Fix topology scheduling rule: anti-affinity, feature gates, PDB guidance#18
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openshift-merge-bot[bot] merged 1 commit intoJun 4, 2026
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- Fix anti-affinity recommendation: required anti-affinity with maxUnavailable >= 1 is the correct pattern (used by oauth, openshift- apiserver, image-registry, monitoring). Preferred anti-affinity allows pod co-location, which caused OCPBUGS-65984 (74-second Available=False on two-node fencing when both pods landed on the same node). - Flag the dangerous combination (required anti-affinity + maxUnavailable: 0) instead of flagging required anti-affinity alone. - Make feature gate references version-agnostic: remove hardcoded "tech preview" status and specific feature gate names that change between releases. Point to openshift/api as the source of truth. - Fix wrong feature gate name: DualReplicaTopology -> DualReplica. - Fix wrong label: role.kubernetes.io/arbiter -> node-role.kubernetes.io/arbiter. - Add PDB limitation: PDBs do not protect against TaintManagerEviction (node fencing), only the eviction API (kubectl drain). - Recommend library-go topology-aware scheduling hooks for DeploymentController-based operators.
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/cc @dgoodwin |
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/lgtm Thanks Luis! |
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Summary
Fixes and improvements to the "Topology-Aware Scheduling Compatibility" review rule based on findings from OCPBUGS-65984 investigation and a cross-operator scheduling survey.
Bug fixes
DualReplicaTopology→DualReplica(the enhancement proposedDualReplicaTopologybut the implementation inopenshift/api/features/features.gousesDualReplica)role.kubernetes.io/arbiter→node-role.kubernetes.io/arbiter(missingnode-prefix)HighlyAvailableArbiterwas listed as requiring a feature gate, but it is ungated in the API enum.DualReplicawas listed as tech preview but is now enabled by default.Anti-affinity guidance reversal
The previous rule recommended
preferredDuringSchedulingIgnoredDuringExecutionas the safe alternative to required anti-affinity. This recommendation directly caused OCPBUGS-65984: KSVMO#149 followed it, both migrator pods landed on the same node during a bootstrap timing race, and a 74-secondAvailable=Falseoutage occurred when that node was fenced. Every other HA operator (oauth-openshift, openshift-apiserver, image-registry, monitoring) uses required anti-affinity and survived the same fencing event.The rule now correctly identifies the dangerous combination as required anti-affinity +
maxUnavailable: 0(which deadlocks), not required anti-affinity alone. The recommendation is to use required anti-affinity withmaxUnavailable >= 1.Version-agnostic feature gate references
Feature gate status (TechPreview vs Default) changes between releases, and this rule applies across all branches. Removed hardcoded "tech preview" labels and specific feature gate names. Instead points to
openshift/apias the source of truth for the target release.New guidance
TaintManagerEviction(node fencing/unreachable taints) — only the eviction API (kubectl drain).WithTopologyAwareReplicasHook,WithTopologyAwareSchedulingHook, andWithControlPlaneNodeSelectorHookfrom library-go#2276 for DeploymentController-based operators.References