WAS: Discard logs in simulator context to avoid race during teardown by kavix · Pull Request #14908 · kubernetes-sigs/kueue

kavix · 2026-08-29T18:14:10Z

What type of PR is this?

/kind flake
/area tas
/area was

What this PR does / why we need it:

Fixes a data race in TestScheduleForTAS where background informer reflectors started by the WAS scheduling simulator log stopping messages during context cancellation, racing with testing.T teardown. Wrapping the simulator context with logr.Discard() prevents background teardown logging from racing with the unit test runner.

Which issue(s) this PR fixes:

Fixes #14903

AI Usage:

Assisted by AI tool to diagnose the race trace and prepare the fix.

Special notes for your reviewer:

N/A

Does this PR introduce a user-facing change?

NONE

Summary by CodeRabbit

Bug Fixes
- Improved scheduling simulator initialization for more predictable behavior.
- Prevented initialization logging from interfering with simulator operation.

netlify · 2026-08-29T18:14:16Z

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kubernetes-prow · 2026-08-29T18:14:21Z

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coderabbitai · 2026-08-29T18:14:26Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 1b26bbb and 1734b3f.

📒 Files selected for processing (1)

pkg/cache/scheduler/was/scheduling_simulator.go

Included review availability: Your plan provides up to 8 included reviews per hour; 6 remain after this review.

📝 Walkthrough

Walkthrough

The WAS simulator test constructor now wraps its context with a discarded klog logger before creating the simulator.

Changes

WAS simulator context handling

Layer / File(s)	Summary
Wrap test simulator context for logging `pkg/cache/scheduler/was/scheduling_simulator.go`	The test constructor imports `logr` and `klog`, then passes `klog.NewContext(ctx, logr.Discard())` to `newWASSimulator`.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Merge Risk: ⚪ Minimal · up to 1734b

This change discards simulator teardown logs to prevent a unit-test race and does not alter production behavior; no actionable merge-blocking risk remains beyond normal checks and review.

Suggested reviewers: kannon92, tenzen-y, alien1403, olekzabl

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the main change: discarding simulator logs to prevent a teardown race.
Linked Issues check	✅ Passed	The change directly addresses issue `#14903` by suppressing background informer teardown logs in the WAS simulator context, which targets the reported race in TestScheduleForTAS.
Out of Scope Changes check	✅ Passed	All changes are limited to the simulator context, logging imports, and supporting documentation. No unrelated changes are present.

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tenzen-y · 2026-08-29T19:16:27Z

I replaced the target branch w/ main since this should be fixed in the main branch.
Could you fix conflcts?

tenzen-y · 2026-08-29T19:17:07Z

/retitle WAS: Discard logs in simulator context to avoid race during teardown- #14908

tenzen-y · 2026-08-29T19:17:33Z

/retitle WAS: Discard logs in simulator context to avoid race during teardown

kavix · 2026-08-29T19:22:43Z

@tenzen-y Rebased onto main and resolved the conflicts. Thanks!

tenzen-y · 2026-08-29T19:30:56Z

/ok-to-tet

tenzen-y · 2026-08-29T19:31:00Z

/ok-to-test

coderabbitai

Actionable comments posted: 1

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Inline comments:
In `@pkg/cache/scheduler/was/scheduling_simulator.go`:
- Around line 95-97: Update newWASSimulator to pass the original ctx to
informerFactory.StartWithContext and WaitForCacheSyncWithContext instead of
creating a discarded-logger context there. Keep the discarded logger scoped to
NewWASSimulatorForTest, preserving informer lifecycle diagnostics for
NewWASSimulator callers.

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pkg/cache/scheduler/was/scheduling_simulator.go

Included review availability: Your plan provides up to 8 included reviews per hour; 7 remain after this review.

Background informer reflectors started by the WAS scheduling simulator log stopping messages when their context is canceled. In unit tests where the context carries a test logger, this asynchronous logging races with test teardown in testing.T. Wrap the simulator context with logr.Discard() to ensure background reflector teardown does not race with the test runner.

…logs Move logr.Discard() from newWASSimulator to NewWASSimulatorForTest so background informer goroutines do not suppress SchedulerLibraryIntegration logs (enabled plugins, etc.) in production. The race fix is preserved since NewWASSimulatorForTest, which carries t.Context(), still uses a discard logger.

kavix · 2026-08-29T21:47:05Z

/test all

tenzen-y

Thank you!
/lgtm
/approve

kubernetes-prow · 2026-08-29T21:59:34Z

LGTM label has been added.

Details

Git tree hash: 8e442eb7980b4e3fa7c46ffbdf8c82ad03c50f28

kubernetes-prow · 2026-08-29T21:59:39Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kavix, tenzen-y

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k8s-infra-cherrypick-robot · 2026-08-29T22:02:45Z

@tenzen-y: #14908 failed to apply on top of branch "release-0.19":

Applying: was: Discard logs in simulator context to avoid race during teardown
Using index info to reconstruct a base tree...
M	pkg/cache/scheduler/was/scheduling_simulator.go
Falling back to patching base and 3-way merge...
Auto-merging pkg/cache/scheduler/was/scheduling_simulator.go
CONFLICT (content): Merge conflict in pkg/cache/scheduler/was/scheduling_simulator.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 set advice.mergeConflict false"
Patch failed at 0001 was: Discard logs in simulator context to avoid race during teardown

Details

In response to this:

/cherrypick release-0.19

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tenzen-y · 2026-08-29T22:07:02Z

@kavix can you manually open cp for 0.19?

kavix · 2026-08-29T22:10:01Z

/cherrypick release-0.19

k8s-infra-cherrypick-robot · 2026-08-29T22:10:09Z

@kavix: only kubernetes-sigs org members may request cherry picks. If you are already part of the org, make sure to change your membership to public. Otherwise you can still do the cherry-pick manually.

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In response to this:

/cherrypick release-0.19

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kavix · 2026-08-29T22:24:16Z

Opened manual cherry-pick for release-0.19 in #14913. cc @tenzen-y

kubernetes-prow Bot added the release-note-none Denotes a PR that doesn't merit a release note. label Aug 29, 2026

kubernetes-prow Bot added this to the v0.19 milestone Aug 29, 2026

kubernetes-prow Bot added kind/flake Categorizes issue or PR as related to a flaky test. area/tas Topology-Aware Scheduling area/was Issues or PRs related to the WAS integration labels Aug 29, 2026

kubernetes-prow Bot added cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Aug 29, 2026

kubernetes-prow Bot requested review from kannon92 and tenzen-y August 29, 2026 18:14

kubernetes-prow Bot added the size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. label Aug 29, 2026

tenzen-y changed the base branch from release-0.19 to main August 29, 2026 19:15

kubernetes-prow Bot added size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. and removed size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. labels Aug 29, 2026

kubernetes-prow Bot changed the title ~~[release-0.19] was: Discard logs in simulator context to avoid race during teardown~~ WAS: Discard logs in simulator context to avoid race during teardown- #14908 Aug 29, 2026

kubernetes-prow Bot changed the title ~~WAS: Discard logs in simulator context to avoid race during teardown- #14908~~ WAS: Discard logs in simulator context to avoid race during teardown Aug 29, 2026

kavix force-pushed the fix-test-schedule-for-tas-race branch from 992d209 to ca2ca30 Compare August 29, 2026 19:22

kubernetes-prow Bot added size/S Denotes a PR that changes 10-29 lines, ignoring generated files. and removed needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. labels Aug 29, 2026

kubernetes-prow Bot added the ok-to-test Indicates a non-member PR verified by an org member that is safe to test. label Aug 29, 2026

kubernetes-prow Bot added size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. and removed size/S Denotes a PR that changes 10-29 lines, ignoring generated files. labels Aug 29, 2026

coderabbitai Bot reviewed Aug 29, 2026

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Comment thread pkg/cache/scheduler/was/scheduling_simulator.go Outdated

kavix requested a review from tenzen-y August 29, 2026 21:42

kavix force-pushed the fix-test-schedule-for-tas-race branch from 1b26bbb to ca2ca30 Compare August 29, 2026 21:43

kavix added 2 commits August 30, 2026 03:15

kavix force-pushed the fix-test-schedule-for-tas-race branch from 87bc28a to 1734b3f Compare August 29, 2026 21:45

tenzen-y reviewed Aug 29, 2026

View reviewed changes

kubernetes-prow Bot assigned tenzen-y Aug 29, 2026

kubernetes-prow Bot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Aug 29, 2026

kubernetes-prow Bot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Aug 29, 2026

kubernetes-prow Bot merged commit 5953056 into kubernetes-sigs:main Aug 29, 2026
61 checks passed

kubernetes-prow Bot modified the milestones: v0.19, v0.20 Aug 29, 2026

kavix mentioned this pull request Aug 29, 2026

[release-0.19] WAS: Discard logs in simulator context to avoid race during teardown #14913

Merged

This was referenced Sep 21, 2026

🎲 periodic-kueue-test-unit-shard-0-release-0-19 #15895

Closed

Stop the unit-test logger from writing to a finished test #15966

Merged

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