BuildWebGraph.java

/*
 * Cloud9: A MapReduce Library for Hadoop
 *
 * Licensed 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 edu.umd.cloud9.webgraph;


import java.io.IOException;
import java.util.Collections;
import java.util.Iterator;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.SequenceFileInputFormat;
import org.apache.hadoop.mapred.SequenceFileOutputFormat;
import org.apache.log4j.Logger;

import tl.lin.data.array.ArrayListWritable;
import edu.umd.cloud9.util.PowerTool;
import edu.umd.cloud9.webgraph.data.AnchorText;
import edu.umd.cloud9.webgraph.data.AnchorTextConstants;

/**
 *
 * @author Nima Asadi
 *
 */
public class BuildWebGraph extends PowerTool {
  private static final Logger LOG = Logger.getLogger(BuildWebGraph.class);

  public static class Map extends MapReduceBase implements
    Mapper<IntWritable, ArrayListWritable<AnchorText>,
    IntWritable, ArrayListWritable<AnchorText>> {

    private static final ArrayListWritable<AnchorText>
      arrayList = new ArrayListWritable<AnchorText>();
    private static final IntWritable keyWord = new IntWritable();
    private static byte flag;

    public void map(IntWritable key, ArrayListWritable<AnchorText> anchors,
        OutputCollector<IntWritable, ArrayListWritable<AnchorText>> output,
        Reporter reporter) throws IOException {
      for(AnchorText data : anchors) {
        if(data.isURL()) {
          arrayList.clear();
          arrayList.add(data.clone());
          output.collect(key, arrayList);
        }

        if(!data.isExternalInLink() && !data.isInternalInLink()) {
          continue;
        }

        //set the flag to "outgoing link"
        flag = data.isExternalInLink() ?
          AnchorTextConstants.Type.EXTERNAL_OUT_LINK.val :
          AnchorTextConstants.Type.INTERNAL_OUT_LINK.val;

        arrayList.clear();
        arrayList.add(new AnchorText(flag,
            AnchorTextConstants.EMPTY_STRING, key.get()));
        for(int source : data) {
          keyWord.set(source);
          output.collect(keyWord, arrayList);
        }
      }
    }
  }

  public static class Reduce extends MapReduceBase implements
      Reducer<IntWritable, ArrayListWritable<AnchorText>,
      IntWritable, ArrayListWritable<AnchorText>> {
    private static final ArrayListWritable<AnchorText> arrayList =
      new ArrayListWritable<AnchorText>();
    private static ArrayListWritable<AnchorText> packet;
    private static boolean pushed;
    private static int outdegree;

    public void reduce(IntWritable key,
        Iterator<ArrayListWritable<AnchorText>> values,
        OutputCollector<IntWritable,
        ArrayListWritable<AnchorText>> output,
        Reporter reporter) throws IOException {
      arrayList.clear();
      outdegree = 0;

      while(values.hasNext()) {
        packet = values.next();

        for(AnchorText data : packet) {
          outdegree += data.getSize();
          pushed = false;

          for(int i = 0; i < arrayList.size(); i++) {
            if(arrayList.get(i).equalsIgnoreSources(data)) {
              arrayList.get(i).addDocumentsFrom(data);
              pushed = true;
              break;
            }
          }
          if(!pushed) {
            arrayList.add(data.clone());
          }
        }
      }

      arrayList.add(new AnchorText(
          AnchorTextConstants.Type.OUT_DEGREE.val, null, outdegree));
      Collections.sort(arrayList);
      output.collect(key, arrayList);
    }
  }

  public static final String[] RequiredParameters = {
    "Cloud9.InputPath",
    "Cloud9.OutputPath",
    "Cloud9.Mappers",
    "Cloud9.Reducers"
  };

  public String[] getRequiredParameters() {
    return RequiredParameters;
  }

  public BuildWebGraph(Configuration conf) {
    super(conf);
  }


  public int runTool() throws Exception {
    JobConf conf = new JobConf(getConf(), BuildWebGraph.class);
    FileSystem fs = FileSystem.get(conf);

    int numMappers = conf.getInt("Cloud9.Mappers", 1);
    int numReducers = conf.getInt("Cloud9.Reducers", 200);

    String inputPath = conf.get("Cloud9.InputPath");
    String outputPath = conf.get("Cloud9.OutputPath");

    conf.setJobName("ConstructWebGraph");
    conf.set("mapred.child.java.opts", "-Xmx2048m");
    conf.setInt("mapred.task.timeout", 60000000);
    conf.set("mapreduce.map.memory.mb", "2048");
    conf.set("mapreduce.map.java.opts", "-Xmx2048m");
    conf.set("mapreduce.reduce.memory.mb", "2048");
    conf.set("mapreduce.reduce.java.opts", "-Xmx2048m");
    conf.set("mapreduce.task.timeout", "60000000");

    conf.setNumMapTasks(numMappers);
    conf.setNumReduceTasks(numReducers);

    conf.setMapperClass(Map.class);
    conf.setReducerClass(Reduce.class);

    conf.setOutputKeyClass(IntWritable.class);
    conf.setOutputValueClass(ArrayListWritable.class);

    conf.setMapOutputKeyClass(IntWritable.class);
    conf.setMapOutputValueClass(ArrayListWritable.class);

    conf.setInputFormat(SequenceFileInputFormat.class);
    conf.setOutputFormat(SequenceFileOutputFormat.class);

    SequenceFileOutputFormat.setCompressOutput(conf, true);
    SequenceFileOutputFormat.setOutputCompressionType(conf, SequenceFile.CompressionType.BLOCK);

    SequenceFileInputFormat.setInputPaths(conf, inputPath);
    FileOutputFormat.setOutputPath(conf, new Path(outputPath));

    LOG.info("BuildWebGraph");
    LOG.info(" - input path: " + inputPath);
    LOG.info(" - output path: " + outputPath);

    if(!fs.exists(new Path(outputPath))) {
      JobClient.runJob(conf);
    } else {
      LOG.info(outputPath + " already exists! Skipping this step...");
    }

    return 0;
  }
}