LinkDbReader.java

/**
 * 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.nutch.crawl;

import java.io.IOException;

// Commons Logging imports
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.io.*;
import org.apache.hadoop.fs.*;
import org.apache.hadoop.mapred.*;
import org.apache.hadoop.mapred.lib.HashPartitioner;
import org.apache.hadoop.util.*;
import org.apache.hadoop.conf.Configuration;

import org.apache.nutch.util.NutchConfiguration;
import org.apache.nutch.util.NutchJob;

import java.util.Iterator;

/** . */
public class LinkDbReader extends Configured implements Tool, Closeable {
  public static final Log LOG = LogFactory.getLog(LinkDbReader.class);

  private static final Partitioner<WritableComparable, Writable> PARTITIONER = new HashPartitioner<WritableComparable, Writable>();

  private FileSystem fs;
  private Path directory;
  private MapFile.Reader[] readers;

  public LinkDbReader() {
    
  }
  
  public LinkDbReader(Configuration conf, Path directory) throws Exception {
    setConf(conf);
    init(directory);
  }
  
  public void init(Path directory) throws Exception {
    this.fs = FileSystem.get(getConf());
    this.directory = directory;
  }

  public String[] getAnchors(Text url) throws IOException {
    Inlinks inlinks = getInlinks(url);
    if (inlinks == null)
      return null;
    return inlinks.getAnchors();
  }

  public Inlinks getInlinks(Text url) throws IOException {

    if (readers == null) {
      synchronized(this) {
        readers = MapFileOutputFormat.getReaders
          (fs, new Path(directory, LinkDb.CURRENT_NAME), getConf());
      }
    }
    
    return (Inlinks)MapFileOutputFormat.getEntry
      (readers, PARTITIONER, url, new Inlinks());
  }
  
  public void close() throws IOException {
    if (readers != null) {
      for (int i = 0; i < readers.length; i++) {
        readers[i].close();
      }
    }
  }
  
  public void processDumpJob(String linkdb, String output) throws IOException {

    if (LOG.isInfoEnabled()) {
      LOG.info("LinkDb dump: starting");
      LOG.info("LinkDb db: " + linkdb);
    }
    Path outFolder = new Path(output);

    JobConf job = new NutchJob(getConf());
    job.setJobName("read " + linkdb);

    FileInputFormat.addInputPath(job, new Path(linkdb, LinkDb.CURRENT_NAME));
    job.setInputFormat(SequenceFileInputFormat.class);

    FileOutputFormat.setOutputPath(job, outFolder);
    job.setOutputFormat(TextOutputFormat.class);
    job.setOutputKeyClass(Text.class);
    job.setOutputValueClass(Inlinks.class);

    JobClient.runJob(job);
  }
  
  public static void main(String[] args) throws Exception {
    int res = ToolRunner.run(NutchConfiguration.create(), new LinkDbReader(), args);
    System.exit(res);
  }
  
  public int run(String[] args) throws Exception {
    if (args.length < 2) {
      System.err.println("Usage: LinkDbReader <linkdb> {-dump <out_dir> | -url <url>)");
      System.err.println("\t-dump <out_dir>\tdump whole link db to a text file in <out_dir>");
      System.err.println("\t-url <url>\tprint information about <url> to System.out");
      return -1;
    }
    try {
      if (args[1].equals("-dump")) {
        processDumpJob(args[0], args[2]);
        return 0;
      } else if (args[1].equals("-url")) {
        init(new Path(args[0]));
        Inlinks links = getInlinks(new Text(args[2]));
        if (links == null) {
          System.out.println(" - no link information.");
        } else {
          Iterator<Inlink> it = links.iterator();
          while (it.hasNext()) {
            System.out.println(it.next().toString());
          }
        }
        return 0;
      } else {
        System.err.println("Error: wrong argument " + args[1]);
        return -1;
      }
    } catch (Exception e) {
      LOG.fatal("LinkDbReader: " + StringUtils.stringifyException(e));
      return -1;
    }
  }
}