MapReduce学习笔记

持之以恒，但求对MapReduce有所觉悟

 

理论学习:

http://hadooptutorial.wikispaces.com

http://developer.yahoo.com/hadoop/tutorial/module4.html

 

实践学习:

执行倒排索引程序:

本段代码是Yahoo! Hadoop tutorial的module4——MapReduce最后面的代码

1、从Eclipse中导出Jar包LineIndexer.jar

2、将所有处理的文件上传到HDFS

   

root@ubuntu:/# hadoop dfs -put  *.txt /user/root/input

root@ubuntu:/# hadoop dfs -ls /user/root/input
Found 3 items
-rw-r--r--   1 root supergroup     569218 2012-01-15 19:46 /user/root/input/All's Well That Ends Well.txt
-rw-r--r--   1 root supergroup     569218 2012-01-15 19:46 /user/root/input/As You Like It.txt
-rw-r--r--   1 root supergroup     569218 2012-01-15 19:46 /user/root/input/The Comedy of Errors.txt

 3、执行jar包

root@ubuntu:/usr/hadoop-0.20.2/chenwq# hadoop jar LineIndexer.jar /user/root/input /user/root/output

4、查看Hadoop状态 

http://localhost:50030/     - Hadoop 管理介面

http://localhost:50060/     - Hadoop Task Tracker 状态

http://localhost:50070/     - Hadoop DFS 状态

 

5、输出结果

12/01/16 04:53:14 WARN mapred.JobClient: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
12/01/16 04:53:14 INFO mapred.FileInputFormat: Total input paths to process : 14
12/01/16 04:53:15 INFO mapred.JobClient: Running job: job_201201150129_0001
12/01/16 04:53:16 INFO mapred.JobClient:  map 0% reduce 0%
12/01/16 04:53:38 INFO mapred.JobClient:  map 1% reduce 0%
12/01/16 04:53:44 INFO mapred.JobClient:  map 2% reduce 0%
12/01/16 04:53:50 INFO mapred.JobClient:  map 3% reduce 0%
12/01/16 04:53:56 INFO mapred.JobClient:  map 4% reduce 0%
12/01/16 04:54:08 INFO mapred.JobClient:  map 5% reduce 0%
12/01/16 04:54:11 INFO mapred.JobClient:  map 6% reduce 0%
12/01/16 04:54:58 INFO mapred.JobClient:  map 7% reduce 0%
12/01/16 04:55:06 INFO mapred.JobClient:  map 7% reduce 1%
12/01/16 04:55:12 INFO mapred.JobClient:  map 7% reduce 2%
12/01/16 04:55:15 INFO mapred.JobClient:  map 8% reduce 2%
12/01/16 04:55:21 INFO mapred.JobClient:  map 9% reduce 2%
12/01/16 04:55:27 INFO mapred.JobClient:  map 10% reduce 2%
12/01/16 04:55:33 INFO mapred.JobClient:  map 11% reduce 2%
12/01/16 04:55:42 INFO mapred.JobClient:  map 12% reduce 2%
12/01/16 04:55:48 INFO mapred.JobClient:  map 13% reduce 2%
12/01/16 04:56:23 INFO mapred.JobClient:  map 13% reduce 3%
12/01/16 04:56:26 INFO mapred.JobClient:  map 13% reduce 4%
12/01/16 04:56:38 INFO mapred.JobClient:  map 14% reduce 4%
12/01/16 04:56:41 INFO mapred.JobClient:  map 15% reduce 4%
12/01/16 04:56:47 INFO mapred.JobClient:  map 16% reduce 4%
12/01/16 04:56:53 INFO mapred.JobClient:  map 17% reduce 4%
12/01/16 04:56:59 INFO mapred.JobClient:  map 18% reduce 4%
12/01/16 04:57:05 INFO mapred.JobClient:  map 19% reduce 4%
12/01/16 04:57:11 INFO mapred.JobClient:  map 20% reduce 4%
12/01/16 04:57:48 INFO mapred.JobClient:  map 20% reduce 5%
12/01/16 04:57:51 INFO mapred.JobClient:  map 20% reduce 6%
12/01/16 04:57:54 INFO mapred.JobClient:  map 21% reduce 6%
12/01/16 04:58:00 INFO mapred.JobClient:  map 22% reduce 6%
12/01/16 04:58:06 INFO mapred.JobClient:  map 23% reduce 6%
12/01/16 04:58:12 INFO mapred.JobClient:  map 24% reduce 6%
12/01/16 04:58:18 INFO mapred.JobClient:  map 25% reduce 6%
12/01/16 04:58:24 INFO mapred.JobClient:  map 26% reduce 6%
12/01/16 04:59:05 INFO mapred.JobClient:  map 26% reduce 7%
12/01/16 04:59:12 INFO mapred.JobClient:  map 26% reduce 8%
12/01/16 04:59:15 INFO mapred.JobClient:  map 27% reduce 8%
12/01/16 04:59:21 INFO mapred.JobClient:  map 28% reduce 8%
12/01/16 04:59:27 INFO mapred.JobClient:  map 29% reduce 8%
12/01/16 04:59:33 INFO mapred.JobClient:  map 30% reduce 8%
12/01/16 04:59:36 INFO mapred.JobClient:  map 31% reduce 8%
12/01/16 04:59:42 INFO mapred.JobClient:  map 32% reduce 8%
12/01/16 04:59:48 INFO mapred.JobClient:  map 33% reduce 8%
12/01/16 05:00:30 INFO mapred.JobClient:  map 33% reduce 10%
12/01/16 05:00:33 INFO mapred.JobClient:  map 34% reduce 10%
12/01/16 05:00:36 INFO mapred.JobClient:  map 34% reduce 11%
12/01/16 05:00:42 INFO mapred.JobClient:  map 35% reduce 11%
12/01/16 05:00:48 INFO mapred.JobClient:  map 36% reduce 11%
12/01/16 05:00:54 INFO mapred.JobClient:  map 37% reduce 11%
12/01/16 05:01:00 INFO mapred.JobClient:  map 38% reduce 11%
12/01/16 05:01:06 INFO mapred.JobClient:  map 39% reduce 11%
12/01/16 05:01:12 INFO mapred.JobClient:  map 40% reduce 11%
12/01/16 05:01:55 INFO mapred.JobClient:  map 40% reduce 12%
12/01/16 05:01:58 INFO mapred.JobClient:  map 41% reduce 13%
12/01/16 05:02:04 INFO mapred.JobClient:  map 42% reduce 13%
12/01/16 05:02:10 INFO mapred.JobClient:  map 43% reduce 13%
12/01/16 05:02:16 INFO mapred.JobClient:  map 44% reduce 13%
12/01/16 05:02:22 INFO mapred.JobClient:  map 45% reduce 13%
12/01/16 05:02:28 INFO mapred.JobClient:  map 46% reduce 13%
12/01/16 05:03:15 INFO mapred.JobClient:  map 46% reduce 14%
12/01/16 05:03:19 INFO mapred.JobClient:  map 46% reduce 15%
12/01/16 05:03:22 INFO mapred.JobClient:  map 47% reduce 15%
12/01/16 05:03:30 INFO mapred.JobClient:  map 48% reduce 15%
12/01/16 05:03:36 INFO mapred.JobClient:  map 49% reduce 15%
12/01/16 05:03:42 INFO mapred.JobClient:  map 50% reduce 15%
12/01/16 05:03:48 INFO mapred.JobClient:  map 51% reduce 15%
12/01/16 05:03:54 INFO mapred.JobClient:  map 52% reduce 15%
12/01/16 05:04:00 INFO mapred.JobClient:  map 53% reduce 15%
12/01/16 05:04:37 INFO mapred.JobClient:  map 56% reduce 15%
12/01/16 05:04:40 INFO mapred.JobClient:  map 56% reduce 16%
12/01/16 05:04:43 INFO mapred.JobClient:  map 57% reduce 17%
12/01/16 05:04:46 INFO mapred.JobClient:  map 60% reduce 17%
12/01/16 05:04:49 INFO mapred.JobClient:  map 61% reduce 17%
12/01/16 05:04:52 INFO mapred.JobClient:  map 64% reduce 20%
12/01/16 05:04:55 INFO mapred.JobClient:  map 65% reduce 20%
12/01/16 05:04:58 INFO mapred.JobClient:  map 68% reduce 20%
12/01/16 05:05:01 INFO mapred.JobClient:  map 69% reduce 21%
12/01/16 05:05:04 INFO mapred.JobClient:  map 73% reduce 21%
12/01/16 05:05:07 INFO mapred.JobClient:  map 73% reduce 22%
12/01/16 05:05:10 INFO mapred.JobClient:  map 76% reduce 22%
12/01/16 05:05:16 INFO mapred.JobClient:  map 80% reduce 23%
12/01/16 05:05:22 INFO mapred.JobClient:  map 83% reduce 25%
12/01/16 05:05:25 INFO mapred.JobClient:  map 90% reduce 25%
12/01/16 05:05:31 INFO mapred.JobClient:  map 96% reduce 27%
12/01/16 05:05:34 INFO mapred.JobClient:  map 100% reduce 30%
12/01/16 05:05:44 INFO mapred.JobClient:  map 100% reduce 33%
12/01/16 05:06:45 INFO mapred.JobClient:  map 100% reduce 66%
12/01/16 05:06:48 INFO mapred.JobClient:  map 100% reduce 67%
12/01/16 05:06:51 INFO mapred.JobClient:  map 100% reduce 68%
12/01/16 05:06:57 INFO mapred.JobClient:  map 100% reduce 69%

 

import java.io.IOException;
import java.util.Iterator;
import java.util.StringTokenizer;

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.FileSplit;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;

public class LineIndexer {

  public static class LineIndexMapper extends MapReduceBase
      implements Mapper<LongWritable, Text, Text, Text> {

    private final static Text word = new Text();
    private final static Text location = new Text();

	 public void map(LongWritable key, Text val,
		        OutputCollector<Text, Text> output, Reporter reporter)
		        throws IOException {

		      FileSplit fileSplit = (FileSplit)reporter.getInputSplit();
		      String fileName = fileSplit.getPath().getName();
		      location.set(fileName);

		      String line = val.toString();
		      StringTokenizer itr = new StringTokenizer(line.toLowerCase());
		      while (itr.hasMoreTokens()) {
		        word.set(itr.nextToken());
		        output.collect(word, location);
		      }
		      
		    }
  }



  public static class LineIndexReducer extends MapReduceBase
      implements Reducer<Text, Text, Text, Text> {

    public void reduce(Text key, Iterator<Text> values,
        OutputCollector<Text, Text> output, Reporter reporter)
        throws IOException {

      boolean first = true;
      StringBuilder toReturn = new StringBuilder();
      while (values.hasNext()){
        if (!first)
          toReturn.append(", ");
        first=false;
        toReturn.append(values.next().toString());
      }

      output.collect(key, new Text(toReturn.toString()));
    }
  }


  /**
   * The actual main() method for our program; this is the
   * "driver" for the MapReduce job.
   */
  public static void main(String[] args) {
    JobClient client = new JobClient();
    JobConf conf = new JobConf(LineIndexer.class);

    conf.setJobName("LineIndexer");

    conf.setOutputKeyClass(Text.class);
    conf.setOutputValueClass(Text.class);

    FileInputFormat.addInputPath(conf, new Path(args[0]));
    FileOutputFormat.setOutputPath(conf, new Path(args[1]));

    conf.setMapperClass(LineIndexMapper.class);
    conf.setReducerClass(LineIndexReducer.class);

    client.setConf(conf);

    try {
      JobClient.runJob(conf);
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}