PodDisruptionBudget's more flexible configuration

Please, answer some short questions which should help us to understand your problem / question better?

• Which image of the operator are you using? ghcr.io/zalando/postgres-operator:v1.13.0
• Where do you run it - cloud or metal? Kubernetes or OpenShift? AWS EKS, Metal (rke2, minikube)
• Are you running Postgres Operator in production? Yes
• Type of issue? Feature request

I feel that the podDisruptionBudget should be more flexible in its configuration, allowing to configure the pdb parameters as minAvailable and maxUnavailable, as currently you can only configure to enable the pdb (enable_pod_disruption_budget) and to include or not the master label in the selector (pdb_master_label_selector).

I understand the need to remove the master label from the selector, e.g. to allow node upgrades (we ourselves have had the same problem whenever we upgraded EKS). However, if you disable the master label, since you can't configure anything else in the PDB, you get a PDB that is not very useful. For example, for a case of 3 replicas, you would be left with a PDB that allowed 2 disruptions, which would lose quorum:

NAME                              MIN AVAILABLE   MAX UNAVAILABLE   ALLOWED DISRUPTIONS   AGE
postgres-ghale-psql-cluster-pdb   1               N/A               2                     10m

Wouldn't it be better to be able to configure the minAvailable and maxUnavailable parameters? In this way, by disabling the master label in PDB, you could configure a PDB with a maxUnavailable 2 for the case of 3 replicas, and you would be sure not to lose the quorum.

Maybe I'm misunderstanding something, or maybe removing the master label is intended to be only temporary, for example, while you upgrade, but this seems a bit weird IMO.

Start by locating the configuration and PDB generation paths for enable_pod_disruption_budget and pdb_master_label_selector. Review the operator's existing tests around PodDisruptionBudgets, then define and test configurable minAvailable and maxUnavailable behavior, including the expected handling when both or neither is set.