test: fix flaky TestAttachedServer_DeleteEmitsSessionExited#3418
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Emit and read a first SSE event to guarantee the handler has subscribed to the event log before calling DeleteSession, avoiding a race where the stream closed with EOF before session_exited was delivered. Assisted-By: Claude
docker-agent
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Jul 2, 2026
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Assessment: 🟢 APPROVE
The sentinel-event synchronization approach is correct and well-designed. The "hello" event is emitted before DeleteSession is called, providing a deterministic proof that the SSE handler is actively subscribed — eliminating the race that caused intermittent failures. No bugs were introduced by the changed lines.
Sayt-0
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Jul 2, 2026
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The SSE handler in the attached server flushes response headers before it subscribes to the event log via
StreamEvents. In the test, theHasEventSourceguard was effectively a no-op because the test itself registers the event source — soDeleteSessioncould race ahead and remove the event log before the handler had a chance to subscribe. The stream then closed with a clean EOF and nosession_exitedevent, causing the test to fail intermittently (observed in CI run https://github.com/docker/docker-agent/actions/runs/28590850454/job/84773735898).The fix adds a "hello" sentinel event to the fake event source. The test now reads that event from the SSE stream before calling
DeleteSession, which proves the handler is actively subscribed before the session is torn down. The test then asserts the terminalsession_exitedevent as before.Validated with 100 runs under
-race, the fullpkg/serversuite,go vet, andgolangci-lintwith zero issues.