chia7712 commented on a change in pull request #8657: URL: https://github.com/apache/kafka/pull/8657#discussion_r479692892
########## File path: core/src/main/scala/kafka/server/ActionQueue.scala ########## @@ -0,0 +1,46 @@ +/** + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package kafka.server + +import java.util.concurrent.LinkedBlockingDeque + +/** + * This queue is used to collect actions which need to be executed later. One use case is that ReplicaManager#appendRecords + * produces record changes so we need to check and complete delayed requests. In order to avoid conflicting locking, + * we add those actions to this queue and then complete them at the end of KafkaApis.handle() or DelayedJoin.onExpiration. + */ +class ActionQueue { + private val queue = new LinkedBlockingDeque[() => Unit]() Review comment: Handler (thread) can have local ActionQueue and it is passed to each method to collect delayed action. ```DelayedJoin``` is specific case since the delayed actions are possible to be access by two thread (timeout thread and handler thread). A simple way to address thread local is that ```DelayedJoin``` owns a ActionQueue and the queue is passed to ```coordinator.onCompleteJoin``` and then the queue is consumed by ```DelayedJoin.onExpiration```. Both ```onComplete``` and ```onExpiration``` are thread-safe so use a thread local queue is safe. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
