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 }