/*
    * 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.io.IOException;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Objects;
  import java.util.Queue;
  
  import org.apache.commons.lang.math.RandomUtils;
  import org.apache.hadoop.hbase.ServerName;
  import org.apache.hadoop.hbase.chaos.monkies.PolicyBasedChaosMonkey;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Restarts a ratio of the regionservers in a rolling fashion. At each step, either kills a
   * server, or starts one, sleeping randomly (0-sleepTime) in between steps.
   * The parameter maxDeadServers limits the maximum number of servers that
   * can be down at the same time during rolling restarts.
   */
  public class RollingBatchRestartRsAction extends BatchRestartRsAction {
    private static final Logger LOG = LoggerFactory.getLogger(RollingBatchRestartRsAction.class);
    protected int maxDeadServers; // number of maximum dead servers at any given time. Defaults to 5
  
    public RollingBatchRestartRsAction(long sleepTime, float ratio) {
      this(sleepTime, ratio, 5);
    }
  
    public RollingBatchRestartRsAction(long sleepTime, float ratio, int maxDeadServers) {
      super(sleepTime, ratio);
      this.maxDeadServers = maxDeadServers;
    }
  
    enum KillOrStart {
      KILL,
      START
    }
  
    @Override protected Logger getLogger() {
      return LOG;
    }
  
    @Override
    public void perform() throws Exception {
      getLogger().info(
        String.format("Performing action: Rolling batch restarting %d%% of region servers",
          (int)(ratio * 100)));
      List<ServerName> selectedServers = selectServers();
  
      Queue<ServerName> serversToBeKilled = new LinkedList<ServerName>(selectedServers);
      LinkedList<ServerName> deadServers = new LinkedList<ServerName>();
  
      // loop while there are servers to be killed or dead servers to be restarted
      while ((!serversToBeKilled.isEmpty() || !deadServers.isEmpty())  && !context.isStopping()) {
        KillOrStart action = KillOrStart.KILL;
  
        if (serversToBeKilled.isEmpty()) { // no more servers to kill
          action = KillOrStart.START;
        } else if (deadServers.isEmpty()) {
          action = KillOrStart.KILL; // no more servers to start
        } else if (deadServers.size() >= maxDeadServers) {
          // we have too many dead servers. Don't kill any more
          action = KillOrStart.START;
        } else {
          // do a coin toss
          action = RandomUtils.nextBoolean() ? KillOrStart.KILL : KillOrStart.START;
        }
  
        ServerName server;
  
        switch (action) {
          case KILL:
            server = serversToBeKilled.remove();
            try {
              killRs(server);
            } catch (org.apache.hadoop.util.Shell.ExitCodeException e) {
              // We've seen this in test runs where we timeout but the kill went through. HBASE-9743
              // So, add to deadServers even if exception so the start gets called.
              getLogger().info("Problem killing but presume successful; code=" + e.getExitCode(), e);
           }
           deadServers.add(server);
           break;
         case START:
           server = Objects.requireNonNull(deadServers.peek());
           try {
             startRs(server);
             // only remove the server from the known dead list if `startRs` succeeds.
             deadServers.remove(server);
           } catch (org.apache.hadoop.util.Shell.ExitCodeException e) {
             // The start may fail but better to just keep going though we may lose server.
             // Shuffle the dead list to avoid getting stuck on a single stubborn host.
             Collections.shuffle(deadServers);
             getLogger().info(String.format(
               "Problem starting %s, will retry; code=%s", server, e.getExitCode(), e));
           }
           break;
       }
 
       sleep(RandomUtils.nextInt((int)sleepTime));
     }
   }
 
   protected List<ServerName> selectServers() throws IOException {
     return PolicyBasedChaosMonkey.selectRandomItems(getCurrentServers(), ratio);
   }
 
   /**
    * Small test to ensure the class basically works.
    * @param args
    * @throws Exception
    */
   public static void main(final String[] args) throws Exception {
     RollingBatchRestartRsAction action = new RollingBatchRestartRsAction(1, 1.0f) {
       private int invocations = 0;
       @Override
       protected ServerName[] getCurrentServers() throws IOException {
         final int count = 4;
         List<ServerName> serverNames = new ArrayList<ServerName>(count);
         for (int i = 0; i < 4; i++) {
           serverNames.add(ServerName.valueOf(i + ".example.org", i, i));
         }
         return serverNames.toArray(new ServerName[serverNames.size()]);
       }
 
       @Override
       protected void killRs(ServerName server) throws IOException {
         getLogger().info("Killed " + server);
         if (this.invocations++ % 3 == 0) {
           throw new org.apache.hadoop.util.Shell.ExitCodeException(-1, "Failed");
         }
       }
 
       @Override
       protected void startRs(ServerName server) throws IOException {
         getLogger().info("Started " + server);
         if (this.invocations++ % 3 == 0) {
           throw new org.apache.hadoop.util.Shell.ExitCodeException(-1, "Failed");
         }
       }
     };
 
     action.perform();
   }
 }