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From "Milind Bhandarkar (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1815) Separate client and server jars
Date Thu, 30 Aug 2007 17:46:30 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1815?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12523895

Milind Bhandarkar commented on HADOOP-1815:

Actually, we faced this problem while using distcp also. (Sorry for not mentioning it in the
original mail.) disctcp (i.e. o.a.h.util.CopyFiles) is a mapred and dfs client appplication.
However, since it is part of THE hadoop jar, if we make modifications to it, and use the modified
version as a client jar, it is not reflected on the server-side (i.e. the tasktrackers pick
up the original version of CopyFiles, rather than from the client one.) This is also true
for streaming, now that the contrib jars are on the class path and are searched before the
user-supplied jar. So, in that case, there is a situation that the JobClient side changes
in user-supplied jar work, but the Task-side changes are picked up from the deployed jars
on tasktrackers.

I do not claim to have a solution for this. But I am sure someone out there has come across
this before and solved this problem.

> Separate client and server jars
> -------------------------------
>                 Key: HADOOP-1815
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1815
>             Project: Hadoop
>          Issue Type: Bug
>          Components: build
>    Affects Versions: 0.14.0
>         Environment: All
>            Reporter: Milind Bhandarkar
>             Fix For: 0.15.0
> For the ease of deployment, one should not have to change the server jars, and restart
clusters, when minor features on the client side are changed. This requireds separating client
and server jars for hadoop. Version numbers appended to hadoop jars can reflect the compatibility.
e.g. the server jar could be at 0.13.1, and the client jar could be at 0.13.2. In short, we
can treat the part following 0. as the "major" version number for now.
> This allows major client frameworks such as streaming and Pig happy. To my knowledge,
Pig uses hadoop's default jobclient. Whereas streaming uses its own jobclient. I would love
to change streaming to use the default hadoop jobclient, if I can make modifications to it
(e.g. to print more stats that are available from TaskReport, for example), if I do not have
to deploy the new version of the whole jar to the backend and restart the mapreduce cluster.
> (I thought there was already a bug filed for separating the client and server jar, but
I could not find it. Hence the new Jira. Sorry about duplication, if any.)

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