/**
    * 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.HashSet;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Set;
  
  import org.apache.commons.lang.math.RandomUtils;
  import org.apache.hadoop.hbase.ClusterStatus;
  import org.apache.hadoop.hbase.ServerName;
  import org.junit.Assert;
  
  /** This action is too specific to put in ChaosMonkey; put it here */
  public class UnbalanceKillAndRebalanceAction extends Action {
    /** Fractions of servers to get regions and live and die respectively; from all other
     * servers, HOARD_FRC_OF_REGIONS will be removed to the above randomly */
    private static final double FRC_SERVERS_THAT_HOARD_AND_LIVE = 0.1;
    private static final double FRC_SERVERS_THAT_HOARD_AND_DIE = 0.1;
    private static final double HOARD_FRC_OF_REGIONS = 0.8;
    /** Waits between calling unbalance and killing servers, kills and rebalance, and rebalance
     * and restarting the servers; to make sure these events have time to impact the cluster. */
    private long waitForUnbalanceMilliSec;
    private long waitForKillsMilliSec;
    private long waitAfterBalanceMilliSec;
    private boolean killMetaRs;
  
    public UnbalanceKillAndRebalanceAction(long waitUnbalance, long waitKill, long waitAfterBalance,
        boolean killMetaRs) {
      super();
      waitForUnbalanceMilliSec = waitUnbalance;
      waitForKillsMilliSec = waitKill;
      waitAfterBalanceMilliSec = waitAfterBalance;
      this.killMetaRs = killMetaRs;
    }
  
    @Override
    public void perform() throws Exception {
      ClusterStatus status = this.cluster.getClusterStatus();
      List<ServerName> victimServers = new LinkedList<ServerName>(status.getServers());
      Set<ServerName> killedServers = new HashSet<ServerName>();
  
      int liveCount = (int)Math.ceil(FRC_SERVERS_THAT_HOARD_AND_LIVE * victimServers.size());
      int deadCount = (int)Math.ceil(FRC_SERVERS_THAT_HOARD_AND_DIE * victimServers.size());
      Assert.assertTrue(
          "There are not enough victim servers: " + victimServers.size(),
          liveCount + deadCount < victimServers.size());
      List<ServerName> targetServers = new ArrayList<ServerName>(liveCount);
      for (int i = 0; i < liveCount + deadCount; ++i) {
        int victimIx = RandomUtils.nextInt(victimServers.size());
        targetServers.add(victimServers.remove(victimIx));
      }
      unbalanceRegions(status, victimServers, targetServers, HOARD_FRC_OF_REGIONS);
      Thread.sleep(waitForUnbalanceMilliSec);
      ServerName metaServer = cluster.getServerHoldingMeta();
      for (ServerName targetServer: targetServers) {
        // Don't keep killing servers if we're
        // trying to stop the monkey.
        if (context.isStopping()) {
          break;
        }
        if (killedServers.size() >= liveCount) {
          break;
        }
  
        if (!killMetaRs && targetServer.equals(metaServer)) {
          LOG.info("Not killing server because it holds hbase:meta.");
        } else {
          killRs(targetServer);
          killedServers.add(targetServer);
        }
      }
  
      Thread.sleep(waitForKillsMilliSec);
      forceBalancer();
      Thread.sleep(waitAfterBalanceMilliSec);
      for (ServerName server:killedServers) {
        startRs(server);
      }
    }
  }