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 java.util.Random; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.conf.Configured; import org.apache.hadoop.fs.FSDataOutputStream; import org.apache.hadoop.fs.FileStatus; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.fs.PathFilter; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.Mapper; import org.apache.hadoop.mapreduce.Reducer; import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat; 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.DocnoMapping; /** * Tool that builds the mapping from docids (String identifiers) to docnos (sequentially-numbered * ints) for TREC web collections (wt10g, gov2). Run without any arguments for help. The guava jar * must be included using {@code -libjar}. * * @author Jimmy Lin */ public class TrecWebDocnoMappingBuilder extends Configured implements Tool, DocnoMapping.Builder { private static final Logger LOG = Logger.getLogger(TrecWebDocnoMappingBuilder.class); private static final Random random = new Random(); protected static enum Documents { Total }; private static class MyMapper extends Mapper<LongWritable, TrecWebDocument, Text, IntWritable> { private final static Text text = new Text(); private final static IntWritable out = new IntWritable(1); @Override public void map(LongWritable key, TrecWebDocument doc, Context context) throws IOException, InterruptedException { context.getCounter(Documents.Total).increment(1); text.set(doc.getDocid()); context.write(text, out); } } private static class MyReducer extends Reducer<Text, IntWritable, Text, IntWritable> { private final static IntWritable cnt = new IntWritable(1); @Override public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException { context.write(key, cnt); cnt.set(cnt.get() + 1); } } public TrecWebDocnoMappingBuilder() { } @Override public int build(Path src, Path dest, Configuration conf) throws IOException { super.setConf(conf); return run(new String[] { "-" + DocnoMapping.BuilderUtils.COLLECTION_OPTION + "=" + src.toString(), "-" + DocnoMapping.BuilderUtils.MAPPING_OPTION + "=" + dest.toString() }); } @Override public int run(String[] args) throws IOException { DocnoMapping.DefaultBuilderOptions options = DocnoMapping.BuilderUtils.parseDefaultOptions(args); if (options == null) { return -1; } // Temp directory. String tmpDir = "tmp-" + TrecWebDocnoMappingBuilder.class.getSimpleName() + "-" + random.nextInt(10000); LOG.info("Tool name: " + TrecWebDocnoMappingBuilder.class.getCanonicalName()); LOG.info(" - input path: " + options.collection); LOG.info(" - output file: " + options.docnoMapping); Job job = new Job(getConf(), TrecWebDocnoMappingBuilder.class.getSimpleName() + ":" + options.collection); FileSystem fs = FileSystem.get(job.getConfiguration()); job.setJarByClass(TrecWebDocnoMappingBuilder.class); job.setNumReduceTasks(1); PathFilter filter = new PathFilter() { @Override public boolean accept(Path path) { return !path.getName().startsWith("_"); } }; // Note: Gov2 and Wt10g raw collections are organized into sub-directories. Path collectionPath = new Path(options.collection); for (FileStatus status : fs.listStatus(collectionPath, filter)) { if (status.isDirectory()) { for (FileStatus s : fs.listStatus(status.getPath(), filter)) { FileInputFormat.addInputPath(job, s.getPath()); } } else { FileInputFormat.addInputPath(job, status.getPath()); } } FileOutputFormat.setOutputPath(job, new Path(tmpDir)); FileOutputFormat.setCompressOutput(job, false); job.setInputFormatClass(options.inputFormat); job.setOutputKeyClass(Text.class); job.setOutputValueClass(IntWritable.class); job.setOutputFormatClass(TextOutputFormat.class); job.setMapperClass(MyMapper.class); job.setReducerClass(MyReducer.class); // Delete the output directory if it exists already. fs.delete(new Path(tmpDir), true); try { job.waitForCompletion(true); } catch (Exception e) { throw new RuntimeException(e); } writeMappingData(new Path(tmpDir + "/part-r-00000"), new Path(options.docnoMapping), fs); fs.delete(new Path(tmpDir), true); return 0; } private static void writeMappingData(Path input, Path output, FileSystem fs) throws IOException { LOG.info("Writing docids to " + output); LineReader reader = new LineReader(fs.open(input)); LOG.info("Reading " + input); int cnt = 0; Text line = new Text(); while (reader.readLine(line) > 0) { cnt++; } reader.close(); LOG.info("Done!"); LOG.info("Writing " + output); FSDataOutputStream out = fs.create(output, true); reader = new LineReader(fs.open(input)); out.writeInt(cnt); cnt = 0; while (reader.readLine(line) > 0) { String[] arr = line.toString().split("\\t"); out.writeUTF(arr[0]); cnt++; if (cnt % 100000 == 0) { LOG.info(cnt + " documents"); } } reader.close(); out.close(); LOG.info("Done! " + cnt + " documents total."); } /** * Dispatches command-line arguments to the tool via the {@code ToolRunner}. */ public static void main(String[] args) throws Exception { LOG.info("Running " + TrecWebDocnoMappingBuilder.class.getCanonicalName() + " with args " + Arrays.toString(args)); ToolRunner.run(new Configuration(), new TrecWebDocnoMappingBuilder(), args); } }