CNTRLPLANE-2652: Implement 5.0 EUS schedule in KAS-O

[tjungblu]

Implements the new EUS schedule (every third release instead of every second) in the kubelet skew guard controller.

This is intended to be merged into the 5.0 branch, once it opens. Targeting 4.23 for now, as this will become 5.0 with a FF rule in the future.

/hold

---

Note

High Risk
Changes upgradeability gating logic for kubelet/API minor-version skew, which can block or allow cluster upgrades. A small off-by-one or cadence mismatch could impact upgrade safety across versions.

Overview
Updates the kubelet version skew controller to follow the 5.x EUS cadence (every third minor) by changing minSupportedKubeletSkewForOpenShiftVersion from even/odd logic to Minor % 3 thresholds (allowing up to 1/2/3 minor lag depending on the release).

Tightens the “next upgrade would be unsupported” check from < to <=, and refreshes unit tests to model 5.0–5.2/k8s 1.36–1.38 scenarios with new expected upgradeability outcomes. Also removes an unused regexp helper.

^{Written by Cursor Bugbot for commit e0b95d5. This will update automatically on new commits. Configure here.}

[openshift-ci-robot]

@tjungblu: This pull request references CNTRLPLANE-2652 which is a valid jira issue.

Warning: The referenced jira issue has an invalid target version for the target branch this PR targets: expected the story to target the "4.23.0" version, but no target version was set.

Details

In response to this:

Implements the new EUS schedule (every third release instead of every second) in the kubelet skew guard controller.

This is intended to be merged into the 5.0 branch, once it opens. Targeting 4.23 for now, as this will become 5.0 with a FF rule in the future.

/hold

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[openshift-ci]

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[openshift-ci-robot]

@tjungblu: This pull request references CNTRLPLANE-2652 which is a valid jira issue.

Warning: The referenced jira issue has an invalid target version for the target branch this PR targets: expected the story to target the "4.23.0" version, but no target version was set.

Details

In response to this:

Implements the new EUS schedule (every third release instead of every second) in the kubelet skew guard controller.

This is intended to be merged into the 5.0 branch, once it opens. Targeting 4.23 for now, as this will become 5.0 with a FF rule in the future.

/hold

---

[!NOTE]
^{Cursor Bugbot is generating a summary for commit e0b95d5. Configure here.}

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]

@tjungblu: This pull request references CNTRLPLANE-2652 which is a valid jira issue.

Warning: The referenced jira issue has an invalid target version for the target branch this PR targets: expected the story to target the "4.23.0" version, but no target version was set.

Details

In response to this:

Implements the new EUS schedule (every third release instead of every second) in the kubelet skew guard controller.

This is intended to be merged into the 5.0 branch, once it opens. Targeting 4.23 for now, as this will become 5.0 with a FF rule in the future.

/hold

---

[!NOTE]
High Risk
Changes upgradeability gating logic for kubelet/API minor-version skew, which can block or allow cluster upgrades. A small off-by-one or cadence mismatch could impact upgrade safety across versions.

Overview
Updates the kubelet version skew controller to follow the 5.x EUS cadence (every third minor) by changing minSupportedKubeletSkewForOpenShiftVersion from even/odd logic to Minor % 3 thresholds (allowing up to 1/2/3 minor lag depending on the release).

Tightens the “next upgrade would be unsupported” check from < to <=, and refreshes unit tests to model 5.0–5.2/k8s 1.36–1.38 scenarios with new expected upgradeability outcomes. Also removes an unused regexp helper.

^{Written by Cursor Bugbot for commit e0b95d5. This will update automatically on new commits. Configure here.}

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]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: tjungblu
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[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

[cursor]

Comparison change incorrectly flags supported kubelet versions

Medium Severity

The change from < to <= on line 133 causes kubelets that would be exactly at the minimum supported skew after upgrade to be incorrectly flagged as "will not be supported". If minSupportedSkewNextVersion is -3, a kubelet that would be at skew -3 after upgrade IS supported (at the boundary). The minSupportedSkew check on line 130 uses <, correctly treating the minimum as an inclusive boundary. Using <= here creates an inconsistency where kubelets at the exact supported boundary are incorrectly reported as unsupported for the next upgrade.

 

[tjungblu]

I actually added a unit test to cover this with the spreadsheet that Luis created. I think the reason it worked before was the "skew-1" and "mod 2" combination. With mod 3 this doesn't evaluate correctly anymore.

[openshift-ci]

@tjungblu: all tests passed!

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