wiki:III140503/Lab5

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實作五 Lab 5

在單機模式執行 MapReduce 基本運算
Running MapReduce in local mode by Examples
以下練習,請在本機的 Hadoop4Win 環境操作。

範例一『字數統計(WordCount)』

  • STEP 1 : 練習 MapReduce 丟 Job 指令: 『hadoop jar <local jar file> <class name> <parameters>
    Jazz@human ~
    $ cd /opt/hadoop/
    
    Jazz@human /opt/hadoop
    $ hadoop jar hadoop-*-examples.jar wordcount input output
    11/10/21 14:08:58 INFO input.FileInputFormat: Total input paths to process : 12
    11/10/21 14:09:00 INFO mapred.JobClient: Running job: job_201110211130_0001
    11/10/21 14:09:01 INFO mapred.JobClient:  map 0% reduce 0%
    11/10/21 14:09:31 INFO mapred.JobClient:  map 16% reduce 0%
    11/10/21 14:10:29 INFO mapred.JobClient:  map 100% reduce 27%
    11/10/21 14:10:33 INFO mapred.JobClient:  map 100% reduce 100%
    11/10/21 14:10:35 INFO mapred.JobClient: Job complete: job_201110211130_0001
    11/10/21 14:10:35 INFO mapred.JobClient: Counters: 17
    11/10/21 14:10:35 INFO mapred.JobClient:   Job Counters
    11/10/21 14:10:35 INFO mapred.JobClient:     Launched reduce tasks=1
    11/10/21 14:10:35 INFO mapred.JobClient:     Launched map tasks=12
    11/10/21 14:10:35 INFO mapred.JobClient:     Data-local map tasks=12
    11/10/21 14:10:35 INFO mapred.JobClient:   FileSystemCounters
    11/10/21 14:10:35 INFO mapred.JobClient:     FILE_BYTES_READ=16578
    11/10/21 14:10:35 INFO mapred.JobClient:     HDFS_BYTES_READ=18312
    11/10/21 14:10:35 INFO mapred.JobClient:     FILE_BYTES_WRITTEN=32636
    11/10/21 14:10:35 INFO mapred.JobClient:     HDFS_BYTES_WRITTEN=10922
    11/10/21 14:10:35 INFO mapred.JobClient:   Map-Reduce Framework
    11/10/21 14:10:35 INFO mapred.JobClient:     Reduce input groups=592
    11/10/21 14:10:35 INFO mapred.JobClient:     Combine output records=750
    11/10/21 14:10:35 INFO mapred.JobClient:     Map input records=553
    11/10/21 14:10:35 INFO mapred.JobClient:     Reduce shuffle bytes=15674
    11/10/21 14:10:35 INFO mapred.JobClient:     Reduce output records=592
    11/10/21 14:10:35 INFO mapred.JobClient:     Spilled Records=1500
    11/10/21 14:10:35 INFO mapred.JobClient:     Map output bytes=24438
    11/10/21 14:10:35 INFO mapred.JobClient:     Combine input records=1755
    11/10/21 14:10:35 INFO mapred.JobClient:     Map output records=1755
    11/10/21 14:10:35 INFO mapred.JobClient:     Reduce input records=750
    

  • STEP 3 : 使用 HDFS 指令: 『hadoop fs -get <HDFS file/dir> <local file/dir>』,並了解輸出檔案檔名均為 part-r-*,且執行參數會紀錄於 <HOSTNAME>_<TIME>_job_<JOBID>_0001_conf.xml,不妨可以觀察 xml 內容與 hadoop config 檔的參數關聯。
    Jazz@human /opt/hadoop
    $ hadoop fs -get output my_output
    
    Jazz@human /opt/hadoop
    $ ls -alR my_output
    my_output:
    total 12
    drwxr-xr-x+  3 Jazz None     0 Oct 21 14:12 .
    drwxr-xr-x+ 15 Jazz None     0 Oct 21 14:12 ..
    drwxr-xr-x+  3 Jazz None     0 Oct 21 14:12 _logs
    -rwxr-xr-x   1 Jazz None 10922 Oct 21 14:12 part-r-00000
    
    my_output/_logs:
    total 0
    drwxr-xr-x+ 3 Jazz None 0 Oct 21 14:12 .
    drwxr-xr-x+ 3 Jazz None 0 Oct 21 14:12 ..
    drwxr-xr-x+ 2 Jazz None 0 Oct 21 14:12 history
    
    my_output/_logs/history:
    total 48
    drwxr-xr-x+ 2 Jazz None     0 Oct 21 14:12 .
    drwxr-xr-x+ 3 Jazz None     0 Oct 21 14:12 ..
    -rwxr-xr-x  1 Jazz None 26004 Oct 21 14:12 localhost_1319167815125_job_201110211130_0001_Jazz_word+count
    -rwxr-xr-x  1 Jazz None 16984 Oct 21 14:12 localhost_1319167815125_job_201110211130_0001_conf.xml
    

  • 比較熟悉 Windows 的,也可以用 cgystart my_output 用檔案總管開啟下載的內容
    Jazz@human /opt/hadoop
    $ cgystart my_output
    

範例二『用標準表示法過濾內容 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.
    Jazz@human /opt/hadoop
    $ hadoop jar hadoop-*-examples.jar  grep input lab5_out1 'dfs[a-z.]+'
    
  • 運作的畫面如下:
    You should see procedure like this:
    Jazz@human /opt/hadoop
    $ hadoop jar hadoop-*-examples.jar  grep input lab5_out1 'dfs[a-z.]+'
    11/10/21 14:17:39 INFO mapred.FileInputFormat: Total input paths to process : 12
    
    11/10/21 14:17:39 INFO mapred.JobClient: Running job: job_201110211130_0002
    11/10/21 14:17:40 INFO mapred.JobClient:  map 0% reduce 0%
    11/10/21 14:17:54 INFO mapred.JobClient:  map 8% reduce 0%
    11/10/21 14:17:57 INFO mapred.JobClient:  map 16% reduce 0%
    11/10/21 14:18:03 INFO mapred.JobClient:  map 33% reduce 0%
    11/10/21 14:18:13 INFO mapred.JobClient:  map 41% reduce 0%
    11/10/21 14:18:16 INFO mapred.JobClient:  map 50% reduce 11%
    11/10/21 14:18:19 INFO mapred.JobClient:  map 58% reduce 11%
    11/10/21 14:18:23 INFO mapred.JobClient:  map 66% reduce 11%
    11/10/21 14:18:30 INFO mapred.JobClient:  map 83% reduce 16%
    11/10/21 14:18:33 INFO mapred.JobClient:  map 83% reduce 22%
    11/10/21 14:18:36 INFO mapred.JobClient:  map 91% reduce 22%
    11/10/21 14:18:39 INFO mapred.JobClient:  map 100% reduce 22%
    11/10/21 14:18:42 INFO mapred.JobClient:  map 100% reduce 27%
    11/10/21 14:18:48 INFO mapred.JobClient:  map 100% reduce 30%
    11/10/21 14:18:54 INFO mapred.JobClient:  map 100% reduce 100%
    11/10/21 14:18:56 INFO mapred.JobClient: Job complete: job_201110211130_0002
    11/10/21 14:18:56 INFO mapred.JobClient: Counters: 18
    11/10/21 14:18:56 INFO mapred.JobClient:   Job Counters
    11/10/21 14:18:56 INFO mapred.JobClient:     Launched reduce tasks=1
    11/10/21 14:18:56 INFO mapred.JobClient:     Launched map tasks=12
    11/10/21 14:18:56 INFO mapred.JobClient:     Data-local map tasks=12
    11/10/21 14:18:56 INFO mapred.JobClient:   FileSystemCounters
    11/10/21 14:18:56 INFO mapred.JobClient:     FILE_BYTES_READ=888
    11/10/21 14:18:56 INFO mapred.JobClient:     HDFS_BYTES_READ=18312
    11/10/21 14:18:56 INFO mapred.JobClient:     FILE_BYTES_WRITTEN=1496
    11/10/21 14:18:56 INFO mapred.JobClient:     HDFS_BYTES_WRITTEN=280
    11/10/21 14:18:56 INFO mapred.JobClient:   Map-Reduce Framework
    11/10/21 14:18:56 INFO mapred.JobClient:     Reduce input groups=7
    11/10/21 14:18:56 INFO mapred.JobClient:     Combine output records=7
    11/10/21 14:18:56 INFO mapred.JobClient:     Map input records=553
    11/10/21 14:18:56 INFO mapred.JobClient:     Reduce shuffle bytes=224
    11/10/21 14:18:56 INFO mapred.JobClient:     Reduce output records=7
    11/10/21 14:18:56 INFO mapred.JobClient:     Spilled Records=14
    11/10/21 14:18:56 INFO mapred.JobClient:     Map output bytes=193
    11/10/21 14:18:56 INFO mapred.JobClient:     Map input bytes=18312
    11/10/21 14:18:56 INFO mapred.JobClient:     Combine input records=10
    11/10/21 14:18:56 INFO mapred.JobClient:     Map output records=10
    11/10/21 14:18:56 INFO mapred.JobClient:     Reduce input records=7
    11/10/21 14:18:56 WARN mapred.JobClient: Use GenericOptionsParser for parsing th
    e arguments. Applications should implement Tool for the same.
    11/10/21 14:18:57 INFO mapred.FileInputFormat: Total input paths to process : 1
    11/10/21 14:18:57 INFO mapred.JobClient: Running job: job_201110211130_0003
    ( ... skip ... )
    
  • 接著查看結果
    Let's check the computed result of grep from HDFS :
  • 這個例子是要從 input 目錄中的所有檔案中找出符合 dfs 後面接著 a-z 字母一個以上的字串
    Jazz@human /opt/hadoop
    $ hadoop fs -ls lab5_out1
    Found 2 items
    drwxr-xr-x   - Jazz supergroup          0 2011-10-21 14:18 /user/Jazz/lab5_out1/_logs
    -rw-r--r--   1 Jazz supergroup         96 2011-10-21 14:19 /user/Jazz/lab5_out1/part-00000
    
    Jazz@human /opt/hadoop
    $ hadoop fs -cat lab5_out1/part-00000
    3       dfs.class
    2       dfs.period
    1       dfs.file
    1       dfs.replication
    1       dfs.servers
    1       dfsadmin
    1       dfsmetrics.log
    
Last modified 8 years ago Last modified on May 4, 2014, 1:08:41 PM