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Previous to MySQL 5.1.6, asynchronous replication, more usually referred to simply as “replication”, was not available when using MySQL Cluster. MySQL 5.1.6 introduces master-slave replication of this type for MySQL Cluster databases. This section explains how to set up and manage a configuration wherein 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 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
storage engine for clustering functionality, it is not necessary to
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
binlog 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
For information about performing point-in-time recovery with MySQL Cluster and MySQL Cluster Replication, see Section 8.9.2, “Point-In-Time Recovery Using MySQL Cluster Replication”.
NDB API _slave status variables.
Beginning with MySQL Cluster NDB 7.0.22 and MySQL Cluster NDB
7.1.11, NDB API counters provide enhanced monitoring capabilities
on MySQL Cluster replication slaves. These are implelemented as
_slave status variables, as seen
in the output of
SHOW STATUS, or in
the results of queries against the
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
Section 7.15, “NDB API Statistics Counters and Variables”, provides
Replication from NDB to non-NDB tables.
It is possible to replicate
tables from a MySQL Cluster acting as the master to tables using
other MySQL storage engines such as
MyISAM on a slave
mysqld. This is subject to a number of
Replication from NDB to other storage engines, and
Replication from NDB to a nontransactional storage engine,
for more information.