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 test environment configuration for watcher-related checks to use a faster in-process storage setup.
  • No user-facing behavior or product functionality was changed.

[ti-chi-bot]

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[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.

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The list of commits missing DCO signoff:

• eb91e20 fix: stabilize flaky issue TestLoadLargeRules is flaky #10346

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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: db110cc3-de8f-48d1-bb05-8026a63224a7

📥 Commits

Reviewing files that changed from the base of the PR and between 51f4146 and eb91e20.

📒 Files selected for processing (1)

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

---

📝 Walkthrough

Walkthrough

The watcher test helper now starts embedded etcd with UnsafeNoFsync enabled. No watcher or rule-loading logic changed.

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

Possibly related PRs

• tikv/pd#10884: Also changes pkg/mcs/scheduling/server/rule/watcher_test.go test setup around embedded etcd/rule loading behavior.

Suggested labels

lgtm, approved

Suggested reviewers

• bufferflies
• rleungx

Poem

A tiny test burrow, a flick of the nose,
fsync took a nap while the little server rose.
One switch for the watcher, neat and bright,
And the carrot-lit tests scampered through the night.
🐇

🚥 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 states the main change: stabilizing TestLoadLargeRules.
Description check	✅ Passed	The description includes the required issue link, problem, fix, verification, and release note fields.
Linked Issues check	✅ Passed	The change directly addresses #10346 by reducing embedded-etcd fsync overhead to stabilize TestLoadLargeRules.
Out of Scope Changes check	✅ Passed	The PR only changes the test setup needed to fix the flaky rule-loading test.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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