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 configuration based upon how evenly distributed tables
025 * are.
026 */
027@InterfaceAudience.Private
028class TableSkewCostFunction extends CostFunction {
029
030  private static final String TABLE_SKEW_COST_KEY =
031    "hbase.master.balancer.stochastic.tableSkewCost";
032  private static final float DEFAULT_TABLE_SKEW_COST = 35;
033  DoubleArrayCost[] costsPerTable;
034
035  TableSkewCostFunction(Configuration conf) {
036    this.setMultiplier(conf.getFloat(TABLE_SKEW_COST_KEY, DEFAULT_TABLE_SKEW_COST));
037  }
038
039  @Override
040  void prepare(BalancerClusterState cluster) {
041    super.prepare(cluster);
042    costsPerTable = new DoubleArrayCost[cluster.numTables];
043    for (int tableIdx = 0; tableIdx < cluster.numTables; tableIdx++) {
044      costsPerTable[tableIdx] = new DoubleArrayCost();
045      costsPerTable[tableIdx].prepare(cluster.numServers);
046      final int tableIndex = tableIdx;
047      costsPerTable[tableIdx].applyCostsChange(costs -> {
048        // Keep a cached deep copy for change-only recomputation
049        for (int i = 0; i < cluster.numServers; i++) {
050          costs[i] = cluster.numRegionsPerServerPerTable[tableIndex][i];
051        }
052      });
053    }
054  }
055
056  @Override
057  protected void regionMoved(int region, int oldServer, int newServer) {
058    int tableIdx = cluster.regionIndexToTableIndex[region];
059    costsPerTable[tableIdx].applyCostsChange(costs -> {
060      costs[oldServer] = cluster.numRegionsPerServerPerTable[tableIdx][oldServer];
061      costs[newServer] = cluster.numRegionsPerServerPerTable[tableIdx][newServer];
062    });
063  }
064
065  @Override
066  protected double cost() {
067    double cost = 0;
068    for (int tableIdx = 0; tableIdx < cluster.numTables; tableIdx++) {
069      cost += costsPerTable[tableIdx].cost();
070    }
071    return cost;
072  }
073}