unbridled-41 commented on PR #10992:
URL: https://github.com/apache/rocketmq/pull/10992#issuecomment-5468005513
### Test evidence (before → after)
`ConsumerOffsetManagerTest#testConcurrentCommitOffsetDoesNotLoseQueues` was
run repeatedly on JDK 8 with the fix reverted and with the fix applied (5 runs
each, `mvn -pl broker test
-Dtest='ConsumerOffsetManagerTest#testConcurrentCommitOffsetDoesNotLoseQueues'`):
**On the unfixed code: 5/5 runs fail.** Example failure (queues 0 and 7 of
`topic1` lost — the loser's map was overwritten):
```
java.lang.AssertionError:
[offsets of topic1]
Expected size: 8 but was: 6 in:
{1=1L, 2=1L, 3=1L, 4=1L, 5=1L, 6=1L}
```
The race window is the very first
`offsetTable.get(key)`/`offsetTable.put(key, map)` pair per fresh `topic@group`
key, so it reproduces reliably, not stochastically.
**With this PR: 5/5 runs pass** (`Tests run: 1, Failures: 0, Errors: 0,
Skipped: 0` each run; the whole `ConsumerOffsetManagerTest` is 6/6 green).
The loss is not just a test artifact: every commit the losing thread made
for that queue is gone until that queue's next commit (5s flush cadence, but
`queryOffset` returns `-1` immediately), so a consumer reconnect in that window
re-initializes the queue per `consumeFromWhere`.
Side note on CI: the workflow runs for this PR are in `action_required`
state (first-time contributor) and will start once a maintainer approves them.
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