[jira] Updated: (HADOOP-4652) RAgzip: multiple map tasks for a large gzipped file

["Daehyun Kim (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-4652?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Daehyun Kim updated HADOOP-4652:
--------------------------------

    Attachment: HADOOP-4652-forCORE.patch

the patch file for the hadoop core.

> RAgzip: multiple map tasks for a large gzipped file
> ---------------------------------------------------
>
>                 Key: HADOOP-4652
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4652
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: io, mapred, native
>    Affects Versions: 0.18.2
>            Reporter: Daehyun Kim
>         Attachments: HADOOP-4652-forCORE.patch
>
>
> Currently, the hadoop processes gzipped files with only one map.
> We have made a patch that enables multiple map tasks for one large *gzipped* file. We call the patch RAgzip.
> To process multiple map tasks for gzipped file, you may use RAgzip by just changing InputFormat to RAGZIPInputFormat.
> The option used in RAGZIPInputFormat can be found at the javadoc of RAGZIPInputFormat part.
> RAgzip uses zlib's inflatePrime function which supports random access on a gzipped file. 
> Since the inflatePrime is supported from the version of 1.2.2.4, it requires zlib 1.2.2.4 or higher. (We tested on zlib 1.2.3)
> RAgzip requires the preprocessing step that creates an access point (.ap) file, which is like the index of the gzipped file chunks. 
> The access point(.ap) file is located in same path of the gzipped file.
> If there is a "/user/hadoop/test.gz", the .ap file is created with "/user/hadoop/test.gz.ap".
> We made two patches. 
> 1. One makes changes in the source of the hadoop core. This is the main patch. 
> If the zlib version of the hadoop cluster is greater than 1.2.2.4, you should use this patch.
> 2. On the other hand, if there is a computer with zlib version less than 1.2.2.4 in hadoop cluster, you should use the other patch. 
> This patch uses static link library of the zlib. So if you compile this patch once at a computer with zlib version greater than 1.2.2.4, RAgzip can be used in hadoop cluster even if a computer with zlib version less than 1.2.2.4 exists in the cluster.
> As you know, second patch creates jar file(build/contrib/ragzip/hadoop-x.xx.x-dev-ragzip.jar) as a result of its installation.

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