Fix flaky TestReadersWritersStress: nil guards and longer WaitGroup timeouts

[Copilot]

TestReadersWritersStress fails intermittently due to two bugs in stressTestInATopic.

Nil pointer dereference on StartWriter/StartReader failure

writeToTopic and readFromTopic declared writer/reader as nil before the defer, then called Close unconditionally. Any transient error from StartWriter/StartReader would trigger a nil dereference panic in the deferred cleanup.

// Before: panics if StartWriter fails
defer func() {
    closeErr := writer.Close(context.Background()) // nil deref
    wg.Done()
}()

// After: guarded
defer func() {
    if writer != nil {
        closeErr := writer.Close(context.Background())
    }
    wg.Done()
}()

WaitGroup timeout too short for stress test cleanup

xtest.WaitGroup uses commonWaitTimeout = 1s. After stopping writers/readers, cleanup involves closing gRPC streams and flushing buffers—operations that routinely exceed 1s under CI load. Replaced both xtest.WaitGroup calls with xtest.WaitGroupWithTimeout(..., time.Minute), consistent with the time.Minute already used for SpinWaitProgressWithTimeout in the same function.

[robot-vibe-db]

AI Review Summary

Verdict: ✅ No critical issues found

Critical issues

No critical issues found.

Other findings

None.

---

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[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Fixes intermittent TestReadersWritersStress failures by preventing nil dereference panics in deferred cleanup and by increasing stress-test shutdown wait time to better match CI conditions.

Changes:

• Add nil guards before calling Close() in writer/reader deferred cleanup to avoid panics when StartWriter/StartReader fails.
• Replace short xtest.WaitGroup waits with xtest.WaitGroupWithTimeout(..., time.Minute) for more reliable stress-test teardown.

---

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[github-actions]

summary

Inferred base version: v3.135.10
Suggested version: v3.135.11

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.97%. Comparing base (9955e4c) to head (e6e59f0).
⚠️ Report is 91 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2073      +/-   ##
==========================================
- Coverage   75.16%   74.97%   -0.20%     
==========================================
  Files         427      427              
  Lines       36974    36974              
==========================================
- Hits        27792    27721      -71     
- Misses       7993     8057      +64     
- Partials     1189     1196       +7     

Flag	Coverage Δ
experiment	74.76% <ø> (-0.19%)	⬇️
go-1.21.x	72.44% <ø> (-0.23%)	⬇️
go-1.26.x	74.91% <ø> (-0.21%)	⬇️
integration	57.03% <ø> (-0.34%)	⬇️
macOS	46.21% <ø> (-0.01%)	⬇️
ubuntu	74.97% <ø> (-0.20%)	⬇️
unit	46.21% <ø> (-0.03%)	⬇️
windows	46.19% <ø> (-0.03%)	⬇️
ydb-24.4	56.46% <ø> (-0.49%)	⬇️
ydb-edge	56.78% <ø> (-0.39%)	⬇️
ydb-latest	56.73% <ø> (-0.34%)	⬇️
ydb-nightly	74.76% <ø> (-0.19%)	⬇️

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