Using Cooperative Locking for HA with MaxScale's MariaDB Monitor


MaxScale's MariaDB Monitor (mariadbmon) monitors MariaDB replicationMariaDB replication deployments.

When multiple MaxScale instances are used in a highly available deployment, MariaDB Monitor needs to ensure that only one MaxScale instance performs automatic failover operations at a given time. It does this by using cooperative locks on the back-end servers.

How MariaDB Monitor uses Cooperative Locks

When cooperative locking is enabled for MariaDB Monitor, it tries to acquire locks on the back-end servers with with GET_LOCK() function. If a specific MaxScale instance is able to acquire the lock on a majority of servers, then it is considered the primary MaxScale instance, which means that it can handle automatic failover.

Configuring Cooperative Locking

  1. Configure cooperative locking by configuring the cooperative_monitoring_locks parameter for the MariaDB Monitor in maxscale.cnf. It has several possible values.




    Do not use any cooperative locking. This is the default value.


    Primary monitor requires locks on a majority of servers, even those which are down.


    Primary monitor requires locks on a majority of running servers.

    For example:

    type                     = monitor
    module                   = mariadbmon
    cooperative_monitoring_locks = majority_of_running
  2. Restart the MaxScale instance.

    $ sudo systemctl restart maxscale