Java tutorial
/** * 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; 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) { setConf(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) { result.add(it.next()); } } 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)); } JobClient.runJob(job); FileSystem fs = FileSystem.get(getConf()); fs.mkdirs(output); 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.setInputFormat(SequenceFileInputFormat.class); job.setMapperClass(LinkDbFilter.class); job.setBoolean(LinkDbFilter.URL_NORMALIZING, normalize); job.setBoolean(LinkDbFilter.URL_FILTERING, filter); job.setReducerClass(LinkDbMerger.class); FileOutputFormat.setOutputPath(job, newLinkDb); job.setOutputFormat(MapFileOutputFormat.class); job.setBoolean("mapred.output.compress", true); job.setOutputKeyClass(Text.class); job.setOutputValueClass(Inlinks.class); // 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); System.exit(res); } 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; } } }