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. */ import java.io.IOException; import java.util.Random; 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.Configured; import org.apache.hadoop.fs.FSDataOutputStream; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapred.Counters; 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.MapRunnable; import org.apache.hadoop.mapred.OutputCollector; import org.apache.hadoop.mapred.RecordReader; import org.apache.hadoop.mapred.Reporter; import org.apache.hadoop.mapred.RunningJob; import org.apache.hadoop.mapred.lib.IdentityReducer; import org.apache.hadoop.util.LineReader; import org.apache.hadoop.util.Tool; import org.apache.hadoop.util.ToolRunner; import org.apache.log4j.Logger; import edu.umd.cloud9.collection.wikipedia.WikipediaPage; import edu.umd.cloud9.mapred.NoSplitSequenceFileInputFormat; /** * Tool for building a document forward index for Wikipedia. * * @author Jimmy Lin * @author Peter Exner */ public class WikipediaForwardIndexBuilder extends Configured implements Tool { private static final Logger LOG = Logger.getLogger(WikipediaForwardIndexBuilder.class); private static final Random RANDOM = new Random(); private static enum Blocks { Total }; private static class MyMapRunner implements MapRunnable<IntWritable, WikipediaPage, IntWritable, Text> { private static final IntWritable keyOut = new IntWritable(); private static final Text valOut = new Text(); private int fileno; private String language; @Override public void configure(JobConf job) { String file = job.get("map.input.file"); fileno = Integer.parseInt(file.substring(file.indexOf("part-") + 7)); language = job.get("wiki.language"); } @Override public void run(RecordReader<IntWritable, WikipediaPage> input, OutputCollector<IntWritable, Text> output, Reporter reporter) throws IOException { IntWritable key = new IntWritable(); //WikipediaPage value = WikipediaPageFactory.createWikipediaPage(language); WikipediaPage value = new WikipediaPage(); long pos = -1; long prevPos = -1; int prevDocno = 0; pos = input.getPos(); while (input.next(key, value)) { if (prevPos != -1 && prevPos != pos) { LOG.info("- beginning of block at " + prevPos + ", docno:" + prevDocno + ", file:" + fileno); keyOut.set(prevDocno); valOut.set(prevPos + "\t" + fileno); output.collect(keyOut, valOut); reporter.incrCounter(Blocks.Total, 1); } prevPos = pos; pos = input.getPos(); prevDocno = key.get(); } } } private static final String INPUT_OPTION = "input"; private static final String INDEX_FILE_OPTION = "index_file"; private static final String LANGUAGE_OPTION = "wiki_language"; @SuppressWarnings("static-access") @Override public int run(String[] args) throws Exception { Options options = new Options(); options.addOption(OptionBuilder.withArgName("path").hasArg().withDescription("input").create(INPUT_OPTION)); options.addOption( OptionBuilder.withArgName("path").hasArg().withDescription("index file").create(INDEX_FILE_OPTION)); options.addOption(OptionBuilder.withArgName("en|sv|de|cs|es|zh|ar|tr").hasArg() .withDescription("two-letter language code").create(LANGUAGE_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(INPUT_OPTION) || !cmdline.hasOption(INDEX_FILE_OPTION)) { HelpFormatter formatter = new HelpFormatter(); formatter.printHelp(this.getClass().getName(), options); ToolRunner.printGenericCommandUsage(System.out); return -1; } Path inputPath = new Path(cmdline.getOptionValue(INPUT_OPTION)); String indexFile = cmdline.getOptionValue(INDEX_FILE_OPTION); String tmpPath = "tmp-" + WikipediaForwardIndexBuilder.class.getSimpleName() + "-" + RANDOM.nextInt(10000); if (!inputPath.isAbsolute()) { System.err.println("Error: " + INPUT_OPTION + " must be an absolute path!"); return -1; } String language = null; if (cmdline.hasOption(LANGUAGE_OPTION)) { language = cmdline.getOptionValue(LANGUAGE_OPTION); if (language.length() != 2) { System.err.println("Error: \"" + language + "\" unknown language!"); return -1; } } JobConf conf = new JobConf(getConf(), WikipediaForwardIndexBuilder.class); FileSystem fs = FileSystem.get(conf); LOG.info("Tool name: " + this.getClass().getName()); LOG.info(" - input path: " + inputPath); LOG.info(" - index file: " + indexFile); LOG.info(" - language: " + language); LOG.info("Note: This tool only works on block-compressed SequenceFiles!"); conf.setJobName(String.format("BuildWikipediaForwardIndex[%s: %s, %s: %s, %s: %s]", INPUT_OPTION, inputPath, INDEX_FILE_OPTION, indexFile, LANGUAGE_OPTION, language)); conf.setNumReduceTasks(1); FileInputFormat.setInputPaths(conf, inputPath); FileOutputFormat.setOutputPath(conf, new Path(tmpPath)); FileOutputFormat.setCompressOutput(conf, false); if (language != null) { conf.set("wiki.language", language); } conf.setInputFormat(NoSplitSequenceFileInputFormat.class); conf.setOutputKeyClass(IntWritable.class); conf.setOutputValueClass(Text.class); conf.setMapRunnerClass(MyMapRunner.class); conf.setReducerClass(IdentityReducer.class); // Delete the output directory if it exists already. fs.delete(new Path(tmpPath), true); RunningJob job = JobClient.runJob(conf); Counters counters = job.getCounters(); int blocks = (int) counters.getCounter(Blocks.Total); LOG.info("number of blocks: " + blocks); LOG.info("Writing index file..."); LineReader reader = new LineReader(fs.open(new Path(tmpPath + "/part-00000"))); FSDataOutputStream out = fs.create(new Path(indexFile), true); out.writeUTF(edu.umd.cloud9.collection.wikipedia.WikipediaForwardIndex.class.getCanonicalName()); out.writeUTF(inputPath.toString()); out.writeInt(blocks); int cnt = 0; Text line = new Text(); while (reader.readLine(line) > 0) { String[] arr = line.toString().split("\\s+"); int docno = Integer.parseInt(arr[0]); int offset = Integer.parseInt(arr[1]); short fileno = Short.parseShort(arr[2]); out.writeInt(docno); out.writeInt(offset); out.writeShort(fileno); cnt++; if (cnt % 100000 == 0) { LOG.info(cnt + " blocks written"); } } reader.close(); out.close(); if (cnt != blocks) { throw new RuntimeException("Error: mismatch in block count!"); } // Clean up. fs.delete(new Path(tmpPath), true); return 0; } public WikipediaForwardIndexBuilder() { } public static void main(String[] args) throws Exception { ToolRunner.run(new WikipediaForwardIndexBuilder(), args); } }