zjncs opened a new pull request, #11114:
URL: https://github.com/apache/rocketmq/pull/11114
## Motivation
`ConsumerManager` has three paths that remove a consumer group from
`consumerTable` once its last channel is gone: `unregisterConsumer`,
`doChannelCloseEvent`, and `scanNotActiveChannel`. The first two clean up the
group's `topicGroupTable` entries and fire the `UNREGISTER` listener event:
```java
ConsumerGroupInfo remove = this.consumerTable.remove(group);
if (remove != null) {
...
callConsumerIdsChangeListener(ConsumerGroupEvent.UNREGISTER, group);
clearTopicGroupTable(remove);
}
```
`scanNotActiveChannel` only does `it.remove()`:
```java
if (channelInfoTable.isEmpty()) {
LOGGER.warn("SCAN: remove expired channel ... consumerGroup={}", group);
it.remove();
}
```
When a consumer client dies without closing the channel (process kill,
network partition), the scan path is the one that eventually removes the group.
Its omission means:
- `queryTopicConsumeByWho(topic)` keeps returning the dead group forever —
`QUERY_TOPIC_CONSUME_BY_WHO` (used by admin tools/mqadmin/console) reports
groups as consumers of a topic long after they went offline, and nothing ever
cleans the entry since only re-registration writes to `topicGroupTable`.
- The `UNREGISTER` event is never fired, so
`DefaultConsumerIdsChangeListener` never calls
`consumerFilterManager.unRegister(group)` and the group's consumer filter
registrations leak.
## Modification
In `scanNotActiveChannel`, after removing the empty group, fire the
`UNREGISTER` listener event and call `clearTopicGroupTable(consumerGroupInfo)`,
exactly matching the other two removal paths.
## Test Evidence
**Fail-before** (unpatched code, new test
`ConsumerManagerTest#scanNotActiveChannelClearsTopicGroupTableTest` — register
a consumer on a topic, expire its channel, scan, then ask who consumes the
topic):
```
docker exec rmq-build mvn -q -pl broker test
-Dtest='ConsumerManagerTest#scanNotActiveChannelClearsTopicGroupTableTest'
-Dsurefire.failIfNoSpecifiedTests=true
Tests run: 1, Failures: 1 ... java.lang.AssertionError
// queryTopicConsumeByWho(TOPIC) still returns the removed group
```
**Pass-after** (full class with the fix):
```
docker exec rmq-build mvn -q -pl broker test -Dtest='ConsumerManagerTest'
-Dsurefire.failIfNoSpecifiedTests=true
Tests run: 14, Failures: 0, Errors: 0, Skipped: 0
```
No associated issue (self-discovered during a broker-module self-audit).
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