REP-6785 Persist resume token after rechecks #161
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tdq45gj
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Nov 6, 2025
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tdq45gj
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I'm not sure if oaux/timer is used anywhere but it's imported in this PR. The rest of the changes LGTM.
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For some time the verifier has had a race condition where it would, immediately after passing a batch of events to the recheck-enqueue thread, persist the change stream’s resume token. Thus, if the recheck-enqueue thread failed, the verifier could have restarted and skipped documents.
PR #156 aggravated this by storing multiple batches of change events in the channel between the reader and recheck-enqueue threads. Now, if there’s a failure after persisting a resume token, there are very good odds that documents will be skipped.
This changeset fixes that by moving the resume token’s persistence to the recheck-enqueue thread. Now each resume token is sent along with its batch to the recheck-enqueue thread, and only after that batch is persisted is its resume token persisted.