ExtractWikipediaLinkGraph.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.collection.wikipedia.graph;

import java.io.IOException;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import org.apache.commons.cli.CommandLine;
import org.apache.commons.cli.CommandLineParser;
import org.apache.commons.cli.GnuParser;
import org.apache.commons.cli.HelpFormatter;
import org.apache.commons.cli.OptionBuilder;
import org.apache.commons.cli.Options;
import org.apache.commons.cli.ParseException;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
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.Partitioner;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.SequenceFileInputFormat;
import org.apache.hadoop.mapred.TextInputFormat;
import org.apache.hadoop.mapred.TextOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
import org.apache.log4j.Logger;

import tl.lin.data.pair.PairOfStringInt;
import edu.umd.cloud9.collection.wikipedia.WikipediaPage;

/**
 * Tool for extracting the link graph out of Wikipedia.
 * 
 * @author Jimmy Lin
 */
public class ExtractWikipediaLinkGraph extends Configured implements Tool {
  private static final Logger LOG = Logger.getLogger(ExtractWikipediaLinkGraph.class);

  private static enum PageTypes { TOTAL, REDIRECT, DISAMBIGUATION, EMPTY, ARTICLE, STUB, NON_ARTICLE };

  private static enum GraphInfo { TOTAL_VERTICES, VERTICES_WITH_OUTLINKS, EDGES };

  private static class MyMapper1 extends MapReduceBase implements
      Mapper<IntWritable, WikipediaPage, PairOfStringInt, Text> {
    private static Text text = new Text();
    private static PairOfStringInt pair = new PairOfStringInt();

    public void map(IntWritable key, WikipediaPage p,
        OutputCollector<PairOfStringInt, Text> output, Reporter reporter) throws IOException {
      reporter.incrCounter(PageTypes.TOTAL, 1);

      String title = p.getTitle();

      // This is a caveat and a potential gotcha: Wikipedia article titles
      // are not case sensitive on the initial character, so a link to
      // "commodity" will go to the article titled "Commodity" without any
      // issue. Therefore we need to emit two versions of article titles.
      text.set(p.getDocid());
      pair.set(title, 0);
      output.collect(pair, text);

      String fc = title.substring(0, 1);
      if (fc.matches("[A-Z]")) {
        title = title.replaceFirst(fc, fc.toLowerCase());

        pair.set(title, 0);
        output.collect(pair, text);
      }

      if (p.isRedirect()) {
        reporter.incrCounter(PageTypes.REDIRECT, 1);
      } else if (p.isDisambiguation()) {
        reporter.incrCounter(PageTypes.DISAMBIGUATION, 1);
      } else if (p.isEmpty()) {
        reporter.incrCounter(PageTypes.EMPTY, 1);
      } else if (p.isArticle()) {
        reporter.incrCounter(PageTypes.ARTICLE, 1);

        if (p.isStub()) {
          reporter.incrCounter(PageTypes.STUB, 1);
        }
      } else {
        reporter.incrCounter(PageTypes.NON_ARTICLE, 1);
      }

      for (String t : p.extractLinkTargets()) {
        pair.set(t, 1);
        text.set(p.getDocid());

        output.collect(pair, text);
      }
    }
  }

  private static class MyReducer1 extends MapReduceBase implements
      Reducer<PairOfStringInt, Text, IntWritable, IntWritable> {

    private static final IntWritable finalSrc = new IntWritable();
    private static final IntWritable finalDest = new IntWritable();

    private static String curArticle;
    private static int curDocid;

    public void reduce(PairOfStringInt key, Iterator<Text> values,
        OutputCollector<IntWritable, IntWritable> output, Reporter reporter) throws IOException {

      if (key.getRightElement() == 0) {
        // We want to emit a placeholder in case this is a dangling node.
        curArticle = key.getLeftElement();
        curDocid = Integer.parseInt(values.next().toString());

        finalSrc.set(curDocid);
        finalDest.set(curDocid);
        output.collect(finalSrc, finalDest);
      } else {
        if (!key.getLeftElement().equals(curArticle)) {
          return;
        }

        while (values.hasNext()) {
          finalSrc.set(Integer.parseInt(values.next().toString()));
          finalDest.set(curDocid);
          output.collect(finalSrc, finalDest);
        }
      }
    }
  }

  private static class MyPartitioner1 implements Partitioner<PairOfStringInt, Text> {
    public void configure(JobConf job) {
    }

    public int getPartition(PairOfStringInt key, Text value, int numReduceTasks) {
      return (key.getLeftElement().hashCode() & Integer.MAX_VALUE) % numReduceTasks;
    }
  }

  private static class MyMapper2 extends MapReduceBase implements
      Mapper<LongWritable, Text, IntWritable, IntWritable> {

    private static IntWritable keyOut = new IntWritable();
    private static IntWritable valOut = new IntWritable();

    public void map(LongWritable key, Text t, OutputCollector<IntWritable, IntWritable> output,
        Reporter reporter) throws IOException {

      String[] arr = t.toString().split("\\s+");

      keyOut.set(Integer.parseInt(arr[0]));
      valOut.set(Integer.parseInt(arr[1]));

      output.collect(keyOut, valOut);
    }
  }

  private static class MyReducer2 extends MapReduceBase implements
      Reducer<IntWritable, IntWritable, IntWritable, Text> {

    private final static Text text = new Text();

    public void reduce(IntWritable key, Iterator<IntWritable> values,
        OutputCollector<IntWritable, Text> output, Reporter reporter) throws IOException {

      StringBuilder sb = new StringBuilder();
      Set<Integer> set = new HashSet<Integer>();

      reporter.incrCounter(GraphInfo.TOTAL_VERTICES, 1);
      IntWritable cur;
      while (values.hasNext()) {
        cur = values.next();

        // Remove the self-links we added from the previous MapReduce job.
        if (cur.get() == key.get()) {
          continue;
        }
        if (set.contains(cur.get())) {
          continue;
        } // Keep only one link to target.

        set.add(cur.get());
        reporter.incrCounter(GraphInfo.EDGES, 1);

        sb.append(cur.get());
        sb.append("\t");
      }

      if (set.size() != 0) {
        reporter.incrCounter(GraphInfo.VERTICES_WITH_OUTLINKS, 1);
      }

      text.set(sb.toString());
      output.collect(key, text);
    }
  }

  private static final String INPUT_OPTION = "input";
  private static final String EDGES_OUTPUT_OPTION = "edges_output";
  private static final String ADJ_OUTPUT_OPTION = "adjacency_list_output";
  private static final String NUM_PARTITIONS_OPTION = "num_partitions";

  @SuppressWarnings("static-access")
  @Override
  public int run(String[] args) throws Exception {
    Options options = new Options();
    options.addOption(OptionBuilder.withArgName("path").hasArg()
        .withDescription("input").create(INPUT_OPTION));
    options.addOption(OptionBuilder.withArgName("path").hasArg()
        .withDescription("output for edges").create(EDGES_OUTPUT_OPTION));
    options.addOption(OptionBuilder.withArgName("path").hasArg()
        .withDescription("output for adjacency list").create(ADJ_OUTPUT_OPTION));
    options.addOption(OptionBuilder.withArgName("num").hasArg()
        .withDescription("number of partitions").create(NUM_PARTITIONS_OPTION));

    CommandLine cmdline;
    CommandLineParser parser = new GnuParser();
    try {
      cmdline = parser.parse(options, args);
    } catch (ParseException exp) {
      System.err.println("Error parsing command line: " + exp.getMessage());
      return -1;
    }

    if (!cmdline.hasOption(INPUT_OPTION) || !cmdline.hasOption(EDGES_OUTPUT_OPTION)
        || !cmdline.hasOption(ADJ_OUTPUT_OPTION) || !cmdline.hasOption(NUM_PARTITIONS_OPTION)) {
      HelpFormatter formatter = new HelpFormatter();
      formatter.printHelp(this.getClass().getName(), options);
      ToolRunner.printGenericCommandUsage(System.out);
      return -1;
    }

    int numPartitions = Integer.parseInt(cmdline.getOptionValue(NUM_PARTITIONS_OPTION));

    task1(cmdline.getOptionValue(INPUT_OPTION), cmdline.getOptionValue(EDGES_OUTPUT_OPTION), numPartitions);
    task2(cmdline.getOptionValue(EDGES_OUTPUT_OPTION), cmdline.getOptionValue(ADJ_OUTPUT_OPTION), numPartitions);

    return 0;
  }

  private void task1(String inputPath, String outputPath, int partitions) throws IOException {
    LOG.info("Exracting edges...");
    LOG.info(" - input: " + inputPath);
    LOG.info(" - output: " + outputPath);

    JobConf conf = new JobConf(getConf(), ExtractWikipediaLinkGraph.class);
    conf.setJobName(String.format(
        "ExtractWikipediaLinkGraph:Edges[input: %s, output: %s, num_partitions: %d]", inputPath,
        outputPath, partitions));

    conf.setNumReduceTasks(partitions);

    SequenceFileInputFormat.addInputPath(conf, new Path(inputPath));
    TextOutputFormat.setOutputPath(conf, new Path(outputPath));

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

    conf.setMapOutputKeyClass(PairOfStringInt.class);
    conf.setMapOutputValueClass(Text.class);

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

    conf.setMapperClass(MyMapper1.class);
    conf.setReducerClass(MyReducer1.class);
    conf.setPartitionerClass(MyPartitioner1.class);

    // Delete the output directory if it exists already.
    FileSystem.get(conf).delete(new Path(outputPath), true);

    JobClient.runJob(conf);
  }

  private void task2(String inputPath, String outputPath, int partitions) throws IOException {
    LOG.info("Building adjacency lists...");
    LOG.info(" - input: " + inputPath);
    LOG.info(" - output: " + outputPath);

    JobConf conf = new JobConf(getConf(), ExtractWikipediaLinkGraph.class);
    conf.setJobName(String.format(
        "ExtractWikipediaLinkGraph:AdjacencyList[input: %s, output: %s, num_partitions: %d]",
        inputPath, outputPath, partitions));

    conf.setNumReduceTasks(partitions);

    TextInputFormat.addInputPath(conf, new Path(inputPath));
    TextOutputFormat.setOutputPath(conf, new Path(outputPath));

    conf.setInputFormat(TextInputFormat.class);
    conf.setOutputFormat(TextOutputFormat.class);

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

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

    conf.setMapperClass(MyMapper2.class);
    conf.setReducerClass(MyReducer2.class);

    // Delete the output directory if it exists already.
    FileSystem.get(conf).delete(new Path(outputPath), true);

    JobClient.runJob(conf);
  }

  public ExtractWikipediaLinkGraph() {
  }

  public static void main(String[] args) throws Exception {
    int res = ToolRunner.run(new ExtractWikipediaLinkGraph(), args);
    System.exit(res);
  }
}