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 */
019
020package org.apache.hadoop.hbase.zookeeper;
021
022import java.util.UUID;
023
024import org.apache.hadoop.hbase.Abortable;
025import org.apache.hadoop.hbase.ClusterId;
026import org.apache.hadoop.hbase.exceptions.DeserializationException;
027import org.apache.yetus.audience.InterfaceAudience;
028import org.apache.zookeeper.KeeperException;
029
030/**
031 * Publishes and synchronizes a unique identifier specific to a given HBase
032 * cluster.  The stored identifier is read from the file system by the active
033 * master on startup, and is subsequently available to all watchers (including
034 * clients).
035 */
036@InterfaceAudience.Private
037public class ZKClusterId {
038  private final ZKWatcher watcher;
039  private final Abortable abortable;
040  private String id;
041
042  public ZKClusterId(ZKWatcher watcher, Abortable abortable) {
043    this.watcher = watcher;
044    this.abortable = abortable;
045  }
046
047  public boolean hasId() {
048    return getId() != null;
049  }
050
051  public String getId() {
052    try {
053      if (id == null) {
054        id = readClusterIdZNode(watcher);
055      }
056    } catch (KeeperException ke) {
057      abortable.abort("Unexpected exception from ZooKeeper reading cluster ID",
058          ke);
059    }
060    return id;
061  }
062
063  public static String readClusterIdZNode(ZKWatcher watcher)
064  throws KeeperException {
065    if (ZKUtil.checkExists(watcher, watcher.znodePaths.clusterIdZNode) != -1) {
066      byte [] data;
067      try {
068        data = ZKUtil.getData(watcher, watcher.znodePaths.clusterIdZNode);
069      } catch (InterruptedException e) {
070        Thread.currentThread().interrupt();
071        return null;
072      }
073      if (data != null) {
074        try {
075          return ClusterId.parseFrom(data).toString();
076        } catch (DeserializationException e) {
077          throw ZKUtil.convert(e);
078        }
079      }
080    }
081    return null;
082  }
083
084  public static void setClusterId(ZKWatcher watcher, ClusterId id)
085      throws KeeperException {
086    ZKUtil.createSetData(watcher, watcher.znodePaths.clusterIdZNode, id.toByteArray());
087  }
088
089  /**
090   * Get the UUID for the provided ZK watcher. Doesn't handle any ZK exceptions
091   * @param zkw watcher connected to an ensemble
092   * @return the UUID read from zookeeper
093   * @throws KeeperException if a ZooKeeper operation fails
094   */
095  public static UUID getUUIDForCluster(ZKWatcher zkw) throws KeeperException {
096    String uuid = readClusterIdZNode(zkw);
097    return uuid == null ? null : UUID.fromString(uuid);
098  }
099}