tillrohrmann commented on a change in pull request #17485: URL: https://github.com/apache/flink/pull/17485#discussion_r791540131
########## 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) { + switch (newState) { + case CONNECTED: + LOG.debug("Connected to ZooKeeper quorum. Leader election can start."); + break; + case SUSPENDED: + LOG.warn("Connection to ZooKeeper suspended, waiting for reconnection."); + break; + case RECONNECTED: + LOG.info( + "Connection to ZooKeeper was reconnected. Leader election can be restarted."); + break; + case LOST: + // Maybe we have to throw an exception here to terminate the JobManager + LOG.warn( + "Connection to ZooKeeper lost. The contender " + + leaderContenderDescription + + " no longer participates in the leader election."); + break; + } + } + + @Override + public void isLeader() { + LOG.debug("{} obtained the leadership.", this); + leaderElectionListener.isLeader(); + } + + @Override + public void notLeader() { + LOG.debug("{} lost the leadership.", this); + leaderElectionListener.notLeader(); + } + + private void handleChangedLeaderInformation(ChildData childData) { + if (running.get() && leaderLatch.hasLeadership() && isConnectionInfoNode(childData)) { + + final String path = childData.getPath(); + final String[] splits = path.split("/"); + + Preconditions.checkState( + splits.length >= 2, + String.format( + "Expecting path consisting of <leader_name>/connection_info. Got path '%s'", + path)); + final String leaderName = splits[splits.length - 2]; + + final LeaderInformation leaderInformation = + tryReadingLeaderInformation(childData, leaderName); + + leaderElectionListener.notifyLeaderInformationChange(leaderName, leaderInformation); + } + } + + private boolean isConnectionInfoNode(ChildData childData) { + return childData.getPath().endsWith(ZooKeeperUtils.CONNECTION_INFO_NODE); + } + + private LeaderInformation tryReadingLeaderInformation(ChildData childData, String id) { + LeaderInformation leaderInformation; + try { + leaderInformation = ZooKeeperUtils.readLeaderInformation(childData.getData()); + + LOG.debug("Leader information for {} has changed to {}.", id, leaderInformation); + } catch (IOException | ClassNotFoundException e) { + LOG.debug( + "Could not read leader information for {}. Rewriting the information.", id, e); + leaderInformation = LeaderInformation.empty(); + } + + return leaderInformation; + } + + private static class ConnectionInfoNodeSelector implements TreeCacheSelector { Review comment: Will do. -- 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. To unsubscribe, e-mail: issues-unsubscr...@flink.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
