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
029  static final String REGION_COUNT_SKEW_COST_KEY =
030    "hbase.master.balancer.stochastic.regionCountCost";
031  static final float DEFAULT_REGION_COUNT_SKEW_COST = 500;
032
033  private final DoubleArrayCost cost = new DoubleArrayCost();
034
035  RegionCountSkewCostFunction(Configuration conf) {
036    // Load multiplier should be the greatest as it is the most general way to balance data.
037    this.setMultiplier(conf.getFloat(REGION_COUNT_SKEW_COST_KEY, DEFAULT_REGION_COUNT_SKEW_COST));
038  }
039
040  @Override
041  void prepare(BalancerClusterState cluster) {
042    super.prepare(cluster);
043    cost.prepare(cluster.numServers);
044    cost.applyCostsChange(costs -> {
045      for (int i = 0; i < cluster.numServers; i++) {
046        costs[i] = cluster.regionsPerServer[i].length;
047      }
048    });
049  }
050
051  @Override
052  protected double cost() {
053    return cost.cost();
054  }
055
056  @Override
057  protected void regionMoved(int region, int oldServer, int newServer) {
058    cost.applyCostsChange(costs -> {
059      costs[oldServer] = cluster.regionsPerServer[oldServer].length;
060      costs[newServer] = cluster.regionsPerServer[newServer].length;
061    });
062  }
063
064  @Override
065  public final void updateWeight(double[] weights) {
066    weights[StochasticLoadBalancer.GeneratorType.LOAD.ordinal()] += cost();
067  }
068}