/*

  * 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.giraph.job;

 import org.apache.giraph.conf.GiraphConfiguration;

 import org.apache.giraph.conf.GiraphConstants;

 import org.apache.giraph.utils.CounterUtils;

 import org.apache.hadoop.mapreduce.Job;

 import org.apache.log4j.Logger;

 /**

  * Utility methods for halting application while running

  */

 public class HaltApplicationUtils {

   /** Do not instantiate */

   private HaltApplicationUtils() { }

   /**

    * Wait for halt info to become available and print instructions on how to

    * halt

    *

    * @param submittedJob Submitted job

    * @param conf         Configuration

    */

   public static void printHaltInfo(Job submittedJob,

       GiraphConfiguration conf) {

     String zkServer = CounterUtils.waitAndGetCounterNameFromGroup(

         submittedJob, GiraphConstants.ZOOKEEPER_SERVER_PORT_COUNTER_GROUP);

     String haltNode = CounterUtils.waitAndGetCounterNameFromGroup(

         submittedJob, GiraphConstants.ZOOKEEPER_HALT_NODE_COUNTER_GROUP);

     if (zkServer != null && haltNode != null) {

       GiraphConstants.HALT_INSTRUCTIONS_WRITER_CLASS.newInstance(

           conf).writeHaltInstructions(zkServer, haltNode);

     }

   }

   /**

    * Writer of instructions about how to halt

    */

   public interface HaltInstructionsWriter {

     /**

      * Write instructions about how to halt

      *

      * @param zkServer ZooKeeper server

      * @param haltNode ZooKeeper node which should be created in order to halt

      */

     void writeHaltInstructions(String zkServer, String haltNode);

   }

   /**

    * Default implementation of {@link HaltInstructionsWriter} - points to how

    * to use {@link org.apache.giraph.zk.ZooKeeperNodeCreator} to halt

    */

   public static class DefaultHaltInstructionsWriter implements

       HaltInstructionsWriter {

     /** Class logger */

     private static final Logger LOG = Logger.getLogger(

         DefaultHaltInstructionsWriter.class);

     @Override

     public void writeHaltInstructions(String zkServer, String haltNode) {

       if (LOG.isInfoEnabled()) {

         LOG.info("writeHaltInstructions: " +

             "To halt after next superstep execute: " +

             "'bin/halt-application --zkServer " + zkServer +

             " --zkNode " + haltNode + "'");

       }

     }

   }

 }