A Galera cluster is a true synchronous multi-master replication system. Any or all nodes composing the cluster can be used as master at any time meaning that there is no failover in the traditional MySQL master-slave sense. Though, you may encounter issues with your Galera cluster after restarting the cluster during maintenance or upgrade.
This section instructs you on how to troubleshoot the Galera cluster as well as how to restart, restore, and rejoin nodes to the cluster.