wangyang0918 commented on a change in pull request #13644: URL: https://github.com/apache/flink/pull/13644#discussion_r509888875
########## File path: flink-kubernetes/src/main/java/org/apache/flink/kubernetes/highavailability/KubernetesLeaderElectionService.java ########## @@ -0,0 +1,219 @@ +/* + * 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.kubeclient.FlinkKubeClient; +import org.apache.flink.kubernetes.kubeclient.KubernetesLeaderElectionConfiguration; +import org.apache.flink.kubernetes.kubeclient.resources.KubernetesConfigMap; +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.AbstractLeaderElectionService; +import org.apache.flink.runtime.leaderelection.LeaderContender; +import org.apache.flink.util.function.FunctionUtils; + +import java.util.List; +import java.util.Map; +import java.util.Objects; +import java.util.Optional; +import java.util.concurrent.CompletableFuture; +import java.util.concurrent.Executor; + +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.util.Preconditions.checkNotNull; + +/** + * Leader election service for multiple JobManagers. The active JobManager 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 KubernetesLeaderElectionService extends AbstractLeaderElectionService { + + private final FlinkKubeClient kubeClient; + + private final Executor executor; + + private final String configMapName; + + private final KubernetesLeaderElector leaderElector; + + private KubernetesWatch kubernetesWatch; + + // Labels will be used to clean up the ha related ConfigMaps. + private Map<String, String> configMapLabels; + + KubernetesLeaderElectionService( + FlinkKubeClient kubeClient, + Executor executor, + KubernetesLeaderElectionConfiguration leaderConfig) { + + this.kubeClient = checkNotNull(kubeClient, "Kubernetes client should not be null."); + this.executor = checkNotNull(executor, "Executor should not be null."); + this.configMapName = leaderConfig.getConfigMapName(); + this.leaderElector = kubeClient.createLeaderElector(leaderConfig, new LeaderCallbackHandlerImpl()); + this.leaderContender = null; + this.configMapLabels = KubernetesUtils.getConfigMapLabels( + leaderConfig.getClusterId(), LABEL_CONFIGMAP_TYPE_HIGH_AVAILABILITY); + } + + @Override + public void internalStart(LeaderContender contender) { + CompletableFuture.runAsync(leaderElector::run, executor); + kubernetesWatch = kubeClient.watchConfigMaps(configMapName, new ConfigMapCallbackHandlerImpl()); + } + + @Override + public void internalStop() { + if (kubernetesWatch != null) { + kubernetesWatch.close(); + } + } + + @Override + protected void writeLeaderInformation() { + try { + kubeClient.checkAndUpdateConfigMap( + configMapName, + configMap -> { + if (leaderElector.hasLeadership(configMap)) { + // Get the updated ConfigMap with new leader information + if (confirmedLeaderAddress != null && confirmedLeaderSessionID != null) { + configMap.getData().put(LEADER_ADDRESS_KEY, confirmedLeaderAddress); + configMap.getData().put(LEADER_SESSION_ID_KEY, confirmedLeaderSessionID.toString()); + } + configMap.getLabels().putAll(configMapLabels); + return Optional.of(configMap); + } + return Optional.empty(); + }).get(); + } catch (Exception e) { + leaderContender.handleError(new Exception("Could not update ConfigMap " + configMapName, e)); + } + } + + @Override + protected boolean hasLeadership() { + return kubeClient.getConfigMap(configMapName) + .map(leaderElector::hasLeadership) + .orElse(false); + } + + @Override + public String toString() { + return "KubernetesLeaderElectionService{configMapName='" + configMapName + "'}"; + } + + private class LeaderCallbackHandlerImpl extends KubernetesLeaderElector.LeaderCallbackHandler { + + @Override + public void isLeader() { + onGrantLeadership(); + } + + @Override + public void notLeader() { + // Clear the leader information in ConfigMap + try { + kubeClient.checkAndUpdateConfigMap( + configMapName, + configMap -> { + // Do not need to check the leader here + configMap.getData().remove(LEADER_ADDRESS_KEY); + configMap.getData().remove(LEADER_SESSION_ID_KEY); Review comment: Hmm. After checking the implementation in fabric8 Kubernetes client `LeaderElector` implementation, the leader annotation will not be cleared even the current leadership is revoked. So you are right we could still check the leadership here. Only when the annotation is matched to the current `lockIdentity`, which means a next leader has not been elected, we could safely clear the leader information in the ConfigMap. ---------------------------------------------------------------- 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
