/*
    * 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.LinkedList;
  import java.util.List;
  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.apache.hadoop.hbase.util.Threads;
  import org.apache.hadoop.util.Shell;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Suspend then resume a ratio of the regionservers in a rolling fashion. At each step, either
   * suspend a server, or resume one, sleeping (sleepTime) in between steps. The parameter
   * maxSuspendedServers limits the maximum number of servers that can be down at the same time
   * during rolling restarts.
   */
  public class RollingBatchSuspendResumeRsAction extends Action {
    private static final Logger LOG =
        LoggerFactory.getLogger(RollingBatchSuspendResumeRsAction.class);
    private float ratio;
    private long sleepTime;
    private int maxSuspendedServers; // number of maximum suspended servers at any given time.
  
    public RollingBatchSuspendResumeRsAction(long sleepTime, float ratio) {
      this(sleepTime, ratio, 5);
    }
  
    public RollingBatchSuspendResumeRsAction(long sleepTime, float ratio, int maxSuspendedServers) {
      this.ratio = ratio;
      this.sleepTime = sleepTime;
      this.maxSuspendedServers = maxSuspendedServers;
    }
  
    enum SuspendOrResume {
      SUSPEND, RESUME
    }
  
    @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> serversToBeSuspended = new LinkedList<>(selectedServers);
      Queue<ServerName> suspendedServers = new LinkedList<>();
  
      // loop while there are servers to be suspended or suspended servers to be resumed
      while ((!serversToBeSuspended.isEmpty() || !suspendedServers.isEmpty()) && !context
          .isStopping()) {
        SuspendOrResume action;
  
        if (serversToBeSuspended.isEmpty()) { // no more servers to suspend
          action = SuspendOrResume.RESUME;
        } else if (suspendedServers.isEmpty()) {
          action = SuspendOrResume.SUSPEND; // no more servers to resume
        } else if (suspendedServers.size() >= maxSuspendedServers) {
          // we have too many suspended servers. Don't suspend any more
          action = SuspendOrResume.RESUME;
        } else {
          // do a coin toss
          action = RandomUtils.nextBoolean() ? SuspendOrResume.SUSPEND : SuspendOrResume.RESUME;
        }
  
        ServerName server;
        switch (action) {
          case SUSPEND:
            server = serversToBeSuspended.remove();
            try {
              suspendRs(server);
            } catch (Shell.ExitCodeException e) {
              getLogger().warn("Problem suspending but presume successful; code="
               + e.getExitCode(), e);
           }
           suspendedServers.add(server);
           break;
         case RESUME:
           server = suspendedServers.remove();
           try {
             resumeRs(server);
           } catch (Shell.ExitCodeException e) {
             getLogger().info("Problem resuming, will retry; code= " + e.getExitCode(), e);
           }
           break;
         default:
           throw new IllegalArgumentException(
               "Encountered unexpected action type: " + action.name());
       }
 
       getLogger().info("Sleeping for: " + sleepTime);
       Threads.sleep(sleepTime);
     }
   }
 
   protected List<ServerName> selectServers() throws IOException {
     return PolicyBasedChaosMonkey.selectRandomItems(getCurrentServers(), ratio);
   }
 
 }