18.6.2 General Requirements for MySQL Cluster Replication

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 18.6.6, “Starting MySQL Cluster Replication (Single Replication Channel)”. For general information about row-based replication, see Section 17.1.2, “Replication Formats”.

Important

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 18.6.4, “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 7.3 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=id option, where 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 17.4.2, “Replication Compatibility Between MySQL Versions”). It is due to such differences between the binaries in the MySQL Cluster and MySQL Server 5.6 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.

Note

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 17.1.2.1, “Advantages and Disadvantages of Statement-Based and Row-Based Replication”, for more specific information concerning the differences between the two replication formats.