Sort源代码注释
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.filecache.DistributedCache;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.*;import org.apache.hadoop.mapred.lib.IdentityMapper;import org.apache.hadoop.mapred.lib.IdentityReducer;import org.apache.hadoop.mapred.lib.InputSampler;import org.apache.hadoop.mapred.lib.TotalOrderPartitioner;import org.apache.hadoop.util.Tool;import org.apache.hadoop.util.ToolRunner;/** hadoop 的map/reduce例子，排序，由于map传给reduce的中间结果是排序的，所以这个例子不用写mapper和reducer。都用默认的map/reduce的实现，IdentityMapper和IdentityReducer。例子中可以用排序采样器TotalOrderPartitioner，参数设置可以是 -totalOrder 0.1 10000 10 * 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 * [-m <i>maps</i>] [-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 { private RunningJob jobResult = null; static int printUsage() { System.out.println("sort [-m <maps>] [-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 -1; } /**driver代码 * 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 { JobConf jobConf = new JobConf(getConf(), Sort.class); jobConf.setJobName("sorter"); jobConf.setMapperClass(IdentityMapper.class); //设置mapper jobConf.setReducerClass(IdentityReducer.class);//设置reducer JobClient client = new JobClient(jobConf); ClusterStatus cluster = client.getClusterStatus();//获得集群的状态 int num_reduces = (int) (cluster.getMaxReduceTasks() * 0.9); String sort_reduces = jobConf.get("test.sort.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 ("-m".equals(args[i])) { jobConf.setNumMapTasks(Integer.parseInt(args[++i])); } else 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])) { //设置采样器3个参数 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 jobConf.setNumReduceTasks(num_reduces); jobConf.setInputFormat(inputFormatClass); jobConf.setOutputFormat(outputFormatClass); jobConf.setOutputKeyClass(outputKeyClass); jobConf.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(jobConf, otherArgs.get(0)); FileOutputFormat.setOutputPath(jobConf, new Path(otherArgs.get(1))); if (sampler != null) { System.out.println("Sampling input to effect total-order sort..."); jobConf.setPartitionerClass(TotalOrderPartitioner.class);//设置采样器 Path inputDir = FileInputFormat.getInputPaths(jobConf)[0]; inputDir = inputDir.makeQualified(inputDir.getFileSystem(jobConf)); Path partitionFile = new Path(inputDir, "_sortPartitioning"); TotalOrderPartitioner.setPartitionFile(jobConf, partitionFile);//采样设置采样文件 InputSampler.<K,V>writePartitionFile(jobConf, sampler); URI partitionUri = new URI(partitionFile.toString() + "#" + "_sortPartitioning"); DistributedCache.addCacheFile(partitionUri, jobConf); DistributedCache.createSymlink(jobConf); } System.out.println("Running on " + cluster.getTaskTrackers() + " nodes to sort from " + FileInputFormat.getInputPaths(jobConf)[0] + " into " + FileOutputFormat.getOutputPath(jobConf) + " with " + num_reduces + " reduces."); Date startTime = new Date(); System.out.println("Job started: " + startTime); jobResult = JobClient.runJob(jobConf); 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 0; } 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 RunningJob getResult() { return jobResult; }}?