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 com.cloudera; import java.io.IOException; import java.nio.ByteBuffer; import java.util.Iterator; import java.util.Map.Entry; import java.util.Properties; import org.apache.commons.cli.BasicParser; import org.apache.commons.cli.CommandLine; import org.apache.commons.cli.CommandLineParser; import org.apache.commons.cli.Option; import org.apache.commons.cli.OptionBuilder; import org.apache.commons.cli.Options; import org.apache.commons.cli.ParseException; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.ByteWritable; import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.mapred.JobConf; import org.apache.hadoop.mapreduce.Counter; import org.apache.hadoop.mapreduce.Counters; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.MRJobConfig; 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.util.GenericOptionsParser; import com.cloudera.ByteBufferRecordReader.READ_COUNTER; public class ByteCount { public static class ByteCountMapper extends Mapper<LongWritable, ByteBufferWritable, ByteWritable, LongWritable> { @Override public void map(LongWritable offset, ByteBufferWritable bufferWritable, Context context) throws IOException, InterruptedException { ByteBuffer buf = bufferWritable.getBuffer(); final int bytesLength = buf.limit(); long[] counts = new long[256]; for (int i = 0; i < bytesLength; i++) { int value = buf.get() & 0xFF; counts[value]++; } for (int i = 0; i < counts.length; i++) { ByteWritable key = new ByteWritable((byte) i); LongWritable value = new LongWritable(counts[i]); context.write(key, value); } } } public static class ByteCountReducer extends Reducer<ByteWritable, LongWritable, ByteWritable, LongWritable> { protected void reduce(ByteWritable key, Iterable<LongWritable> values, Context context) throws IOException, InterruptedException { long count = 0; for (Iterator<LongWritable> iter = values.iterator(); iter.hasNext();) { count += iter.next().get(); } context.write(key, new LongWritable(count)); } } public static void printCounter(Counters counters, Enum<?> key) { Counter c = counters.findCounter(key); System.out.println("\t\t" + c.getDisplayName() + " = " + c.getValue()); } public static void main(String[] args) throws Exception { JobConf conf = new JobConf(new Configuration()); // Trim off the hadoop-specific args String[] remArgs = new GenericOptionsParser(conf, args).getRemainingArgs(); // Pull in properties Options options = new Options(); Option property = OptionBuilder.withArgName("property=value").hasArgs(2).withValueSeparator() .withDescription("use value for given property").create("D"); options.addOption(property); Option skipChecksums = new Option("skipChecksums", "skip checksums"); options.addOption(skipChecksums); Option profile = new Option("profile", "profile tasks"); options.addOption(profile); CommandLineParser parser = new BasicParser(); CommandLine line = parser.parse(options, remArgs); Properties properties = line.getOptionProperties("D"); for (Entry<Object, Object> prop : properties.entrySet()) { conf.set(prop.getKey().toString(), prop.getValue().toString()); System.out.println("Set config key " + prop.getKey() + " to " + prop.getValue()); } if (line.hasOption("skipChecksums")) { conf.setBoolean("bytecount.skipChecksums", true); System.out.println("Skipping checksums"); } if (line.hasOption("profile")) { conf.setBoolean("mapred.task.profile", true); conf.set("mapred.task.profile.params", "-agentlib:hprof=cpu=samples,depth=100,interval=1ms,lineno=y,thread=y,file=%s"); conf.set(MRJobConfig.NUM_MAP_PROFILES, "0"); conf.set("mapred.task.profile.maps", "1"); System.out.println("Profiling map tasks"); } // Get the positional arguments out remArgs = line.getArgs(); if (remArgs.length != 2) { System.err.println("Usage: ByteCount <inputBase> <outputBase>"); System.exit(1); } String inputBase = remArgs[0]; String outputBase = remArgs[1]; Job job = Job.getInstance(conf); job.setInputFormatClass(ByteBufferInputFormat.class); job.setMapOutputKeyClass(ByteWritable.class); job.setMapOutputValueClass(LongWritable.class); job.setMapperClass(ByteCountMapper.class); job.setReducerClass(ByteCountReducer.class); job.setCombinerClass(ByteCountReducer.class); job.setOutputKeyClass(ByteWritable.class); job.setOutputValueClass(LongWritable.class); FileInputFormat.addInputPath(job, new Path(inputBase)); FileOutputFormat.setOutputPath(job, new Path(outputBase)); job.setJarByClass(ByteCount.class); boolean success = job.waitForCompletion(true); Counters counters = job.getCounters(); System.out.println("\tRead counters"); printCounter(counters, READ_COUNTER.BYTES_READ); printCounter(counters, READ_COUNTER.LOCAL_BYTES_READ); printCounter(counters, READ_COUNTER.SCR_BYTES_READ); printCounter(counters, READ_COUNTER.ZCR_BYTES_READ); System.exit(success ? 0 : 1); } }