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From "Sangjin Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-10893) isolated classloader on the client side
Date Thu, 21 Aug 2014 18:25:12 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-10893?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14105724#comment-14105724

Sangjin Lee commented on HADOOP-10893:

The comments in hadoop-env.sh in the trunk patch are found in hadoop-config.sh in the branch-2
patch. It appears that the existing comments pre-HADOOP-9902 in hadoop-config.sh were replaced
by (shorter) comments in hadoop-env.sh. Hadoop-env.sh did not have comments on things like
HADOOP_USER_CLASSPATH_FIRST prior to HADOOP-9902. Following the movement, I basically moved
the new comments from hadoop-config.sh to hadoop-env.sh. If we were to move those comments
to hadoop-env.sh in branch-2, then I think we'd need to move other existing comments similarly,
or the new comments would look out of place. Thoughts?

Also, prior to HADOOP-9902, hadoop-config.cmd did not have the mirroring comments for the
environment variables. That kind of felt awkward but again I felt that either we recreate
the same comments for all environment variables or none. Now that has been corrected with
HADOOP-9902, I decided to add the same comments to hadoop.cmd in the trunk, thus the discrepancy
between branch-2 and trunk.

Let me know what you think about these two... Thanks!

> 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-branch-2.patch, HADOOP-10893-branch-2.patch, HADOOP-10893.patch,
HADOOP-10893.patch, HADOOP-10893.patch, 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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