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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-10893) isolated classloader on the client side
Date Mon, 18 Aug 2014 15:11:20 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-10893?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14100729#comment-14100729
] 

Kihwal Lee commented on HADOOP-10893:
-------------------------------------

The latest patch looks good. One thing I am not sure about is leaving the conf in mapred-default.xml.
 Since the default system classes are in the code, the entry in mapred-site.xml kind of serves
as documentation, which needs to be kept in sync with the code. From pure functionality point
of view, we can simply remove them, but then those who want to modify the list need to look
at the code?  Maybe we can have MR logs show list of system classes when the app class loader
is activated. Then it might be easier for users to figure out the default/current list and
modify. Any other thoughts?

> 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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