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Update PDB docs for critical-op maxUnavailable semantics 

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
Juhani Pelli 2026-07-24 18:58:31 +03:00
parent 61e506dea0
commit 187e88e5cd
1 changed files with 7 additions and 4 deletions
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docs/administrator.md
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@ -639,9 +639,11 @@ masters in single-node clusters and/or the last remaining running instance in a
cluster.
## PDB for critical operations
The `MinAvailable` parameter of this PDB is equal to the `numberOfInstances` set in the
cluster manifest, while label selector includes `critical-operation=true` condition. This
allows to protect all pods of a cluster, given they are labeled accordingly.
The `MaxUnavailable` parameter of this PDB is set to `0`, while label selector includes
`critical-operation=true` condition. This blocks voluntary disruptions for all pods of a
cluster that are labeled accordingly, without leaving an unsatisfiable budget behind when
no pods carry the label (which previously kept monitoring alerts like
`KubePdbNotEnoughHealthyPods` firing permanently).
For example, Operator labels all Spilo pods with `critical-operation=true` during the major
version upgrade run. You may want to protect cluster pods during other critical operations
by assigning the label to pods yourself or using other means of automation.
@ -651,7 +653,8 @@ The PDB is only relaxed in two scenarios:
* If a cluster is scaled down to `0` instances (e.g. for draining nodes)
* If the PDB is disabled in the configuration (`enable_pod_disruption_budget`)
The PDBs are still in place having `MinAvailable` set to `0`. Disabling PDBs
The PDBs are still in place: the primary PDB with `MinAvailable` set to `0` and the
critical operations PDB with `MaxUnavailable` set to `100%`. Disabling PDBs
helps avoiding blocking Kubernetes upgrades in managed K8s environments at the
cost of prolonged DB downtime. See PR [#384](https://github.com/zalando/postgres-operator/pull/384)
for the use case.