test: stabilize flaky TestLoadLargeRules

[flaky-claw]

What problem does this PR solve?

Issue Number: close #10346

Problem Summary:
Flaky test TestLoadLargeRules in github.com/tikv/pd/pkg/mcs/scheduling/server/rule intermittently fails, so this PR stabilizes that path.

What changed and how does it work?

Root Cause

Durable embedded-etcd setup writes could consume the test budget before the watcher load assertion was reached.

Fix

Setting UnsafeNoFsync removes irrelevant unit-test disk durability cost while preserving etcd-backed bulk setup and watcher loading.

Verification

Spec:

• target: github.com/tikv/pd/pkg/mcs/scheduling/server/rule :: TestLoadLargeRules
• strategy: pd.issue_scoped.v1
• plan mode: BASELINE_ONLY
• requirements: required case must execute; no skip; repeat count = 1
• baseline gates: required_flaky_gate, build_safety_gate, intent_guard_gate
• feedback surface source: baseline_only

Observed result:

• status: passed
• required case executed: yes
• submission decision: ALLOWED
• note: Required flaky case executed during validation.
  Required flaky case was not skipped.
  target_flaky_corrected passed.

Gate checklist:

• diagnostic_timing_repro: SKIPPED
• target_flaky_corrected: PASS
• supplied_path_mismatch: SKIPPED
• package_surface: SKIPPED
• build: SKIPPED
• external_ci: SKIPPED

Commands:

• go test -json ./pkg/mcs/scheduling/server/rule -run '^TestLoadLargeRules$' -count=1

Release note

None

Fixes #10346

Summary by CodeRabbit

• Tests
  • Updated the in-process test storage configuration for watcher-related checks to run faster by changing the durability setting.
  • No user-facing behavior or product functionality was changed.

[ti-chi-bot]

Hi @flaky-claw. Thanks for your PR.

I'm waiting for a tikv 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.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: ace9895f-da1f-4eed-8cdb-bf35d6cefcfd

📥 Commits

Reviewing files that changed from the base of the PR and between eb91e20 and 85c6938.

📒 Files selected for processing (1)

• pkg/mcs/scheduling/server/rule/watcher_test.go

🚧 Files skipped from review as they are similar to previous changes (1)

• pkg/mcs/scheduling/server/rule/watcher_test.go

---

📝 Walkthrough

Walkthrough

The watcher test helper enables UnsafeNoFsync for embedded etcd before startup. Watcher initialization and rule-loading logic are unchanged.

Changes

Watcher test setup

Layer / File(s)	Summary
Embedded etcd config pkg/mcs/scheduling/server/rule/watcher_test.go	prepare sets cfg.UnsafeNoFsync = true before starting the embedded etcd instance.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Suggested labels: lgtm, ok-to-test

Suggested reviewers: bufferflies, rleungx

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly matches the main change: stabilizing TestLoadLargeRules.
Description check	✅ Passed	The description covers the problem, fix, verification, and release note, with the required issue reference present.
Linked Issues check	✅ Passed	The change addresses #10346 by reducing embedded-etcd test overhead to prevent the test timeout.
Out of Scope Changes check	✅ Passed	The PR only changes the test etcd setup, with no unrelated code or scope creep evident.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lhy1024

The full list of commands accepted by this bot can be found here.

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Details

Needs approval from an approver in each of these files:

• OWNERS [lhy1024]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-07-08 11:46:51.765596933 +0000 UTC m=+195797.801691979: ☑️ agreed by lhy1024.

[rleungx]

/retest

[ti-chi-bot]

@flaky-claw: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-unit-test-next-gen-3	85c6938	link	true	/test pull-unit-test-next-gen-3

Full PR test history. Your PR dashboard.

Details

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. I understand the commands that are listed here.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.27%. Comparing base (51f4146) to head (85c6938).
⚠️ Report is 37 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #10938      +/-   ##
==========================================
+ Coverage   79.18%   79.27%   +0.09%     
==========================================
  Files         540      541       +1     
  Lines       74894    75983    +1089     
==========================================
+ Hits        59307    60239     +932     
- Misses      11414    11501      +87     
- Partials     4173     4243      +70     

Flag	Coverage Δ
unittests	79.27% <ø> (+0.09%)	⬆️

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