Java tutorial
/** * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you 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 org.apache.hadoop.examples; import java.io.IOException; import java.net.URI; import java.util.*; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.conf.Configured; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.BytesWritable; import org.apache.hadoop.io.Writable; import org.apache.hadoop.io.WritableComparable; import org.apache.hadoop.mapred.ClusterStatus; import org.apache.hadoop.mapred.JobClient; import org.apache.hadoop.mapreduce.*; import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; import org.apache.hadoop.mapreduce.lib.input.SequenceFileInputFormat; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; import org.apache.hadoop.mapreduce.lib.output.SequenceFileOutputFormat; import org.apache.hadoop.mapreduce.lib.partition.InputSampler; import org.apache.hadoop.mapreduce.lib.partition.TotalOrderPartitioner; import org.apache.hadoop.util.Tool; import org.apache.hadoop.util.ToolRunner; /** * This is the trivial map/reduce program that does absolutely nothing * other than use the framework to fragment and sort the input values. * * To run: bin/hadoop jar build/hadoop-examples.jar sort * [-r <i>reduces</i>] * [-inFormat <i>input format class</i>] * [-outFormat <i>output format class</i>] * [-outKey <i>output key class</i>] * [-outValue <i>output value class</i>] * [-totalOrder <i>pcnt</i> <i>num samples</i> <i>max splits</i>] * <i>in-dir</i> <i>out-dir</i> */ public class Sort<K, V> extends Configured implements Tool { public static final String REDUCES_PER_HOST = "mapreduce.sort.reducesperhost"; private Job job = null; static int printUsage() { System.out.println( "sort [-r <reduces>] " + "[-inFormat <input format class>] " + "[-outFormat <output format class>] " + "[-outKey <output key class>] " + "[-outValue <output value class>] " + "[-totalOrder <pcnt> <num samples> <max splits>] " + "<input> <output>"); ToolRunner.printGenericCommandUsage(System.out); return 2; } /** * The main driver for sort program. * Invoke this method to submit the map/reduce job. * @throws IOException When there is communication problems with the * job tracker. */ public int run(String[] args) throws Exception { Configuration conf = getConf(); JobClient client = new JobClient(conf); ClusterStatus cluster = client.getClusterStatus(); int num_reduces = (int) (cluster.getMaxReduceTasks() * 0.9); String sort_reduces = conf.get(REDUCES_PER_HOST); if (sort_reduces != null) { num_reduces = cluster.getTaskTrackers() * Integer.parseInt(sort_reduces); } Class<? extends InputFormat> inputFormatClass = SequenceFileInputFormat.class; Class<? extends OutputFormat> outputFormatClass = SequenceFileOutputFormat.class; Class<? extends WritableComparable> outputKeyClass = BytesWritable.class; Class<? extends Writable> outputValueClass = BytesWritable.class; List<String> otherArgs = new ArrayList<String>(); InputSampler.Sampler<K, V> sampler = null; for (int i = 0; i < args.length; ++i) { try { if ("-r".equals(args[i])) { num_reduces = Integer.parseInt(args[++i]); } else if ("-inFormat".equals(args[i])) { inputFormatClass = Class.forName(args[++i]).asSubclass(InputFormat.class); } else if ("-outFormat".equals(args[i])) { outputFormatClass = Class.forName(args[++i]).asSubclass(OutputFormat.class); } else if ("-outKey".equals(args[i])) { outputKeyClass = Class.forName(args[++i]).asSubclass(WritableComparable.class); } else if ("-outValue".equals(args[i])) { outputValueClass = Class.forName(args[++i]).asSubclass(Writable.class); } else if ("-totalOrder".equals(args[i])) { double pcnt = Double.parseDouble(args[++i]); int numSamples = Integer.parseInt(args[++i]); int maxSplits = Integer.parseInt(args[++i]); if (0 >= maxSplits) maxSplits = Integer.MAX_VALUE; sampler = new InputSampler.RandomSampler<K, V>(pcnt, numSamples, maxSplits); } else { otherArgs.add(args[i]); } } catch (NumberFormatException except) { System.out.println("ERROR: Integer expected instead of " + args[i]); return printUsage(); } catch (ArrayIndexOutOfBoundsException except) { System.out.println("ERROR: Required parameter missing from " + args[i - 1]); return printUsage(); // exits } } // Set user-supplied (possibly default) job configs job = Job.getInstance(conf); job.setJobName("sorter"); job.setJarByClass(Sort.class); job.setMapperClass(Mapper.class); job.setReducerClass(Reducer.class); job.setNumReduceTasks(num_reduces); job.setInputFormatClass(inputFormatClass); job.setOutputFormatClass(outputFormatClass); job.setOutputKeyClass(outputKeyClass); job.setOutputValueClass(outputValueClass); // Make sure there are exactly 2 parameters left. if (otherArgs.size() != 2) { System.out.println("ERROR: Wrong number of parameters: " + otherArgs.size() + " instead of 2."); return printUsage(); } FileInputFormat.setInputPaths(job, otherArgs.get(0)); FileOutputFormat.setOutputPath(job, new Path(otherArgs.get(1))); if (sampler != null) { System.out.println("Sampling input to effect total-order sort..."); job.setPartitionerClass(TotalOrderPartitioner.class); Path inputDir = FileInputFormat.getInputPaths(job)[0]; FileSystem fs = inputDir.getFileSystem(conf); inputDir = inputDir.makeQualified(fs.getUri(), fs.getWorkingDirectory()); Path partitionFile = new Path(inputDir, "_sortPartitioning"); TotalOrderPartitioner.setPartitionFile(conf, partitionFile); InputSampler.<K, V>writePartitionFile(job, sampler); URI partitionUri = new URI(partitionFile.toString() + "#" + "_sortPartitioning"); job.addCacheFile(partitionUri); } System.out.println("Running on " + cluster.getTaskTrackers() + " nodes to sort from " + FileInputFormat.getInputPaths(job)[0] + " into " + FileOutputFormat.getOutputPath(job) + " with " + num_reduces + " reduces."); Date startTime = new Date(); System.out.println("Job started: " + startTime); int ret = job.waitForCompletion(true) ? 0 : 1; Date end_time = new Date(); System.out.println("Job ended: " + end_time); System.out.println("The job took " + (end_time.getTime() - startTime.getTime()) / 1000 + " seconds."); return ret; } public static void main(String[] args) throws Exception { int res = ToolRunner.run(new Configuration(), new Sort(), args); System.exit(res); } /** * Get the last job that was run using this instance. * @return the results of the last job that was run */ public Job getResult() { return job; } }