/*

  * 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.io.superstep_output;

 import org.apache.giraph.conf.ImmutableClassesGiraphConfiguration;

 import org.apache.giraph.graph.Vertex;

 import org.apache.giraph.io.SimpleVertexWriter;

 import org.apache.giraph.io.VertexWriter;

 import org.apache.giraph.io.internal.WrappedVertexOutputFormat;

 import org.apache.hadoop.io.Writable;

 import org.apache.hadoop.io.WritableComparable;

 import org.apache.hadoop.mapreduce.Mapper;

 import java.io.IOException;

 /**

  * Class to use as {@link SuperstepOutput} when chosen VertexOutputFormat is

  * not thread-safe.

  *

  * @param <I> Vertex id

  * @param <V> Vertex value

  * @param <E> Edge value

  */

 public class SynchronizedSuperstepOutput<I extends WritableComparable,

     V extends Writable, E extends Writable> implements

     SuperstepOutput<I, V, E> {

   /** Mapper context */

   private final Mapper<?, ?, ?, ?>.Context context;

   /** Main vertex writer */

   private final VertexWriter<I, V, E> vertexWriter;

   /** Vertex output format */

   private final WrappedVertexOutputFormat<I, V, E> vertexOutputFormat;

   /**

    * Simple vertex writer, wrapper for {@link #vertexWriter}.

    * Call to writeVertex is thread-safe.

    */

   private final SimpleVertexWriter<I, V, E> simpleVertexWriter;

   /**

    * Constructor

    *

    * @param conf Configuration

    * @param context Mapper context

    */

   @SuppressWarnings("unchecked")

   public SynchronizedSuperstepOutput(

       ImmutableClassesGiraphConfiguration<I, V, E> conf,

       Mapper<?, ?, ?, ?>.Context context) {

     this.context = context;

     try {

       vertexOutputFormat = conf.createWrappedVertexOutputFormat();

       vertexOutputFormat.preWriting(context);

       vertexWriter = vertexOutputFormat.createVertexWriter(context);

       vertexWriter.setConf(conf);

       vertexWriter.initialize(context);

     } catch (IOException e) {

       throw new IllegalStateException("SynchronizedSuperstepOutput: " +

           "IOException occurred", e);

     } catch (InterruptedException e) {

       throw new IllegalStateException("SynchronizedSuperstepOutput: " +

           "InterruptedException occurred", e);

     }

     simpleVertexWriter = new SimpleVertexWriter<I, V, E>() {

       @Override

       public synchronized void writeVertex(

           Vertex<I, V, E> vertex) throws IOException, InterruptedException {

         vertexWriter.writeVertex(vertex);

       }

     };

   }

   @Override

   public SimpleVertexWriter<I, V, E> getVertexWriter() {

     return simpleVertexWriter;

   }

   @Override

   public void returnVertexWriter(SimpleVertexWriter<I, V, E> vertexWriter) {

   }

   @Override

   public void postApplication() throws IOException, InterruptedException {

     vertexWriter.close(context);

     vertexOutputFormat.postWriting(context);

   }

 }