Configuring MariaDB Galera Cluster
Contents
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:
wsrep_provider
— Path to the Galera librarywsrep_cluster_address
— See Galera Cluster address format and usagebinlog_format=ROW
— See Binary Log Formatsdefault_storage_engine=InnoDB
innodb_autoinc_lock_mode=2
innodb_doublewrite=1
— This is the default value, but it should not be changed when using Galera provider version >= 2.0.query_cache_size=0
— Only mandatory for MariaDB versions prior to MariaDB Galera Cluster 5.5.40, MariaDB Galera Cluster 10.0.14, and MariaDB 10.1.2.wsrep_on=ON
— Enable wsrep replication (starting 10.1.1)
Performance-related Options
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:
- Standard MariaDB Port (default: 3306) - For MySQL client connections and State Snapshot Transfers that use the
mysqldump
method. This can be changed by settingport
. - Galera Replication Port (default: 4567) - For Galera Cluster replication traffic, multicast replication uses both UDP transport and TCP on this port. Can be changed by setting
wsrep_node_address
. - Galera Replication Listening Interface (default:
0.0.0.0:4567
) needs to be set using gmcast.listen_addr, either- in wsrep_provider_options:
wsrep_provider_options='gmcast.listen_addr=tcp://<IP_ADDR>:<PORT>;'
- or in wsrep_cluster_address
- in wsrep_provider_options:
- IST Port (default: 4568) - For Incremental State Transfers. Can be changed by setting
ist.recv_addr
inwsrep_provider_options
. - SST Port (default: 4444) - For all State Snapshot Transfer methods other than
mysqldump
. Can be changed by settingwsrep_sst_receive_address
.
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.