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Fix race in ConnectionsCountForAPollingSubscriptionChangesOneConnectionAtATime - #735
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…rFixture The server completes the failed request before it releases the connection lease, so the 1 -> 0 count change can be recorded after the client's SayHelloAsync has already returned. Retry the assertion as the final close check already does. Fixes LEV-2276 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
LukeButters
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Nov 9, 2026
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November 9, 2026 00:56
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Background
ConnectionsCountForAPollingSubscriptionChangesOneConnectionAtATimeis flaky due to a race condition.This PR fixes it by adding a retry loop waiting for the eventual state to be reached.
Details
After the port forwarder drops the polling connection, the next request fails on the server's dead connection. In
MessageExchangeProtocol.ProcessReceiverInternalAsync, the server:pendingRequests.ApplyResponse(...)with the error, which completes the client'sSayHelloAsync, and thenfalse, which exits theusing (LeaseActiveTcpConnection(...))block inExchangeAsServerAsyncand only then reports the 1 → 0 count change.The test resumes after step 1 and immediately reads the second observed event, which may not have been recorded yet.
Results
Before
ConnectionsCountForAPollingSubscriptionChangesOneConnectionAtATimeintermittently failed withInvalidOperationException: Sequence contains no elements(1 in ~97 runs on Windows 2019).After
We loop in the test and wait for the expected connections count change.
Testing
ConnectionObserverFixturepasses locally on net10.0 (9/9). The original failure is rare, so a local pass doesn't prove the race is gone.