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.master.balancer;
019
020import org.apache.hadoop.conf.Configuration;
021import org.apache.yetus.audience.InterfaceAudience;
022
023/**
024 * Compute the cost of a potential cluster state from skew in number of regions on a cluster.
025 */
026@InterfaceAudience.Private
027class RegionCountSkewCostFunction extends CostFunction {
028  static final String REGION_COUNT_SKEW_COST_KEY =
029    "hbase.master.balancer.stochastic.regionCountCost";
030  static final float DEFAULT_REGION_COUNT_SKEW_COST = 500;
031
032  private final DoubleArrayCost cost = new DoubleArrayCost();
033
034  RegionCountSkewCostFunction(Configuration conf) {
035    // Load multiplier should be the greatest as it is the most general way to balance data.
036    this.setMultiplier(conf.getFloat(REGION_COUNT_SKEW_COST_KEY, DEFAULT_REGION_COUNT_SKEW_COST));
037  }
038
039  @Override
040  void prepare(BalancerClusterState cluster) {
041    super.prepare(cluster);
042    cost.prepare(cluster.numServers);
043    cost.applyCostsChange(costs -> {
044      for (int i = 0; i < cluster.numServers; i++) {
045        costs[i] = cluster.regionsPerServer[i].length;
046      }
047    });
048  }
049
050  @Override
051  protected double cost() {
052    return cost.cost();
053  }
054
055  @Override
056  protected void regionMoved(int region, int oldServer, int newServer) {
057    cost.applyCostsChange(costs -> {
058      costs[oldServer] = cluster.regionsPerServer[oldServer].length;
059      costs[newServer] = cluster.regionsPerServer[newServer].length;
060    });
061  }
062
063  @Override
064  public final void updateWeight(double[] weights) {
065    weights[StochasticLoadBalancer.GeneratorType.LOAD.ordinal()] += cost();
066  }
067}