The GaleraClusterSizeMismatch alert fires when the Galera wsrep_cluster_state_uuid status variable has multiple visible values.
Error / Incident
The datastore used by all OpenStack services might be in a split-brain situation.
Find the node with a different
wsrep_cluster_state_uuid, and do something about it.
Add here any new common issues you find.
Add here any new tasks for incidents you might encounter.