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1   /**
2    * Copyright 2010 The Apache Software Foundation
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *     http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing, software
15   * distributed under the License is distributed on an "AS IS" BASIS,
16   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17   * See the License for the specific language governing permissions and
18   * limitations under the License.
19   */
20  package org.apache.hadoop.hbase.zookeeper;
21  
22  import org.apache.hadoop.hbase.Abortable;
23  import org.apache.hadoop.hbase.HServerAddress;
24  import org.apache.hadoop.hbase.catalog.RootLocationEditor;
25  import org.apache.hadoop.hbase.regionserver.RegionServerServices;
26  import org.apache.hadoop.hbase.util.Bytes;
27  
28  /**
29   * Tracks the root region server location node in zookeeper.
30   * Root region location is set by {@link RootLocationEditor} usually called
31   * out of <code>RegionServerServices</code>.
32   * This class has a watcher on the root location and notices changes.
33   */
34  public class RootRegionTracker extends ZooKeeperNodeTracker {
35    /**
36     * Creates a root region location tracker.
37     *
38     * <p>After construction, use {@link #start} to kick off tracking.
39     *
40     * @param watcher
41     * @param abortable
42     */
43    public RootRegionTracker(ZooKeeperWatcher watcher, Abortable abortable) {
44      super(watcher, watcher.rootServerZNode, abortable);
45    }
46  
47    /**
48     * Checks if the root region location is available.
49     * @return true if root region location is available, false if not
50     */
51    public boolean isLocationAvailable() {
52      return super.getData() != null;
53    }
54  
55    /**
56     * Gets the root region location, if available.  Null if not.  Does not block.
57     * @return server address for server hosting root region, null if none available
58     * @throws InterruptedException 
59     */
60    public HServerAddress getRootRegionLocation() throws InterruptedException {
61      return dataToHServerAddress(super.getData());
62    }
63  
64    /**
65     * Gets the root region location, if available, and waits for up to the
66     * specified timeout if not immediately available.
67     * @param timeout maximum time to wait, in millis
68     * @return server address for server hosting root region, null if timed out
69     * @throws InterruptedException if interrupted while waiting
70     */
71    public HServerAddress waitRootRegionLocation(long timeout)
72    throws InterruptedException {
73      return dataToHServerAddress(super.blockUntilAvailable(timeout));
74    }
75  
76    /*
77     * @param data
78     * @return Returns null if <code>data</code> is null else converts passed data
79     * to an HServerAddress instance.
80     */
81    private static HServerAddress dataToHServerAddress(final byte [] data) {
82      return data == null ? null: new HServerAddress(Bytes.toString(data));
83    }
84  }