Install & Configure MaxScale for MySQL Read/Write Splitting & Load Balancing

What is MaxScale?

After configuring MySQL master‑slave replication, we often need read/write splitting and load balancing across slaves. These are basic requirements for a MySQL cluster, and MaxScale provides an easy way to achieve them.

Basic Architecture of MaxScale

MaxScale is developed by MariaDB, a sister company of MySQL, and has matured into a plugin‑based system that allows users to develop custom plugins. Currently MaxScale offers five types of plugins:

Authentication plugins : cache user table information and validate connections.

Protocol plugins : handle client‑to‑server and server‑to‑client protocols.

Routing plugins : decide how client requests are forwarded, implementing read/write splitting and load balancing.

Monitoring plugins : monitor server health and exclude slow servers.

Logging and filtering plugins : provide simple firewall functions, SQL filtering and fault tolerance.

Installing and Using MaxScale

Assume a three‑node MySQL cluster (one master, two slaves).

Step 1: Prepare the cluster environment

Set up MySQL master‑slave replication on three servers (refer to existing guides).

Step 2: Install MaxScale

Download from https://downloads.mariadb.com/files/MaxScale and install the appropriate package. For CentOS 7:

yum install libaio.x86_64 libaio-devel.x86_64 novacom-server.x86_64 libedit -y
rpm -ivh maxscale-1.4.3-1.centos.7.x86_64.rpm

Step 3: Configure MaxScale

Create two MySQL users on the master for monitoring and routing:

mysql> create user scalemon@'%' identified by '111111';
mysql> grant replication slave, replication client on *.* to scalemon@'%';
mysql> create user maxscale@'%' identified by '111111';
mysql> grant select on mysql.* to maxscale@'%';

Edit /etc/maxscale.cnf:

Define [server1], [server2], [server3] sections with appropriate address and port.

In [MySQL Monitor] set servers=server1,server2,server3 and the monitoring user credentials.

In [Read-Write Service] set the same servers and routing user credentials.

Remove the default [Read-Only Service] section.

Step 4: Start MaxScale maxscale --config=/etc/maxscale.cnf Verify listening ports (e.g., 4006 for client connections, 6603 for the manager) with netstat -ntelp.

Log into the manager with maxadmin --user=admin --password=mariadb and run list servers to see connected master and slaves.

Step 5: Test

Create a test user on the master:

mysql> grant ALL PRIVILEGES on *.* to rtest@'%' identified by '111111';

Connect through MaxScale: mysql -h <MaxScale_IP> -P 4006 -u rtest -p111111 Running a transaction routes queries to the master, while regular SELECTs are served by slaves, confirming that read/write splitting works.

MaxScale configuration is now complete.