21.5.9 MySQL Server Usage for NDB Cluster
mysqld is the traditional MySQL server process. To be used with NDB Cluster, mysqld needs to be built with support for the
NDB storage engine, as it is in the precompiled binaries available from https://dev.mysql.com/downloads/ . If you build MySQL from source, you must invoke CMake with the
-DWITH_NDBCLUSTER=1 option to include support for
For more information about compiling NDB Cluster from source, see Section 126.96.36.199, “Building NDB Cluster from Source on Linux”, and Section 188.8.131.52, “Compiling and Installing NDB Cluster from Source on Windows”.
(For information about mysqld options and variables, in addition to those discussed in this section, which are relevant to NDB Cluster, see Section 184.108.40.206, “MySQL Server Options and Variables for NDB Cluster”.)
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 220.127.116.11, “NDB 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 an NDB Cluster, the mysqld process must be started with both the options
--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 an NDB Cluster, you must restart the server without the