/*

  * 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.examples;

 import java.io.IOException;

 import java.util.Map.Entry;

 import org.apache.giraph.graph.AggregatorWriter;

 import org.apache.hadoop.fs.FSDataOutputStream;

 import org.apache.hadoop.fs.FileSystem;

 import org.apache.hadoop.fs.Path;

 import org.apache.hadoop.io.Writable;

 import org.apache.hadoop.mapreduce.Mapper.Context;

 /**

  * This is a simple example for an aggregator writer. After each superstep

  * the writer will persist the aggregator values to disk, by use of the

  * Writable interface. The file will be created on the current working

  * directory.

  */

 public class SimpleAggregatorWriter implements AggregatorWriter {

   /** Name of the file we wrote to */

   private static String FILENAME;

   /** Saved output stream to write to */

   private FSDataOutputStream output;

   public static String getFilename() {

     return FILENAME;

   }

   @SuppressWarnings("rawtypes")

   @Override

   public void initialize(Context context, long applicationAttempt)

     throws IOException {

     FILENAME = "aggregatedValues_" + applicationAttempt;

     Path p = new Path(FILENAME);

     FileSystem fs = FileSystem.get(context.getConfiguration());

     output = fs.create(p, true);

   }

   @Override

   public void writeAggregator(

       Iterable<Entry<String, Writable>> aggregatorMap,

       long superstep) throws IOException {

     for (Entry<String, Writable> entry : aggregatorMap) {

       entry.getValue().write(output);

     }

     output.flush();

   }

   @Override

   public void close() throws IOException {

     output.close();

   }

 }