* 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,
 * See the License for the specific language governing permissions and
 * limitations under the License.
package org.apache.nutch.crawl;

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.Random;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapFileOutputFormat;
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.util.StringUtils;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
import org.apache.nutch.util.NutchConfiguration;
import org.apache.nutch.util.NutchJob;
import org.apache.nutch.util.TimingUtil;

 * This tool merges several LinkDb-s into one, optionally filtering
 * URLs through the current URLFilters, to skip prohibited URLs and
 * links.
 * <p>It's possible to use this tool just for filtering - in that case
 * only one LinkDb should be specified in arguments.</p>
 * <p>If more than one LinkDb contains information about the same URL,
 * all inlinks are accumulated, but only at most <code>db.max.inlinks</code>
 * inlinks will ever be added.</p>
 * <p>If activated, URLFilters will be applied to both the target URLs and
 * to any incoming link URL. If a target URL is prohibited, all
 * inlinks to that target will be removed, including the target URL. If
 * some of incoming links are prohibited, only they will be removed, and they
 * won't count when checking the above-mentioned maximum limit.
 * @author Andrzej Bialecki
public class LinkDbMerger extends Configured implements Tool, Reducer<Text, Inlinks, Text, Inlinks> {
  private static final Logger LOG = LoggerFactory.getLogger(LinkDbMerger.class);
  private int maxInlinks;
  public LinkDbMerger() {
  public LinkDbMerger(Configuration conf) {

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

    Inlinks result = new Inlinks();

    while (values.hasNext()) {
      Inlinks inlinks = values.next();

      int end = Math.min(maxInlinks - result.size(), inlinks.size());
      Iterator<Inlink> it = inlinks.iterator();
      int i = 0;
      while(it.hasNext() && i++ < end) {
    if (result.size() == 0) return;
    output.collect(key, result);

  public void configure(JobConf job) {
    maxInlinks = job.getInt("db.max.inlinks", 10000);

  public void close() throws IOException { }

  public void merge(Path output, Path[] dbs, boolean normalize, boolean filter) throws Exception {
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    long start = System.currentTimeMillis();
    LOG.info("LinkDb merge: starting at " + sdf.format(start));

    JobConf job = createMergeJob(getConf(), output, normalize, filter);
    for (int i = 0; i < dbs.length; i++) {
      FileInputFormat.addInputPath(job, new Path(dbs[i], LinkDb.CURRENT_NAME));      
    FileSystem fs = FileSystem.get(getConf());
    fs.rename(FileOutputFormat.getOutputPath(job), new Path(output, LinkDb.CURRENT_NAME));

    long end = System.currentTimeMillis();
    LOG.info("LinkDb merge: finished at " + sdf.format(end) + ", elapsed: " + TimingUtil.elapsedTime(start, end));

  public static JobConf createMergeJob(Configuration config, Path linkDb, boolean normalize, boolean filter) {
    Path newLinkDb =
      new Path("linkdb-merge-" + 
               Integer.toString(new Random().nextInt(Integer.MAX_VALUE)));

    JobConf job = new NutchJob(config);
    job.setJobName("linkdb merge " + linkDb);


    job.setBoolean(LinkDbFilter.URL_NORMALIZING, normalize);
    job.setBoolean(LinkDbFilter.URL_FILTERING, filter);

    FileOutputFormat.setOutputPath(job, newLinkDb);
    job.setBoolean("mapred.output.compress", true);

    // https://issues.apache.org/jira/browse/NUTCH-1069
    job.setBoolean("mapreduce.fileoutputcommitter.marksuccessfuljobs", false);

    return job;
   * @param args
  public static void main(String[] args) throws Exception {
    int res = ToolRunner.run(NutchConfiguration.create(), new LinkDbMerger(), args);
  public int run(String[] args) throws Exception {
    if (args.length < 2) {
      System.err.println("Usage: LinkDbMerger <output_linkdb> <linkdb1> [<linkdb2> <linkdb3> ...] [-normalize] [-filter]");
      System.err.println("\toutput_linkdb\toutput LinkDb");
      System.err.println("\tlinkdb1 ...\tinput LinkDb-s (single input LinkDb is ok)");
      System.err.println("\t-normalize\tuse URLNormalizer on both fromUrls and toUrls in linkdb(s) (usually not needed)");
      System.err.println("\t-filter\tuse URLFilters on both fromUrls and toUrls in linkdb(s)");
      return -1;
    Path output = new Path(args[0]);
    ArrayList<Path> dbs = new ArrayList<Path>();
    boolean normalize = false;
    boolean filter = false;
    for (int i = 1; i < args.length; i++) {
      if (args[i].equals("-filter")) {
        filter = true;
      } else if (args[i].equals("-normalize")) {
        normalize = true;
      } else dbs.add(new Path(args[i]));
    try {
      merge(output, dbs.toArray(new Path[dbs.size()]), normalize, filter);
      return 0;
    } catch (Exception e) {
      LOG.error("LinkDbMerger: " + StringUtils.stringifyException(e));
      return -1;