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https://issues.apache.org/jira/browse/HBASE-20332?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16441107#comment-16441107
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stack commented on HBASE-20332:
-------------------------------
Go [~busbey]! This is hard work.
> shaded mapreduce module shouldn't include hadoop
> ------------------------------------------------
>
> Key: HBASE-20332
> URL: https://issues.apache.org/jira/browse/HBASE-20332
> Project: HBase
> Issue Type: Sub-task
> Components: mapreduce, shading
> Affects Versions: 2.0.0
> Reporter: Sean Busbey
> Assignee: Sean Busbey
> Priority: Critical
> Fix For: 2.0.0
>
> Attachments: HBASE-20332.0.patch
>
>
> AFAICT, we should just entirely skip including hadoop in our shaded mapreduce
> module
> 1) Folks expect to run yarn / mr apps via {{hadoop jar}} / {{yarn jar}}
> 2) those commands include all the needed Hadoop jars in your classpath by
> default (both client side and in the containers)
> 3) If you try to use "user classpath first" for your job as a workaround
> (e.g. for some library your application needs that hadoop provides) then our
> inclusion of *some but not all* hadoop classes then causes everything to fall
> over because of mixing rewritten and non-rewritten hadoop classes
> 4) if you don't use "user classpath first" then all of our
> non-relocated-but-still-shaded hadoop classes are ignored anyways so we're
> just wasting space
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