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Clarify why the two PDBs use different budget fields 

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
Juhani Pelli 2026-07-24 19:41:05 +03:00
parent 187e88e5cd
commit 935ffec3b8
1 changed files with 8 additions and 2 deletions
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docs/administrator.md
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@ -653,8 +653,14 @@ The PDB is only relaxed in two scenarios:
* If a cluster is scaled down to `0` instances (e.g. for draining nodes) * 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`) * If the PDB is disabled in the configuration (`enable_pod_disruption_budget`)
The PDBs are still in place: the primary PDB with `MinAvailable` set to `0` and the The PDBs are still in place but fully relaxed: the primary PDB with `MinAvailable`
critical operations PDB with `MaxUnavailable` set to `100%`. Disabling PDBs set to `0` and the critical operations PDB with `MaxUnavailable` set to `100%`.
The two PDBs intentionally use different budget fields matching their purposes:
the primary PDB guarantees a minimum count of always-present pods
(`MinAvailable`), while the critical operations PDB freezes disruptions for
whatever pods currently carry the `critical-operation=true` label - a
usually-empty set, which `MaxUnavailable: 0` expresses without producing an
unsatisfiable budget while idle. Disabling PDBs
helps avoiding blocking Kubernetes upgrades in managed K8s environments at the 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) cost of prolonged DB downtime. See PR [#384](https://github.com/zalando/postgres-operator/pull/384)
for the use case. for the use case.