counters, as reflected by the increased values of
Ndb_api_read_row_count_session
and
Ndb_api_trans_local_read_row_count_session
.
MySQL Cluster supports asynchronous replication, more usually referred to simply as “replication”. This section explains how to set up and manage a configuration in which one group of computers operating as a MySQL Cluster replicates to a second computer or group of computers. We assume some familiarity on the part of the reader with standard MySQL replication as discussed elsewhere in this Manual. (See Chapter 18, Replication).
Normal (non-clustered) replication involves a “master”
server and a “slave” server, the master being the
source of the operations and data to be replicated and the slave
being the recipient of these. In MySQL Cluster, replication is
conceptually very similar but can be more complex in practice, as it
may be extended to cover a number of different configurations
including replicating between two complete clusters. Although a
MySQL Cluster itself depends on the NDB
storage engine for clustering functionality, it is not necessary to
use NDB
as the storage engine for the
slave's copies of the replicated tables (see
Replication from NDB to other storage engines).
However, for maximum availability, it is possible (and preferable)
to replicate from one MySQL Cluster to another, and it is this
scenario that we discuss, as shown in the following figure:
In this scenario, the replication process is one in which successive
states of a master cluster are logged and saved to a slave cluster.
This process is accomplished by a special thread known as the NDB
binary log injector thread, which runs on each MySQL server and
produces a binary log (binlog
). This thread
ensures that all changes in the cluster producing the binary
log—and not just those changes that are effected through the
MySQL Server—are inserted into the binary log with the correct
serialization order. We refer to the MySQL replication master and
replication slave servers as replication servers or replication
nodes, and the data flow or line of communication between them as a
replication channel.
For information about performing point-in-time recovery with MySQL Cluster and MySQL Cluster Replication, see Section 19.6.9.2, “Point-In-Time Recovery Using MySQL Cluster Replication”.
NDB API _slave status variables.
NDB API counters can provide enhanced monitoring capabilities on
MySQL Cluster replication slaves. These are implemented as NDB
statistics _slave
status variables, as seen in
the output of SHOW STATUS
, or in
the results of queries against the
SESSION_STATUS
or
GLOBAL_STATUS
table in a mysql client session connected to a
MySQL Server that is acting as a slave in MySQL Cluster
Replication. By comparing the values of these status variables
before and after the execution of statements affecting replicated
NDB
tables, you can observe the
corresponding actions taken on the NDB API level by the slave,
which can be useful when monitoring or troubleshooting MySQL
Cluster Replication.
Section 19.5.16, “NDB API Statistics Counters and Variables”, provides
additional information.
Replication from NDB to non-NDB tables.
It is possible to replicate NDB
tables from a MySQL Cluster acting as the master to tables using
other MySQL storage engines such as
InnoDB
or
MyISAM
on a slave
mysqld. This is subject to a number of
conditions; see
Replication from NDB to other storage engines, and
Replication from NDB to a nontransactional storage engine,
for more information.
Throughout this section, we use the following abbreviations or symbols for referring to the master and slave clusters, and to processes and commands run on the clusters or cluster nodes:
Symbol or Abbreviation | Description (Refers to...) |
---|---|
M | The cluster serving as the (primary) replication master |
S | The cluster acting as the (primary) replication slave |
shell | Shell command to be issued on the master cluster |
mysql | MySQL client command issued on a single MySQL server running as an SQL node on the master cluster |
mysql | MySQL client command to be issued on all SQL nodes participating in the replication master cluster |
shell | Shell command to be issued on the slave cluster |
mysql | MySQL client command issued on a single MySQL server running as an SQL node on the slave cluster |
mysql | MySQL client command to be issued on all SQL nodes participating in the replication slave cluster |
C | Primary replication channel |
C' | Secondary replication channel |
M' | Secondary replication master |
S' | Secondary replication slave |
A replication channel requires two MySQL servers acting as replication servers (one each for the master and slave). For example, this means that in the case of a replication setup with two replication channels (to provide an extra channel for redundancy), there will be a total of four replication nodes, two per cluster.
Replication of a MySQL Cluster as described in this section and
those following is dependent on row-based replication. This means
that the replication master MySQL server must be running with
--binlog-format=ROW
or
--binlog-format=MIXED
, as described
in Section 19.6.6, “Starting MySQL Cluster Replication (Single Replication Channel)”. For
general information about row-based replication, see
Section 18.2.1, “Replication Formats”.
If you attempt to use MySQL Cluster Replication with
--binlog-format=STATEMENT
,
replication fails to work properly because the
ndb_binlog_index
table on the master and the
epoch
column of the
ndb_apply_status
table on the slave are not
updated (see
Section 19.6.4, “MySQL Cluster Replication Schema and Tables”). Instead,
only updates on the MySQL server acting as the replication
master propagate to the slave, and no updates from any other SQL
nodes on the master cluster are replicated.
The default value for the
--binlog-format
option in MySQL
Cluster NDB 7.5 is MIXED
.
Each MySQL server used for replication in either cluster must be
uniquely identified among all the MySQL replication servers
participating in either cluster (you cannot have replication
servers on both the master and slave clusters sharing the same
ID). This can be done by starting each SQL node using the
--server-id=
option,
where id
id
is a unique integer. Although
it is not strictly necessary, we will assume for purposes of this
discussion that all MySQL Cluster binaries are of the same release
version.
It is generally true in MySQL Replication that both MySQL servers (mysqld processes) involved must be compatible with one another with respect to both the version of the replication protocol used and the SQL feature sets which they support (see Section 18.4.2, “Replication Compatibility Between MySQL Versions”). It is due to such differences between the binaries in the MySQL Cluster and MySQL Server 5.7 distributions that MySQL Cluster Replication has the additional requirement that both mysqld binaries come from a MySQL Cluster distribution. The simplest and easiest way to assure that the mysqld servers are compatible is to use the same MySQL Cluster distribution for all master and slave mysqld binaries.
We assume that the slave server or cluster is dedicated to replication of the master, and that no other data is being stored on it.
All NDB
tables being replicated must be created
using a MySQL server and client. Tables and other database objects
created using the NDB API (with, for example,
Dictionary::createTable()
) are
not visible to a MySQL server and so are not replicated. Updates
by NDB API applications to existing tables that were created using
a MySQL server can be replicated.
It is possible to replicate a MySQL Cluster using statement-based replication. However, in this case, the following restrictions apply:
All updates to data rows on the cluster acting as the master must be directed to a single MySQL server.
It is not possible to replicate a cluster using multiple simultaneous MySQL replication processes.
Only changes made at the SQL level are replicated.
These are in addition to the other limitations of statement-based replication as opposed to row-based replication; see Section 18.2.1.1, “Advantages and Disadvantages of Statement-Based and Row-Based Replication”, for more specific information concerning the differences between the two replication formats.
This section discusses known problems or issues when using replication with MySQL Cluster NDB 7.5.
Loss of master-slave connection.
A loss of connection can occur either between the replication
master SQL node and the replication slave SQL node, or between
the replication master SQL node and the data nodes in the master
cluster. In the latter case, this can occur not only as a result
of loss of physical connection (for example, a broken network
cable), but due to the overflow of data node event buffers; if
the SQL node is too slow to respond, it may be dropped by the
cluster (this is controllable to some degree by adjusting the
MaxBufferedEpochs
and
TimeBetweenEpochs
configuration parameters). If this occurs, it is
entirely possible for new data to be inserted into the master
cluster without being recorded in the replication master's
binary log. For this reason, to guarantee high
availability, it is extremely important to maintain a backup
replication channel, to monitor the primary channel, and to fail
over to the secondary replication channel when necessary to keep
the slave cluster synchronized with the master. MySQL Cluster is
not designed to perform such monitoring on its own; for this, an
external application is required.
The replication master issues a “gap” event when
connecting or reconnecting to the master cluster. (A gap event is
a type of “incident event,” which indicates an
incident that occurs that affects the contents of the database but
that cannot easily be represented as a set of changes. Examples of
incidents are server crashes, database resynchronization, (some)
software updates, and (some) hardware changes.) When the slave
encounters a gap in the replication log, it stops with an error
message. This message is available in the output of
SHOW SLAVE STATUS
, and indicates
that the SQL thread has stopped due to an incident registered in
the replication stream, and that manual intervention is required.
See Section 19.6.8, “Implementing Failover with MySQL Cluster Replication”, for more
information about what to do in such circumstances.
Because MySQL Cluster is not designed on its own to monitor replication status or provide failover, if high availability is a requirement for the slave server or cluster, then you must set up multiple replication lines, monitor the master mysqld on the primary replication line, and be prepared fail over to a secondary line if and as necessary. This must be done manually, or possibly by means of a third-party application. For information about implementing this type of setup, see Section 19.6.7, “Using Two Replication Channels for MySQL Cluster Replication”, and Section 19.6.8, “Implementing Failover with MySQL Cluster Replication”.
However, if you are replicating from a standalone MySQL server to a MySQL Cluster, one channel is usually sufficient.
Circular replication. MySQL Cluster Replication supports circular replication, as shown in the next example. The replication setup involves three MySQL Clusters numbered 1, 2, and 3, in which Cluster 1 acts as the replication master for Cluster 2, Cluster 2 acts as the master for Cluster 3, and Cluster 3 acts as the master for Cluster 1, thus completing the circle. Each MySQL Cluster has two SQL nodes, with SQL nodes A and B belonging to Cluster 1, SQL nodes C and D belonging to Cluster 2, and SQL nodes E and F belonging to Cluster 3.
Circular replication using these clusters is supported as long as the following conditions are met:
The SQL nodes on all masters and slaves are the same
All SQL nodes acting as replication masters and slaves are
started using the
--log-slave-updates
option
This type of circular replication setup is shown in the following diagram:
In this scenario, SQL node A in Cluster 1 replicates to SQL node C in Cluster 2; SQL node C replicates to SQL node E in Cluster 3; SQL node E replicates to SQL node A. In other words, the replication line (indicated by the red arrows in the diagram) directly connects all SQL nodes used as replication masters and slaves.
It should also be possible to set up circular replication in which not all master SQL nodes are also slaves, as shown here:
In this case, different SQL nodes in each cluster are used as
replication masters and slaves. However, you must
not start any of the SQL nodes using
--log-slave-updates
. This type of
circular replication scheme for MySQL Cluster, in which the line
of replication (again indicated by the red arrows in the diagram)
is discontinuous, should be possible, but it should be noted that
it has not yet been thoroughly tested and must therefore still be
considered experimental.
The NDB
storage engine uses
idempotent execution mode,
which suppresses duplicate-key and other errors that otherwise
break circular replication of MySQL Cluster. This is equivalent
to setting the global
slave_exec_mode
system variable
to IDEMPOTENT
, although this is not necessary
in MySQL Cluster replication, since MySQL Cluster sets this
variable automatically and ignores any attempts to set it
explicitly.
MySQL Cluster replication and primary keys.
In the event of a node failure, errors in replication of
NDB
tables without primary keys can
still occur, due to the possibility of duplicate rows being
inserted in such cases. For this reason, it is highly
recommended that all NDB
tables
being replicated have primary keys.
MySQL Cluster Replication and Unique Keys.
In older versions of MySQL Cluster, operations that updated
values of unique key columns of NDB
tables could result in duplicate-key errors when replicated.
This issue is solved for replication between
NDB
tables by deferring unique key
checks until after all table row updates have been performed.
Deferring constraints in this way is currently supported only by
NDB
. Thus, updates of unique keys
when replicating from NDB
to a
different storage engine such as
MyISAM
or
InnoDB
are still not supported.
The problem encountered when replicating without deferred checking
of unique key updates can be illustrated using
NDB
table such as
t
, is created and populated on the master (and
replicated to a slave that does not support deferred unique key
updates) as shown here:
CREATE TABLE t ( p INT PRIMARY KEY, c INT, UNIQUE KEY u (c) ) ENGINE NDB; INSERT INTO t VALUES (1,1), (2,2), (3,3), (4,4), (5,5);
The following UPDATE
statement on
t
succeeded on the master, since the rows
affected are processed in the order determined by the
ORDER BY
option, performed over the entire
table:
UPDATE t SET c = c - 1 ORDER BY p;
However, the same statement failed with a duplicate key error or other constraint violation on the slave, because the ordering of the row updates was done for one partition at a time, rather than for the table as a whole.
Every NDB
table is implicitly
partitioned by key when it is created. See
Section 20.2.5, “KEY Partitioning”, for more information.
GTIDs not supported.
Replication using global transaction IDs is not compatible with
the NDB
storage engine, and is not supported.
Enabling GTIDs is likely to cause MySQL Cluster Replication to
fail.
Multi-threaded slaves not supported.
MySQL Cluster does not support multi-threaded slaves, and
setting related system variables such as
slave_parallel_workers
,
slave_checkpoint_group
, and
slave_checkpoint_group
(or the
equivalent mysqld startup options) has no
effect.
This is because the slave may not be able to separate transactions
occurring in one database from those in another if they are
written within the same epoch. In addition, every transaction
handled by the NDB
storage engine
involves at least two databases—the target database and the
mysql
system database—due to the
requirement for updating the
mysql.ndb_apply_status
table (see
Section 19.6.4, “MySQL Cluster Replication Schema and Tables”). This in turn
breaks the requirement for multi-threading that the transaction is
specific to a given database.
Restarting with --initial.
Restarting the cluster with the
--initial
option causes the
sequence of GCI and epoch numbers to start over from
0
. (This is generally true of MySQL Cluster
and not limited to replication scenarios involving Cluster.) The
MySQL servers involved in replication should in this case be
restarted. After this, you should use the
RESET MASTER
and
RESET SLAVE
statements to clear
the invalid ndb_binlog_index
and
ndb_apply_status
tables, respectively.
Replication from NDB to other storage engines.
It is possible to replicate an NDB
table on the master to a table using a different storage engine
on the slave, taking into account the restrictions listed here:
Multi-master and circular replication are not supported
(tables on both the master and the slave must use the
NDB
storage engine for this to
work).
Using a storage engine which does not perform binary logging for slave tables requires special handling.
Use of a nontransactional storage engine for slave tables also requires special handling.
The master mysqld must be started with
--ndb-log-update-as-write=0
or
--ndb-log-update-as-write=OFF
.
The next few paragraphs provide additional information about each of the issues just described.
Multiple masters not supported when replicating NDB to other storage
engines.
For replication from NDB
to a
different storage engine, the relationship between the two
databases must be a simple master-slave one. This means that
circular or master-master replication is not supported between
MySQL Cluster and other storage engines.
In addition, it is not possible to configure more than one
replication channel when replicating between
NDB
and a different storage engine.
(However, a MySQL Cluster database can
simultaneously replicate to multiple slave MySQL Cluster
databases.) If the master uses NDB
tables, it is still possible to have more than one MySQL Server
maintain a binary log of all changes; however, for the slave to
change masters (fail over), the new master-slave relationship must
be explicitly defined on the slave.
Replicating NDB to a slave storage engine that does not perform binary logging. If you attempt to replicate from a MySQL Cluster to a slave that uses a storage engine that does not handle its own binary logging, the replication process aborts with the error Binary logging not possible ... Statement cannot be written atomically since more than one engine involved and at least one engine is self-logging (Error 1595). It is possible to work around this issue in one of the following ways:
Turn off binary logging on the slave.
This can be accomplished by setting
sql_log_bin = 0
.
Change the storage engine used for the mysql.ndb_apply_status table.
Causing this table to use an engine that does not handle its
own binary logging can also eliminate the conflict. This can
be done by issuing a statement such as
ALTER TABLE
mysql.ndb_apply_status ENGINE=MyISAM
on the slave.
It is safe to do this when using a
non-NDB
storage engine on the
slave, since you do not then need to worry about keeping
multiple slave SQL nodes synchronized.
Filter out changes to the mysql.ndb_apply_status table on the slave.
This can be done by starting the slave SQL node with
--replicate-ignore-table=mysql.ndb_apply_status
.
If you need for other tables to be ignored by replication,
you might wish to use an appropriate
--replicate-wild-ignore-table
option instead.
You should not disable replication or
binary logging of mysql.ndb_apply_status
or
change the storage engine used for this table when replicating
from one MySQL Cluster to another. See
Replication and binary log filtering rules with replication between
MySQL Clusters,
for details.
Replication from NDB to a nontransactional storage engine.
When replicating from NDB
to a
nontransactional storage engine such as
MyISAM
, you may encounter
unnecessary duplicate key errors when replicating
INSERT ...
ON DUPLICATE KEY UPDATE
statements. You can suppress
these by using
--ndb-log-update-as-write=0
,
which forces updates to be logged as writes (rather than as
updates).
Replication and binary log filtering rules with replication between
MySQL Clusters.
If you are using any of the options
--replicate-do-*
,
--replicate-ignore-*
,
--binlog-do-db
, or
--binlog-ignore-db
to filter
databases or tables being replicated, care must be taken not to
block replication or binary logging of the
mysql.ndb_apply_status
, which is required for
replication between MySQL Clusters to operate properly. In
particular, you must keep in mind the following:
Using
--replicate-do-db=
(and no other db_name
--replicate-do-*
or
--replicate-ignore-*
options) means that
only tables in database
db_name
are replicated. In this
case, you should also use
--replicate-do-db=mysql
,
--binlog-do-db=mysql
, or
--replicate-do-table=mysql.ndb_apply_status
to ensure that mysql.ndb_apply_status
is
populated on slaves.
Using
--binlog-do-db=
(and no other db_name
--binlog-do-db
options) means that changes only to
tables in database db_name
are
written to the binary log. In this case, you should also use
--replicate-do-db=mysql
,
--binlog-do-db=mysql
, or
--replicate-do-table=mysql.ndb_apply_status
to ensure that mysql.ndb_apply_status
is
populated on slaves.
Using
--replicate-ignore-db=mysql
means that no tables in the mysql
database
are replicated. In this case, you should also use
--replicate-do-table=mysql.ndb_apply_status
to ensure that mysql.ndb_apply_status
is
replicated.
Using --binlog-ignore-db=mysql
means that no changes to tables in the
mysql
database are written to the binary
log. In this case, you should also use
--replicate-do-table=mysql.ndb_apply_status
to ensure that mysql.ndb_apply_status
is
replicated.
You should also remember that each replication rule requires the following:
Its own --replicate-do-*
or
--replicate-ignore-*
option, and that
multiple rules cannot be expressed in a single replication
filtering option. For information about these rules, see
Section 18.1.6, “Replication and Binary Logging Options and Variables”.
Its own --binlog-do-db
or
--binlog-ignore-db
option, and
that multiple rules cannot be expressed in a single binary log
filtering option. For information about these rules, see
Section 6.4.4, “The Binary Log”.
If you are replicating a MySQL Cluster to a slave that uses a
storage engine other than NDB
, the
considerations just given previously may not apply, as discussed
elsewhere in this section.
MySQL Cluster Replication and IPv6. Currently, the NDB API and MGM API do not support IPv6. However, MySQL Servers—including those acting as SQL nodes in a MySQL Cluster—can use IPv6 to contact other MySQL Servers. This means that you can replicate between MySQL Clusters using IPv6 to connect the master and slave SQL nodes as shown by the dotted arrow in the following diagram:
However, all connections originating within the MySQL Cluster—represented in the preceding diagram by solid arrows—must use IPv4. In other words, all MySQL Cluster data nodes, management servers, and management clients must be accessible from one another using IPv4. In addition, SQL nodes must use IPv4 to communicate with the cluster.
Since there is currently no support in the NDB and MGM APIs for IPv6, any applications written using these APIs must also make all connections using IPv4.
Attribute promotion and demotion.
MySQL Cluster Replication includes support for attribute
promotion and demotion. The implementation of the latter
distinguishes between lossy and non-lossy type conversions, and
their use on the slave can be controlled by setting the
slave_type_conversions
global
server system variable.
For more information about attribute promotion and demotion in MySQL Cluster, see Row-based replication: attribute promotion and demotion.
Replication in MySQL Cluster makes use of a number of dedicated
tables in the mysql
database on each MySQL
Server instance acting as an SQL node in both the cluster being
replicated and the replication slave (whether the slave is a
single server or a cluster). These tables are created during the
MySQL installation process by the
mysql_install_db script, and include a table
for storing the binary log's indexing data. Since the
ndb_binlog_index
table is local to each MySQL
server and does not participate in clustering, it uses the
InnoDB
storage engine. This means that it must
be created separately on each mysqld
participating in the master cluster. (However, the binary log
itself contains updates from all MySQL servers in the cluster to
be replicated.) This table is defined as follows:
CREATE TABLE `ndb_binlog_index` ( `Position` BIGINT(20) UNSIGNED NOT NULL, `File` VARCHAR(255) NOT NULL, `epoch` BIGINT(20) UNSIGNED NOT NULL, `inserts` INT(10) UNSIGNED NOT NULL, `updates` INT(10) UNSIGNED NOT NULL, `deletes` INT(10) UNSIGNED NOT NULL, `schemaops` INT(10) UNSIGNED NOT NULL, `orig_server_id` INT(10) UNSIGNED NOT NULL, `orig_epoch` BIGINT(20) UNSIGNED NOT NULL, `gci` INT(10) UNSIGNED NOT NULL, `next_position` bigint(20) unsigned NOT NULL, `next_file` varchar(255) NOT NULL, PRIMARY KEY (`epoch`,`orig_server_id`,`orig_epoch`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
Prior to MySQL Cluster NDB 7.5.2, this table always used the
MyISAM
storage engine. If you are
upgrading from an earlier release, you can use
mysql_upgrade with the
--force
and
--upgrade-system-tables
options to cause it to execute an
ALTER TABLE ...
ENGINE=INNODB
statement on this table. Use of the
MyISAM
storage engine for this table
continues to be supported in MySQL Cluster NDB 7.5.2 and later
for backward compatibility.
ndb_binlog_index
may require additional disk
space after being converted to InnoDB
. If
this becomes an issue, you may be able to conserve space by
using an InnoDB
tablespace for this table,
changing its ROW_FORMAT
to
COMPRESSED
, or both. For more information,
see Section 14.1.19, “CREATE TABLESPACE Syntax”, and
Section 14.1.18, “CREATE TABLE Syntax”, as well as
Section 15.5, “InnoDB Tablespace Management”.
The size of this table is dependent on the number of epochs per
binary log file and the number of binary log files. The number of
epochs per binary log file normally depends on the amount of
binary log generated per epoch and the size of the binary log
file, with smaller epochs resulting in more epochs per file. You
should be aware that empty epochs produce inserts to the
ndb_binlog_index
table, even when the
--ndb-log-empty-epochs
option is
OFF
, meaning that the number of entries per
file depends on the length of time that the file is in use; that
is,
[number of epochs per file] = [time spent per file] / TimeBetweenEpochs
A busy MySQL Cluster writes to the binary log regularly and
presumably rotates binary log files more quickly than a quiet one.
This means that a “quiet” MySQL Cluster with
--ndb-log-empty-epochs=ON
can
actually have a much higher number of
ndb_binlog_index
rows per file than one with a
great deal of activity.
When mysqld is started with the
--ndb-log-orig
option, the
orig_server_id
and
orig_epoch
columns store, respectively, the ID
of the server on which the event originated and the epoch in which
the event took place on the originating server, which is useful in
MySQL Cluster replication setups employing multiple masters. The
SELECT
statement used to find the
closest binary log position to the highest applied epoch on the
slave in a multi-master setup (see
Section 19.6.10, “MySQL Cluster Replication: Multi-Master and Circular Replication”) employs
these two columns, which are not indexed. This can lead to
performance issues when trying to fail over, since the query must
perform a table scan, especially when the master has been running
with --ndb-log-empty-epochs=ON
. You
can improve multi-master failover times by adding an index to
these columns, as shown here:
ALTER TABLE mysql.ndb_binlog_index ADD INDEX orig_lookup USING BTREE (orig_server_id, orig_epoch);
Adding this index provides no benefit when replicating from a
single master to a single slave, since the query used to get the
binary log position in such cases makes no use of
orig_server_id
or
orig_epoch
.
See Section 19.6.8, “Implementing Failover with MySQL Cluster Replication”, for more
information about using the next_position
and
next_file
columns.
The following figure shows the relationship of the MySQL Cluster
replication master server, its binary log injector thread, and the
mysql.ndb_binlog_index
table.
An additional table, named ndb_apply_status
, is
used to keep a record of the operations that have been replicated
from the master to the slave. Unlike the case with
ndb_binlog_index
, the data in this table is not
specific to any one SQL node in the (slave) cluster, and so
ndb_apply_status
can use the
NDBCLUSTER
storage engine, as shown here:
CREATE TABLE `ndb_apply_status` ( `server_id` INT(10) UNSIGNED NOT NULL, `epoch` BIGINT(20) UNSIGNED NOT NULL, `log_name` VARCHAR(255) CHARACTER SET latin1 COLLATE latin1_bin NOT NULL, `start_pos` BIGINT(20) UNSIGNED NOT NULL, `end_pos` BIGINT(20) UNSIGNED NOT NULL, PRIMARY KEY (`server_id`) USING HASH ) ENGINE=NDBCLUSTER DEFAULT CHARSET=latin1;
The ndb_apply_status
table is populated only on
slaves, which means that, on the master, this table never contains
any rows; thus, there is no need to allow for
DataMemory
or
IndexMemory
to be allotted
to ndb_apply_status
there.
Because this table is populated from data originating on the
master, it should be allowed to replicate; any replication
filtering or binary log filtering rules that inadvertently prevent
the slave from updating ndb_apply_status
or the
master from writing into the binary log may prevent replication
between clusters from operating properly. For more information
about potential problems arising from such filtering rules, see
Replication and binary log filtering rules with replication between
MySQL Clusters.
The ndb_binlog_index
and
ndb_apply_status
tables are created in the
mysql
database because they should not be
explicitly replicated by the user. User intervention is normally
not required to create or maintain either of these tables, since
both ndb_binlog_index
and the
ndb_apply_status
are maintained by the
NDB
binary log (binlog) injector
thread. This keeps the master mysqld process
updated to changes performed by the
NDB
storage engine. The
NDB
binlog
injector thread receives events directly from the
NDB
storage engine. The
NDB
injector is responsible for
capturing all the data events within the cluster, and ensures that
all events which change, insert, or delete data are recorded in
the ndb_binlog_index
table. The slave I/O
thread transfers the events from the master's binary log to the
slave's relay log.
However, it is advisable to check for the existence and integrity
of these tables as an initial step in preparing a MySQL Cluster
for replication. It is possible to view event data recorded in the
binary log by querying the
mysql.ndb_binlog_index
table directly on the
master. This can be also be accomplished using the
SHOW BINLOG EVENTS
statement on
either the replication master or slave MySQL servers. (See
Section 14.7.5.2, “SHOW BINLOG EVENTS Syntax”.)
You can also obtain useful information from the output of
SHOW ENGINE NDB
STATUS
.
The ndb_schema
table is used to track schema
changes made to NDB
tables. It is
defined as shown here:
CREATE TABLE ndb_schema ( `db` VARBINARY(63) NOT NULL, `name` VARBINARY(63) NOT NULL, `slock` BINARY(32) NOT NULL, `query` BLOB NOT NULL, `node_id` INT UNSIGNED NOT NULL, `epoch` BIGINT UNSIGNED NOT NULL, `id` INT UNSIGNED NOT NULL, `version` INT UNSIGNED NOT NULL, `type` INT UNSIGNED NOT NULL, PRIMARY KEY USING HASH (db,name) ) ENGINE=NDB DEFAULT CHARSET=latin1;
Unlike the two tables previously mentioned in this section, the
ndb_schema
table is not visible either to MySQL
SHOW
statements, or in any
INFORMATION_SCHEMA
tables; however, it can be
seen in the output of ndb_show_tables, as shown
here:
shell> ndb_show_tables -t 2
id type state logging database schema name
4 UserTable Online Yes mysql def ndb_apply_status
5 UserTable Online Yes ndbworld def City
6 UserTable Online Yes ndbworld def Country
3 UserTable Online Yes mysql def NDB$BLOB_2_3
7 UserTable Online Yes ndbworld def CountryLanguage
2 UserTable Online Yes mysql def ndb_schema
NDBT_ProgramExit: 0 - OK
It is also possible to SELECT
from
this table in mysql and other MySQL client
applications, as shown here:
mysql> SELECT * FROM mysql.ndb_schema WHERE name='City' \G
*************************** 1. row ***************************
db: ndbworld
name: City
slock:
query: alter table City engine=ndb
node_id: 4
epoch: 0
id: 0
version: 0
type: 7
1 row in set (0.00 sec)
This can sometimes be useful when debugging applications.
When performing schema changes on
NDB
tables, applications should
wait until the ALTER TABLE
statement has returned in the MySQL client connection that
issued the statement before attempting to use the updated
definition of the table.
If the ndb_apply_status
table or the
ndb_schema
table does not exist on the slave,
ndb_restore re-creates the missing table or
tables (Bug #14612).
Conflict resolution for MySQL Cluster Replication requires the
presence of an additional mysql.ndb_replication
table. Currently, this table must be created manually. For
information about how to do this, see
Section 19.6.11, “MySQL Cluster Replication Conflict Resolution”.
Preparing the MySQL Cluster for replication consists of the following steps:
Check all MySQL servers for version compatibility (see Section 19.6.2, “General Requirements for MySQL Cluster Replication”).
Create a slave account on the master Cluster with the appropriate privileges:
mysqlM
>GRANT REPLICATION SLAVE
->ON *.* TO '
->slave_user
'@'slave_host
'IDENTIFIED BY '
slave_password
';
In the previous statement,
slave_user
is the slave account
user name, slave_host
is the host
name or IP address of the replication slave, and
slave_password
is the password to
assign to this account.
For example, to create a slave user account with the name
“myslave
,” logging in from the
host named “rep-slave
,” and
using the password “53cr37
,”
use the following GRANT
statement:
mysqlM
>GRANT REPLICATION SLAVE
->ON *.* TO 'myslave'@'rep-slave'
->IDENTIFIED BY '53cr37';
For security reasons, it is preferable to use a unique user account—not employed for any other purpose—for the replication slave account.
Configure the slave to use the master. Using the MySQL
Monitor, this can be accomplished with the
CHANGE MASTER TO
statement:
mysqlS
>CHANGE MASTER TO
->MASTER_HOST='
->master_host
',MASTER_PORT=
->master_port
,MASTER_USER='
->slave_user
',MASTER_PASSWORD='
slave_password
';
In the previous statement,
master_host
is the host name or IP
address of the replication master,
master_port
is the port for the
slave to use for connecting to the master,
slave_user
is the user name set up
for the slave on the master, and
slave_password
is the password set
for that user account in the previous step.
For example, to tell the slave to replicate from the MySQL
server whose host name is
“rep-master
,” using the
replication slave account created in the previous step, use
the following statement:
mysqlS
>CHANGE MASTER TO
->MASTER_HOST='rep-master',
->MASTER_PORT=3306,
->MASTER_USER='myslave',
->MASTER_PASSWORD='53cr37';
For a complete list of options that can be used with this statement, see Section 14.4.2.1, “CHANGE MASTER TO Syntax”.
To provide replication backup capability, you also need to add
an --ndb-connectstring
option
to the slave's my.cnf
file prior to
starting the replication process. See
Section 19.6.9, “MySQL Cluster Backups With MySQL Cluster Replication”, for
details.
For additional options that can be set in
my.cnf
for replication slaves, see
Section 18.1.6, “Replication and Binary Logging Options and Variables”.
If the master cluster is already in use, you can create a backup of the master and load this onto the slave to cut down on the amount of time required for the slave to synchronize itself with the master. If the slave is also running MySQL Cluster, this can be accomplished using the backup and restore procedure described in Section 19.6.9, “MySQL Cluster Backups With MySQL Cluster Replication”.
ndb-connectstring=management_host
[:port
]
In the event that you are not using MySQL Cluster on the replication slave, you can create a backup with this command on the replication master:
shellM
>mysqldump --master-data=1
Then import the resulting data dump onto the slave by copying
the dump file over to the slave. After this, you can use the
mysql client to import the data from the
dumpfile into the slave database as shown here, where
dump_file
is the name of the file
that was generated using mysqldump on the
master, and db_name
is the name of
the database to be replicated:
shellS
>mysql -u root -p
db_name
<dump_file
For a complete list of options to use with mysqldump, see Section 5.5.4, “mysqldump — A Database Backup Program”.
If you copy the data to the slave in this fashion, you
should make sure that the slave is started with the
--skip-slave-start
option on
the command line, or else include
skip-slave-start
in the slave's
my.cnf
file to keep it from trying to
connect to the master to begin replicating before all the
data has been loaded. Once the data loading has completed,
follow the additional steps outlined in the next two
sections.
Ensure that each MySQL server acting as a replication master
is configured with a unique server ID, and with binary logging
enabled, using the row format. (See
Section 18.2.1, “Replication Formats”.) These options can be
set either in the master server's my.cnf
file, or on the command line when starting the master
mysqld process. See
Section 19.6.6, “Starting MySQL Cluster Replication (Single Replication Channel)”, for
information regarding the latter option.
This section outlines the procedure for starting MySQL Cluster replication using a single replication channel.
Start the MySQL replication master server by issuing this command:
shellM
>mysqld --ndbcluster --server-id=
id
\--log-bin &
In the previous statement, id
is
this server's unique ID (see
Section 19.6.2, “General Requirements for MySQL Cluster Replication”). This
starts the server's mysqld process with
binary logging enabled using the proper logging format.
You can also start the master with
--binlog-format=MIXED
, in
which case row-based replication is used automatically when
replicating between clusters. STATEMENT
based binary logging is not supported for MySQL Cluster
Replication (see
Section 19.6.2, “General Requirements for MySQL Cluster Replication”).
Start the MySQL replication slave server as shown here:
shellS
>mysqld --ndbcluster --server-id=
id
&
In the command just shown, id
is
the slave server's unique ID. It is not necessary to enable
logging on the replication slave.
You should use the
--skip-slave-start
option
with this command or else you should include
skip-slave-start
in the slave server's
my.cnf
file, unless you want
replication to begin immediately. With the use of this
option, the start of replication is delayed until the
appropriate START SLAVE
statement has been issued, as explained in Step 4 below.
It is necessary to synchronize the slave server with the master server's replication binary log. If binary logging has not previously been running on the master, run the following statement on the slave:
mysqlS
>CHANGE MASTER TO
->MASTER_LOG_FILE='',
->MASTER_LOG_POS=4;
This instructs the slave to begin reading the master's binary
log from the log's starting point. Otherwise—that is, if
you are loading data from the master using a backup—see
Section 19.6.8, “Implementing Failover with MySQL Cluster Replication”, for
information on how to obtain the correct values to use for
MASTER_LOG_FILE
and
MASTER_LOG_POS
in such cases.
Finally, you must instruct the slave to begin applying replication by issuing this command from the mysql client on the replication slave:
mysqlS
>START SLAVE;
This also initiates the transmission of replication data from the master to the slave.
It is also possible to use two replication channels, in a manner similar to the procedure described in the next section; the differences between this and using a single replication channel are covered in Section 19.6.7, “Using Two Replication Channels for MySQL Cluster Replication”.
It is also possible to improve cluster replication performance by
enabling batched updates.
This can be accomplished by setting the
slave_allow_batching
system
variable on the slave mysqld processes.
Normally, updates are applied as soon as they are received.
However, the use of batching causes updates to be applied in 32 KB
batches, which can result in higher throughput and less CPU usage,
particularly where individual updates are relatively small.
Slave batching works on a per-epoch basis; updates belonging to more than one transaction can be sent as part of the same batch.
All outstanding updates are applied when the end of an epoch is reached, even if the updates total less than 32 KB.
Batching can be turned on and off at runtime. To activate it at runtime, you can use either of these two statements:
SET GLOBAL slave_allow_batching = 1; SET GLOBAL slave_allow_batching = ON;
If a particular batch causes problems (such as a statement whose effects do not appear to be replicated correctly), slave batching can be deactivated using either of the following statements:
SET GLOBAL slave_allow_batching = 0; SET GLOBAL slave_allow_batching = OFF;
You can check whether slave batching is currently being used by
means of an appropriate SHOW
VARIABLES
statement, like this one:
mysql> SHOW VARIABLES LIKE 'slave%';
+---------------------------+-------+
| Variable_name | Value |
+---------------------------+-------+
| slave_allow_batching | ON |
| slave_compressed_protocol | OFF |
| slave_load_tmpdir | /tmp |
| slave_net_timeout | 3600 |
| slave_skip_errors | OFF |
| slave_transaction_retries | 10 |
+---------------------------+-------+
6 rows in set (0.00 sec)
In a more complete example scenario, we envision two replication channels to provide redundancy and thereby guard against possible failure of a single replication channel. This requires a total of four replication servers, two masters for the master cluster and two slave servers for the slave cluster. For purposes of the discussion that follows, we assume that unique identifiers are assigned as shown here:
Server ID | Description |
---|---|
1 | Master - primary replication channel (M) |
2 | Master - secondary replication channel (M') |
3 | Slave - primary replication channel (S) |
4 | Slave - secondary replication channel (S') |
Setting up replication with two channels is not radically
different from setting up a single replication channel. First, the
mysqld processes for the primary and secondary
replication masters must be started, followed by those for the
primary and secondary slaves. Then the replication processes may
be initiated by issuing the START
SLAVE
statement on each of the slaves. The commands and
the order in which they need to be issued are shown here:
Start the primary replication master:
shellM
>mysqld --ndbcluster --server-id=1 \
--log-bin &
Start the secondary replication master:
shellM'
>mysqld --ndbcluster --server-id=2 \
--log-bin &
Start the primary replication slave server:
shellS
>mysqld --ndbcluster --server-id=3 \
--skip-slave-start &
Start the secondary replication slave:
shellS'
>mysqld --ndbcluster --server-id=4 \
--skip-slave-start &
Finally, initiate replication on the primary channel by
executing the START SLAVE
statement on the primary slave as shown here:
mysqlS
>START SLAVE;
Only the primary channel is to be started at this point. The secondary replication channel is to be started only in the event that the primary replication channel fails, as described in Section 19.6.8, “Implementing Failover with MySQL Cluster Replication”. Running multiple replication channels simultaneously can result in unwanted duplicate records being created on the replication slaves.
As mentioned previously, it is not necessary to enable binary logging on replication slaves.
In the event that the primary Cluster replication process fails, it is possible to switch over to the secondary replication channel. The following procedure describes the steps required to accomplish this.
Obtain the time of the most recent global checkpoint (GCP).
That is, you need to determine the most recent epoch from the
ndb_apply_status
table on the slave
cluster, which can be found using the following query:
mysqlS'
>SELECT @latest:=MAX(epoch)
->FROM mysql.ndb_apply_status;
In a circular replication topology, with a master and a slave
running on each host, when you are using
ndb_log_apply_status=1
, MySQL
Cluster epochs are written in the slave binary logs. This
means that the ndb_apply_status
table
contains information for the slave on this host as well as for
any other host which acts as a slave of the master running on
this host.
In this case, you need to determine the latest epoch on this
slave to the exclusion of any epochs from any other slaves in
this slave's binary log that were not listed in the
IGNORE_SERVER_IDS
options of the
CHANGE MASTER TO
statement used
to set up this slave. The reason for excluding such epochs is
that rows in the mysql.ndb_apply_status
table whose server IDs have a match in the
IGNORE_SERVER_IDS
list used with the CHANGE
MASTER TO statement used to prepare this slave's master
are also considered to be from local servers, in addition to
those having the slave's own server ID. You can retrieve
this list as Replicate_Ignore_Server_Ids
from the output of SHOW SLAVE
STATUS
. We assume that you have obtained this list
and are substituting it for
ignore_server_ids
in the query
shown here, which like the previous version of the query,
selects the greatest epoch into a variable named
@latest
:
mysqlS'
>SELECT @latest:=MAX(epoch)
->FROM mysql.ndb_apply_status
->WHERE server_id NOT IN (
ignore_server_ids
);
In some cases, it may be simpler or more efficient (or both)
to use a list of the server IDs to be included and
server_id IN
in the
server_id_list
WHERE
condition of the preceding query.
Using the information obtained from the query shown in Step 1,
obtain the corresponding records from the
ndb_binlog_index
table on the master
cluster.
You can use the following query to obtain the needed records
from the master's ndb_binlog_index
table:
mysqlM'
>SELECT
->@file:=SUBSTRING_INDEX(next_file, '/', -1),
->@pos:=next_position
->FROM mysql.ndb_binlog_index
->WHERE epoch = @latest
->ORDER BY epoch ASC LIMIT 1;
These are the records saved on the master since the failure of
the primary replication channel. We have employed a user
variable @latest
here to represent the
value obtained in Step 1. Of course, it is not possible for
one mysqld instance to access user
variables set on another server instance directly. These
values must be “plugged in” to the second query
manually or in application code.
You must ensure that the slave mysqld is
started with
--slave-skip-errors=ddl_exist_errors
before executing START SLAVE
.
Otherwise, replication may stop with duplicate DDL errors.
Now it is possible to synchronize the secondary channel by running the following query on the secondary slave server:
mysqlS'
>CHANGE MASTER TO
->MASTER_LOG_FILE='@file',
->MASTER_LOG_POS=@pos;
Again we have employed user variables (in this case
@file
and @pos
) to
represent the values obtained in Step 2 and applied in Step 3;
in practice these values must be inserted manually or using
application code that can access both of the servers involved.
@file
is a string value such as
'/var/log/mysql/replication-master-bin.00001'
,
and so must be quoted when used in SQL or application code.
However, the value represented by @pos
must not be quoted. Although MySQL
normally attempts to convert strings to numbers, this case
is an exception.
You can now initiate replication on the secondary channel by issuing the appropriate command on the secondary slave mysqld:
mysqlS'
>START SLAVE;
Once the secondary replication channel is active, you can investigate the failure of the primary and effect repairs. The precise actions required to do this will depend upon the reasons for which the primary channel failed.
The secondary replication channel is to be started only if and when the primary replication channel has failed. Running multiple replication channels simultaneously can result in unwanted duplicate records being created on the replication slaves.
If the failure is limited to a single server, it should (in
theory) be possible to replicate from M
to S'
, or from
M'
to S
;
however, this has not yet been tested.
This section discusses making backups and restoring from them using MySQL Cluster replication. We assume that the replication servers have already been configured as covered previously (see Section 19.6.5, “Preparing the MySQL Cluster for Replication”, and the sections immediately following). This having been done, the procedure for making a backup and then restoring from it is as follows:
There are two different methods by which the backup may be started.
Method A.
This method requires that the cluster backup process was
previously enabled on the master server, prior to
starting the replication process. This can be done by
including the following line in a
[mysql_cluster]
section in the
my.cnf file
, where
management_host
is the IP
address or host name of the
NDB
management server for
the master cluster, and port
is the management server's port number:
ndb-connectstring=management_host
[:port
]
The port number needs to be specified only if the default port (1186) is not being used. See Section 19.2.4, “Initial Configuration of MySQL Cluster”, for more information about ports and port allocation in MySQL Cluster.
In this case, the backup can be started by executing this statement on the replication master:
shellM
>ndb_mgm -e "START BACKUP"
Method B.
If the my.cnf
file does not specify
where to find the management host, you can start the
backup process by passing this information to the
NDB
management client as
part of the START
BACKUP
command. This can be done as shown
here, where management_host
and port
are the host name
and port number of the management server:
shellM
>ndb_mgm
management_host
:port
-e "START BACKUP"
In our scenario as outlined earlier (see Section 19.6.5, “Preparing the MySQL Cluster for Replication”), this would be executed as follows:
shellM
>ndb_mgm rep-master:1186 -e "START BACKUP"
Copy the cluster backup files to the slave that is being
brought on line. Each system running an
ndbd process for the master cluster will
have cluster backup files located on it, and
all of these files must be copied to the
slave to ensure a successful restore. The backup files can be
copied into any directory on the computer where the slave
management host resides, so long as the MySQL and NDB binaries
have read permissions in that directory. In this case, we will
assume that these files have been copied into the directory
/var/BACKUPS/BACKUP-1
.
It is not necessary that the slave cluster have the same
number of ndbd processes (data nodes) as
the master; however, it is highly recommended this number be
the same. It is necessary that the slave
be started with the
--skip-slave-start
option, to
prevent premature startup of the replication process.
Create any databases on the slave cluster that are present on the master cluster that are to be replicated to the slave.
A CREATE DATABASE
(or
CREATE
SCHEMA
) statement corresponding to each database
to be replicated must be executed on each SQL node in the
slave cluster.
Reset the slave cluster using this statement in the MySQL Monitor:
mysqlS
>RESET SLAVE;
You can now start the cluster restoration process on the
replication slave using the ndb_restore
command for each backup file in turn. For the first of these,
it is necessary to include the -m
option to
restore the cluster metadata:
shellS
>ndb_restore -c
slave_host
:port
-nnode-id
\-b
backup-id
-m -rdir
dir
is the path to the directory
where the backup files have been placed on the replication
slave. For the ndb_restore commands
corresponding to the remaining backup files, the
-m
option should not be
used.
For restoring from a master cluster with four data nodes (as
shown in the figure in
Section 19.6, “MySQL Cluster Replication”) where the backup
files have been copied to the directory
/var/BACKUPS/BACKUP-1
, the proper
sequence of commands to be executed on the slave might look
like this:
shellS
>ndb_restore -c rep-slave:1186 -n 2 -b 1 -m \
-r ./var/BACKUPS/BACKUP-1
shellS
>ndb_restore -c rep-slave:1186 -n 3 -b 1 \
-r ./var/BACKUPS/BACKUP-1
shellS
>ndb_restore -c rep-slave:1186 -n 4 -b 1 \
-r ./var/BACKUPS/BACKUP-1
shellS
>ndb_restore -c rep-slave:1186 -n 5 -b 1 -e \
-r ./var/BACKUPS/BACKUP-1
The -e
(or
--restore_epoch
) option
in the final invocation of ndb_restore in
this example is required in order that the epoch is written
to the slave mysql.ndb_apply_status
.
Without this information, the slave will not be able to
synchronize properly with the master. (See
Section 19.4.20, “ndb_restore — Restore a MySQL Cluster Backup”.)
Now you need to obtain the most recent epoch from the
ndb_apply_status
table on the slave (as
discussed in
Section 19.6.8, “Implementing Failover with MySQL Cluster Replication”):
mysqlS
>SELECT @latest:=MAX(epoch)
FROM mysql.ndb_apply_status;
Using @latest
as the epoch value obtained
in the previous step, you can obtain the correct starting
position @pos
in the correct binary log
file @file
from the master's
mysql.ndb_binlog_index
table using the
query shown here:
mysqlM
>SELECT
->@file:=SUBSTRING_INDEX(File, '/', -1),
->@pos:=Position
->FROM mysql.ndb_binlog_index
->WHERE epoch > @latest
->ORDER BY epoch ASC LIMIT 1;
In the event that there is currently no replication traffic,
you can get this information by running
SHOW MASTER STATUS
on the
master and using the value in the Position
column for the file whose name has the suffix with the
greatest value for all files shown in the
File
column. However, in this case, you
must determine this and supply it in the next step manually or
by parsing the output with a script.
Using the values obtained in the previous step, you can now
issue the appropriate CHANGE MASTER
TO
statement in the slave's mysql
client:
mysqlS
>CHANGE MASTER TO
->MASTER_LOG_FILE='@file',
->MASTER_LOG_POS=@pos;
Now that the slave “knows” from what point in which binary log file to start reading data from the master, you can cause the slave to begin replicating with this standard MySQL statement:
mysqlS
>START SLAVE;
To perform a backup and restore on a second replication channel, it is necessary only to repeat these steps, substituting the host names and IDs of the secondary master and slave for those of the primary master and slave replication servers where appropriate, and running the preceding statements on them.
For additional information on performing Cluster backups and restoring Cluster from backups, see Section 19.5.3, “Online Backup of MySQL Cluster”.
It is possible to automate much of the process described in the
previous section (see
Section 19.6.9, “MySQL Cluster Backups With MySQL Cluster Replication”). The
following Perl script reset-slave.pl
serves
as an example of how you can do this.
#!/user/bin/perl -w # file: reset-slave.pl # Copyright ©2005 MySQL AB # This program is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation; either version 2 of the License, or # (at your option) any later version. # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # You should have received a copy of the GNU General Public License # along with this program; if not, write to: # Free Software Foundation, Inc. # 59 Temple Place, Suite 330 # Boston, MA 02111-1307 USA # # Version 1.1 ######################## Includes ############################### use DBI; ######################## Globals ################################ my $m_host=''; my $m_port=''; my $m_user=''; my $m_pass=''; my $s_host=''; my $s_port=''; my $s_user=''; my $s_pass=''; my $dbhM=''; my $dbhS=''; ####################### Sub Prototypes ########################## sub CollectCommandPromptInfo; sub ConnectToDatabases; sub DisconnectFromDatabases; sub GetSlaveEpoch; sub GetMasterInfo; sub UpdateSlave; ######################## Program Main ########################### CollectCommandPromptInfo; ConnectToDatabases; GetSlaveEpoch; GetMasterInfo; UpdateSlave; DisconnectFromDatabases; ################## Collect Command Prompt Info ################## sub CollectCommandPromptInfo { ### Check that user has supplied correct number of command line args die "Usage:\n reset-slave >master MySQL host< >master MySQL port< \n >master user< >master pass< >slave MySQL host< \n >slave MySQL port< >slave user< >slave pass< \n All 8 arguments must be passed. Use BLANK for NULL passwords\n" unless @ARGV == 8; $m_host = $ARGV[0]; $m_port = $ARGV[1]; $m_user = $ARGV[2]; $m_pass = $ARGV[3]; $s_host = $ARGV[4]; $s_port = $ARGV[5]; $s_user = $ARGV[6]; $s_pass = $ARGV[7]; if ($m_pass eq "BLANK") { $m_pass = '';} if ($s_pass eq "BLANK") { $s_pass = '';} } ############### Make connections to both databases ############# sub ConnectToDatabases { ### Connect to both master and slave cluster databases ### Connect to master $dbhM = DBI->connect( "dbi:mysql:database=mysql;host=$m_host;port=$m_port", "$m_user", "$m_pass") or die "Can't connect to Master Cluster MySQL process! Error: $DBI::errstr\n"; ### Connect to slave $dbhS = DBI->connect( "dbi:mysql:database=mysql;host=$s_host", "$s_user", "$s_pass") or die "Can't connect to Slave Cluster MySQL process! Error: $DBI::errstr\n"; } ################ Disconnect from both databases ################ sub DisconnectFromDatabases { ### Disconnect from master $dbhM->disconnect or warn " Disconnection failed: $DBI::errstr\n"; ### Disconnect from slave $dbhS->disconnect or warn " Disconnection failed: $DBI::errstr\n"; } ###################### Find the last good GCI ################## sub GetSlaveEpoch { $sth = $dbhS->prepare("SELECT MAX(epoch) FROM mysql.ndb_apply_status;") or die "Error while preparing to select epoch from slave: ", $dbhS->errstr; $sth->execute or die "Selecting epoch from slave error: ", $sth->errstr; $sth->bind_col (1, \$epoch); $sth->fetch; print "\tSlave Epoch = $epoch\n"; $sth->finish; } ####### Find the position of the last GCI in the binary log ######## sub GetMasterInfo { $sth = $dbhM->prepare("SELECT SUBSTRING_INDEX(File, '/', -1), Position FROM mysql.ndb_binlog_index WHERE epoch > $epoch ORDER BY epoch ASC LIMIT 1;") or die "Prepare to select from master error: ", $dbhM->errstr; $sth->execute or die "Selecting from master error: ", $sth->errstr; $sth->bind_col (1, \$binlog); $sth->bind_col (2, \$binpos); $sth->fetch; print "\tMaster binary log = $binlog\n"; print "\tMaster binary log position = $binpos\n"; $sth->finish; } ########## Set the slave to process from that location ######### sub UpdateSlave { $sth = $dbhS->prepare("CHANGE MASTER TO MASTER_LOG_FILE='$binlog', MASTER_LOG_POS=$binpos;") or die "Prepare to CHANGE MASTER error: ", $dbhS->errstr; $sth->execute or die "CHANGE MASTER on slave error: ", $sth->errstr; $sth->finish; print "\tSlave has been updated. You may now start the slave.\n"; } # end reset-slave.pl
Point-in-time
recovery—that is, recovery of data changes made since a
given point in time—is performed after restoring a full
backup that returns the server to its state when the backup was
made. Performing point-in-time recovery of MySQL Cluster tables
with MySQL Cluster and MySQL Cluster Replication can be
accomplished using a native NDB
data backup (taken by issuing CREATE
BACKUP
in the ndb_mgm client) and
restoring the ndb_binlog_index
table (from a
dump made using mysqldump).
To perform point-in-time recovery of MySQL Cluster, it is necessary to follow the steps shown here:
Back up all NDB
databases in the cluster,
using the START BACKUP
command in the ndb_mgm client (see
Section 19.5.3, “Online Backup of MySQL Cluster”).
At some later point, prior to restoring the cluster, make a
backup of the mysql.ndb_binlog_index
table. It is probably simplest to use
mysqldump for this task. Also back up the
binary log files at this time.
This backup should be updated regularly—perhaps even hourly—depending on your needs.
(Catastrophic failure or error occurs.)
Locate the last known good backup.
Clear the data node file systems (using
ndbd
--initial
or
ndbmtd
--initial
).
MySQL Cluster Disk Data tablespace and log files are not
removed by --initial
. You
must delete these manually.
Use DROP TABLE
or
TRUNCATE TABLE
with the
mysql.ndb_binlog_index
table.
Execute ndb_restore, restoring all data.
You must include the
--restore_epoch
option
when you run ndb_restore, so that the
ndb_apply_status
table is populated
correctly. (See
Section 19.4.20, “ndb_restore — Restore a MySQL Cluster Backup”, for
more information.)
Restore the ndb_binlog_index
table from
the output of mysqldump and restore the
binary log files from backup, if necessary.
Find the epoch applied most recently—that is, the
maximum epoch
column value in the
ndb_apply_status
table—as the user
variable @LATEST_EPOCH
(emphasized):
SELECT @LATEST_EPOCH:=MAX(epoch)
FROM mysql.ndb_apply_status;
Find the latest binary log file
(@FIRST_FILE
) and position
(Position
column value) within this file
that correspond to @LATEST_EPOCH
in the
ndb_binlog_index
table:
SELECT Position, @FIRST_FILE:=File FROM mysql.ndb_binlog_index WHERE epoch > @LATEST_EPOCH ORDER BY epoch ASC LIMIT 1;
Using mysqlbinlog, replay the binary log events from the given file and position up to the point of the failure. (See Section 5.6.7, “mysqlbinlog — Utility for Processing Binary Log Files”.)
See also Section 8.5, “Point-in-Time (Incremental) Recovery Using the Binary Log”, for more information about the binary log, replication, and incremental recovery.
It is possible to use MySQL Cluster in multi-master replication, including circular replication between a number of MySQL Clusters.
Circular replication example. In the next few paragraphs we consider the example of a replication setup involving three MySQL Clusters numbered 1, 2, and 3, in which Cluster 1 acts as the replication master for Cluster 2, Cluster 2 acts as the master for Cluster 3, and Cluster 3 acts as the master for Cluster 1. Each cluster has two SQL nodes, with SQL nodes A and B belonging to Cluster 1, SQL nodes C and D belonging to Cluster 2, and SQL nodes E and F belonging to Cluster 3.
Circular replication using these clusters is supported as long as the following conditions are met:
The SQL nodes on all masters and slaves are the same
All SQL nodes acting as replication masters and slaves are
started using the
--log-slave-updates
option
This type of circular replication setup is shown in the following diagram:
In this scenario, SQL node A in Cluster 1 replicates to SQL node C in Cluster 2; SQL node C replicates to SQL node E in Cluster 3; SQL node E replicates to SQL node A. In other words, the replication line (indicated by the red arrows in the diagram) directly connects all SQL nodes used as replication masters and slaves.
It is also possible to set up circular replication in such a way that not all master SQL nodes are also slaves, as shown here:
In this case, different SQL nodes in each cluster are used as
replication masters and slaves. However, you must
not start any of the SQL nodes using
--log-slave-updates
. This type of
circular replication scheme for MySQL Cluster, in which the line
of replication (again indicated by the red arrows in the diagram)
is discontinuous, should be possible, but it should be noted that
it has not yet been thoroughly tested and must therefore still be
considered experimental.
Using NDB-native backup and restore to initialize a slave MySQL Cluster.
When setting up circular replication, it is possible to
initialize the slave cluster by using the management client
BACKUP
command on one MySQL Cluster to create
a backup and then applying this backup on another MySQL Cluster
using ndb_restore. However, this does not
automatically create binary logs on the second MySQL
Cluster's SQL node acting as the replication slave. In
order to cause the binary logs to be created, you must issue a
SHOW TABLES
statement on that SQL
node; this should be done prior to running
START SLAVE
.
This is a known issue which we intend to address in a future release.
Multi-master failover example. In this section, we discuss failover in a multi-master MySQL Cluster replication setup with three MySQL Clusters having server IDs 1, 2, and 3. In this scenario, Cluster 1 replicates to Clusters 2 and 3; Cluster 2 also replicates to Cluster 3. This relationship is shown here:
In other words, data replicates from Cluster 1 to Cluster 3 through 2 different routes: directly, and by way of Cluster 2.
Not all MySQL servers taking part in multi-master replication must act as both master and slave, and a given MySQL Cluster might use different SQL nodes for different replication channels. Such a case is shown here:
MySQL servers acting as replication slaves must be run with the
--log-slave-updates
option. Which
mysqld processes require this option is also
shown in the preceding diagram.
Using the --log-slave-updates
option has no effect on servers not being run as replication
slaves.
The need for failover arises when one of the replicating clusters goes down. In this example, we consider the case where Cluster 1 is lost to service, and so Cluster 3 loses 2 sources of updates from Cluster 1. Because replication between MySQL Clusters is asynchronous, there is no guarantee that Cluster 3's updates originating directly from Cluster 1 are more recent than those received through Cluster 2. You can handle this by ensuring that Cluster 3 catches up to Cluster 2 with regard to updates from Cluster 1. In terms of MySQL servers, this means that you need to replicate any outstanding updates from MySQL server C to server F.
On server C, perform the following queries:
mysqlC> SELECT @latest:=MAX(epoch) -> FROM mysql.ndb_apply_status -> WHERE server_id=1; mysqlC> SELECT -> @file:=SUBSTRING_INDEX(File, '/', -1), -> @pos:=Position -> FROM mysql.ndb_binlog_index -> WHERE orig_epoch >= @latest -> AND orig_server_id = 1 -> ORDER BY epoch ASC LIMIT 1;
You can improve the performance of this query, and thus likely
speed up failover times significantly, by adding the appropriate
index to the ndb_binlog_index
table. See
Section 19.6.4, “MySQL Cluster Replication Schema and Tables”, for more
information.
Copy over the values for @file
and
@pos
manually from server C to server F
(or have your application perform the equivalent). Then, on server
F, execute the following CHANGE MASTER
TO
statement:
mysqlF> CHANGE MASTER TO -> MASTER_HOST = 'serverC' -> MASTER_LOG_FILE='@file', -> MASTER_LOG_POS=@pos;
Once this has been done, you can issue a
START SLAVE
statement on MySQL
server F, and any missing updates originating from server B will
be replicated to server F.
The CHANGE MASTER TO
statement also
supports an IGNORE_SERVER_IDS
option which
takes a comma-separated list of server IDs and causes events
originating from the corresponding servers to be ignored. For more
information, see Section 14.4.2.1, “CHANGE MASTER TO Syntax”, and
Section 14.7.5.34, “SHOW SLAVE STATUS Syntax”. For information about how
this option intereacts with the
ndb_log_apply_status
variable,
see Section 19.6.8, “Implementing Failover with MySQL Cluster Replication”.
When using a replication setup involving multiple masters (including circular replication), it is possible that different masters may try to update the same row on the slave with different data. Conflict resolution in MySQL Cluster Replication provides a means of resolving such conflicts by permitting a user-defined resolution column to be used to determine whether or not an update on a given master should be applied on the slave.
Some types of conflict resolution supported by MySQL Cluster
(NDB$OLD()
, NDB$MAX()
,
NDB$MAX_DELETE_WIN()
) implement this
user-defined column as a “timestamp” column (although
its type cannot be TIMESTAMP
, as
explained later in this section). These types of conflict
resolution are always applied a row-by-row basis rather than a
transactional basis. The epoch-based conflict resolution functions
NDB$EPOCH()
and
NDB$EPOCH_TRANS()
compare the order in which
epochs are replicated (and thus these functions are
transactional). Different methods can be used to compare
resolution column values on the slave when conflicts occur, as
explained later in this section; the method used can be set on a
per-table basis.
You should also keep in mind that it is the application's responsibility to ensure that the resolution column is correctly populated with relevant values, so that the resolution function can make the appropriate choice when determining whether to apply an update.
Requirements. Preparations for conflict resolution must be made on both the master and the slave. These tasks are described in the following list:
On the master writing the binary logs, you must determine
which columns are sent (all columns or only those that have
been updated). This is done for the MySQL Server as a whole by
applying the mysqld startup option
--ndb-log-updated-only
(described later in this section) or on a per-table basis by
entries in the mysql.ndb_replication
table
(see The ndb_replication system table).
If you are replicating tables with very large columns (such
as TEXT
or
BLOB
columns),
--ndb-log-updated-only
can
also be useful for reducing the size of the master and slave
binary logs and avoiding possible replication failures due
to exceeding
max_allowed_packet
.
See Section 18.4.1.22, “Replication and max_allowed_packet”, for more information about this issue.
On the slave, you must determine which type of conflict
resolution to apply (“latest timestamp wins”,
“same timestamp wins”, “primary
wins”, “primary wins, complete
transaction”, or none). This is done using the
mysql.ndb_replication
system table, on a
per-table basis (see
The ndb_replication system table).
MySQL Cluster also supports read conflict detection, that is,
detecting conflicts between reads of a given row in one
cluster and updates or deletes of the same row in another
cluster. This requires exclusive read locks obtained by
setting
ndb_log_exclusive_reads
equal
to 1 on the slave. All rows read by a conflicting read are
logged in the exceptions table. For more information, see
Read conflict detection and resolution.
When using the functions NDB$OLD()
,
NDB$MAX()
, and
NDB$MAX_DELETE_WIN()
for timestamp-based
conflict resolution, we often refer to the column used for
determining updates as a “timestamp” column. However,
the data type of this column is never
TIMESTAMP
; instead, its data type
should be INT
(INTEGER
) or
BIGINT
. The
“timestamp” column should also be
UNSIGNED
and NOT NULL
.
The NDB$EPOCH()
and
NDB$EPOCH_TRANS()
functions discussed later in
this section work by comparing the relative order of replication
epochs applied on a primary and secondary MySQL Cluster, and do
not make use of timestamps.
Master column control.
We can see update operations in terms of “before”
and “after” images—that is, the states of the
table before and after the update is applied. Normally, when
updating a table with a primary key, the “before”
image is not of great interest; however, when we need to
determine on a per-update basis whether or not to use the
updated values on a replication slave, we need to make sure that
both images are written to the master's binary log. This is
done with the
--ndb-log-update-as-write
option
for mysqld, as described later in this
section.
Whether logging of complete rows or of updated columns only is done is decided when the MySQL server is started, and cannot be changed online; you must either restart mysqld, or start a new mysqld instance with different logging options.
Command-Line Format | --ndb-log-updated-only | ||
System Variable | Name | ndb_log_updated_only | |
Variable Scope | Global | ||
Dynamic Variable | Yes | ||
Permitted Values | Type | boolean | |
Default | ON |
For purposes of conflict resolution, there are two basic methods
of logging rows, as determined by the setting of the
--ndb-log-updated-only
option for
mysqld:
Log complete rows
Log only column data that has been updated—that is, column data whose value has been set, regardless of whether or not this value was actually changed. This is the default behavior.
It is usually sufficient—and more efficient—to log
updated columns only; however, if you need to log full rows, you
can do so by setting
--ndb-log-updated-only
to
0
or OFF
.
Command-Line Format | --ndb-log-update-as-write | ||
System Variable | Name | ndb_log_update_as_write | |
Variable Scope | Global | ||
Dynamic Variable | Yes | ||
Permitted Values | Type | boolean | |
Default | ON |
The setting of the MySQL Server's
--ndb-log-update-as-write
option
determines whether logging is performed with or without the
“before” image. Because conflict resolution is done
in the MySQL Server's update handler, it is necessary to
control logging on the master such that updates are updates and
not writes; that is, such that updates are treated as changes in
existing rows rather than the writing of new rows (even though
these replace existing rows). This option is turned on by default;
in other words, updates are treated as writes. (That is, updates
are by default written as write_row
events in
the binary log, rather than as update_row
events.)
To turn off the option, start the master mysqld
with --ndb-log-update-as-write=0
or
--ndb-log-update-as-write=OFF
. You must do this
when replicating from NDB tables to tables using a different
storage engine; see
Replication from NDB to other storage engines, and
Replication from NDB to a nontransactional storage engine,
for more information.
Conflict resolution control.
Conflict resolution is usually enabled on the server where
conflicts can occur. Like logging method selection, it is
enabled by entries in the
mysql.ndb_replication
table.
The ndb_replication system table.
To enable conflict resolution, it is necessary to create an
ndb_replication
table in the
mysql
system database on the master, the
slave, or both, depending on the conflict resolution type and
method to be employed. This table is used to control logging and
conflict resolution functions on a per-table basis, and has one
row per table involved in replication.
ndb_replication
is created and filled with
control information on the server where the conflict is to be
resolved. In a simple master-slave setup where data can also be
changed locally on the slave this will typically be the slave.
In a more complex master-master (2-way) replication schema this
will usually be all of the masters involved. Each row in
mysql.ndb_replication
corresponds to a table
being replicated, and specifies how to log and resolve conflicts
(that is, which conflict resolution function, if any, to use)
for that table. The definition of the
mysql.ndb_replication
table is shown here:
CREATE TABLE mysql.ndb_replication ( db VARBINARY(63), table_name VARBINARY(63), server_id INT UNSIGNED, binlog_type INT UNSIGNED, conflict_fn VARBINARY(128), PRIMARY KEY USING HASH (db, table_name, server_id) ) ENGINE=NDB PARTITION BY KEY(db,table_name);
The columns in this table are described in the next few paragraphs.
db.
The name of the database containing the table to be replicated.
You may employ either or both of the wildcards
_
and %
as part of the
database name. Matching is similar to what is implemented for
the LIKE
operator.
table_name.
The name of the table to be replicated. The table name may
include either or both of the wildcards _
and
%
. Matching is similar to what is implemented
for the LIKE
operator.
server_id. The unique server ID of the MySQL instance (SQL node) where the table resides.
binlog_type. The type of binary logging to be employed. This is determined as shown in the following table:
Value | Internal Value | Description |
---|---|---|
0 | NBT_DEFAULT | Use server default |
1 | NBT_NO_LOGGING | Do not log this table in the binary log |
2 | NBT_UPDATED_ONLY | Only updated attributes are logged |
3 | NBT_FULL | Log full row, even if not updated (MySQL server default behavior) |
4 | NBT_USE_UPDATE | (For generating NBT_UPDATED_ONLY_USE_UPDATE and
NBT_FULL_USE_UPDATE values
only—not intended for separate use) |
5 | [Not used] | --- |
6 | NBT_UPDATED_ONLY_USE_UPDATE (equal to
NBT_UPDATED_ONLY | NBT_USE_UPDATE ) | Use updated attributes, even if values are unchanged |
7 | NBT_FULL_USE_UPDATE (equal to NBT_FULL |
NBT_USE_UPDATE ) | Use full row, even if values are unchanged |
conflict_fn. The conflict resolution function to be applied. This function must be specified as one of those shown in the following list:
NULL
: Indicates that conflict resolution is
not to be used for the corresponding table.
These functions are described in the next few paragraphs.
NDB$OLD(column_name).
If the value of column_name
is the
same on both the master and the slave, then the update is
applied; otherwise, the update is not applied on the slave and
an exception is written to the log. This is illustrated by the
following pseudocode:
if (master_old_column_value
==slave_current_column_value
) apply_update(); else log_exception();
This function can be used for “same value wins” conflict resolution. This type of conflict resolution ensures that updates are not applied on the slave from the wrong master.
The column value from the master's “before” image is used by this function.
NDB$MAX(column_name). If the “timestamp” column value for a given row coming from the master is higher than that on the slave, it is applied; otherwise it is not applied on the slave. This is illustrated by the following pseudocode:
if (master_new_column_value
>slave_current_column_value
) apply_update();
This function can be used for “greatest timestamp wins” conflict resolution. This type of conflict resolution ensures that, in the event of a conflict, the version of the row that was most recently updated is the version that persists.
The column value from the master's “after” image is used by this function.
NDB$MAX_DELETE_WIN().
This is a variation on NDB$MAX()
. Due to the
fact that no timestamp is available for a delete operation, a
delete using NDB$MAX()
is in fact processed
as NDB$OLD
. However, for some use cases, this
is not optimal. For NDB$MAX_DELETE_WIN()
, if
the “timestamp” column value for a given row adding
or updating an existing row coming from the master is higher
than that on the slave, it is applied. However, delete
operations are treated as always having the higher value. This
is illustrated in the following pseudocode:
if ( (master_new_column_value
>slave_current_column_value
) ||operation.type
== "delete") apply_update();
This function can be used for “greatest timestamp, delete wins” conflict resolution. This type of conflict resolution ensures that, in the event of a conflict, the version of the row that was deleted or (otherwise) most recently updated is the version that persists.
As with NDB$MAX()
, the column value from the
master's “after” image is the value used by
this function.
NDB$EPOCH() and NDB$EPOCH_TRANS().
The NDB$EPOCH()
function tracks the order in
which replicated epochs are applied on a slave MySQL Cluster
relative to changes originating on the slave. This relative
ordering is used to determine whether changes originating on the
slave are concurrent with any changes that originate locally,
and are therefore potentially in conflict.
Most of what follows in the description of
NDB$EPOCH()
also applies to
NDB$EPOCH_TRANS()
. Any exceptions are noted in
the text.
NDB$EPOCH()
is asymmetric, operating on one
MySQL Cluster in a two-cluster circular replication configuration
(sometimes referred to as “active-active”
replication). We refer here to cluster on which it operates as the
primary, and the other as the secondary. The slave on the primary
is responsible for detecting and handling conflicts, while the
slave on the secondary is not involved in any conflict detection
or handling.
When the slave on the primary detects conflicts, it injects events into its own binary log to compensate for these; this ensures that the secondary MySQL Cluster eventually realigns itself with the primary and so keeps the primary and secondary from diverging. This compensation and realignment mechanism requires that the primary MySQL Cluster always wins any conflicts with the secondary—that is, that the primary's changes are always used rather than those from the secondary in event of a conflict. This “primary always wins” rule has the following implications:
Operations that change data, once committed on the primary, are fully persistent and will not be undone or rolled back by conflict detection and resolution.
Data read from the primary is fully consistent. Any changes committed on the Primary (locally or from the slave) will not be reverted later.
Operations that change data on the secondary may later be reverted if the primary determines that they are in conflict.
Individual rows read on the secondary are self-consistent at all times, each row always reflecting either a state committed by the secondary, or one committed by the primary.
Sets of rows read on the secondary may not necessarily be
consistent at a given single point in time. For
NDB$EPOCH_TRANS()
, this is a transient
state; for NDB$EPOCH()
, it can be a
persistent state.
Assuming a period of sufficient length without any conflicts, all data on the secondary MySQL Cluster (eventually) becomes consistent with the primary's data.
NDB$EPOCH()
and
NDB$EPOCH_TRANS()
do not require any user
schema modifications, or application changes to provide conflict
detection. However, careful thought must be given to the schema
used, and the access patterns used, to verify that the complete
system behaves within specified limits.
Each of the NDB$EPOCH()
and
NDB$EPOCH_TRANS()
functions can take an
optional parameter; this is the number of bits to use to represent
the lower 32 bits of the epoch, and should be set to no less than
CEIL( LOG2(TimeBetweenGlobalCheckpoints
/TimeBetweenEpochs
), 1)
For the default values of these configuration parameters (2000 and
100 milliseconds, respectively), this gives a value of 5 bits, so
the default value (6) should be sufficient, unless other values
are used for
TimeBetweenGlobalCheckpoints
,
TimeBetweenEpochs
, or
both. A value that is too small can result in false positives,
while one that is too large could lead to excessive wasted space
in the database.
Both NDB$EPOCH()
and
NDB$EPOCH_TRANS()
insert entries for
conflicting rows into the relevant exceptions tables, provided
that these tables have been defined according to the same
exceptions table schema rules as described elsewhere in this
section (see NDB$OLD(column_name)).
You need to create any exceptions table before creating the table
with which it is to be used.
As with the other conflict detection functions discussed in this
section, NDB$EPOCH()
and
NDB$EPOCH_TRANS()
are activated by including
relevant entries in the mysql.ndb_replication
table (see The ndb_replication system table).
The roles of the primary and secondary MySQL Clusters in this
scenario are fully determined by
mysql.ndb_replication
table entries.
Because the conflict detection algorithms employed by
NDB$EPOCH()
and
NDB$EPOCH_TRANS()
are asymmetric, you must use
different values for the primary slave's and secondary
slave's server_id
entries.
A conflict between DELETE
operations alone is
not sufficient to trigger a conflict using
NDB$EPOCH()
or
NDB$EPOCH_TRANS()
, and the relative placement
within epochs does not matter. (Bug #18454499)
Conflict detection status variables.
Several status variables can be used to monitor conflict
detection. You can see how many rows have been found in conflict
by NDB$EPOCH()
since this slave was last
restarted from the current value of the
Ndb_conflict_fn_epoch
system
status variable.
Ndb_conflict_fn_epoch_trans
provides the number of rows that have been found directly in
conflict by NDB$EPOCH_TRANS()
.
Ndb_conflict_fn_epoch2
and
Ndb_conflict_fn_epoch2_trans
show the number of rows found in conflict by
NDB$EPOCH2()
and
NDB$EPOCH2_TRANS()
, respectively. The number of
rows actually realigned, including those affected due to their
membership in or dependency on the same transactions as other
conflicting rows, is given by
Ndb_conflict_trans_row_reject_count
.
For more information, see Section 19.3.3.8.3, “MySQL Cluster Status Variables”.
Limitations on NDB$EPOCH().
The following limitations currently apply when using
NDB$EPOCH()
to perform conflict detection:
Conflicts are detected using MySQL Cluster epoch boundaries,
with granularity proportional to
TimeBetweenEpochs
(default: 100 milliseconds). The minimum conflict window is
the minimum time during which concurrent updates to the same
data on both clusters always report a conflict. This is always
a nonzero length of time, and is roughly proportional to
2 * (latency + queueing +
TimeBetweenEpochs)
. This implies that—assuming
the default for
TimeBetweenEpochs
and
ignoring any latency between clusters (as well as any queuing
delays)—the minimum conflict window size is
approximately 200 milliseconds. This minimum window should be
considered when looking at expected application
“race” patterns.
Additional storage is required for tables using the
NDB$EPOCH()
and
NDB$EPOCH_TRANS()
functions; from 1 to 32
bits extra space per row is required, depending on the value
passed to the function.
Conflicts between delete operations may result in divergence between the primary and secondary. When a row is deleted on both clusters concurrently, the conflict can be detected, but is not recorded, since the row is deleted. This means that further conflicts during the propagation of any subsequent realignment operations will not be detected, which can lead to divergence.
Deletes should be externally serialized, or routed to one cluster only. Alternatively, a separate row should be updated transactionally with such deletes and any inserts that follow them, so that conflicts can be tracked across row deletes. This may require changes in applications.
Only two MySQL Clusters in a circular
“active-active” configuration are currently
supported when using NDB$EPOCH()
or
NDB$EPOCH_TRANS()
for conflict detection.
Tables having BLOB
or
TEXT
columns are not currently
supported with NDB$EPOCH()
or
NDB$EPOCH_TRANS()
.
NDB$EPOCH_TRANS().
NDB$EPOCH_TRANS()
extends the
NDB$EPOCH()
function. Conflicts are detected
and handled in the same way using the “primary wins
all” rule (see
NDB$EPOCH() and NDB$EPOCH_TRANS()) but with
the extra condition that any other rows updated in the same
transaction in which the conflict occurred are also regarded as
being in conflict. In other words, where
NDB$EPOCH()
realigns individual conflicting
rows on the secondary, NDB$EPOCH_TRANS()
realigns conflicting transactions.
In addition, any transactions which are detectably dependent on a conflicting transaction are also regarded as being in conflict, these dependencies being determined by the contents of the secondary cluster's binary log. Since the binary log contains only data modification operations (inserts, updates, and deletes), only overlapping data modifications are used to determine dependencies between transactions.
NDB$EPOCH_TRANS()
is subject to the same
conditions and limitations as NDB$EPOCH()
, and
in addition requires that Version 2 binary log row events are used
(--log-bin-use-v1-row-events
equal
to 0), which adds a storage overhead of 2 bytes per event in the
binary log. In addition, all transaction IDs must be recorded in
the secondary's binary log
(--ndb-log-transaction-id
option),
which adds a further variable overhead (up to 13 bytes per row).
See NDB$EPOCH() and NDB$EPOCH_TRANS().
Status information.
A server status variable
Ndb_conflict_fn_max
provides a
count of the number of times that a row was not applied on the
current SQL node due to “greatest timestamp wins”
conflict resolution since the last time that
mysqld was started.
The number of times that a row was not applied as the result of
“same timestamp wins” conflict resolution on a given
mysqld since the last time it was restarted is
given by the global status variable
Ndb_conflict_fn_old
. In addition
to incrementing
Ndb_conflict_fn_old
, the primary
key of the row that was not used is inserted into an
exceptions table, as
explained later in this section.
NDB$EPOCH2().
The NDB$EPOCH2()
function is similar to
NDB$EPOCH()
, except that
NDB$EPOCH2()
provides for delete-delete
handling with a circular replication
(“master-master”) topology. In this scenario,
primary and secondary roles are assigned to the two masters by
setting the
ndb_slave_conflict_role
system
variable to the appropriate value on each master (usually one
each of PRIMARY
,
SECONDARY
). When this is done, modifications
made by the secondary are reflected by the primary back to the
secondary which then conditionally applies them.
NDB$EPOCH2_TRANS().
NDB$EPOCH2_TRANS()
extends the
NDB$EPOCH2()
function. Conflicts are detected
and handled in the same way, and assigning primary and secondary
roles to the replicating clusters, but with the extra condition
that any other rows updated in the same transaction in which the
conflict occurred are also regarded as being in conflict. That
is, NDB$EPOCH2()
realigns individual
conflicting rows on the secondary, while
NDB$EPOCH_TRANS()
realigns conflicting
transactions.
Where NDB$EPOCH()
and
NDB$EPOCH_TRANS()
use metadata that is
specified per row, per last modified epoch, to determine on the
primary whether an incoming replicated row change from the
secondary is concurrent with a locally committed change;
concurrent changes are regarded as conflicting, with subesequent
exceptions table updates and realignment of the secondary. A
problem arises when a row is deleted on the primary so there is no
longer any last-modified epoch available to determine whether any
replicated operations conflict, which means that conflicting
delete operationss are not detected. This can result in
divergence, an example being a delete on one cluster which is
concurrent with a delete and insert on the other; this why delete
operations can be routed to only one cluster when using
NDB$EPOCH()
and
NDB$EPOCH_TRANS()
.
NDB$EPOCH2()
bypasses the issue just
described—storing information about deleted rows on the
PRIMARY—by ignoring any delete-delete conflict, and by
avoiding any potential resultant divergence as well. This is
accomplished by reflecting any operation successfully applied on
and replicated from the secondary back to the secondary. On its
return to the secondary, it can be used to reapply an operation on
the secondary which was deleted by an operation originating from
the primary.
When using NDB$EPOCH2()
, you should keep in
mind that the secondary applies the delete from the primary,
removing the new row until it is restored by a reflected
operation. In theory, the subsequent insert or update on the
secondary conflicts with the delete from the primary, but in this
case, we choose to ignore this and allow the secondary to
“win”, in the interest of preventing divergence
between the clusters. In other words, after a delete, the primary
does not detect conflicts, and instead adopts the secondary's
following changes immediately. Because of this, the
secondary's state can revisit multiple previous committed
states as it progresses to a final (stable) state, and some of
these may be visible.
You should also be aware that reflecting all operations from the secondary back to the primary increases the size of the primary's logbinary log, as well as demands on bandwidth, CPU usage, and disk I/O.
Application of reflected operations on the secondary depends on
the state of the target row on the secondary. Whether or not
reflected changes are applied on the secondary can be tracked by
checking the
Ndb_conflict_reflected_op_prepare_count
and
Ndb_conflict_reflected_op_discard_count
status variables. The number of changes applied is simply the
difference between these two values (note that
Ndb_conflict_reflected_op_prepare_count
is
always greater than or equal to
Ndb_conflict_reflected_op_discard_count
).
Events are applied if and only if both of the following conditions are true:
The existence of the row—that is, whether or not it exists—is in accordance with the type of event. For delete and update operations, the row must already exist; for insert operations, the row must not exist.
The row was last modified by the primary. It is possible that the modification was accomplished through the execution of a reflected operation.
If both of the conditions are not met, the reflected operation is discarded by the secondary.
Conflict resolution exceptions table.
To use the NDB$OLD()
conflict resolution
function, it is also necessary to create an exceptions table
corresponding to each NDB
table for
which this type of conflict resolution is to be employed. This
is also true when using NDB$EPOCH()
or
NDB$EPOCH_TRANS()
. The name of this table is
that of the table for which conflict resolution is to be
applied, with the string $EX
appended. (For
example, if the name of the original table is
mytable
, the name of the corresponding
exceptions table name should be mytable$EX
.)
The syntax for creating the exceptions table is as shown here:
CREATE TABLEoriginal_table
$EX ( [NDB$]server_id INT UNSIGNED, [NDB$]master_server_id INT UNSIGNED, [NDB$]master_epoch BIGINT UNSIGNED, [NDB$]count INT UNSIGNED, [NDB$OP_TYPE ENUM('WRITE_ROW','UPDATE_ROW', 'DELETE_ROW', 'REFRESH_ROW', 'READ_ROW') NOT NULL,] [NDB$CFT_CAUSE ENUM('ROW_DOES_NOT_EXIST', 'ROW_ALREADY_EXISTS', 'DATA_IN_CONFLICT', 'TRANS_IN_CONFLICT') NOT NULL,] [NDB$ORIG_TRANSID BIGINT UNSIGNED NOT NULL,]original_table_pk_columns
, [orig_table_column
|orig_table_column
$OLD|orig_table_column
$NEW,] [additional_columns
,] PRIMARY KEY([NDB$]server_id, [NDB$]master_server_id, [NDB$]master_epoch, [NDB$]count) ) ENGINE=NDB;
The first four columns are required. The names of the first four
columns and the columns matching the original table's primary
key columns are not critical; however, we suggest for reasons of
clarity and consistency, that you use the names shown here for the
server_id
, master_server_id
,
master_epoch
, and count
columns, and that you use the same names as in the original table
for the columns matching those in the original table's
primary key.
If the exceptions table uses one or more of the optional columns
NDB$OP_TYPE
, NDB$CFT_CAUSE
,
or NDB$ORIG_TRANSID
discussed later in this
section, then each of the required columns must also be named
using the prefix NDB$
. If desired, you can use
the NDB$
prefix to name the required columns
even if you do not define any optional columns, but in this case,
all four of the required columns must be named using the prefix.
Following these columns, the columns making up the original table's primary key should be copied in the order in which they are used to define the primary key of the original table. The data types for the columns duplicating the primary key columns of the original table should be the same as (or larger than) those of the original columns. A subset of the primary key columns may be used.
Regardless of the MySQL Cluster version employed, the exceptions
table must use the NDB
storage
engine. (An example that uses NDB$OLD()
with an
exceptions table is shown later in this section.)
Additional columns may optionally be defined following the copied
primary key columns, but not before any of them; any such extra
columns cannot be NOT NULL
. MySQL Cluster
supports three additional, predefined optional columns
NDB$OP_TYPE
, NDB$CFT_CAUSE
,
and NDB$ORIG_TRANSID
, which are described in
the next few paragraphs.
NDB$OP_TYPE
: This column can be used to obtain
the type of operation causing the conflict. If you use this
column, define it as shown here:
NDB$OP_TYPE ENUM('WRITE_ROW', 'UPDATE_ROW', 'DELETE_ROW', 'REFRESH_ROW', 'READ_ROW') NOT NULL
The WRITE_ROW
, UPDATE_ROW
,
and DELETE_ROW
operation types represent
user-initiated operations. REFRESH_ROW
operations are operations generated by conflict resolution in
compensating transactions sent back to the originating cluster
from the cluster that detected the conflict.
READ_ROW
operations are user-initiated read
tracking operations defined with exclusive row locks.
NDB$CFT_CAUSE
: You can define an optional
column NDB$CFT_CAUSE
which provides the cause
of the registered conflict. This column, if used, is defined as
shown here:
NDB$CFT_CAUSE ENUM('ROW_DOES_NOT_EXIST', 'ROW_ALREADY_EXISTS', 'DATA_IN_CONFLICT', 'TRANS_IN_CONFLICT') NOT NULL
ROW_DOES_NOT_EXIST
can be reported as the cause
for UPDATE_ROW
and WRITE_ROW
operations; ROW_ALREADY_EXISTS
can be reported
for WRITE_ROW
events.
DATA_IN_CONFLICT
is reported when a row-based
conflict function detects a conflict;
TRANS_IN_CONFLICT
is reported when a
transactional conflict function rejects all of the operations
belonging to a complete transaction.
NDB$ORIG_TRANSID
: The
NDB$ORIG_TRANSID
column, if used, contains the
ID of the originating transaction. This column should be defined
as follows:
NDB$ORIG_TRANSID BIGINT UNSIGNED NOT NULL
NDB$ORIG_TRANSID
is a 64-bit value generated by
NDB
. This value can be used to correlate
multiple exceptions table entries belonging to the same
conflicting transaction from the same or different exceptions
tables.
Additional reference columns which are not part of the original
table's primary key can be named
or
colname
$OLD
.
colname
$NEW
references old values in update and delete operations—that
is, operations containing colname
$OLDDELETE_ROW
events.
can be
used to reference new values in insert and update
operations—in other words, operations using
colname
$NEWWRITE_ROW
events, UPDATE_ROW
events, or both types of events. Where a conflicting operation
does not supply a value for a given non-primary-key reference
column, the exceptions table row contains either
NULL
, or a defined default value for that
column.
The mysql.ndb_replication
table is read when
a data table is set up for replication, so the row corresponding
to a table to be replicated must be inserted into
mysql.ndb_replication
before the table to be replicated is
created.
The following examples assume that you have already a working MySQL Cluster replication setup, as described in Section 19.6.5, “Preparing the MySQL Cluster for Replication”, and Section 19.6.6, “Starting MySQL Cluster Replication (Single Replication Channel)”.
NDB$MAX() example.
Suppose you wish to enable “greatest timestamp
wins” conflict resolution on table
test.t1
, using column
mycol
as the “timestamp”. This
can be done using the following steps:
Make sure that you have started the master
mysqld with
--ndb-log-update-as-write=OFF
.
On the master, perform this
INSERT
statement:
INSERT INTO mysql.ndb_replication VALUES ('test', 't1', 0, NULL, 'NDB$MAX(mycol)');
Inserting a 0 into the
server_id
indicates that all
SQL nodes accessing this table should use conflict resolution.
If you want to use conflict resolution on a specific
mysqld only, use the actual server ID.
Inserting NULL
into the
binlog_type
column has the same effect as
inserting 0 (NBT_DEFAULT
); the server
default is used.
Create the test.t1
table:
CREATE TABLE test.t1 (columns
mycol INT UNSIGNED,columns
) ENGINE=NDB;
Now, when updates are done on this table, conflict resolution
is applied, and the version of the row having the greatest
value for mycol
is written to the slave.
Other binlog_type
options—such as
NBT_UPDATED_ONLY_USE_UPDATE
should be used to
control logging on the master using the
ndb_replication
table rather than by using
command-line options.
NDB$OLD() example.
Suppose an NDB
table such as the
one defined here is being replicated, and you wish to enable
“same timestamp wins” conflict resolution for
updates to this table:
CREATE TABLE test.t2 ( a INT UNSIGNED NOT NULL, b CHAR(25) NOT NULL,columns
, mycol INT UNSIGNED NOT NULL,columns
, PRIMARY KEY pk (a, b) ) ENGINE=NDB;
The following steps are required, in the order shown:
First—and prior to creating
test.t2
—you must insert a row into
the
mysql.ndb_replication
table, as shown here:
INSERT INTO mysql.ndb_replication VALUES ('test', 't2', 0, NULL, 'NDB$OLD(mycol)');
Possible values for the binlog_type
column
are shown earlier in this section. The value
'NDB$OLD(mycol)'
should be inserted into
the conflict_fn
column.
Create an appropriate exceptions table for
test.t2
. The table creation statement shown
here includes all required columns; any additional columns
must be declared following these columns, and before the
definition of the table's primary key.
CREATE TABLE test.t2$EX (
server_id SMALLINT UNSIGNED,
master_server_id INT UNSIGNED,
master_epoch BIGINT UNSIGNED,
count BIGINT UNSIGNED,
a INT UNSIGNED NOT NULL,
b CHAR(25) NOT NULL,
[additional_columns
,]
PRIMARY KEY(server_id, master_server_id, master_epoch, count)
) ENGINE=NDB;
We can include additional columns for information about the type, cause, and originating transaction ID for a given conflict. We are also not required to supply matching columns for all primary key columns in the original table. This means you can create the exceptions table like this:
CREATE TABLE test.t2$EX (
NDB$server_id SMALLINT UNSIGNED,
NDB$master_server_id INT UNSIGNED,
NDB$master_epoch BIGINT UNSIGNED,
NDB$count BIGINT UNSIGNED,
a INT UNSIGNED NOT NULL,
NDB$OP_TYPE ENUM('WRITE_ROW','UPDATE_ROW', 'DELETE_ROW',
'REFRESH_ROW', 'READ_ROW') NOT NULL,
NDB$CFT_CAUSE ENUM('ROW_DOES_NOT_EXIST', 'ROW_ALREADY_EXISTS',
'DATA_IN_CONFLICT', 'TRANS_IN_CONFLICT') NOT NULL,
NDB$ORIG_TRANSID BIGINT UNSIGNED NOT NULL,
[additional_columns
,]
PRIMARY KEY(NDB$server_id, NDB$master_server_id, NDB$master_epoch, NDB$count)
) ENGINE=NDB;
The NDB$
prefix is required for the four
required columns since we included at least one of the
columns NDB$OP_TYPE
,
NDB$CFT_CAUSE
, or
NDB$ORIG_TRANSID
in the table definition.
Create the table test.t2
as shown
previously.
These steps must be followed for every table for which you wish to
perform conflict resolution using NDB$OLD()
.
For each such table, there must be a corresponding row in
mysql.ndb_replication
, and there must be an
exceptions table in the same database as the table being
replicated.
Read conflict detection and resolution.
MySQL Cluster also supports tracking of read operations, which
makes it possible in circular replication setups to manage
conflicts between reads of a given row in one cluster and
updates or deletes of the same row in another. This example uses
employee
and department
tables to model a scenario in which an employee is moved from
one department to another on the master cluster (which we refer
to hereafter as cluster A) while the slave
cluster (hereafter B) updates the employee
count of the employee's former department in an interleaved
transaction.
The data tables have been created using the following SQL statements:
# Employee table CREATE TABLE employee ( id INT PRIMARY KEY, name VARCHAR(2000), dept INT NOT NULL ) ENGINE=NDB; # Department table CREATE TABLE department ( id INT PRIMARY KEY, name VARCHAR(2000), members INT ) ENGINE=NDB;
The contents of the two tables include the rows shown in the
(partial) output of the following
SELECT
statements:
mysql>SELECT id, name, dept FROM employee;
+---------------+------+ | id | name | dept | +------+--------+------+ ... | 998 | Mike | 3 | | 999 | Joe | 3 | | 1000 | Mary | 3 | ... +------+--------+------+ mysql>SELECT id, name, members FROM department;
+-----+-------------+---------+ | id | name | members | +-----+-------------+---------+ ... | 3 | Old project | 24 | ... +-----+-------------+---------+
We assume that we are already using an exceptions table that includes the four required columns (and these are used for this table's primary key), the optional columns for operation type and cause, and the original table's primary key column, created using the SQL statement shown here:
CREATE TABLE employee$EX ( NDB$server_id INT UNSIGNED, NDB$master_server_id INT UNSIGNED, NDB$master_epoch BIGINT UNSIGNED, NDB$count INT UNSIGNED, NDB$OP_TYPE ENUM( 'WRITE_ROW','UPDATE_ROW', 'DELETE_ROW', 'REFRESH_ROW','READ_ROW') NOT NULL, NDB$CFT_CAUSE ENUM( 'ROW_DOES_NOT_EXIST', 'ROW_ALREADY_EXISTS', 'DATA_IN_CONFLICT', 'TRANS_IN_CONFLICT') NOT NULL, id INT NOT NULL, PRIMARY KEY(NDB$server_id, NDB$master_server_id, NDB$master_epoch, NDB$count) ) ENGINE=NDB;
Suppose there occur the two simultaneous transactions on the two clusters. On cluster A, we create a new department, then move employee number 999 into that department, using the following SQL statements:
BEGIN
;INSERT
INTO department VALUES (4, "New project", 1);UPDATE
employee SET dept = 4 WHERE id = 999; COMMIT;
At the same time, on cluster B, another
transaction reads from employee
, as shown here:
BEGIN;
SELECT name FROM employee WHERE id = 999;
UPDATE department SET members = members - 1 WHERE id = 3;
commit;
The conflicting transactions are not normally detected by the
conflict resolution mechanism, since the conflict is between a
read (SELECT
) and an update operation. You can
circumvent this issue by executing
SET
ndb_log_exclusive_reads
= 1
on the slave cluster. Acquiring exclusive
read locks in this way causes any rows read on the master to be
flagged as needing conflict resolution on the slave cluster. If we
enable exclusive reads in this way prior to the logging of these
transactions, the read on cluster B is
tracked and sent to cluster A for resolution;
the conflict on the employee row will be detected and the
transaction on cluster B is aborted.
The conflict is registered in the exceptions table (on cluster
A) as a READ_ROW
operation
(see Conflict resolution exceptions table,
for a description of operation types), as shown here:
mysql> SELECT id, NDB$OP_TYPE, NDB$CFT_CAUSE FROM employee$EX;
+-------+-------------+-------------------+
| id | NDB$OP_TYPE | NDB$CFT_CAUSE |
+-------+-------------+-------------------+
...
| 999 | READ_ROW | TRANS_IN_CONFLICT |
+-------+-------------+-------------------+
Any existing rows found in the read operation are flagged. This means that multiple rows resulting from the same conflict may be logged in the exception table, as shown by examining the effects a conflict between an update on cluster A and a read of multiple rows on cluster B from the same table in simultaneous transactions. The transaction executed on cluster A is shown here:
BEGIN;
INSERT INTO department VALUES (4, "New project", 0);
UPDATE employee SET dept = 4 WHERE dept = 3;
SELECT COUNT(*) INTO @count FROM employee WHERE dept = 4;
UPDATE department SET members = @count WHERE id = 4;
COMMIT;
Concurrently a transaction containing the statements shown here runs on cluster B:
SET ndb_log_exclusive_reads = 1; # Must be set if not already enabled
...
BEGIN;
SELECT COUNT(*) INTO @count FROM employee WHERE dept = 3 FOR UPDATE;
UPDATE department SET members = @count WHERE id = 3;
COMMIT;
In this case, all three rows matching the WHERE
condition in the second transaction's
SELECT
are read, and are thus flagged in the
exceptions table, as shown here:
mysql> SELECT id, NDB$OP_TYPE, NDB$CFT_CAUSE FROM employee$EX;
+-------+-------------+-------------------+
| id | NDB$OP_TYPE | NDB$CFT_CAUSE |
+-------+-------------+-------------------+
...
| 998 | READ_ROW | TRANS_IN_CONFLICT |
| 999 | READ_ROW | TRANS_IN_CONFLICT |
| 1000 | READ_ROW | TRANS_IN_CONFLICT |
...
+-------+-------------+-------------------+
Read tracking is performed on the basis of existing rows only. A read based on a given condition track conflicts only of any rows that are found and not of any rows that are inserted in an interleaved transaction. This is similar to how exclusive row locking is performed in a single instance of MySQL Cluster.
Changes in MySQL Cluster releases are documented separately from this reference manual; you can find release notes for the changes in each MySQL Cluster NDB 7.5 release at MySQL Cluster NDB 7.5 Release Notes.
You can obtain release notes for older versions of MySQL Cluster from MySQL Cluster Release Notes.