CRE-4150: fix race in Test_DataSource/Observe/records_telemetry#22344
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CRE-4150: fix race in Test_DataSource/Observe/records_telemetry#22344
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The test captures `ch := tm.ch` after `ds.Observe()` returns, but the production observation loop's next iteration calls MakeObservationScopedTelemetryCh again and overwrites tm.ch with a fresh empty channel before the test reads it. With the fast loopWakeCh pacing, the next iteration can begin in microseconds, so the test can end up ranging over an empty/closed channel and panicking on `telems[:3]` with "slice bounds out of range [:3] with capacity 0". Track every channel the mock creates in a `channels []chan any` slice (under the existing mu) and have the test read `channels[0]` instead of the latest tm.ch. The first channel is the one populated by the asserted first iteration (stream IDs 21/22/23), and it is provably non-empty by the time Observe returns since loopStartedCh only closes after the first MakeObservationScopedTelemetryCh call. Verified: 35 consecutive passes with -race -shuffle=on after the change.
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Summary
Fixes flake in
Test_DataSource/Observe/records_telemetry(Trunk:panic: runtime error: slice bounds out of range [:3] with capacity 0atdata_source_test.go:345).The test captures
ch := tm.chafterds.Observe()returns. Under fastloopWakeChpacing (microseconds), the production observation loop's next iteration callsMakeObservationScopedTelemetryChagain and overwritestm.chwith a fresh empty channel before the test reads it. The test then ranges over an empty/closed channel, getstelemsof length 0, and panics ontelems[:3].Fix
Track every channel the mock creates in a new
channels []chan anyslice (guarded by the existingtm.mu). Readchannels[0]instead of the racytm.ch— the first channel is the one populated by the asserted first iteration (stream IDs 21/22/23), and is provably non-empty by the timeObservereturns becauseloopStartedChonly closes afterMakeObservationScopedTelemetryChhas been called at least once.Test code only — no production-code changes.
Flaky test fixes
Test plan
Flakiness-classification: TEST (user override from AMBIGUOUS — Tier 1 string-match signals did not match the goroutine-shared-state race pattern, but stack trace and code analysis pinpoint a clear test-side race)
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