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/**
* Copyright 2010 The Apache Software Foundation
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hbase;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.zookeeper.ZooKeeperNodeTracker;
import org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher;
/**
* Manages the location of the current active Master for this RegionServer.
*
* Listens for ZooKeeper events related to the master address. The node
* /master will contain the address of the current master.
* This listener is interested in
* NodeDeleted and NodeCreated events on
* /master.
*
* Utilizes {@link ZooKeeperNodeTracker} for zk interactions.
*
* You can get the current master via {@link #getMasterAddress()}
*/
public class MasterAddressTracker extends ZooKeeperNodeTracker {
/**
* Construct a master address listener with the specified
* zookeeper reference.
*
* This constructor does not trigger any actions, you must call methods
* explicitly. Normally you will just want to execute {@link #start()} to
* begin tracking of the master address.
*
* @param watcher zk reference and watcher
* @param abortable abortable in case of fatal error
*/
public MasterAddressTracker(ZooKeeperWatcher watcher, Abortable abortable) {
super(watcher, watcher.masterAddressZNode, abortable);
}
/**
* Get the address of the current master if one is available. Returns null
* if no current master.
* @return Server name or null if timed out.
*/
public ServerName getMasterAddress() {
return bytesToServerName(super.getData(false));
}
/**
* Check if there is a master available.
* @return true if there is a master set, false if not.
*/
public boolean hasMaster() {
return super.getData(false) != null;
}
/**
* @param bytes Byte array of {@link ServerName#toString()}
* @return A {@link ServerName} instance.
*/
private ServerName bytesToServerName(final byte [] bytes) {
return bytes == null ? null: ServerName.parseVersionedServerName(bytes);
}
}