[improve][broker] Remove the atomicity on active consumer of a dispatcher #22285
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…cher ### Motivation The modifications on `AbstractDispatcherSingleActiveConsumer#activeConsumer` only happen on `pickAndScheduleActiveConsumer`, which is only called in `addConsumer` and `removeConsumer`. However, both `addConsumer` and `removeConsumer` are synchronized methods so that we don't have to perform an atomic operation on `activeConsumer`. The composite operations on `activeConsumer` also happen on synchronized methods like `disconnectActiveConsumers`. The only access to `activeConsumer` that is not synchronized is the read on `activeConsumer` like `getActiveConsumer()` and `isConsumerConnected()`. ### Modifications Remove the `ACTIVE_CONSUMER_UPDATER` and note some methods are not thread safe or there is no need to make them thread safe. Besides, since `pickAndScheduleActiveConsumer` is never called concurrently, we don't need a double-checked locking on `readOnActiveConsumerTask`. Instead, just synchronize the modification in the scheduled task.
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poorbarcode
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Motivation
The modifications on
AbstractDispatcherSingleActiveConsumer#activeConsumeronly happen onpickAndScheduleActiveConsumer, which is only called inaddConsumerandremoveConsumer. However, bothaddConsumerandremoveConsumerare synchronized methods so that we don't have to perform an atomic operation onactiveConsumer.The composite operations on
activeConsumeralso happen on synchronized methods likedisconnectActiveConsumers. The only access toactiveConsumerthat is not synchronized is the read onactiveConsumerlikegetActiveConsumer()andisConsumerConnected().Modifications
Remove the
ACTIVE_CONSUMER_UPDATERand note some methods are not thread safe or there is no need to make them thread safe.Besides, since
pickAndScheduleActiveConsumeris never called concurrently, we don't need a double-checked locking onreadOnActiveConsumerTask. Instead, just synchronize the modification in the scheduled task.Documentation
docdoc-requireddoc-not-neededdoc-completeMatching PR in forked repository
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