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 */
018
019package org.apache.hadoop.hbase.master.balancer;
020
021import org.apache.yetus.audience.InterfaceAudience;
022
023@InterfaceAudience.Private
024class LoadCandidateGenerator extends CandidateGenerator {
025
026  @Override
027  BaseLoadBalancer.Cluster.Action generate(BaseLoadBalancer.Cluster cluster) {
028    cluster.sortServersByRegionCount();
029    int thisServer = pickMostLoadedServer(cluster, -1);
030    int otherServer = pickLeastLoadedServer(cluster, thisServer);
031    return pickRandomRegions(cluster, thisServer, otherServer);
032  }
033
034  private int pickLeastLoadedServer(final BaseLoadBalancer.Cluster cluster, int thisServer) {
035    Integer[] servers = cluster.serverIndicesSortedByRegionCount;
036
037    int index = 0;
038    while (servers[index] == null || servers[index] == thisServer) {
039      index++;
040      if (index == servers.length) {
041        return -1;
042      }
043    }
044    return servers[index];
045  }
046
047  private int pickMostLoadedServer(final BaseLoadBalancer.Cluster cluster, int thisServer) {
048    Integer[] servers = cluster.serverIndicesSortedByRegionCount;
049
050    int index = servers.length - 1;
051    while (servers[index] == null || servers[index] == thisServer) {
052      index--;
053      if (index < 0) {
054        return -1;
055      }
056    }
057    return servers[index];
058  }
059
060}