go/store/nbs: Fix a race between the journal persister and PruneTableFiles. - #11312
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…Files. Racing GC and/or crashing at an inopportune time could result in "root hash not found" or a panic on attempting to remove a missing journal file.
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@reltuk DOLT
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…ve this test case test running SIGKILL against the process as well.
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@reltuk DOLT
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Could you add a more detailed description to the PR, explaining why the race necessitates the creating the concept of a "protected journal file", and outlining a sequence of events that previously would have resulted in data corruption and why it wouldn't happen under the new PR? |
nicktobey
approved these changes
Jul 17, 2026
| // the NomsBlockStore mutex, while PruneTableFiles runs under the persister's | ||
| // pruneMu; before the fix these disjoint lock domains let a prune delete a live | ||
| // journal file, and left ChunkJournal.PruneTableFiles reading j.wr without | ||
| // synchronization. Run under `-race` this reliably catches the unsynchronized |
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If this reliably catches the race condition as the comment says, why does it run 300 iterations? Do we use a "race" flag in our tests?
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When PruneTableFiles runs, it is willing to delete the journal file if there is no longer a reference to it in the manifest. This can race with bootstrapJournal making a new journal file. The journal file can be on disk, and seen by PruneTableFiles and thus selected for removal, before the journal has been added to the chunk store proper.
This change makes the journal writer participate in the retained files machinery, same as the table file persister, so that the journal is correctly considered not-safe-for-delete-by-PruneTableFiles before it is ever created on disk and potentially selected for deletion by PruneTableFiles.