001/*
002 *
003 * Licensed to the Apache Software Foundation (ASF) under one
004 * or more contributor license agreements.  See the NOTICE file
005 * distributed with this work for additional information
006 * regarding copyright ownership.  The ASF licenses this file
007 * to you under the Apache License, Version 2.0 (the
008 * "License"); you may not use this file except in compliance
009 * with the License.  You may obtain a copy of the License at
010 *
011 *     http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing, software
014 * distributed under the License is distributed on an "AS IS" BASIS,
015 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
016 * See the License for the specific language governing permissions and
017 * limitations under the License.
018 */
019package org.apache.hadoop.hbase.zookeeper;
020
021import org.apache.hadoop.hbase.Abortable;
022import org.apache.yetus.audience.InterfaceAudience;
023import org.apache.zookeeper.KeeperException;
024import org.slf4j.Logger;
025import org.slf4j.LoggerFactory;
026
027import org.apache.hadoop.hbase.shaded.protobuf.ProtobufUtil;
028import org.apache.hadoop.hbase.shaded.protobuf.generated.ZooKeeperProtos;
029
030/**
031 * Tracker on cluster settings up in zookeeper.
032 * This is not related to {@link org.apache.hadoop.hbase.ClusterStatus}. That class
033 * is a data structure that holds snapshot of current view on cluster. This class
034 * is about tracking cluster attributes up in zookeeper.
035 *
036 */
037@InterfaceAudience.Private
038public class ClusterStatusTracker extends ZKNodeTracker {
039  private static final Logger LOG = LoggerFactory.getLogger(ClusterStatusTracker.class);
040
041  /**
042   * Creates a cluster status tracker.
043   *
044   * <p>After construction, use {@link #start} to kick off tracking.
045   *
046   * @param watcher reference to the {@link ZKWatcher} which also contains configuration and
047   *                constants
048   * @param abortable used to abort if a fatal error occurs
049   */
050  public ClusterStatusTracker(ZKWatcher watcher, Abortable abortable) {
051    super(watcher, watcher.getZNodePaths().clusterStateZNode, abortable);
052  }
053
054  /**
055   * Checks if cluster is up.
056   * @return true if the cluster up ('shutdown' is its name up in zk) znode
057   *         exists with data, false if not
058   */
059  public boolean isClusterUp() {
060    return super.getData(false) != null;
061  }
062
063  /**
064   * Sets the cluster as up.
065   * @throws KeeperException unexpected zk exception
066   */
067  public void setClusterUp()
068    throws KeeperException {
069    byte [] upData = toByteArray();
070    try {
071      ZKUtil.createAndWatch(watcher, watcher.getZNodePaths().clusterStateZNode, upData);
072    } catch(KeeperException.NodeExistsException nee) {
073      ZKUtil.setData(watcher, watcher.getZNodePaths().clusterStateZNode, upData);
074    }
075  }
076
077  /**
078   * Sets the cluster as down by deleting the znode.
079   * @throws KeeperException unexpected zk exception
080   */
081  public void setClusterDown()
082    throws KeeperException {
083    try {
084      ZKUtil.deleteNode(watcher, watcher.getZNodePaths().clusterStateZNode);
085    } catch(KeeperException.NoNodeException nne) {
086      LOG.warn("Attempted to set cluster as down but already down, cluster " +
087          "state node (" + watcher.getZNodePaths().clusterStateZNode + ") not found");
088    }
089  }
090
091  /**
092   * @return Content of the clusterup znode as a serialized pb with the pb
093   *         magic as prefix.
094   */
095  static byte [] toByteArray() {
096    ZooKeeperProtos.ClusterUp.Builder builder =
097      ZooKeeperProtos.ClusterUp.newBuilder();
098    builder.setStartDate(new java.util.Date().toString());
099    return ProtobufUtil.prependPBMagic(builder.build().toByteArray());
100  }
101}