001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.master;
019
020import java.io.IOException;
021import java.util.List;
022import java.util.NavigableSet;
023import java.util.TreeSet;
024import org.apache.hadoop.hbase.Abortable;
025import org.apache.hadoop.hbase.ServerName;
026import org.apache.hadoop.hbase.zookeeper.ZKListener;
027import org.apache.hadoop.hbase.zookeeper.ZKUtil;
028import org.apache.hadoop.hbase.zookeeper.ZKWatcher;
029import org.apache.yetus.audience.InterfaceAudience;
030import org.apache.zookeeper.KeeperException;
031import org.slf4j.Logger;
032import org.slf4j.LoggerFactory;
033
034/**
035 * Tracks the list of draining region servers via ZK.
036 * <p>
037 * This class is responsible for watching for changes to the draining servers list. It handles
038 * adds/deletes in the draining RS list and watches each node.
039 * <p>
040 * If an RS gets deleted from draining list, we call
041 * {@link ServerManager#removeServerFromDrainList(ServerName)}
042 * <p>
043 * If an RS gets added to the draining list, we add a watcher to it and call
044 * {@link ServerManager#addServerToDrainList(ServerName)}
045 * <p>
046 * This class is deprecated in 2.0 because decommission/draining API goes through master in 2.0. Can
047 * remove this class in 3.0.
048 */
049@InterfaceAudience.Private
050public class DrainingServerTracker extends ZKListener {
051  private static final Logger LOG = LoggerFactory.getLogger(DrainingServerTracker.class);
052
053  private ServerManager serverManager;
054  private final NavigableSet<ServerName> drainingServers = new TreeSet<>();
055  private Abortable abortable;
056
057  public DrainingServerTracker(ZKWatcher watcher, Abortable abortable,
058    ServerManager serverManager) {
059    super(watcher);
060    this.abortable = abortable;
061    this.serverManager = serverManager;
062  }
063
064  /**
065   * Starts the tracking of draining RegionServers.
066   * <p>
067   * All Draining RSs will be tracked after this method is called. n
068   */
069  public void start() throws KeeperException, IOException {
070    watcher.registerListener(this);
071    // Add a ServerListener to check if a server is draining when it's added.
072    serverManager.registerListener(new ServerListener() {
073      @Override
074      public void serverAdded(ServerName sn) {
075        if (drainingServers.contains(sn)) {
076          serverManager.addServerToDrainList(sn);
077        }
078      }
079    });
080    List<String> servers =
081      ZKUtil.listChildrenAndWatchThem(watcher, watcher.getZNodePaths().drainingZNode);
082    add(servers);
083  }
084
085  private void add(final List<String> servers) throws IOException {
086    synchronized (this.drainingServers) {
087      this.drainingServers.clear();
088      for (String n : servers) {
089        final ServerName sn = ServerName.valueOf(ZKUtil.getNodeName(n));
090        this.drainingServers.add(sn);
091        this.serverManager.addServerToDrainList(sn);
092        LOG.info("Draining RS node created, adding to list [" + sn + "]");
093
094      }
095    }
096  }
097
098  private void remove(final ServerName sn) {
099    synchronized (this.drainingServers) {
100      this.drainingServers.remove(sn);
101      this.serverManager.removeServerFromDrainList(sn);
102    }
103  }
104
105  @Override
106  public void nodeDeleted(final String path) {
107    if (path.startsWith(watcher.getZNodePaths().drainingZNode)) {
108      final ServerName sn = ServerName.valueOf(ZKUtil.getNodeName(path));
109      LOG.info("Draining RS node deleted, removing from list [" + sn + "]");
110      remove(sn);
111    }
112  }
113
114  @Override
115  public void nodeChildrenChanged(final String path) {
116    if (path.equals(watcher.getZNodePaths().drainingZNode)) {
117      try {
118        final List<String> newNodes =
119          ZKUtil.listChildrenAndWatchThem(watcher, watcher.getZNodePaths().drainingZNode);
120        add(newNodes);
121      } catch (KeeperException e) {
122        abortable.abort("Unexpected zk exception getting RS nodes", e);
123      } catch (IOException e) {
124        abortable.abort("Unexpected zk exception getting RS nodes", e);
125      }
126    }
127  }
128}