wiki:III140503/Lab6

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實作六 Lab 6

在完全分散模式執行 MapReduce 基本運算
Running MapReduce in Full Distributed Mode by Examples
以下練習,請連線至 hadoop.3du.me 操作。底下的 userXX 等於您的用戶名稱。

Sample 1 : WordCount

  • 如名稱,WordCount會對所有的字作字數統計,並且從a-z作排列
    WordCount example will count each word shown in documents and sorting from a to z.
    ~$ hadoop fs -put /opt/hadoop/conf lab5_input
    ~$ hadoop fs -rmr lab5_out2        ## 這行是預防上次有執行過這個範例的防呆步驟
    ~$ hadoop jar hadoop-examples.jar wordcount lab5_input lab5_out2
    
  • 檢查輸出結果的方法同之前方法
    Let's check the computed result of wordcount from HDFS :
    $ hadoop fs -ls lab5_out2
    $ hadoop fs -cat lab5_out2/part-r-00000 
    
  • 結果如下
    You should see results like this:
    "".	4
    "*"	9
    "127.0.0.1"	3
    "AS	2
    "License");	2
    "_logs/history/"	1
    "alice,bob	9
    
    ( ... skip ... )
    

Sample 2: grep

  • grep 這個命令是擷取文件裡面特定的字元,在Hadoop example中此指令可以擷取文件中有此指定文字的字串,並作計數統計
    grep is a command to extract specific characters in documents. In hadoop examples, you can use this command to extract strings match the regular expression and count for matched strings.
    $ hadoop fs -ls lab5_input
    $ hadoop jar hadoop-examples.jar grep lab5_input lab5_out3 'dfs[a-z.]+' 
    
  • 運作的畫面如下:
    You should see procedure like this:
    11/04/19 10:00:20 INFO mapred.FileInputFormat: Total input paths to process : 25
    11/04/19 10:00:20 INFO mapred.JobClient: Running job: job_201104120101_0645
    11/04/19 10:00:21 INFO mapred.JobClient:  map 0% reduce 0%
    ( ... skip ... )
    
  • 接著查看結果
    Let's check the computed result of grep from HDFS :
    $ hadoop fs -ls lab5_out3
    Found 2 items
    drwx------   - hXXXX supergroup          0 2011-04-19 10:00 /user/hXXXX/lab5_out1/_logs
    -rw-r--r--   2 hXXXX supergroup       1146 2011-04-19 10:00 /user/hXXXX/lab5_out1/part-00000
    $ hadoop fs -cat lab5_out3/part-00000 
    
  • 結果如下
    You should see results like this:
    4	dfs.permissions
    4	dfs.replication
    4	dfs.name.dir
    3	dfs.namenode.decommission.interval.
    3	dfs.namenode.decommission.nodes.per.interval
    3	dfs.
    ( ... skip ... )
    

More Examples

可執行的指令一覽表:
Here is a list of hadoop examples :

aggregatewordcount An Aggregate based map/reduce program that counts the words in the input files.
aggregatewordhist An Aggregate based map/reduce program that computes the histogram of the words in the input files.
grep A map/reduce program that counts the matches of a regex in the input.
join A job that effects a join over sorted, equally partitioned datasets
multifilewc A job that counts words from several files.
pentomino A map/reduce tile laying program to find solutions to pentomino problems.
pi A map/reduce program that estimates Pi using monte-carlo method.
randomtextwriter A map/reduce program that writes 10GB of random textual data per node.
randomwriter A map/reduce program that writes 10GB of random data per node.
sleep A job that sleeps at each map and reduce task.
sort A map/reduce program that sorts the data written by the random writer.
sudoku A sudoku solver.
wordcount A map/reduce program that counts the words in the input files.

You could find more detail at org.apache.hadoop.examples

Last modified 8 years ago Last modified on May 4, 2014, 1:14:53 PM