tillrohrmann commented on a change in pull request #13644: URL: https://github.com/apache/flink/pull/13644#discussion_r516788405
########## File path: flink-kubernetes/src/main/java/org/apache/flink/kubernetes/highavailability/KubernetesLeaderElectionDriver.java ########## @@ -0,0 +1,225 @@ +/* + * 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.kubernetes.highavailability; + +import org.apache.flink.kubernetes.configuration.KubernetesLeaderElectionConfiguration; +import org.apache.flink.kubernetes.kubeclient.FlinkKubeClient; +import org.apache.flink.kubernetes.kubeclient.resources.KubernetesConfigMap; +import org.apache.flink.kubernetes.kubeclient.resources.KubernetesException; +import org.apache.flink.kubernetes.kubeclient.resources.KubernetesLeaderElector; +import org.apache.flink.kubernetes.kubeclient.resources.KubernetesWatch; +import org.apache.flink.kubernetes.utils.KubernetesUtils; +import org.apache.flink.runtime.leaderelection.LeaderElectionDriver; +import org.apache.flink.runtime.leaderelection.LeaderElectionEventHandler; +import org.apache.flink.runtime.leaderelection.LeaderElectionException; +import org.apache.flink.runtime.leaderelection.LeaderInformation; +import org.apache.flink.runtime.rpc.FatalErrorHandler; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.util.List; +import java.util.Map; +import java.util.Optional; +import java.util.UUID; + +import static org.apache.flink.kubernetes.utils.Constants.LABEL_CONFIGMAP_TYPE_HIGH_AVAILABILITY; +import static org.apache.flink.kubernetes.utils.Constants.LEADER_ADDRESS_KEY; +import static org.apache.flink.kubernetes.utils.Constants.LEADER_SESSION_ID_KEY; +import static org.apache.flink.kubernetes.utils.KubernetesUtils.checkConfigMaps; +import static org.apache.flink.kubernetes.utils.KubernetesUtils.getLeaderInformationFromConfigMap; +import static org.apache.flink.util.Preconditions.checkNotNull; + +/** + * {@link LeaderElectionDriver} implementation for Kubernetes. The active leader is elected using Kubernetes. + * The current leader's address as well as its leader session ID is published via Kubernetes ConfigMap. + * Note that the contending lock and leader storage are using the same ConfigMap. And every component(e.g. + * ResourceManager, Dispatcher, RestEndpoint, JobManager for each job) will have a separate ConfigMap. + */ +public class KubernetesLeaderElectionDriver implements LeaderElectionDriver { + + private static final Logger LOG = LoggerFactory.getLogger(KubernetesLeaderElectionDriver.class); + + private final FlinkKubeClient kubeClient; + + private final String configMapName; + + private final String lockIdentity; + + private final KubernetesLeaderElector leaderElector; + + // Labels will be used to clean up the ha related ConfigMaps. + private final Map<String, String> configMapLabels; + + private final LeaderElectionEventHandler leaderElectionEventHandler; + + private final KubernetesWatch kubernetesWatch; + + private final FatalErrorHandler fatalErrorHandler; + + private volatile boolean running; + + public KubernetesLeaderElectionDriver( + FlinkKubeClient kubeClient, + KubernetesLeaderElectionConfiguration leaderConfig, + LeaderElectionEventHandler leaderElectionEventHandler, + FatalErrorHandler fatalErrorHandler) { + + this.kubeClient = checkNotNull(kubeClient, "Kubernetes client"); + checkNotNull(leaderConfig, "Leader election configuration"); + this.leaderElectionEventHandler = checkNotNull(leaderElectionEventHandler, "LeaderElectionEventHandler"); + this.fatalErrorHandler = checkNotNull(fatalErrorHandler); + + this.configMapName = leaderConfig.getConfigMapName(); + this.lockIdentity = leaderConfig.getLockIdentity(); + this.leaderElector = kubeClient.createLeaderElector(leaderConfig, new LeaderCallbackHandlerImpl()); + this.configMapLabels = KubernetesUtils.getConfigMapLabels( + leaderConfig.getClusterId(), LABEL_CONFIGMAP_TYPE_HIGH_AVAILABILITY); + + leaderElector.run(); + kubernetesWatch = kubeClient.watchConfigMaps(configMapName, new ConfigMapCallbackHandlerImpl()); + running = true; + } + + @Override + public void close() { + if (!running) { + return; + } + running = false; + + LOG.info("Closing {}.", this); + leaderElector.stop(); + kubernetesWatch.close(); + } + + @Override + public void writeLeaderInformation(LeaderInformation leaderInformation) { + assert(running); + final UUID confirmedLeaderSessionID = leaderInformation.getLeaderSessionID(); + final String confirmedLeaderAddress = leaderInformation.getLeaderAddress(); + try { + kubeClient.checkAndUpdateConfigMap( + configMapName, + configMap -> { + if (KubernetesLeaderElector.hasLeadership(configMap, lockIdentity)) { + // Get the updated ConfigMap with new leader information + if (confirmedLeaderAddress == null) { + configMap.getData().remove(LEADER_ADDRESS_KEY); + } else { + configMap.getData().put(LEADER_ADDRESS_KEY, confirmedLeaderAddress); + } + if (confirmedLeaderSessionID == null) { + configMap.getData().remove(LEADER_SESSION_ID_KEY); + } else { + configMap.getData().put(LEADER_SESSION_ID_KEY, confirmedLeaderSessionID.toString()); + } + configMap.getLabels().putAll(configMapLabels); + return Optional.of(configMap); + } + return Optional.empty(); + }).get(); + if (LOG.isDebugEnabled()) { + LOG.debug( + "Successfully wrote leader information: Leader={}, session ID={}.", + confirmedLeaderAddress, + confirmedLeaderSessionID); + } + } catch (Exception e) { + fatalErrorHandler.onFatalError( + new KubernetesException("Could not write leader information since ConfigMap " + configMapName + + " does not exist.", e)); + } + } + + @Override + public boolean hasLeadership() { + assert(running); + final Optional<KubernetesConfigMap> configMapOpt = kubeClient.getConfigMap(configMapName); + if (configMapOpt.isPresent()) { + return KubernetesLeaderElector.hasLeadership(configMapOpt.get(), lockIdentity); + } else { + fatalErrorHandler.onFatalError( + new KubernetesException("ConfigMap " + configMapName + " does not exist.", null)); + return false; + } + } + + private class LeaderCallbackHandlerImpl extends KubernetesLeaderElector.LeaderCallbackHandler { + + @Override + public void isLeader() { + leaderElectionEventHandler.onGrantLeadership(); + } + + @Override + public void notLeader() { + leaderElectionEventHandler.onRevokeLeadership(); + // Continue to contend the leader + leaderElector.run(); + } + } + + private class ConfigMapCallbackHandlerImpl implements FlinkKubeClient.WatchCallbackHandler<KubernetesConfigMap> { + @Override + public void onAdded(List<KubernetesConfigMap> configMaps) { + // noop + } + + @Override + public void onModified(List<KubernetesConfigMap> configMaps) { + // We should only receive events for the watched ConfigMap + final KubernetesConfigMap configMap = checkConfigMaps(configMaps, configMapName); + + if (KubernetesLeaderElector.hasLeadership(configMap, lockIdentity)) { + leaderElectionEventHandler.onLeaderInformationChange(getLeaderInformationFromConfigMap(configMap)); Review comment: This contracts makes sense. Sorry I overlooked this piece of information. ---------------------------------------------------------------- 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: [email protected]
