001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.zookeeper;
019
020import java.io.IOException;
021
022import org.apache.hadoop.hbase.Abortable;
023import org.apache.hadoop.hbase.exceptions.DeserializationException;
024import org.apache.hadoop.hbase.util.Bytes;
025import org.apache.yetus.audience.InterfaceAudience;
026import org.apache.zookeeper.KeeperException;
027import org.slf4j.Logger;
028import org.slf4j.LoggerFactory;
029
030import org.apache.hadoop.hbase.shaded.protobuf.ProtobufUtil;
031import org.apache.hadoop.hbase.shaded.protobuf.generated.LoadBalancerProtos;
032
033/**
034 * Tracks the load balancer state up in ZK
035 */
036@InterfaceAudience.Private
037public class LoadBalancerTracker extends ZKNodeTracker {
038  private static final Logger LOG = LoggerFactory.getLogger(LoadBalancerTracker.class);
039
040  public LoadBalancerTracker(ZKWatcher watcher,
041      Abortable abortable) {
042    super(watcher, watcher.getZNodePaths().balancerZNode, abortable);
043  }
044
045  /**
046   * Return true if the balance switch is on, false otherwise
047   */
048  public boolean isBalancerOn() {
049    byte [] upData = super.getData(false);
050    try {
051      // if data in ZK is null, use default of on.
052      return upData == null || parseFrom(upData).getBalancerOn();
053    } catch (DeserializationException dex) {
054      LOG.error("ZK state for LoadBalancer could not be parsed {}", Bytes.toStringBinary(upData));
055      // return false to be safe.
056      return false;
057    }
058  }
059
060  /**
061   * Set the balancer on/off.
062   *
063   * @param balancerOn true if the balancher should be on, false otherwise
064   * @throws KeeperException if a ZooKeeper operation fails
065   */
066  public void setBalancerOn(boolean balancerOn) throws KeeperException {
067    byte [] upData = toByteArray(balancerOn);
068
069    try {
070      ZKUtil.setData(watcher, watcher.getZNodePaths().balancerZNode, upData);
071    } catch(KeeperException.NoNodeException nne) {
072      ZKUtil.createAndWatch(watcher, watcher.getZNodePaths().balancerZNode, upData);
073    }
074    super.nodeDataChanged(watcher.getZNodePaths().balancerZNode);
075  }
076
077  private byte [] toByteArray(boolean isBalancerOn) {
078    LoadBalancerProtos.LoadBalancerState.Builder builder =
079      LoadBalancerProtos.LoadBalancerState.newBuilder();
080    builder.setBalancerOn(isBalancerOn);
081    return ProtobufUtil.prependPBMagic(builder.build().toByteArray());
082  }
083
084  private LoadBalancerProtos.LoadBalancerState parseFrom(byte [] pbBytes)
085    throws DeserializationException {
086    ProtobufUtil.expectPBMagicPrefix(pbBytes);
087    LoadBalancerProtos.LoadBalancerState.Builder builder =
088      LoadBalancerProtos.LoadBalancerState.newBuilder();
089    try {
090      int magicLen = ProtobufUtil.lengthOfPBMagic();
091      ProtobufUtil.mergeFrom(builder, pbBytes, magicLen, pbBytes.length - magicLen);
092    } catch (IOException e) {
093      throw new DeserializationException(e);
094    }
095    return builder.build();
096  }
097}