[4.22] OCPBUGS-98604: Add NodeSelectorAdjuster admission plugin for HCP clusters by joelsmith · Pull Request #2718 · openshift/kubernetes

joelsmith · 2026-07-14T00:56:00Z

Cherry-pick of #2695

Add a new kube-apiserver admission plugin that removes the node-role.kubernetes.io/master node selector to qualifying control-plane-adjacent Day 2 operator pods at admission time.

On hosted-control plane clusters, there are no master nodes so Day 2 operators which expect to run on a master node are unable to run without manual intervention. On standalone OpenShift clusters, operators like the VPA operator must run on master nodes for security reasons (e.g., limiting blast radius of privilege escalation from a worker-node compromise). HCP clusters have a different security posture (using the cluster rather than the node as a security boundary) and no master nodes exist in the guest cluster, so the plugin provides a means of running the VPA on HCP without manual intervention. The plugin detects standalone clusters by checking POD_NAMESPACE=openshift-kube-apiserver at start-up.

Currently the VPA Operator pod is the only registered workload. The design is extensible to other control-plane-adjacent operators by adding label matchers to requiresNodeSelectorAdjustment().

…clusters Add a new kube-apiserver admission plugin that removes the node-role.kubernetes.io/master node selector to qualifying control-plane-adjacent Day 2 operator pods at admission time. On hosted-control plane clusters, there are no master nodes so Day 2 operators which expect to run on a master node are unable to run without manual intervention. On standalone OpenShift clusters, operators like the VPA operator must run on master nodes for security reasons (e.g., limiting blast radius of privilege escalation from a worker-node compromise). HCP clusters have a different security posture (using the cluster rather than the node as a security boundary) and no master nodes exist in the guest cluster, so the plugin provides a means of running the VPA on HCP without manual intervention. The plugin detects standalone clusters by checking POD_NAMESPACE=openshift-kube-apiserver at start-up. Currently the VPA Operator pod is the only registered workload. The design is extensible to other control-plane-adjacent operators by adding label matchers to requiresNodeSelectorAdjustment(). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

openshift-ci-robot · 2026-07-14T00:56:06Z

@joelsmith: This pull request references Jira Issue OCPBUGS-98604, which is invalid:

expected the bug to target either version "4.22." or "openshift-4.22.", but it targets "5.0.0" instead
expected dependent Jira Issue OCPBUGS-42343 to be in one of the following states: MODIFIED, ON_QA, VERIFIED, but it is Closed (Done) instead

Comment /jira refresh to re-evaluate validity if changes to the Jira bug are made, or edit the title of this pull request to link to a different bug.

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

Details

In response to this:

Cherry-pick of #2695

Add a new kube-apiserver admission plugin that removes the node-role.kubernetes.io/master node selector to qualifying control-plane-adjacent Day 2 operator pods at admission time.

On hosted-control plane clusters, there are no master nodes so Day 2 operators which expect to run on a master node are unable to run without manual intervention. On standalone OpenShift clusters, operators like the VPA operator must run on master nodes for security reasons (e.g., limiting blast radius of privilege escalation from a worker-node compromise). HCP clusters have a different security posture (using the cluster rather than the node as a security boundary) and no master nodes exist in the guest cluster, so the plugin provides a means of running the VPA on HCP without manual intervention. The plugin detects standalone clusters by checking POD_NAMESPACE=openshift-kube-apiserver at start-up.

Currently the VPA Operator pod is the only registered workload. The design is extensible to other control-plane-adjacent operators by adding label matchers to requiresNodeSelectorAdjustment().

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.

openshift-ci-robot · 2026-07-14T00:56:10Z

@joelsmith: the contents of this pull request could not be automatically validated.

The following commits could not be validated and must be approved by a top-level approver:

d4e61a2|UPSTREAM: : Add NodeSelectorAdjuster admission plugin for HCP clusters: does not specify an upstream backport in the commit message

Comment /validate-backports to re-evaluate validity of the upstream PRs, for example when they are merged upstream.

coderabbitai · 2026-07-14T00:56:10Z

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openshift-ci · 2026-07-14T00:56:40Z

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: joelsmith
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joelsmith · 2026-07-14T00:58:21Z

/jira refresh

openshift-ci-robot · 2026-07-14T00:58:29Z

@joelsmith: This pull request references Jira Issue OCPBUGS-98604, which is valid. The bug has been moved to the POST state.

7 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)
release note text is set and does not match the template
dependent bug Jira Issue OCPBUGS-42343 is in the state Verified, which is one of the valid states (MODIFIED, ON_QA, VERIFIED)
dependent Jira Issue OCPBUGS-42343 targets the "5.0.0" version, which is one of the valid target versions: 5.0.0
bug has dependents

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

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

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In response to this:

/jira refresh

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joelsmith · 2026-07-15T00:22:32Z

/retest

openshift-ci · 2026-07-15T03:50:28Z

@joelsmith: all tests passed!

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openshift-ci Bot requested review from benluddy and jerpeter1 July 14, 2026 00:56

joelsmith changed the title ~~OCPBUGS-98604: Add NodeSelectorAdjuster admission plugin for HCP clusters~~ [4.22] OCPBUGS-98604: Add NodeSelectorAdjuster admission plugin for HCP clusters Jul 14, 2026

openshift-ci-robot added jira/valid-bug Indicates that a referenced Jira bug is valid for the branch this PR is targeting. and removed jira/invalid-bug Indicates that a referenced Jira bug is invalid for the branch this PR is targeting. labels Jul 14, 2026

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[4.22] OCPBUGS-98604: Add NodeSelectorAdjuster admission plugin for HCP clusters#2718

[4.22] OCPBUGS-98604: Add NodeSelectorAdjuster admission plugin for HCP clusters#2718
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