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https://issues.apache.org/jira/browse/HADOOP-10893?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14100957#comment-14100957
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Sangjin Lee commented on HADOOP-10893:
--------------------------------------
On the other hand, mapred-default.xml had a good description on the format of
the system classes value:
{panel}
A comma-separated list of classes that should be loaded from the system
classpath, not the user-supplied JARs, when mapreduce.job.classloader is
enabled. Names ending in '.' (period) are treated as package names, and names
starting with a '-' are treated as negative matches.
{panel}
We could move that to the javadoc of ApplicationClassLoader, but that's a
little less than satisfying, as users (not developers) are the ones who need to
override this value.
> isolated classloader on the client side
> ---------------------------------------
>
> Key: HADOOP-10893
> URL: https://issues.apache.org/jira/browse/HADOOP-10893
> Project: Hadoop Common
> Issue Type: New Feature
> Components: util
> Affects Versions: 2.4.0
> Reporter: Sangjin Lee
> Assignee: Sangjin Lee
> Attachments: HADOOP-10893.patch, HADOOP-10893.patch,
> HADOOP-10893.patch, HADOOP-10893.patch, classloader-test.tar.gz
>
>
> We have the job classloader on the mapreduce tasks that run on the cluster.
> It has a benefit of being able to isolate class space for user code and avoid
> version clashes.
> Although it occurs less often, version clashes do occur on the client JVM. It
> would be good to introduce an isolated classloader on the client side as well
> to address this. A natural point to introduce this may be through RunJar, as
> that's how most of hadoop jobs are run.
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