/* * 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.kubeclient.resources; import org.apache.flink.annotation.VisibleForTesting; import org.apache.flink.kubernetes.configuration.KubernetesLeaderElectionConfiguration; import org.apache.flink.runtime.util.ExecutorThreadFactory; import io.fabric8.kubernetes.client.NamespacedKubernetesClient; import io.fabric8.kubernetes.client.extended.leaderelection.LeaderCallbacks; import io.fabric8.kubernetes.client.extended.leaderelection.LeaderElectionConfig; import io.fabric8.kubernetes.client.extended.leaderelection.LeaderElectionConfigBuilder; import io.fabric8.kubernetes.client.extended.leaderelection.LeaderElector; import io.fabric8.kubernetes.client.extended.leaderelection.resourcelock.ConfigMapLock; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; /** * Represent {@link KubernetesLeaderElector} in kubernetes. {@link LeaderElector#run()} is a * blocking call. It should be run in the IO executor, not the main thread. The lifecycle is bound * to single leader election. Once the leadership is revoked, as well as the {@link * LeaderCallbackHandler#notLeader()} is called, the {@link LeaderElector#run()} will finish. To * start another round of election, we need to trigger again. * *
{@link LeaderElector#run()} is responsible for creating the leader ConfigMap and continuously
* update the annotation. The annotation key is {@link #LEADER_ANNOTATION_KEY} and the value is in
* the following json format. metadata: annotations: control-plane.alpha.kubernetes.io/leader:
* '{"holderIdentity":"623e39fb-70c3-44f1-811f-561ec4a28d75","leaseDuration":15.000000000,"acquireTime":"2020-10-20T04:06:31.431000Z","renewTime":"2020-10-22T08:51:36.843000Z","leaderTransitions":37981}'
*/
public class KubernetesLeaderElector {
private static final Logger LOG = LoggerFactory.getLogger(KubernetesLeaderElector.class);
@VisibleForTesting
public static final String LEADER_ANNOTATION_KEY = "control-plane.alpha.kubernetes.io/leader";
private final ExecutorService executorService =
Executors.newSingleThreadExecutor(
new ExecutorThreadFactory("KubernetesLeaderElector-ExecutorService"));
private final LeaderElector