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https://issues.apache.org/jira/browse/MAPREDUCE-1700?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13526775#comment-13526775
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Kihwal Lee commented on MAPREDUCE-1700:
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{quote}
bq. Tom, one thing I've forgot to mention in my previous comment, we should see
how to enable the classloader on the client side as well as it may be required
(to use different JARs) for the submission code.
I think this is a slightly different problem, since users generally have more
control over the JVM they submit from than the JVM the task runs in. So, yes,
another JIRA would be appropriate.
{quote}
I think AM also runs user code, if a custom output format is defined.
> User supplied dependencies may conflict with MapReduce system JARs
> ------------------------------------------------------------------
>
> Key: MAPREDUCE-1700
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-1700
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: task
> Reporter: Tom White
> Assignee: Tom White
> Attachments: MAPREDUCE-1700-ccl.patch, MAPREDUCE-1700-ccl.patch,
> MAPREDUCE-1700.patch, MAPREDUCE-1700.patch, MAPREDUCE-1700.patch,
> MAPREDUCE-1700.patch, MAPREDUCE-1700.patch, MAPREDUCE-1700.patch
>
>
> If user code has a dependency on a version of a JAR that is different to the
> one that happens to be used by Hadoop, then it may not work correctly. This
> happened with user code using a different version of Avro, as reported
> [here|https://issues.apache.org/jira/browse/AVRO-493?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12852081#action_12852081].
> The problem is analogous to the one that application servers have with WAR
> loading. Using a specialized classloader in the Child JVM is probably the way
> to solve this.
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