/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
    *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.apache.hadoop.hbase.chaos.actions;
  
  import java.util.ArrayList;
  import java.util.LinkedList;
  import java.util.List;
  
  import org.apache.commons.lang.math.RandomUtils;
  import org.apache.hadoop.hbase.ClusterStatus;
  import org.apache.hadoop.hbase.ServerName;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
  * Action that tries to unbalance the regions of a cluster.
  */
  public class UnbalanceRegionsAction extends Action {
    private static final Logger LOG =
        LoggerFactory.getLogger(UnbalanceRegionsAction.class);
    private double fractionOfRegions;
    private double fractionOfServers;
  
    /**
     * Unbalances the regions on the cluster by choosing "target" servers, and moving
     * some regions from each of the non-target servers to random target servers.
     * @param fractionOfRegions Fraction of regions to move from each server.
     * @param fractionOfServers Fraction of servers to be chosen as targets.
     */
    public UnbalanceRegionsAction(double fractionOfRegions, double fractionOfServers) {
      this.fractionOfRegions = fractionOfRegions;
      this.fractionOfServers = fractionOfServers;
    }
  
    @Override protected Logger getLogger() {
      return LOG;
    }
  
    @Override
    public void perform() throws Exception {
      getLogger().info("Unbalancing regions");
      ClusterStatus status = this.cluster.getClusterStatus();
      List<ServerName> victimServers = new LinkedList<ServerName>(status.getServers());
      int targetServerCount = (int)Math.ceil(fractionOfServers * victimServers.size());
      List<ServerName> targetServers = new ArrayList<ServerName>(targetServerCount);
      for (int i = 0; i < targetServerCount; ++i) {
        int victimIx = RandomUtils.nextInt(victimServers.size());
        targetServers.add(victimServers.remove(victimIx));
      }
      unbalanceRegions(status, victimServers, targetServers, fractionOfRegions);
    }
  }