Goal:

A Pod Disruption Budget (PDB) is a safety rule that guarantees a minimum number of your application's pods remain running during planned maintenance. It prevents voluntary disruptions, like draining a node for an update, from taking down too many replicas simultaneously and causing an outage.

Services like galera and rabbitmq must not lose more then one pod to preserve quorum. For any of those service (there might be more) a PDB should/could be used. It also prevent multiple replicas to go down when e.g. 2 instances get somehow scheduled on a single node (node draining).

Acceptance Criteria:

• add functionality in lib-common to manage PDBs
• add PDB to rabbitmq after verification of being useful

https://kubernetes.io/docs/tasks/run-application/configure-pdb/ 

https://www.rabbitmq.com/kubernetes/operator/using-operator#set-pdb