Mitigation/Recovery from an OpenStack Clustering Outage Replacing a Controller

Issue

• A controller went down and is not recoverable.
• The OS is corrupt on a controller.
• A controller needs to be replaced in the environment, but time is needed to schedule a maintenance window and prepare for the activity.
• How to restore service to an HA environment that has lost one controller?
• Galera cluster will not sync after the loss of a controller and the remaining two nodes created a split cluster.