wangyang0918 commented on a change in pull request #13644: URL: https://github.com/apache/flink/pull/13644#discussion_r507515399
########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/leaderelection/AbstractLeaderElectionService.java ########## @@ -0,0 +1,190 @@ +/* + * 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 org.apache.flink.runtime.leaderelection; + +import org.apache.flink.util.Preconditions; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import javax.annotation.Nonnull; +import java.util.UUID; + +/** + * Abstract class for leader election service based on distributed coordination system(e.g. Zookeeper, Kubernetes, etc.). + */ +public abstract class AbstractLeaderElectionService implements LeaderElectionService { + + protected final Logger logger = LoggerFactory.getLogger(getClass()); + + protected final Object lock = new Object(); + + /** The leader contender which applies for leadership. */ + protected volatile LeaderContender leaderContender; + + private volatile UUID issuedLeaderSessionID; + + protected volatile UUID confirmedLeaderSessionID; + + protected volatile String confirmedLeaderAddress; + + protected volatile boolean running; + + protected AbstractLeaderElectionService() { + leaderContender = null; + + issuedLeaderSessionID = null; + confirmedLeaderSessionID = null; + confirmedLeaderAddress = null; + + running = false; + } + + @Override + public final void start(LeaderContender contender) throws Exception { + Preconditions.checkNotNull(contender, "Contender must not be null."); + Preconditions.checkState(leaderContender == null, "Contender was already set."); + + logger.info("Starting LeaderElectionService {}.", this); + + synchronized (lock) { + leaderContender = contender; + running = true; + internalStart(contender); + } + } + + @Override + public final void stop() throws Exception { + synchronized (lock) { + if (!running) { + return; + } + running = false; + clearConfirmedLeaderInformation(); + } + + logger.info("Stopping LeaderElectionService {}.", this); + + internalStop(); + } Review comment: Actually, there's no valid harm to also put `internalStop` in the `synchronized` block. Since the old behavior in `ZookeeperLeaderElectionService` is like this, I keep them in the `AbstractLeaderElectionService`. Just like you said, it is a little hard for the maintenance. I agree that we could move the `internalStop` into the `synchronized` block. ---------------------------------------------------------------- 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
