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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.commons.logging.Log;
23  import org.apache.commons.logging.LogFactory;
24  import org.apache.hadoop.hbase.Abortable;
25  import org.apache.hadoop.hbase.ClusterStatus;
26  import org.apache.hadoop.hbase.util.Bytes;
27  import org.apache.zookeeper.KeeperException;
28  
29  /**
30   * Tracker on cluster settings up in zookeeper.
31   * This is not related to {@link ClusterStatus}.  That class is a data structure
32   * that holds snapshot of current view on cluster.  This class is about tracking
33   * cluster attributes up in zookeeper.
34   *
35   */
36  public class ClusterStatusTracker extends ZooKeeperNodeTracker {
37    private static final Log LOG = LogFactory.getLog(ClusterStatusTracker.class);
38  
39    /**
40     * Creates a cluster status tracker.
41     *
42     * <p>After construction, use {@link #start} to kick off tracking.
43     *
44     * @param watcher
45     * @param abortable
46     */
47    public ClusterStatusTracker(ZooKeeperWatcher watcher, Abortable abortable) {
48      super(watcher, watcher.clusterStateZNode, abortable);
49    }
50  
51    /**
52     * Checks if cluster is up.
53     * @return true if root region location is available, false if not
54     */
55    public boolean isClusterUp() {
56      return super.getData(false) != null;
57    }
58  
59    /**
60     * Sets the cluster as up.
61     * @throws KeeperException unexpected zk exception
62     */
63    public void setClusterUp()
64    throws KeeperException {
65      byte [] upData = Bytes.toBytes(new java.util.Date().toString());
66      try {
67        ZKUtil.createAndWatch(watcher, watcher.clusterStateZNode, upData);
68      } catch(KeeperException.NodeExistsException nee) {
69        ZKUtil.setData(watcher, watcher.clusterStateZNode, upData);
70      }
71    }
72  
73    /**
74     * Sets the cluster as down by deleting the znode.
75     * @throws KeeperException unexpected zk exception
76     */
77    public void setClusterDown()
78    throws KeeperException {
79      try {
80        ZKUtil.deleteNode(watcher, watcher.clusterStateZNode);
81      } catch(KeeperException.NoNodeException nne) {
82        LOG.warn("Attempted to set cluster as down but already down, cluster " +
83            "state node (" + watcher.clusterStateZNode + ") not found");
84      }
85    }
86  }