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From "Subir S (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (MAPREDUCE-3924) Partioning Failing in certain scenarios for Hadoop Streaming using Ruby
Date Tue, 08 May 2012 18:37:52 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-3924?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Subir S resolved MAPREDUCE-3924.
--------------------------------

    Resolution: Not A Problem

My mistake. This is not a bug. It was related to how we specified the key field separaters
which invoking the streaming. We had overridden that to be a '|' instead of default 'tab'
and that caused all confusion.
                
> Partioning Failing in certain scenarios for Hadoop Streaming using Ruby
> -----------------------------------------------------------------------
>
>                 Key: MAPREDUCE-3924
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3924
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>    Affects Versions: 0.20.2
>         Environment: Linux OS
> 44 Node cluster
> Hadoop 0.20.2-cdh3u0 is the version
>            Reporter: Subir S
>              Labels: hadoop, map, reduce, ruby, streaming
>
> We noticed a wierd scenario. The partitioning option fails in scenario below. The map
reduce just aggregates values like a word count. However the key is having 2 parts.
> Eg:
> Input Records: (<key1|key2><tab><qty1|amt1|qty2|amt2|qty3|amt3>
> 1201|420 1|24.0|2|26.0|0|0.0
> 1200|420 1|24.0|2|26.0|0|0.0
> 1200|420 1|25.0|3|52.0|1|55.0
> 1403|400 1|25.0|3|52.0|1|55.0
> 1201|420 1|24.0|2|26.0|0|0.0
> 1201|420 1|24.0|2|26.0|0|0.0
> 1403|400 1|25.0|3|52.0|1|55.0
> Partioning option: -k1,1 and Comparator option -k1,1n -k2,2n works fine and the output
we get is expected output
> 1200|420 2|49.0|5|78.0|1|55.0
> 1201|420 3|72.0|6|78.0|0|0.0
> 1403|400 2|50.0|6|104.0|2|110.0
> However if we use
> Partioning option: -k1,1 -k2,2 and Comparator option -k1,1n -k2,2n then the output is
faulty. Seems the same key does not go to same reducer in output we see duplicate records,
however this does not happen to all records. A hypothetical faulty output based on above input
is:
> 1200|420 1|24.0|2|26.0|0|0.0
> 1201|420 3|72.0|6|78.0|0|0.0
> 1403|400 2|50.0|6|104.0|2|110.0
> 1200|420 1|25.0|3|52.0|1|55.0
> See that records with the key (1200|420) is not aggregated. This can happen only if the
record does not go to the same reducer after partioning.
> Any clue why this is happening? I could not understanding what is going wrong.

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