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Posted to mapreduce-issues@hadoop.apache.org by "Kihwal Lee (JIRA)" <ji...@apache.org> on 2012/12/04 18:38:01 UTC
[jira] [Commented] (MAPREDUCE-1700) User supplied dependencies may
conflict with MapReduce system JARs
[ https://issues.apache.org/jira/browse/MAPREDUCE-1700?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13509888#comment-13509888 ]
Kihwal Lee commented on MAPREDUCE-1700:
---------------------------------------
Now that we have a much better way of dealing with dependency conflicts, what will be the fate of "mapreduce.job.user.classpath.first" feature? Is there any use case where this feature works but the CCL approach don't or somehow is preferred over CCL for some reason? If none, shall we deprecate it?
> 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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