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.*; import java.util.Map.Entry; // Commons Logging imports import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.Text; import org.apache.hadoop.io.Writable; import org.apache.hadoop.mapred.*; import org.apache.hadoop.util.*; import org.apache.hadoop.conf.*; import org.apache.nutch.util.NutchConfiguration; import org.apache.nutch.util.NutchJob; import org.apache.nutch.util.TimingUtil; /** * This tool merges several CrawlDb-s into one, optionally filtering * URLs through the current URLFilters, to skip prohibited * pages. * * <p>It's possible to use this tool just for filtering - in that case * only one CrawlDb should be specified in arguments.</p> * <p>If more than one CrawlDb contains information about the same URL, * only the most recent version is retained, as determined by the * value of {@link org.apache.nutch.crawl.CrawlDatum#getFetchTime()}. * However, all metadata information from all versions is accumulated, * with newer values taking precedence over older values. * * @author Andrzej Bialecki */ public class CrawlDbMerger extends Configured implements Tool { private static final Logger LOG = LoggerFactory.getLogger(CrawlDbMerger.class); public static class Merger extends MapReduceBase implements Reducer<Text, CrawlDatum, Text, CrawlDatum> { private org.apache.hadoop.io.MapWritable meta; private CrawlDatum res = new CrawlDatum(); private FetchSchedule schedule; public void close() throws IOException { } public void configure(JobConf conf) { schedule = FetchScheduleFactory.getFetchSchedule(conf); } public void reduce(Text key, Iterator<CrawlDatum> values, OutputCollector<Text, CrawlDatum> output, Reporter reporter) throws IOException { long resTime = 0L; boolean resSet = false; meta = new org.apache.hadoop.io.MapWritable(); while (values.hasNext()) { CrawlDatum val = values.next(); if (!resSet) { res.set(val); resSet = true; resTime = schedule.calculateLastFetchTime(res); for (Entry<Writable, Writable> e : res.getMetaData().entrySet()) { meta.put(e.getKey(), e.getValue()); } continue; } // compute last fetch time, and pick the latest long valTime = schedule.calculateLastFetchTime(val); if (valTime > resTime) { // collect all metadata, newer values override older values for (Entry<Writable, Writable> e : val.getMetaData().entrySet()) { meta.put(e.getKey(), e.getValue()); } res.set(val); resTime = valTime; } else { // insert older metadata before newer for (Entry<Writable, Writable> e : meta.entrySet()) { val.getMetaData().put(e.getKey(), e.getValue()); } meta = val.getMetaData(); } } res.setMetaData(meta); output.collect(key, res); } } public CrawlDbMerger() { } public CrawlDbMerger(Configuration conf) { setConf(conf); } 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("CrawlDb merge: starting at " + sdf.format(start)); JobConf job = createMergeJob(getConf(), output, normalize, filter); for (int i = 0; i < dbs.length; i++) { if (LOG.isInfoEnabled()) { LOG.info("Adding " + dbs[i]); } FileInputFormat.addInputPath(job, new Path(dbs[i], CrawlDb.CURRENT_NAME)); } JobClient.runJob(job); FileSystem fs = FileSystem.get(getConf()); fs.mkdirs(output); fs.rename(FileOutputFormat.getOutputPath(job), new Path(output, CrawlDb.CURRENT_NAME)); long end = System.currentTimeMillis(); LOG.info("CrawlDb merge: finished at " + sdf.format(end) + ", elapsed: " + TimingUtil.elapsedTime(start, end)); } public static JobConf createMergeJob(Configuration conf, Path output, boolean normalize, boolean filter) { Path newCrawlDb = new Path("crawldb-merge-" + Integer.toString(new Random().nextInt(Integer.MAX_VALUE))); JobConf job = new NutchJob(conf); job.setJobName("crawldb merge " + output); job.setInputFormat(SequenceFileInputFormat.class); job.setMapperClass(CrawlDbFilter.class); job.setBoolean(CrawlDbFilter.URL_FILTERING, filter); job.setBoolean(CrawlDbFilter.URL_NORMALIZING, normalize); job.setReducerClass(Merger.class); FileOutputFormat.setOutputPath(job, newCrawlDb); job.setOutputFormat(MapFileOutputFormat.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(CrawlDatum.class); return job; } /** * @param args */ public static void main(String[] args) throws Exception { int res = ToolRunner.run(NutchConfiguration.create(), new CrawlDbMerger(), args); System.exit(res); } public int run(String[] args) throws Exception { if (args.length < 2) { System.err.println( "Usage: CrawlDbMerger <output_crawldb> <crawldb1> [<crawldb2> <crawldb3> ...] [-normalize] [-filter]"); System.err.println("\toutput_crawldb\toutput CrawlDb"); System.err.println("\tcrawldb1 ...\tinput CrawlDb-s (single input CrawlDb is ok)"); System.err.println("\t-normalize\tuse URLNormalizer on urls in the crawldb(s) (usually not needed)"); System.err.println("\t-filter\tuse URLFilters on urls in the crawldb(s)"); return -1; } Path output = new Path(args[0]); ArrayList<Path> dbs = new ArrayList<Path>(); boolean filter = false; boolean normalize = false; FileSystem fs = FileSystem.get(getConf()); for (int i = 1; i < args.length; i++) { if (args[i].equals("-filter")) { filter = true; continue; } else if (args[i].equals("-normalize")) { normalize = true; continue; } final Path dbPath = new Path(args[i]); if (fs.exists(dbPath)) dbs.add(dbPath); } try { merge(output, dbs.toArray(new Path[dbs.size()]), normalize, filter); return 0; } catch (Exception e) { LOG.error("CrawlDb merge: " + StringUtils.stringifyException(e)); return -1; } } }