fix: re-validate compaction boundary to prevent missed deletion events in watch - #7
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fix: re-validate compaction boundary to prevent missed deletion events in watch#7Kasuki354 wants to merge 1 commit into
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… prevent missed deletion events The race condition occurred when a watch was created with startRev close to the compaction boundary. If compaction advanced between the boundary check and the watcher registration, the watcher could be added to the unsynced group with a minRev that had already been compacted, causing it to silently miss deletion events. Fix: 1. In watch(): after adding watcher to unsynced, re-validate minRev against compactMainRev. If compaction advanced, cancel the watcher immediately with ErrCompacted. 2. In syncWatchers(): re-check compactMainRev for every unsynced watcher before any data read, ensuring no watcher reads compacted data. 3. Both checks happen under s.Mu + s.store.Mu locks, ensuring atomicity. Resolves morriganreza973#5
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Summary
Fixes issue #5: Race condition where Watch misses deletion event near compaction boundary.
Root Cause
In watch(), the compaction boundary check (startRev <= compactMainRev) and the watcher registration happen under both s.Mu and s.store.Mu locks. However, there is an edge case: if the watcher is added to the unsynced group with a minRev that is valid at check time, but compaction advances before syncWatchers() runs, the watcher could read compacted data and miss the deletion event.
Fix
watch(): After adding watcher to unsynced, re-validate minRev against compactMainRev. If compaction advanced, cancel the watcher immediately with ErrCompacted.
syncWatchers(): Re-check compactMainRev for every unsynced watcher before any data read attempt. If minRev <= compactMainRev, cancel with ErrCompacted.
Both checks happen under s.Mu + s.store.Mu locks, ensuring atomicity with compaction.
/claim #5