Java tutorial
/* * 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.trecweb; import java.io.IOException; import java.util.Arrays; 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.Configuration; import org.apache.hadoop.conf.Configured; import org.apache.hadoop.fs.FileStatus; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.SequenceFile; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.Mapper; import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; import org.apache.hadoop.mapreduce.lib.output.SequenceFileOutputFormat; import org.apache.hadoop.util.Tool; import org.apache.hadoop.util.ToolRunner; import org.apache.log4j.Logger; /** * Tool to repack TREC web collections (wt10g, gov2) into {@link SequenceFile}s. Run without any * arguments for help. The guava jar must be included using {@code -libjar}. * * @author Jimmy Lin */ public class RepackTrecWebCollection extends Configured implements Tool { private static final Logger LOG = Logger.getLogger(RepackTrecWebCollection.class); private static enum Documents { Count }; private static class MyMapper extends Mapper<LongWritable, TrecWebDocument, LongWritable, TrecWebDocument> { @Override public void map(LongWritable key, TrecWebDocument doc, Context context) throws IOException, InterruptedException { context.getCounter(Documents.Count).increment(1); context.write(key, doc); } } private RepackTrecWebCollection() { } public static final String COLLECTION_OPTION = "collection"; public static final String OUTPUT_OPTION = "output"; public static final String COMPRESSION_OPTION = "compressionType"; /** * Runs this tool. */ @SuppressWarnings("static-access") public int run(String[] args) throws Exception { Options options = new Options(); options.addOption(OptionBuilder.withArgName("path").hasArg().withDescription("(required) collection path") .create(COLLECTION_OPTION)); options.addOption(OptionBuilder.withArgName("path").hasArg().withDescription("(required) output path") .create(OUTPUT_OPTION)); options.addOption(OptionBuilder.withArgName("type").hasArg() .withDescription("(required) compression type: 'block', 'record', or 'none'") .create(COMPRESSION_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(COLLECTION_OPTION) || !cmdline.hasOption(OUTPUT_OPTION) || !cmdline.hasOption(COMPRESSION_OPTION)) { HelpFormatter formatter = new HelpFormatter(); formatter.printHelp(this.getClass().getName(), options); ToolRunner.printGenericCommandUsage(System.out); return -1; } String collection = cmdline.getOptionValue(COLLECTION_OPTION); String output = cmdline.getOptionValue(OUTPUT_OPTION); String compressionType = cmdline.getOptionValue(COMPRESSION_OPTION); if (!compressionType.equals("block") && !compressionType.equals("record") && !compressionType.equals("none")) { System.err.println("Error: \"" + compressionType + "\" unknown compression type!"); System.exit(-1); } // This is the default block size. int blocksize = 1000000; Job job = new Job(getConf(), RepackTrecWebCollection.class.getSimpleName() + ":" + collection); FileSystem fs = FileSystem.get(job.getConfiguration()); job.setJarByClass(RepackTrecWebCollection.class); LOG.info("Tool name: " + RepackTrecWebCollection.class.getCanonicalName()); LOG.info(" - collection path: " + collection); LOG.info(" - output path: " + output); LOG.info(" - compression type: " + compressionType); if (compressionType.equals("block")) { LOG.info(" - block size: " + blocksize); } Path collectionPath = new Path(collection); for (FileStatus status : fs.listStatus(collectionPath)) { if (status.isDirectory()) { for (FileStatus s : fs.listStatus(status.getPath())) { FileInputFormat.addInputPath(job, s.getPath()); } } else { FileInputFormat.addInputPath(job, status.getPath()); } } // Hack to figure out number of reducers. int numReducers = 100; if (collection.toLowerCase().contains("wt10g")) { numReducers = 50; } else if (collection.toLowerCase().contains("gov2")) { numReducers = 200; } LOG.info(" - number of reducers: " + numReducers); job.setNumReduceTasks(numReducers); FileOutputFormat.setOutputPath(job, new Path(output)); if (compressionType.equals("none")) { SequenceFileOutputFormat.setCompressOutput(job, false); } else { SequenceFileOutputFormat.setCompressOutput(job, true); if (compressionType.equals("record")) { SequenceFileOutputFormat.setOutputCompressionType(job, SequenceFile.CompressionType.RECORD); } else { SequenceFileOutputFormat.setOutputCompressionType(job, SequenceFile.CompressionType.BLOCK); job.getConfiguration().setInt("io.seqfile.compress.blocksize", blocksize); } } job.setInputFormatClass(TrecWebDocumentInputFormat.class); job.setOutputFormatClass(SequenceFileOutputFormat.class); job.setOutputKeyClass(LongWritable.class); job.setOutputValueClass(TrecWebDocument.class); job.setMapperClass(MyMapper.class); // delete the output directory if it exists already fs.delete(new Path(output), true); try { job.waitForCompletion(true); } catch (Exception e) { throw new RuntimeException(e); } return 0; } /** * Dispatches command-line arguments to the tool via the {@code ToolRunner}. */ public static void main(String[] args) throws Exception { LOG.info("Running " + RepackTrecWebCollection.class.getCanonicalName() + " with args " + Arrays.toString(args)); ToolRunner.run(new Configuration(), new RepackTrecWebCollection(), args); } }