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From Jagadish Bihani <jagadish.bih...@pubmatic.com>
Subject Re: Flume compression peculiar behaviour while processing compressed files by a map reduce job
Date Tue, 30 Oct 2012 03:06:13 GMT
Does anyone have any inputs about why below mentioned behaviour might 
have happened?

On 10/26/2012 06:32 PM, Jagadish Bihani wrote:
>
> Same thing happens even for gzip.
>
> Regards,
> Jagadish
>
> On 10/26/2012 04:30 PM, Jagadish Bihani wrote:
>> Hi
>>
>> I have a very peculiar scenario.
>>
>>  1. My HDFS sink creates a bz2 file. File is perfectly fine I can 
>> decompress it and
>> read it. It has 0.2 million records.
>> 2. Now I give that file to map-reduce job (hadoop 1.0.3) and 
>> surprisingly it only
>> reads first 100 records.
>> 3. I then decompress the same file on local file system and use bzip2 
>> command of
>> linux to again compress it and copy to HDFS.
>> 4. Now I run the map -reduce job and this time it correctly processes 
>> all the records.
>>
>> I think flume agent writes compressed data to HDFS file in batches. 
>> And somehow
>> bzip2 codec used by hadoop uses only first part of it.
>>
>> This way bz2 files generated by Flume, if used directly, can't be 
>> processed by Map reduce job.
>> Is there any solution to it?
>>
>> Any inputs about other compression formats?
>>
>> P.S.
>> Versions:
>>
>> Flume 1.2.0 (Raw version; downloaded from 
>> http://www.apache.org/dyn/closer.cgi/flume/1.2.0/apache-flume-1.2.0-bin.tar.gz)
>> Hadoop 1.0.3
>>
>> Regards,
>> Jagadish
>


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