24-1: Fix a race between mediator state and pipeline restoring active transactions #3378
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fomichev3000
approved these changes
Apr 8, 2024
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This was referenced Jun 7, 2024
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Changelog entry
Fix a race between mediator state and pipeline restoring active transactions
Changelog category
Additional information
An extremely rare failure was observed under Jepsen, where a debug build would crash, because it detected an invariant violation of a transaction marked as blocking immediate ops, but not present in complete/incomplete sets. The root cause turned out to be updating the current "unprotected read edge" when mediator state is restored, without also marking currently active transactions as complete (or incomplete). When more transactions activate, they assume current complete/incomplete sets are consistent, which turned out not to be the case. This could theoretically cause consistency issues, but those issues have never been observed so far.
Merges #3358.
Fixes #3142.