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fix: Cluster Autoscaler not scaling down nodes where Pods with hard topology spread constraints are scheduled #8164

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Merged
merged 3 commits into from
May 30, 2025
Merged

fix: Cluster Autoscaler not scaling down nodes where Pods with hard topology spread constraints are scheduled #8164

merged 3 commits into from
May 30, 2025

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MenD32
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@MenD32 MenD32 commented May 24, 2025 •
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What type of PR is this?

/kind fix

What this PR does / why we need it:

Nodes are mistakenly marked as unremovable with specific configurations of topology spread constraints

Which issue(s) this PR fixes:

Fixes #8093
Fixes #8162

Special notes for your reviewer:

Does this PR introduce a user-facing change?

deployments with topology spread constraints will no longer block scale down if the removable node changes the global minimum

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

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@MenD32: The label(s) kind/fix cannot be applied, because the repository doesn't have them.

In response to this:

What type of PR is this?

/kind fix

What this PR does / why we need it:

Nodes are mistakenly marked as unremovable with specific configurations of topology spread constraints

Which issue(s) this PR fixes:

Fixes #8093
Fixes #8162

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

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 kubernetes-sigs/prow repository.

@k8s-ci-robot k8s-ci-robot added cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. area/cluster-autoscaler labels May 24, 2025
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Hi @MenD32. Thanks for your PR.

I'm waiting for a kubernetes 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 needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. label May 24, 2025
@k8s-ci-robot k8s-ci-robot added the size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. label May 24, 2025
@k8s-ci-robot k8s-ci-robot added size/M Denotes a PR that changes 30-99 lines, ignoring generated files. and removed size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. labels May 24, 2025
towca
towca reviewed May 27, 2025
View reviewed changes
cluster-autoscaler/simulator/cluster.go
@@ -226,6 +226,7 @@ func (r *RemovalSimulator) findPlaceFor(removedNode string, pods []*apiv1.Pod, n
klog.Errorf("Simulating removal of %s/%s return error; %v", pod.Namespace, pod.Name, err)
}
}
r.clusterSnapshot.RemoveNodeInfo(removedNode)
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nit: Could you add a comment explaining that this is necessary for pod topology spread to work correctly?

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towca commented May 27, 2025

Thanks for picking up the fix!

Could you fill out the "Does this PR introduce a user-facing change?" section? This PR does change behavior, CA will now scale down in scenarios where it previously wouldn't.

/ok-to-test

@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 May 27, 2025
@MenD32 MenD32 changed the title fix: Cluster Autoscaler not scaling down Nodes where Pods with hard topology spread constraints are scheduled fix: Cluster Autoscaler not scaling down nodes where Pods with hard topology spread constraints are scheduled May 29, 2025
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towca commented May 30, 2025

/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 May 30, 2025
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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: MenD32, towca

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Approvers can indicate their approval by writing /approve in a comment
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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 May 30, 2025
@k8s-ci-robot k8s-ci-robot merged commit 2511e44 into kubernetes:master May 30, 2025
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@MenD32 MenD32 deleted the fix/hard-topology-spread-constraints-stop-scaledown branch May 30, 2025 13:22
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/kind bug

@k8s-ci-robot k8s-ci-robot added the kind/bug Categorizes issue or PR as related to a bug. label Aug 27, 2025
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/cherry-pick cluster-autoscaler-release-1.32

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@jackfrancis: new pull request created: #8478

In response to this:

/cherry-pick cluster-autoscaler-release-1.32

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@k8s-infra-cherrypick-robot k8s-infra-cherrypick-robot mentioned this pull request Aug 27, 2025
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/cherry-pick cluster-autoscaler-release-1.31

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@jackfrancis: new pull request created: #8479

In response to this:

/cherry-pick cluster-autoscaler-release-1.31

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@k8s-infra-cherrypick-robot k8s-infra-cherrypick-robot mentioned this pull request Aug 27, 2025
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/cherry-pick cluster-autoscaler-release-1.30

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@jackfrancis: new pull request created: #8480

In response to this:

/cherry-pick cluster-autoscaler-release-1.30

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@k8s-infra-cherrypick-robot k8s-infra-cherrypick-robot mentioned this pull request Aug 27, 2025
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/cherry-pick cluster-autoscaler-release-1.33

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@jackfrancis: #8164 failed to apply on top of branch "cluster-autoscaler-release-1.33":

Applying: fix: hard topology spread constraints stop scaledown
Using index info to reconstruct a base tree...
M	cluster-autoscaler/simulator/cluster.go
Falling back to patching base and 3-way merge...
Auto-merging cluster-autoscaler/simulator/cluster.go
CONFLICT (content): Merge conflict in cluster-autoscaler/simulator/cluster.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config advice.mergeConflict false"
Patch failed at 0001 fix: hard topology spread constraints stop scaledown

In response to this:

/cherry-pick cluster-autoscaler-release-1.33

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Whoops this landed before 1.33.0 was released

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@towca towca towca left review comments

@aleksandra-malinowska aleksandra-malinowska Awaiting requested review from aleksandra-malinowska

@BigDarkClown BigDarkClown Awaiting requested review from BigDarkClown

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