How to do a primary switchover

A user may want to change the primary in a MySQL cluster to improve performance, enable maintenance, recover from failure, or balance load across nodes.

On a healthy cluster, the primary can be changed by running the promote-to-primary action with parameter scope set to unit on the unit that should become the new primary.

juju run-action mysql/1 promote-to-primary scope=unit

In this example, the unit mysql/1 will become the new primary. The previous primary will become a secondary.

Caution

The promote-to-primary action can be used in cluster scope, when using async replication. Check Switchover / Failover for more information.