tillrohrmann commented on a change in pull request #17485: URL: https://github.com/apache/flink/pull/17485#discussion_r791592672
########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/leaderelection/ZooKeeperMultipleComponentLeaderElectionDriver.java ########## @@ -0,0 +1,250 @@ +/* + * 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.runtime.util.ZooKeeperUtils; +import org.apache.flink.util.ExceptionUtils; +import org.apache.flink.util.Preconditions; +import org.apache.flink.util.concurrent.Executors; + +import org.apache.flink.shaded.curator4.org.apache.curator.framework.CuratorFramework; +import org.apache.flink.shaded.curator4.org.apache.curator.framework.recipes.cache.ChildData; +import org.apache.flink.shaded.curator4.org.apache.curator.framework.recipes.cache.TreeCache; +import org.apache.flink.shaded.curator4.org.apache.curator.framework.recipes.cache.TreeCacheSelector; +import org.apache.flink.shaded.curator4.org.apache.curator.framework.recipes.leader.LeaderLatch; +import org.apache.flink.shaded.curator4.org.apache.curator.framework.recipes.leader.LeaderLatchListener; +import org.apache.flink.shaded.curator4.org.apache.curator.framework.state.ConnectionState; +import org.apache.flink.shaded.curator4.org.apache.curator.framework.state.ConnectionStateListener; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.io.IOException; +import java.util.concurrent.atomic.AtomicBoolean; + +/** ZooKeeper based {@link MultipleComponentLeaderElectionDriver} implementation. */ +public class ZooKeeperMultipleComponentLeaderElectionDriver + implements MultipleComponentLeaderElectionDriver, LeaderLatchListener { + + private static final Logger LOG = + LoggerFactory.getLogger(ZooKeeperMultipleComponentLeaderElectionDriver.class); + + private final CuratorFramework curatorFramework; + + private final String leaderContenderDescription; + + private final MultipleComponentLeaderElectionDriver.Listener leaderElectionListener; + + private final LeaderLatch leaderLatch; + + private final TreeCache treeCache; + + private final ConnectionStateListener listener = + (client, newState) -> handleStateChange(newState); + + private AtomicBoolean running = new AtomicBoolean(true); + + public ZooKeeperMultipleComponentLeaderElectionDriver( + CuratorFramework curatorFramework, + String leaderContenderDescription, + MultipleComponentLeaderElectionDriver.Listener leaderElectionListener) + throws Exception { + this.curatorFramework = curatorFramework; + this.leaderContenderDescription = leaderContenderDescription; + this.leaderElectionListener = leaderElectionListener; + + this.leaderLatch = new LeaderLatch(curatorFramework, ZooKeeperUtils.getLeaderLatchNode()); + this.treeCache = + TreeCache.newBuilder(curatorFramework, "/") + .setCacheData(true) + .setCreateParentNodes(false) + .setSelector( + new ZooKeeperMultipleComponentLeaderElectionDriver + .ConnectionInfoNodeSelector()) + .setExecutor(Executors.newDirectExecutorService()) + .build(); + treeCache + .getListenable() + .addListener( + (client, event) -> { + switch (event.getType()) { + case NODE_ADDED: + case NODE_REMOVED: + case NODE_UPDATED: + if (event.getData() != null) { + handleChangedLeaderInformation(event.getData()); + } + } + }); + + leaderLatch.addListener(this); + curatorFramework.getConnectionStateListenable().addListener(listener); + leaderLatch.start(); + treeCache.start(); + } + + @Override + public void close() throws Exception { + if (running.compareAndSet(true, false)) { + LOG.info("Closing {}.", this); + + curatorFramework.getConnectionStateListenable().removeListener(listener); + + Exception exception = null; + + try { + treeCache.close(); + } catch (Exception e) { + exception = e; + } + + try { + leaderLatch.close(); + } catch (Exception e) { + exception = ExceptionUtils.firstOrSuppressed(e, exception); + } + + ExceptionUtils.tryRethrowException(exception); + } + } + + @Override + public boolean hasLeadership() { + return leaderLatch.hasLeadership(); + } + + @Override + public void publishLeaderInformation(String componentId, LeaderInformation leaderInformation) + throws Exception { + Preconditions.checkState(running.get()); + + if (LOG.isDebugEnabled()) { + LOG.debug("Write leader information {} for {}.", leaderInformation, componentId); + } + if (!leaderLatch.hasLeadership() || leaderInformation.isEmpty()) { + return; + } + + final String connectionInformationPath = + ZooKeeperUtils.generateConnectionInformationPath(componentId); + + ZooKeeperUtils.writeLeaderInformationToZooKeeper( + leaderInformation, + curatorFramework, + leaderLatch::hasLeadership, + connectionInformationPath); + } + + @Override + public void deleteLeaderInformation(String leaderName) throws Exception { + ZooKeeperUtils.deleteZNode(curatorFramework, ZooKeeperUtils.makeZooKeeperPath(leaderName)); + } + + private void handleStateChange(ConnectionState newState) { Review comment: I would like to keep it because the `ZooKeeperLeaderElectionDriver` should ideally be removed with the next release. -- This is an automated message from the Apache Git Service. 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