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 java.util.Collection;
021import org.apache.yetus.audience.InterfaceAudience;
022
023/**
024 * Base class the allows writing costs functions from rolling average of some number from
025 * RegionLoad.
026 */
027@InterfaceAudience.Private
028abstract class CostFromRegionLoadFunction extends CostFunction {
029
030  private final DoubleArrayCost cost = new DoubleArrayCost();
031
032  private double computeCostForRegionServer(int regionServerIndex) {
033    // Cost this server has from RegionLoad
034    double cost = 0;
035
036    // for every region on this server get the rl
037    for (int regionIndex : cluster.regionsPerServer[regionServerIndex]) {
038      Collection<BalancerRegionLoad> regionLoadList = cluster.regionLoads[regionIndex];
039
040      // Now if we found a region load get the type of cost that was requested.
041      if (regionLoadList != null) {
042        cost += getRegionLoadCost(regionLoadList);
043      }
044    }
045    return cost;
046  }
047
048  @Override
049  void prepare(BalancerClusterState cluster) {
050    super.prepare(cluster);
051    cost.prepare(cluster.numServers);
052    cost.applyCostsChange(costs -> {
053      for (int i = 0; i < costs.length; i++) {
054        costs[i] = computeCostForRegionServer(i);
055      }
056    });
057  }
058
059  @Override
060  protected void regionMoved(int region, int oldServer, int newServer) {
061    // recompute the stat for the given two region servers
062    cost.applyCostsChange(costs -> {
063      costs[oldServer] = computeCostForRegionServer(oldServer);
064      costs[newServer] = computeCostForRegionServer(newServer);
065    });
066  }
067
068  @Override
069  protected final double cost() {
070    return cost.cost();
071  }
072
073  protected double getRegionLoadCost(Collection<BalancerRegionLoad> regionLoadList) {
074    double cost = 0;
075    for (BalancerRegionLoad rl : regionLoadList) {
076      cost += getCostFromRl(rl);
077    }
078    return cost / regionLoadList.size();
079  }
080
081  protected abstract double getCostFromRl(BalancerRegionLoad rl);
082}