Java tutorial
package uk.bl.wa.hadoop.mapreduce.mdx; /* * #%L * warc-hadoop-recordreaders * %% * Copyright (C) 2013 - 2018 The webarchive-discovery project contributors * %% * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as * published by the Free Software Foundation, either version 2 of the * License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public * License along with this program. If not, see * <http://www.gnu.org/licenses/gpl-2.0.html>. * #L% */ import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; import org.apache.commons.cli.CommandLine; import org.apache.commons.cli.CommandLineParser; import org.apache.commons.cli.HelpFormatter; import org.apache.commons.cli.Options; import org.apache.commons.cli.ParseException; import org.apache.commons.cli.PosixParser; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.hadoop.conf.Configured; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.Text; 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.TextInputFormat; import org.apache.hadoop.mapred.TextOutputFormat; import org.apache.hadoop.mapred.lib.IdentityMapper; import org.apache.hadoop.util.GenericOptionsParser; import org.apache.hadoop.util.Tool; import org.apache.hadoop.util.ToolRunner; import org.apache.zookeeper.KeeperException; /** * * This takes multiple MDX (line-oriented) files and merges them using the * re-duplicating reducer. * * @author Andrew Jackson <Andrew.Jackson@bl.uk> */ @SuppressWarnings({ "deprecation" }) public class MDXMerger extends Configured implements Tool { private static final Log LOG = LogFactory.getLog(MDXMerger.class); private static final String CLI_USAGE = "[-i <input file>] [-o <output dir>] [-r <#reducers>] [-w] (to wait for completion)"; private static final String CLI_HEADER = "MapReduce job for merging MDX files."; private String inputPath; private String outputPath; private boolean wait; // Reducer count: int numReducers = 10; /** * * @param args * @return * @throws IOException * @throws ParseException * @throws InterruptedException * @throws KeeperException */ public void createJobConf(JobConf conf, String[] args) throws IOException, ParseException, KeeperException, InterruptedException { // Parse the command-line parameters. this.setup(args, conf); // Add input paths: LOG.info("Reading input files..."); String line = null; BufferedReader br = new BufferedReader(new FileReader(this.inputPath)); while ((line = br.readLine()) != null) { FileInputFormat.addInputPath(conf, new Path(line)); } br.close(); LOG.info("Read " + FileInputFormat.getInputPaths(conf).length + " input files."); FileOutputFormat.setOutputPath(conf, new Path(this.outputPath)); conf.setJobName(this.inputPath + "_" + System.currentTimeMillis()); // Input conf.setInputFormat(TextInputFormat.class); // M-R conf.setMapperClass(IdentityMapper.class); conf.setReducerClass(MDXReduplicatingReducer.class); // Map outputs conf.setMapOutputKeyClass(Text.class); conf.setMapOutputValueClass(Text.class); // Job outputs conf.setOutputKeyClass(Text.class); conf.setOutputValueClass(Text.class); conf.setOutputFormat(TextOutputFormat.class); LOG.info("Used " + numReducers + " reducers."); conf.setNumReduceTasks(numReducers); // Compress the output from the maps, to cut down temp space // requirements between map and reduce. conf.setBoolean("mapreduce.map.output.compress", true); // Wrong syntax // for 0.20.x ? conf.set("mapred.compress.map.output", "true"); // conf.set("mapred.map.output.compression.codec", // "org.apache.hadoop.io.compress.GzipCodec"); // Ensure the JARs we provide take precedence over ones from Hadoop: conf.setBoolean("mapreduce.task.classpath.user.precedence", true); } /** * * Run the job: * * @throws InterruptedException * @throws KeeperException * */ public int run(String[] args) throws IOException, ParseException, KeeperException, InterruptedException { // Set up the base conf: JobConf conf = new JobConf(getConf(), MDXMerger.class); // Get the job configuration: this.createJobConf(conf, args); // Submit it: if (this.wait) { JobClient.runJob(conf); } else { JobClient client = new JobClient(conf); client.submitJob(conf); } return 0; } private void setup(String[] args, JobConf conf) throws ParseException { // Process Hadoop args first: String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs(); // Process remaining args list this: Options options = new Options(); options.addOption("i", true, "input file list"); options.addOption("o", true, "output directory"); options.addOption("w", false, "wait for job to finish"); options.addOption("r", true, "number of reducers"); CommandLineParser parser = new PosixParser(); CommandLine cmd = parser.parse(options, otherArgs); if (!cmd.hasOption("i") || !cmd.hasOption("o")) { HelpFormatter helpFormatter = new HelpFormatter(); helpFormatter.setWidth(80); helpFormatter.printHelp(CLI_USAGE, CLI_HEADER, options, ""); System.exit(1); } this.inputPath = cmd.getOptionValue("i"); this.outputPath = cmd.getOptionValue("o"); this.wait = cmd.hasOption("w"); if (cmd.hasOption("r")) { this.numReducers = Integer.parseInt(cmd.getOptionValue("r")); } } /** * * @param args * @throws Exception */ public static void main(String[] args) throws Exception { int ret = ToolRunner.run(new MDXMerger(), args); System.exit(ret); } }