/*

  * 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.comm.aggregators;

 import java.io.IOException;

 import java.util.Map;

 import org.apache.giraph.comm.GlobalCommType;

 import org.apache.hadoop.io.LongWritable;

 import org.apache.hadoop.io.Writable;

 import com.google.common.collect.Maps;

 /**

  * Takes and serializes global communication values and keeps them grouped by

  * owner partition id, to be sent in bulk.

  * Includes broadcast messages, reducer registrations and special count.

  */

 public class SendGlobalCommCache extends CountingCache {

   /** Map from worker partition id to global communication output stream */

   private final Map<Integer, GlobalCommValueOutputStream> globalCommMap =

       Maps.newHashMap();

   /** whether to write Class object for values into the stream */

   private final boolean writeClass;

   /**

    * Constructor

    *

    * @param writeClass boolean whether to write Class object for values

    */

   public SendGlobalCommCache(boolean writeClass) {

     this.writeClass = writeClass;

   }

   /**

    * Add global communication value to the cache

    *

    * @param taskId Task id of worker which owns the value

    * @param name Name

    * @param type Global communication type

    * @param value Value

    * @return Number of bytes in serialized data for this worker

    * @throws IOException

    */

   public int addValue(Integer taskId, String name,

       GlobalCommType type, Writable value) throws IOException {

     GlobalCommValueOutputStream out = globalCommMap.get(taskId);

     if (out == null) {

       out = new GlobalCommValueOutputStream(writeClass);

       globalCommMap.put(taskId, out);

     }

     return out.addValue(name, type, value);

   }

   /**

    * Remove and get values for certain worker

    *

    * @param taskId Partition id of worker owner

    * @return Serialized global communication data for this worker

    */

   public byte[] removeSerialized(Integer taskId) {

     incrementCounter(taskId);

     GlobalCommValueOutputStream out = globalCommMap.remove(taskId);

     if (out == null) {

       return new byte[4];

     } else {

       return out.flush();

     }

   }

   /**

    * Creates special value which will hold the total number of global

    * communication requests for worker with selected task id. This should be

    * called after all values for the worker have been added to the cache.

    *

    * @param taskId Destination worker's task id

    * @throws IOException

    */

   public void addSpecialCount(Integer taskId) throws IOException {

     // current number of requests, plus one for the last flush

     long totalCount = getCount(taskId) + 1;

     addValue(taskId, GlobalCommType.SPECIAL_COUNT.name(),

         GlobalCommType.SPECIAL_COUNT, new LongWritable(totalCount));

   }

 }