How To Setup MariaDB Galera Cluster

MariaDB is a relational database management system (RDBMS) and  MariaDB Galera Cluster is a synchronous multi-master cluster for MariaDB. It is available on Linux only, and only supports the XtraDB/InnoDB storage engines. This article explains how to setup MariaDB Galera Cluster 10.0 with 2 nodes running on CentOS 6.5 x86_64 resulting in a HA (high-availability) database cluster.

Step 1: Add MariaDB Repositories

Create a mariadb repository /etc/yum.repos.d/mariadb.repo using following content in your system.

For CentOS 6 – 64bit:

[mariadb]
name = MariaDB
baseurl = http://yum.mariadb.org/10.0/centos6-amd64
gpgkey=https://yum.mariadb.org/RPM-GPG-KEY-MariaDB
gpgcheck=1

For CentOS 6 – 32bit:

[mariadb]
name = MariaDB
baseurl = http://yum.mariadb.org/10.0/centos6-x86
gpgkey=https://yum.mariadb.org/RPM-GPG-KEY-MariaDB
gpgcheck=1

Step 2 – Set SELinux in permissive mode

Before starting the setup put SELinux into permissive mode on all nodes:

sudo setenforce0

Step 3 – Install MariaDB Galera Cluster 10.0 software

If you did a CentOS 6 minimal installation then make sure you install the socat package from the EPEL repository before proceeding with installing the MariaDB Galera Cluster 10.0 software.

You can install socat package directly from EPEL with the following command (for x86_64):

sudo yum install http://dl.fedoraproject.org/pub/epel/6/x86_64/socat-1.7.2.3-1.el6.x86_64.rpm

On CentOS 7 you can install socat package with following command.

sudo yum install socat

Install the MariaDB Galera Cluster 10.0 software by executing the following command on all nodes:

sudo yum install MariaDB-Galera-server MariaDB-client rsync galera

Step 4:  Setup MariaDB security

Start the mysql ( init script in MariaDB 10.0 is still called mysql)

sudo service mysql start

Run the mysql_secure_installation script so we can improve the security. Run the following command on all nodes:

sudo /usr/bin/mysql_secure_installation

I choose password as ‘dbpass’ and accepted all defaults (so answered yes to all questions).

Step 5 – Create MariaDB Galera Cluster users

Now, we have to create some users that must be able to access the database. The ‘sst_user’ is the user which a database node will use for authenticating to another database node in the State Transfer Snapshot (SST) phase. Run the following command on all nodes:

mysql -u root -p

mysql> DELETE FROM mysql.user WHERE user='';
mysql> GRANT ALL ON *.* TO 'root'@'%' IDENTIFIED BY 'dbpass';
mysql> GRANT USAGE ON *.* to sst_user@'%' IDENTIFIED BY 'dbpass';
mysql> GRANT ALL PRIVILEGES on *.* to sst_user@'%';
mysql> FLUSH PRIVILEGES;
mysql> quit

You are suggested to change ‘%’ to hostname(s) or IP addresses from which those users can access the database. Because ‘%’ means that the root or sst_user is allowed to access the database from any host, So less security.

Step 6 – Create the MariaDB Galera Cluster config

First stop the mysql services on all nodes:

sudo service mysql stop

Next, We are going to create the MariaDB Galera Cluster configuration by the following command on all nodes (go through the IMPORTANT NOTE after the config and make required changes for db2):

[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
binlog_format=ROW
bind-address=0.0.0.0
default_storage_engine=innodb
innodb_autoinc_lock_mode=2
innodb_flush_log_at_trx_commit=0
innodb_buffer_pool_size=122M
innodb_locks_unsafe_for_binlog=1
query_cache_size=0
query_cache_type=0
innodb_log_file_size=100M
innodb_file_per_table
innodb_flush_log_at_trx_commit=2

wsrep_provider=/usr/lib64/galera/libgalera_smm.so
wsrep_cluster_address="gcomm://IP_kilo_01,IP_kilo_02"
wsrep_cluster_name='galera_cluster'
wsrep_node_address='IP_kilo_01'
wsrep_node_name='db1'
wsrep_sst_method=rsync
wsrep_sst_auth=sst_user:dbpass



[mysql_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid

Step 7– Initialize the first cluster node

Start MariaDB with the special ‘‐‐wsrep-new-cluster’ option , Do it on node db1 only so the primary node of the cluster is initialized:

sudo /etc/init.d/mysql start --wsrep-new-cluster

Check status by run the following command on node db1 only:

mysql-uroot-p-e"show status like 'wsrep%'"

Some important information in the output are the following lines:

wsrep_local_state_comment | Synced <-- cluster is synced
wsrep_incoming_addresses  | IP_kilo_01:3306 <-- node db1 is a provider
wsrep_cluster_size        | 1 <-- cluster consists of 1 node 
wsrep_ready               | ON <-- good :)

 Check what has changed in the cluster status by executing the following command

mysql -u root -p -e "show status like 'wsrep%'"