Fix | Fix race condition issues between SinglePhaseCommit and TransactionEnded events #1042
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cheenamalhotra
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JRahnama
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…it and TransactionEnded events (dotnet#1042)
cheenamalhotra
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to cheenamalhotra/SqlClient
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Apr 26, 2021
…it and TransactionEnded events (dotnet#1042)
This was referenced Oct 9, 2022
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A race condition exists between "Single Phase Commit" and "Transaction Ended" as both are triggered externally by delegated SqlTransaction. With recent changes to doom connection in "Transaction Ended" Event (#543), "Commit" started failing intermittently leading to this issue. Dooming connection is essential to prevent connection re-use that leads to security issues, so that fix is intact.
But as a consequence, "Commit"'s inconsistent locking leads to this problem. Locking is essential in this design, but in "Single Phase Commit" implementation, late and split locking causes issues between Commit and Abort event handling, leading to intermittent "Transaction Aborted Exception".
This change in lock scope fixes the issue. It wasn't easily reproducible in Microsoft.Data.SqlClient but happens very often with System.Data.SqlClient 4.8.2. Making test-case more rigorous and forcing latency while debugging aided in reproducing this issue.
Link to Repro.
Possibly also related to issue #729 (repro)
P.S. Fix tested with System.Data.SqlClient in debug session.
cc @saurabh500