Configuring MariaDB Galera Cluster

A number of options need to be set in order for Galera Cluster to work when using MariaDB. These should be set in the MariaDB option file.

Mandatory Options

Several options are mandatory, which means that they *must* be set in order for Galera Cluster to be enabled or to work properly with MariaDB. The mandatory options are:

These are optional optimizations that can be made to improve performance.

  • innodb_flush_log_at_trx_commit=0 — This is not usually recommended in the case of standard MariaDB. However, it is a bit safer with Galera Cluster, since inconsistencies can always be fixed by recovering from another node.

Writing Replicated Write Sets to the Binary Log

Like with MariaDB replication, write sets that are received by a node with Galera Cluster's certification-based replication are not written to the binary log by default. If you would like a node to write its replicated write sets to the binary log, then you will have to set log_slave_updates=ON. This is especially helpful if the node is a replication master. See Using MariaDB Replication with MariaDB Galera Cluster: Configuring a Cluster Node as a Replication Master.

Replication Filters

Like with MariaDB replication, replication filters can be used to filter write sets from being replicated by Galera Cluster's certification-based replication. However, they should be used with caution because they may not work as you'd expect.

The following replication filters are honored for InnoDB DML, but not DDL:

The following replication filters are honored for DML and DDL for tables that use both the InnoDB and MyISAM storage engines:

However, it should be kept in mind that if replication filters cause inconsistencies that lead to replication errors, then nodes may abort.

See also MDEV-421 and MDEV-6229.

Network Ports

Galera Cluster needs access to the following ports:

Mutiple Galera Cluster Instances on One Server

If you want to run multiple Galera Cluster instances on one server, then you can do so by starting each instance with mysqld_multi, or if you are using systemd, then you can use the relevant systemd method for interacting with multiple MariaDB instances.

You need to ensure that each instance is configured with a different datadir.

You also need to ensure that each instance is configured with different network ports.

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