Java tutorial
/* * Cloud9: A Hadoop toolkit for working with big data * * 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.honghongie; import java.io.IOException; import java.util.Arrays; import java.util.Collections; import java.util.Iterator; 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.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.io.VIntWritable; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.Mapper; import org.apache.hadoop.mapreduce.Reducer; import org.apache.hadoop.mapreduce.Partitioner; import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; import org.apache.hadoop.mapreduce.lib.output.MapFileOutputFormat; 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; import tl.lin.data.array.ArrayListWritable; import tl.lin.data.fd.Object2IntFrequencyDistribution; import tl.lin.data.fd.Object2IntFrequencyDistributionEntry; import tl.lin.data.pair.PairOfInts; import tl.lin.data.pair.PairOfWritables; import tl.lin.data.pair.PairOfStringLong; public class BuildInvertedIndexCompressed extends Configured implements Tool { private static final Logger LOG = Logger.getLogger(BuildInvertedIndexCompressed.class); private static class MyMapper extends Mapper<LongWritable, Text, PairOfStringLong, IntWritable> { private static final PairOfStringLong PAIR = new PairOfStringLong(); //Whether docid can be saved in Intwritable? private static final IntWritable VALUE = new IntWritable(1); @Override public void map(LongWritable docno, Text doc, Context context) throws IOException, InterruptedException { String text = doc.toString(); String[] terms = text.split("\\s+"); // build work docid paris for (String term : terms) { if (term == null || term.length() == 0) { continue; } long docid = docno.get(); PAIR.set(term, docid); context.write(PAIR, VALUE); //special pairs also emit(term,*) // // PAIR.set(term, "*"); // context.write(PAIR, VALUE); // System.out.println(PAIR); // System.out.println(VALUE); } } } protected static class MyCombiner extends Reducer<PairOfStringLong, IntWritable, PairOfStringLong, IntWritable> { private static final IntWritable SUM = new IntWritable(); @Override public void reduce(PairOfStringLong key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException { int sum = 0; Iterator<IntWritable> iter = values.iterator(); while (iter.hasNext()) { sum += iter.next().get(); } SUM.set(sum); context.write(key, SUM); } } private static class MyReducer extends Reducer<PairOfStringLong, IntWritable, Text, PairOfWritables<IntWritable, ArrayListWritable<VIntWritable>>> { private final static IntWritable DF = new IntWritable(); private final static Text WORD = new Text(); // String tprev = null; ArrayListWritable<VIntWritable> postings = new ArrayListWritable<VIntWritable>(); Long gap = 0L; //Initialize using setup? // @Override // protected void setup(Context context)throws IOException, InterruptedException{ // String tprev = new String(); // ArrayListWritable<VIntWritable> postings = new ArrayListWritable<VIntWritable>(); // } // @Override public void reduce(PairOfStringLong key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException { Iterator<IntWritable> iter = values.iterator(); // get sum of all values int sum = 0; while (iter.hasNext()) { sum += iter.next().get(); } //ensure ascending, if use string, will becomes descending // System.out.println("==============key:"+key); // System.out.println("==============value:"+sum); // wirte out DF and (docid,frequency) pairs VIntWritable docid = new VIntWritable(); VIntWritable tf = new VIntWritable(); String term = key.getLeftElement(); // if (!term.equals(tprev))System.out.println("term not equal to tprev"); // if (tprev!= null)System.out.println("tprev not null"); if (!term.equals(tprev) && tprev != null) { //get to a new term and previous one is not null; first pair is (word,*) WORD.set(tprev); DF.set(postings.size() / 2); // System.out.println("*************DF:"+DF); context.write(WORD, new PairOfWritables<IntWritable, ArrayListWritable<VIntWritable>>(DF, postings)); // System.out.println("**************WORD:"+WORD); // System.out.println("**************postings:"+postings); postings.clear(); gap = 0L; //clear gap of previous list } // no matter whether new key, emit the information long docnum = key.getRightElement(); long docnoc = docnum - gap; //convert to int so that can be converted to VInt String sdocnoc = Long.toString(docnoc); int i = Integer.parseInt(sdocnoc); docid.set(i); tf.set(sum); postings.add(docid); postings.add(tf); tprev = term; gap = docnum; // System.out.println("*****************"+tprev); // System.out.println("docid: "+docid); } //emit last posting-----leave this alone to see whether it works 2.25 @Override protected void cleanup(Context context) throws IOException, InterruptedException { WORD.set(tprev); context.write(WORD, new PairOfWritables<IntWritable, ArrayListWritable<VIntWritable>>(DF, postings)); } } //partitioner according to indexed word protected static class MyPartitioner extends Partitioner<PairOfStringLong, IntWritable> { @Override public int getPartition(PairOfStringLong key, IntWritable value, int numReduceTasks) { return (key.getLeftElement().hashCode() & Integer.MAX_VALUE) % numReduceTasks; } } private BuildInvertedIndexCompressed() { } private static final String INPUT = "input"; private static final String OUTPUT = "output"; private static final String NUM_REDUCERS = "numReducers"; /** * Runs this tool. */ @SuppressWarnings({ "static-access" }) public int run(String[] args) throws Exception { Options options = new Options(); options.addOption(OptionBuilder.withArgName("path").hasArg().withDescription("input path").create(INPUT)); options.addOption(OptionBuilder.withArgName("path").hasArg().withDescription("output path").create(OUTPUT)); options.addOption(OptionBuilder.withArgName("num").hasArg().withDescription("number of reducers") .create(NUM_REDUCERS)); 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) || !cmdline.hasOption(OUTPUT)) { System.out.println("args: " + Arrays.toString(args)); HelpFormatter formatter = new HelpFormatter(); formatter.setWidth(120); formatter.printHelp(this.getClass().getName(), options); ToolRunner.printGenericCommandUsage(System.out); return -1; } String inputPath = cmdline.getOptionValue(INPUT); String outputPath = cmdline.getOptionValue(OUTPUT); int reduceTasks = cmdline.hasOption(NUM_REDUCERS) ? Integer.parseInt(cmdline.getOptionValue(NUM_REDUCERS)) : 1; LOG.info("Tool name: " + BuildInvertedIndexCompressed.class.getSimpleName()); LOG.info(" - input path: " + inputPath); LOG.info(" - output path: " + outputPath); LOG.info(" - num reducers: " + reduceTasks); Job job = Job.getInstance(getConf()); job.setJobName(BuildInvertedIndexCompressed.class.getSimpleName()); job.setJarByClass(BuildInvertedIndexCompressed.class); job.setNumReduceTasks(reduceTasks); FileInputFormat.setInputPaths(job, new Path(inputPath)); FileOutputFormat.setOutputPath(job, new Path(outputPath)); job.setMapOutputKeyClass(PairOfStringLong.class); job.setMapOutputValueClass(IntWritable.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(PairOfWritables.class); job.setOutputFormatClass(MapFileOutputFormat.class); //why mapfileoutputformat? // job.setOutputFormatClass(SequenceFileOutputFormat); job.setMapperClass(MyMapper.class); job.setCombinerClass(MyCombiner.class); job.setReducerClass(MyReducer.class); job.setPartitionerClass(MyPartitioner.class); // Delete the output directory if it exists already. Path outputDir = new Path(outputPath); FileSystem.get(getConf()).delete(outputDir, true); long startTime = System.currentTimeMillis(); job.waitForCompletion(true); System.out.println("Job Finished in " + (System.currentTimeMillis() - startTime) / 1000.0 + " seconds"); return 0; } /** * Dispatches command-line arguments to the tool via the {@code ToolRunner}. */ public static void main(String[] args) throws Exception { ToolRunner.run(new BuildInvertedIndexCompressed(), args); } }