BuildReverseWebGraph.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.io.Text;
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.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.hadoop.mapred.lib.IdentityMapper;
import org.apache.log4j.Logger;

import tl.lin.data.array.ArrayListOfInts;
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 BuildReverseWebGraph extends PowerTool {
  private static final Logger LOG = Logger.getLogger(BuildReverseWebGraph.class);

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

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

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

        for(AnchorText data : packet) {
          //docno field data
          if(data.isDocnoField()) {
            //in theory, there must be only one "docno" packet.
            //Unless there are duplicate pages.
            for(int docno: data) {
              docnos.add(docno);
            }
            continue;
          }

          pushed = false;
          indegree += data.getSize();

          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.IN_DEGREE.val,
                                   null, indegree));
      arrayList.add(new AnchorText(AnchorTextConstants.Type.URL_FIELD.val,
                                   key.toString()));
      Collections.sort(arrayList);

      //if there was no document number detected,
      //this record would not be emitted.
      for(int docno : docnos) {
        keyWord.set(docno);
        output.collect(keyWord, arrayList);
      }
    }
  }

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

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

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


  public int runTool() throws Exception {
    JobConf conf = new JobConf(getConf(), BuildReverseWebGraph.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("ReverseWebGraph");
    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(IdentityMapper.class);
    conf.setReducerClass(Reduce.class);
    conf.setOutputKeyClass(IntWritable.class);
    conf.setOutputValueClass(ArrayListWritable.class);
    conf.setMapOutputKeyClass(Text.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("BuildReverseWebGraph");
    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;
  }
}