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https://issues.apache.org/jira/browse/MAPREDUCE-1700?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13469203#comment-13469203
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Alejandro Abdelnur commented on MAPREDUCE-1700:
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Nice.
What I would add is the capability of blacklisting packages. This is, if a
package is blacklisted and a class under that package hierarchy is found in the
job JARs, the job should fail. This is something avail in webapp classloaders
to avoid webapps for bundling things like servlet/jsp JARs that would break
things. In our case we would blacklist common/hdfs/yarn/mapred packages and
log4j (the factory is a singleton and if present in the job JARs will trash the
log configuration of hadoop). I could see other JARs fitting this blacklist,
thus I'd suggest that we have a config property with the list of blacklisted
packages.
This is isolating MR jobs from Hadoop JARs. I think we should do the same at
YARN level to isolate YARN JARs from AM JARs. Because of this, the
JobClassLoader should be in common and probably have a different name, like
IsolationClassLoader. Also it should receive, in the constructor, the blacklist.
> 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
>
>
> 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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