chia7712 commented on a change in pull request #8657:
URL: https://github.com/apache/kafka/pull/8657#discussion_r482743072
##########
File path:
core/src/test/scala/unit/kafka/coordinator/AbstractCoordinatorConcurrencyTest.scala
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@@ -201,8 +201,8 @@ object AbstractCoordinatorConcurrencyTest {
}
}
val producerRequestKeys =
entriesPerPartition.keys.map(TopicPartitionOperationKey(_)).toSeq
- watchKeys ++= producerRequestKeys
producePurgatory.tryCompleteElseWatch(delayedProduce,
producerRequestKeys)
+ watchKeys ++= producerRequestKeys
Review comment:
@junrao This change avoids deadlock in
```TransactionCoordinatorConcurrencyTest```.
If we update ```watchKeys``` before ```tryCompleteElseWatch```, the other
threads can take the same key to complete delayed request. Hence the deadlock
happens due to following conditions.
**thread_1** holds ```stateLock``` of TransactionStateManager to call
```appendRecords``` and it requires lock of delayed request to call
```tryCompleteElseWatch```.
**thread_2** holds lock of delayed request to call ```onComplete```
(updateCacheCallback) and ```updateCacheCallback``` requires ```stateLock``` of
TransactionStateManager.
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