OCPBUGS-76964: HyperShift: relax ovnkube-control-plane zone anti-affinity

[ricky-rav]

The required zone (topology.kubernetes.io/zone) in the anti-affinity section on the managed ovnkube-control-plane deployment can prevent scheduling when the management cluster has one zone only.

Replace it with:

• a hard hostname anti-affinity (guaranteeing that two replicas land on different nodes) and
• a soft zone anti-affinity (preferring different zones when possible).

The hard requirement comes from the way we ran OVNK on hypershift until 4.13, that is with ovnkube-master running as a stateful set, where each pod had its own OVNDB and we probably wanted to spread DBs across different zones in order to avoid problems related to RAFT quorum when a zone went down.

cluster-network-operator/bindata/network/ovn-kubernetes/managed/ovnkube-master.yaml

Lines 83 to 88 in 5104647

	podAntiAffinity:
	requiredDuringSchedulingIgnoredDuringExecution:
	- labelSelector:
	matchLabels:
	app: ovnkube-master
	topologyKey: topology.kubernetes.io/zone

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

---

Walkthrough

Modifies the ovnkube-control-plane pod anti-affinity configuration, replacing zone-based hard anti-affinity with hostname-based hard anti-affinity while reintroducing zone-based anti-affinity as a soft preference.

Changes

Cohort / File(s)	Summary
Pod Affinity Configuration bindata/network/ovn-kubernetes/managed/ovnkube-control-plane.yaml	Changed pod anti-affinity topologyKey from topology.kubernetes.io/zone to kubernetes.io/hostname in required scheduling rule. Added new preferred anti-affinity block with zone-based soft affinity for app: ovnkube-control-plane pods.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

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[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: ricky-rav
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[openshift-ci-robot]

@ricky-rav: This pull request references Jira Issue OCPBUGS-76964, which is valid. The bug has been moved to the POST state.

3 validation(s) were run on this bug

• bug is open, matching expected state (open)
• bug target version (4.22.0) matches configured target version for branch (4.22.0)
• bug is in the state New, which is one of the valid states (NEW, ASSIGNED, POST)

No GitHub users were found matching the public email listed for the QA contact in Jira (yli2@redhat.com), skipping review request.

The bug has been updated to refer to the pull request using the external bug tracker.

Details

In response to this:

The required zone (topology.kubernetes.io/zone) in the anti-affinity section on the managed ovnkube-control-plane deployment can prevent scheduling when the management cluster has one zone only.

Replace it with:

• a hard hostname anti-affinity (guaranteeing that two replicas land on different nodes) and
• a soft zone anti-affinity (preferring different zones when possible).

The hard requirement comes from the way we ran OVNK on hypershift until 4.13, that is with ovnkube-master running as a stateful set, where each pod had its own OVNDB and we probably wanted to spread DBs across different zones in order to avoid problems related to RAFT quorum when a zone went down.

cluster-network-operator/bindata/network/ovn-kubernetes/managed/ovnkube-master.yaml

Lines 83 to 88 in 5104647

	podAntiAffinity:
	requiredDuringSchedulingIgnoredDuringExecution:
	- labelSelector:
	matchLabels:
	app: ovnkube-master
	topologyKey: topology.kubernetes.io/zone

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the openshift-eng/jira-lifecycle-plugin repository.

[ricky-rav]

/retest-required

[openshift-ci]

@ricky-rav: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/security	223579a	link	false	/test security
ci/prow/e2e-aws-ovn-hypershift-conformance	223579a	link	true	/test e2e-aws-ovn-hypershift-conformance
ci/prow/e2e-aws-ovn-serial-1of2	223579a	link	true	/test e2e-aws-ovn-serial-1of2
ci/prow/e2e-azure-ovn-upgrade	223579a	link	true	/test e2e-azure-ovn-upgrade

Full PR test history. Your PR dashboard.

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