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WIP: kube-controller-manager: Release leader election lease on exit #132620

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WIP: kube-controller-manager: Release leader election lease on exit #132620

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@tchap tchap commented Jun 30, 2025

What type of PR is this?

/kind bug

What this PR does / why we need it:

kube-controller-manager does not release leader election lease on exit. This causes a prolonged period of inactivity when in a HA setup. So this PR makes sure the lease is actually released on exit.

Which issue(s) this PR is related to:

Fixes #132599

Special notes for your reviewer:

This is a WIP. The approach taken so far is to change the termination sequence to actually not exit in leader election callbacks, but rather return from the Run function. This path was taken to ensure both the main and the migration lease is released if possible. This would not happen if one of the leader election threads was to exit immediately, even on success.

I actually implemented a helper object to manage the synchronization, but there are no tests so far. This is a PoC.

Does this PR introduce a user-facing change?

NONE

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

N/A

tchap added 2 commits June 30, 2025 11:07
@tchap
kcm: Release leader election lease on exit
6a4bd78 
Make sure the leader election lease is released on exit.
This is currently not the case and KCM replicas must wait on lease
expiration, which is too long and unnecessary.
@tchap
Synchronize leader election
573eb82
@k8s-ci-robot k8s-ci-robot added release-note-none Denotes a PR that doesn't merit a release note. do-not-merge/work-in-progress Indicates that a PR should not merge because it is a work in progress. kind/bug Categorizes issue or PR as related to a bug. size/L Denotes a PR that changes 100-499 lines, ignoring generated files. cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. do-not-merge/needs-sig Indicates an issue or PR lacks a `sig/foo` label and requires one. needs-triage Indicates an issue or PR lacks a `triage/foo` label and requires one. labels Jun 30, 2025
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This issue is currently awaiting triage.

If a SIG or subproject determines this is a relevant issue, they will accept it by applying the triage/accepted label and provide further guidance.

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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 Jun 30, 2025
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Hi @tchap. 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-priority Indicates a PR lacks a `priority/foo` label and requires one. label Jun 30, 2025
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[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: tchap
Once this PR has been reviewed and has the lgtm label, please assign deads2k for approval. For more information see the Code Review Process.

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@k8s-ci-robot k8s-ci-robot added sig/api-machinery Categorizes an issue or PR as relevant to SIG API Machinery. and removed do-not-merge/needs-sig Indicates an issue or PR lacks a `sig/foo` label and requires one. labels Jun 30, 2025
@k8s-ci-robot k8s-ci-robot requested review from cheftako and luxas June 30, 2025 09:14
@tchap tchap force-pushed the kcm-clean-termination branch 3 times, most recently from 03c0159 to 2b9124f Compare June 30, 2025 09:39
@tchap tchap force-pushed the kcm-clean-termination branch from 2b9124f to 8fc918e Compare June 30, 2025 09:49
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aojea commented Jun 30, 2025

There is already a KEP for this IIUIC https://github.com/kubernetes/enhancements/tree/master/keps/sig-api-machinery/5366-graceful-leader-transition , can you sync with @Jefftree

@aojea aojea mentioned this pull request Jul 1, 2025
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kube-controller-manager: Leader election lease is not released on exit
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