16.7. MySQL Cluster Replication
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 Chapter 6, 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 Cluster storage engine for clustering
functionality, it is not necessary to use the Cluster storage
engine on the slave. However, for maximum availability, it is
possible to replicate from one MySQL Cluster to another, and it is
this type of configuration 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
via 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.
