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https://issues.apache.org/jira/browse/MAPREDUCE-1700?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13501913#comment-13501913
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Steve Loughran commented on MAPREDUCE-1700:
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# {{Task}} should get the string {{"APP_CLASSPATH"}} from the
{{ApplicationConstants}}.
# the test dir logic won't work on windows if {{test.build.data}} isn't set
:{{System.getProperty("test.build.data", "/tmp")}} -that default should be
replaced with {{System.getProperty("java.io.tmpdir')}}
# in {{ApplicationClassLoader.loadClass()}} it looks to me like it is possible
to have the situation {{c==null}} && {{ex==null}} at the {{if (c==null} throw
ex;}} clause -if {{parent.loadClass() => null}}. Some check for a null {{ex}}
value and setting to (something?) would avoid this.
# the tests should look for resource loading too, just to be thorough.
Other than that, with my finite classloader knowledge -looks good. Someone who
understands OSGi should do quick review too.
> 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
>
>
> 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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