mysqld is the traditional MySQL server process.
To be used with MySQL Cluster, mysqld needs to
be built with support for the
NDBCLUSTER
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 configure with one of
the options to enable NDBCLUSTER
storage engine support:
--with-plugins=ndbcluster
--with-plugins=max
--with-plugins=max-no-innodb
(--with-ndbcluster
also works to enable
NDBCLUSTER
support, but is deprecated
and so produces a configure warning as of MySQL
5.1.9.)
For information about other MySQL server options and variables relevant to MySQL Cluster in addition to those discussed in this section, see Section 17.3.4, “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
connectstring either on the command line when starting
mysqld or in my.cnf
. The
connectstring 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 17.3.2.3, “The MySQL Cluster Connectstring”, for more information on connectstrings.
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.
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