🐛 prevent leader election when shutting down a non-elected manager #2724

alexandremahdhaoui · 2024-03-23T17:19:41Z

Context

This PR should address a bug where the runnable group for Leader Election would start while shutting down the manager: #2719

What's happening?

controller-runtime/pkg/manager/internal.go

Line 344 in 395cfc7

stopErr := cm.engageStopProcedure(stopComplete)
controller-runtime/pkg/manager/internal.go

Line 521 in 395cfc7

cm.runnables.LeaderElection.StopAndWait(cm.shutdownCtx)
controller-runtime/pkg/manager/internal.go

Line 521 in 395cfc7

cm.runnables.LeaderElection.StopAndWait(cm.shutdownCtx)
Causes the side-effect of starting the runnableGroup:

controller-runtime/pkg/manager/runnable_group.go

Line 277 in 395cfc7

_ = r.Start(ctx)

However when leader election is enabled, a non-leader manager will never start the LeaderElection runnable group. Thus, the sync.Once allow starting a new election during shutdown. The change in this PR ensures Start is ineffective during shutdown.

This func calls the manager.LeaderElection's runnableGroup.Start()

controller-runtime/pkg/manager/internal.go

Line 557 in 395cfc7

return cm.runnables.LeaderElection.Start(cm.internalCtx)
Which is obviously only called when a member becomes leader:

controller-runtime/pkg/manager/internal.go

Line 568 in 395cfc7

if err := cm.startLeaderElectionRunnables(); err != nil {
In the case leader election is enabled:

controller-runtime/pkg/manager/internal.go

Line 429 in 395cfc7

if err := cm.startLeaderElection(ctx); err != nil {

Changes

On shutdown, perform a noop call to the sync.Once func associated with the LeaderElection runnableGroup to prevent it from starting a new leader election.

linux-foundation-easycla · 2024-03-23T17:19:45Z

The committers listed above are authorized under a signed CLA.

✅ login: alexandremahdhaoui / name: Alexandre Mahdhaoui (d0c20b4)

k8s-ci-robot · 2024-03-23T17:19:50Z

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k8s-ci-robot · 2024-03-23T17:19:50Z

Hi @alexandremahdhaoui. Thanks for your PR.

I'm waiting for a kubernetes-sigs 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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alvaroaleman

/ok-to-test

alvaroaleman · 2024-03-24T15:00:44Z

pkg/manager/internal.go

@@ -518,6 +518,8 @@ func (cm *controllerManager) engageStopProcedure(stopComplete <-chan struct{}) e

 		// Stop all the leader election runnables, which includes reconcilers.
 		cm.logger.Info("Stopping and waiting for leader election runnables")
+		// Prevent leader election when shutting down a non-elected manager
+		cm.runnables.LeaderElection.startOnce.Do(func() {})


Could you add a test, please?

Added the test in 06d575d.

inteon · 2024-03-25T08:00:49Z

pkg/manager/manager_test.go

+
+				Expect(m1.Add(RunnableFunc(func(ctx context.Context) error {
+					defer GinkgoRecover()
+					return nil


Can you simulate a Runnable that blocks until the context is canceled?

& make sure it is stopped before manager.Start returns?

[Edit] Done

When leader election is enabled, a non-leader manager would never start the LeaderElection runnable group. Thus, as the shutdown process calls the sync.Once Start func of the runnableGroup; it will start a new election. This change ensures `Start` is ineffective during shutdown. The test ensures the LeaderElection runnableGroup is not started during shutdown. Signed-off-by: Alexandre Mahdhaoui <alexandre.mahdhaoui@gmail.com>

vincepri · 2024-04-02T14:27:37Z

/lgtm

alvaroaleman

/cherrypick release-0.17

k8s-ci-robot · 2024-04-02T15:01:06Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: alexandremahdhaoui, alvaroaleman

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Needs approval from an approver in each of these files:

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alvaroaleman · 2024-04-02T15:36:04Z

/cherrypick release-0.17

k8s-infra-cherrypick-robot · 2024-04-02T15:36:40Z

@alvaroaleman: new pull request created: #2752

In response to this:

/cherrypick release-0.17

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k8s-ci-robot added the cncf-cla: no Indicates the PR's author has not signed the CNCF CLA. label Mar 23, 2024

k8s-ci-robot requested review from inteon and varshaprasad96 March 23, 2024 17:19

alexandremahdhaoui changed the title ~~🐛 prevent new leader election when a non-elected manager is shutting down #2719~~ 🐛 prevent new leader election when a non-elected manager is shutting down Mar 23, 2024

alexandremahdhaoui changed the title ~~🐛 prevent new leader election when a non-elected manager is shutting down~~ 🐛 prevent leader election when shutting down a non-elected manager Mar 23, 2024

alexandremahdhaoui force-pushed the fix-non-elected-shutdown branch 2 times, most recently from 4ef9863 to 49681ff Compare March 23, 2024 17:32

alvaroaleman reviewed Mar 24, 2024

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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 Mar 24, 2024

alexandremahdhaoui force-pushed the fix-non-elected-shutdown branch from 49681ff to 06d575d Compare March 24, 2024 17:13

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 Mar 24, 2024

alexandremahdhaoui requested a review from alvaroaleman March 24, 2024 18:59

inteon reviewed Mar 25, 2024

View reviewed changes

alexandremahdhaoui force-pushed the fix-non-elected-shutdown branch from aa2bbaa to 66e510a Compare March 26, 2024 15:07

alexandremahdhaoui requested a review from inteon March 26, 2024 17:59

alexandremahdhaoui force-pushed the fix-non-elected-shutdown branch from 66e510a to d0c20b4 Compare March 26, 2024 19:28

k8s-ci-robot assigned vincepri Apr 2, 2024

k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Apr 2, 2024

alvaroaleman approved these changes Apr 2, 2024

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k8s-ci-robot assigned alvaroaleman Apr 2, 2024

k8s-ci-robot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Apr 2, 2024

k8s-ci-robot merged commit a2a90a8 into kubernetes-sigs:main Apr 2, 2024
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k8s-infra-cherrypick-robot mentioned this pull request Apr 2, 2024

[release-0.17] 🐛 prevent leader election when shutting down a non-elected manager #2752

Merged

pleshakov mentioned this pull request Apr 15, 2024

When a non-leader shuts down, leader election runnables are started #2719

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🐛 prevent leader election when shutting down a non-elected manager #2724

🐛 prevent leader election when shutting down a non-elected manager #2724

alexandremahdhaoui commented Mar 23, 2024 •

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alexandremahdhaoui Mar 25, 2024 •

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🐛 prevent leader election when shutting down a non-elected manager #2724

🐛 prevent leader election when shutting down a non-elected manager #2724

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