关于Chukwa配置及运行实例,请参见:
http://my.oschina.net/xiangchen/blog/100424
Chukwa将收集到的数据以Sink Files的形式写入到HDFS中,如果不做Archive和Demux操作的话,默认存储在hdfs:///chukwa/logs目录下。
Sink File是Hadoop Sequence File,包含key-value集合。
其中key的类型为org.apache.hadoop.chukwa.ChukwaArchiveKey;
value的类型为org.apache.hadoop.chukwa.ChunkImpl.
一个完整的MapReduce过程可参考代码:
http://javasourcecode.org/html/open-source/chukwa/chukwa-0.4.0/org/apache/hadoop/chukwa/extraction/demux/Demux.java.html
假定已经有Sequence File文件写入到hdfs:///chukwa/logs目录下,我们要对该文件做一个最基本的Word Count MapReduce操作。代码如下:
Tips: 读取Sequece File需要注明job.setInputFormatClass(SequenceFileInputFormat.class)
public class WordCount_SequenceFile { public static class TokenizerMapper extends Mapper<ChukwaArchiveKey, ChunkImpl, Text, IntWritable> { private final static IntWritable one = new IntWritable(1); private Text word = new Text(); public void map(ChukwaArchiveKey key, ChunkImpl value, Context context) throws IOException, InterruptedException { StringTokenizer itr = new StringTokenizer(new String(value.getData())); while (itr.hasMoreTokens()) { word.set(itr.nextToken()); context.write(word, one); } } } public static class IntSumReducer extends Reducer<Text, IntWritable, Text, IntWritable> { private IntWritable result = new IntWritable(); public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException { int sum = 0; for (IntWritable val : values) { sum += val.get(); } result.set(sum); context.write(key, result); } } public static void main(String[] args) throws Exception { Configuration conf = new Configuration(); String[] otherArgs = new GenericOptionsParser(conf, args) .getRemainingArgs(); if (otherArgs.length != 2) { System.err.println("Usage: wordcount <in> <out>"); System.exit(2); } @SuppressWarnings("deprecation") Job job = new Job(conf, "word count"); job.setJarByClass(WordCount_SequenceFile.class); job.setInputFormatClass(SequenceFileInputFormat.class); job.setMapperClass(TokenizerMapper.class); job.setCombinerClass(IntSumReducer.class); job.setReducerClass(IntSumReducer.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(IntWritable.class); FileInputFormat.addInputPath(job, new Path(otherArgs[0])); FileOutputFormat.setOutputPath(job, new Path(otherArgs[1])); System.exit(job.waitForCompletion(true) ? 0 : 1); } }关于MapReduce程序的编译,请参见:
http://my.oschina.net/xiangchen/blog/102091
在运行时需要添加chukwa-0.5.0.jar库:
hadoop jar MapReduce.jar demo.mapreduce.WordCount_SequenceFile -libjars MapReduce.jar,chukwa-0.5.0.jar /chukwa/logs/xx.done /output_file