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Fix HasHighlyAvailableControlPlane to use AllInstanceGroups - #17740

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pkubicsek-sb:fix-ha-detection-with-instance-group-filter
Mar 27, 2026
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Fix HasHighlyAvailableControlPlane to use AllInstanceGroups#17740
k8s-ci-robot merged 1 commit into
kubernetes:masterfrom
pkubicsek-sb:fix-ha-detection-with-instance-group-filter

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@pkubicsek-sb pkubicsek-sb commented Nov 3, 2025

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What this PR does / why we need it:

Fixes a bug where HasHighlyAvailableControlPlane() incorrectly uses the filtered InstanceGroups list instead of AllInstanceGroups. This causes cluster-wide controllers (aws-load-balancer-controller, node-termination-handler, etc.) to incorrectly downscale from 2 to 1 replica when running kops update cluster with --instance-group or --instance-group-roles filters on HA clusters.

The fix changes the function to use AllInstanceGroups since HA status is a cluster-wide property that should not depend on instance group filtering.

Which issue(s) this PR fixes:
Fixes #17739

Special notes for your reviewer:

  • Added unit tests including a regression test for the filtered instance groups scenario
  • The bug only manifests when using --instance-group or --instance-group-roles flags
  • Change is minimal: single line change in template_functions.go:502

@k8s-ci-robot k8s-ci-robot added the do-not-merge/invalid-commit-message Indicates that a PR should not merge because it has an invalid commit message. label Nov 3, 2025
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linux-foundation-easycla Bot commented Nov 3, 2025 •
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CLA Signed

The committers listed above are authorized under a signed CLA.

  • ✅ login: pkubicsek-sb / name: Peter Kubicsek (e6786c2)

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@k8s-ci-robot k8s-ci-robot added size/L Denotes a PR that changes 100-499 lines, ignoring generated files. needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Nov 3, 2025
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Hi @pkubicsek-sb. Thanks for your PR.

I'm waiting for a github.com member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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@k8s-ci-robot k8s-ci-robot added the cncf-cla: no Indicates the PR's author has not signed the CNCF CLA. label Nov 3, 2025
@pkubicsek-sb
pkubicsek-sb force-pushed the fix-ha-detection-with-instance-group-filter branch from 05cbb11 to c3189b5 Compare November 3, 2025 18:13
@k8s-ci-robot k8s-ci-robot added cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. and removed cncf-cla: no Indicates the PR's author has not signed the CNCF CLA. labels Nov 3, 2025
@pkubicsek-sb
Fix HasHighlyAvailableControlPlane to use AllInstanceGroups
e6786c2 
When using 'kops update cluster' with --instance-group or
--instance-group-roles filters, the HasHighlyAvailableControlPlane
function was incorrectly using the filtered InstanceGroups list
instead of AllInstanceGroups.

This caused cluster-wide controllers like aws-load-balancer-controller
and node-termination-handler to incorrectly downscale replicas from 2
to 1 when updating a specific instance group in an HA cluster.

The fix changes HasHighlyAvailableControlPlane to use AllInstanceGroups
since HA status is a cluster-wide property, not specific to filtered
instance groups.

Signed-off-by: Peter Kubicsek <peter.kubicsek@happening.xyz>
@pkubicsek-sb
pkubicsek-sb force-pushed the fix-ha-detection-with-instance-group-filter branch from c3189b5 to e6786c2 Compare November 3, 2025 18:25
@k8s-ci-robot k8s-ci-robot removed the do-not-merge/invalid-commit-message Indicates that a PR should not merge because it has an invalid commit message. label Nov 3, 2025
@hakman

hakman commented Nov 4, 2025

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Thanks for looking into this @pkubicsek-sb.
/cc @justinsb
/ok-to-test

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k8s-ci-robot requested a review from justinsb November 4, 2025 16:22
@k8s-ci-robot k8s-ci-robot added ok-to-test Indicates a non-member PR verified by an org member that is safe to test. and removed needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Nov 4, 2025
@hakman
hakman removed the request for review from johngmyers November 4, 2025 16:31
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@k8s-ci-robot k8s-ci-robot added the lifecycle/stale Denotes an issue or PR has remained open with no activity and has become stale. label Feb 2, 2026
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The Kubernetes project currently lacks enough active contributors to adequately respond to all PRs.

This bot triages PRs according to the following rules:

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@pkubicsek-sb

pkubicsek-sb commented Mar 26, 2026

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/remove-lifecycle rotten

@k8s-ci-robot k8s-ci-robot removed the lifecycle/rotten Denotes an issue or PR that has aged beyond stale and will be auto-closed. label Mar 26, 2026
@hakman

hakman commented Mar 27, 2026

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Thanks for your patience and your contribution @pkubicsek-sb, and sorry for the slow review.
/lgtm
/approve

@k8s-ci-robot k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Mar 27, 2026
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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hakman

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@k8s-ci-robot k8s-ci-robot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Mar 27, 2026
This was referenced Mar 27, 2026
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k8s-ci-robot merged commit 5e4fad3 into kubernetes:master Mar 27, 2026
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@k8s-ci-robot k8s-ci-robot added this to the v1.36 milestone Mar 27, 2026
k8s-ci-robot added a commit that referenced this pull request Mar 27, 2026
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Merge pull request #18117 from hakman/automated-cherry-pick-of-#17740…
c3dbabe 
…-upstream-release-1.35

Automated cherry pick of #17740: Fix HasHighlyAvailableControlPlane to use AllInstanceGroups
k8s-ci-robot added a commit that referenced this pull request Mar 27, 2026
@k8s-ci-robot
Merge pull request #18118 from hakman/automated-cherry-pick-of-#17740…
0cfe87d 
…-upstream-release-1.34

Automated cherry pick of #17740: Fix HasHighlyAvailableControlPlane to use AllInstanceGroups
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HasHighlyAvailableControlPlane incorrectly uses filtered instance groups

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