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UUID sequencing race in a message.Publisher #259

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jgraettinger opened this issue May 25, 2020 · 0 comments
Closed

UUID sequencing race in a message.Publisher #259

jgraettinger opened this issue May 25, 2020 · 0 comments
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There's a possible race where concurrent calls A & B to PublishCommitted can interleave over the same journal:

  • A: SetUUID
  • B: SetUUID
  • B: StartAppend, Marshal
  • A: StartAppend, Marshal

This is a problem because A is written to the journal after B, but is sequenced as "before" B. message.Sequencer will later discard A, thinking it a duplicate. This impacts services using a single Publisher.PublishCommitted with high concurrency (as is common for HTTP APIs writing event logs). This isn't an issue for PublishUncommitted, as that's already marked unsafe for concurrent use.

Thanks to @michaelschiff for reporting.
@jgraettinger jgraettinger self-assigned this May 25, 2020
jgraettinger added a commit to jgraettinger/gazette that referenced this issue May 25, 2020
@jgraettinger
message: re-order BuildUUID to be synchronized by-journal
0f26b7b 
Update stream-sum example and test to reproduce the motivating bug (and catch any
regressions), by introducing parallel workers using a shared Publisher.

Fixes gazette#259
jgraettinger added a commit to jgraettinger/gazette that referenced this issue May 25, 2020
@jgraettinger
message: re-order BuildUUID to be synchronized by-journal
9a64ca4 
Update stream-sum example and test to reproduce the motivating bug (and catch any
regressions), by introducing parallel workers using a shared Publisher.

Fixes gazette#259
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