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1   /**
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  package org.apache.hadoop.hbase.zookeeper;
19  
20  import java.io.IOException;
21  import java.util.List;
22  import java.util.NavigableSet;
23  import java.util.TreeSet;
24  
25  import org.apache.commons.logging.Log;
26  import org.apache.commons.logging.LogFactory;
27  import org.apache.hadoop.classification.InterfaceAudience;
28  import org.apache.hadoop.hbase.Abortable;
29  import org.apache.hadoop.hbase.ServerName;
30  import org.apache.hadoop.hbase.master.ServerManager;
31  import org.apache.zookeeper.KeeperException;
32  
33  /**
34   * Tracks the list of draining region servers via ZK.
35   *
36   * <p>This class is responsible for watching for changes to the draining
37   * servers list.  It handles adds/deletes in the draining RS list and
38   * watches each node.
39   *
40   * <p>If an RS gets deleted from draining list, we call
41   * {@link ServerManager#removeServerFromDrainList(ServerName)}
42   *
43   * <p>If an RS gets added to the draining list, we add a watcher to it and call
44   * {@link ServerManager#addServerToDrainList(ServerName)}
45   *
46   */
47  @InterfaceAudience.Private
48  public class DrainingServerTracker extends ZooKeeperListener {
49    private static final Log LOG = LogFactory.getLog(DrainingServerTracker.class);
50  
51    private ServerManager serverManager;
52    private final NavigableSet<ServerName> drainingServers = new TreeSet<ServerName>();
53    private Abortable abortable;
54  
55    public DrainingServerTracker(ZooKeeperWatcher watcher,
56        Abortable abortable, ServerManager serverManager) {
57      super(watcher);
58      this.abortable = abortable;
59      this.serverManager = serverManager;
60    }
61  
62    /**
63     * Starts the tracking of draining RegionServers.
64     *
65     * <p>All Draining RSs will be tracked after this method is called.
66     *
67     * @throws KeeperException
68     */
69    public void start() throws KeeperException, IOException {
70      watcher.registerListener(this);
71      List<String> servers =
72        ZKUtil.listChildrenAndWatchThem(watcher, watcher.drainingZNode);
73      add(servers);
74    }
75  
76    private void add(final List<String> servers) throws IOException {
77      synchronized(this.drainingServers) {
78        this.drainingServers.clear();
79        for (String n: servers) {
80          final ServerName sn = ServerName.valueOf(ZKUtil.getNodeName(n));
81          this.drainingServers.add(sn);
82          this.serverManager.addServerToDrainList(sn);
83          LOG.info("Draining RS node created, adding to list [" +
84              sn + "]");
85  
86        }
87      }
88    }
89  
90    private void remove(final ServerName sn) {
91      synchronized(this.drainingServers) {
92        this.drainingServers.remove(sn);
93        this.serverManager.removeServerFromDrainList(sn);
94      }
95    }
96  
97    @Override
98    public void nodeDeleted(final String path) {
99      if(path.startsWith(watcher.drainingZNode)) {
100       final ServerName sn = ServerName.valueOf(ZKUtil.getNodeName(path));
101       LOG.info("Draining RS node deleted, removing from list [" +
102           sn + "]");
103       remove(sn);
104     }
105   }
106 
107   @Override
108   public void nodeChildrenChanged(final String path) {
109     if(path.equals(watcher.drainingZNode)) {
110       try {
111         final List<String> newNodes =
112           ZKUtil.listChildrenAndWatchThem(watcher, watcher.drainingZNode);
113         add(newNodes);
114       } catch (KeeperException e) {
115         abortable.abort("Unexpected zk exception getting RS nodes", e);
116       } catch (IOException e) {
117         abortable.abort("Unexpected zk exception getting RS nodes", e);
118       }
119     }
120   }
121 }