Maintenance in Managed Service for MySQL®

Maintenance in Managed Service for MySQL® includes:

• Automatic installation of DBMS updates and patches for hosts (including for stopped clusters).
• Other maintenance activities.

Changing a DBMS version is not part of maintenance. For more information about version changes, see MySQL® version upgrade.

Maintenance windowMaintenance window

You can set the maintenance window when creating a cluster or updating its settings:

• The At any time option (default) allows performing maintenance at any time.
• The By schedule option allows setting the preferred maintenance start day and time (UTC). For example, you can choose a time when the cluster is least loaded.

Maintenance workflowMaintenance workflow

In Managed Service for MySQL® single-host clusters, a master host undergoes maintenance. Therefore, it may become unavailable in case it is restarted.

In multi-host clusters, the maintenance is run as follows:

1. Replicas undergo maintenance one by one. The replicas are queued randomly. If a replica needs to be restarted during maintenance, it will become unavailable.

2. Master host undergoes maintenance and gets updated. If the master host needs to restart and becomes unavailable, one of the replicas will assume its role. Once the upgrade is complete, the host with the highest failover priority will become the new master. If the cluster has several hosts with maximum priority, the one with the least lag behind the master will be selected.

   For the master host to preserve its master role after an upgrade, set the highest failover priority for it. You can set failover priority when creating a cluster or updating host settings.

   If you access a cluster using the FQDN of the master host, the cluster may become unavailable. To make your application continuously available, access the cluster using a special FQDN that always points to the current master host.