content: /*
   * 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.bookkeeper.stream.storage.impl.cluster;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  import static org.apache.bookkeeper.stream.storage.StorageConstants.getControllerPath;
  
  import lombok.extern.slf4j.Slf4j;
  import org.apache.bookkeeper.stream.storage.api.cluster.ClusterControllerLeader;
  import org.apache.bookkeeper.stream.storage.api.cluster.ClusterControllerLeaderSelector;
  import org.apache.curator.framework.CuratorFramework;
  import org.apache.curator.framework.recipes.leader.LeaderSelector;
  import org.apache.curator.framework.state.ConnectionState;
  import org.apache.curator.framework.state.ConnectionStateListener;
  
  /**
   * A controller leader selector implemented using zookeeper.
   */
  @Slf4j
  public class ZkClusterControllerLeaderSelector implements ClusterControllerLeaderSelector, ConnectionStateListener {
  
      private final CuratorFramework client;
      // the zookeeper path that controller is using for leader election
      private final String controllerZkPath;
  
      // leader selector to select leader
      private ClusterControllerLeader leader;
      private LeaderSelector leaderSelector;
  
      public ZkClusterControllerLeaderSelector(CuratorFramework client,
                                               String zkRootPath) {
          this.client = client;
          this.controllerZkPath = getControllerPath(zkRootPath);
      }
  
      @Override
      public void initialize(ClusterControllerLeader leader) {
          this.leader = leader;
          ZkClusterControllerLeaderSelectorListener zkLeader = new ZkClusterControllerLeaderSelectorListener(leader);
          this.leaderSelector = new LeaderSelector(client, controllerZkPath, zkLeader);
          client.getConnectionStateListenable().addListener(this);
      }
  
      @Override
      public void start() {
          checkNotNull(leaderSelector, "leader selector is not initialized");
          leaderSelector.autoRequeue();
          leaderSelector.start();
      }
  
      @Override
      public void close() {
          if (null != leaderSelector) {
              leaderSelector.interruptLeadership();
              leaderSelector.close();
          }
      }
  
      @Override
      public void stateChanged(CuratorFramework client, ConnectionState newState) {
          switch (newState) {
              case LOST:
                  log.warn("Connection to zookeeper is lost. So interrupt my current leadership.");
                  leaderSelector.interruptLeadership();
                  break;
              case SUSPENDED:
                  if (leaderSelector.hasLeadership()) {
                      log.info("Connection to zookeeper is disconnected, suspend the leader until it is reconnected.");
                      leader.suspend();
                  }
                  break;
              case RECONNECTED:
                  if (leaderSelector.hasLeadership()) {
                      log.info("Connection to zookeeper is reconnected, resume the leader");
                      leader.resume();
                  }
                  break;
              default:
                  break;
          }
      }
  }
  