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https://issues.apache.org/jira/browse/HADOOP-10893?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14102842#comment-14102842
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Jason Lowe commented on HADOOP-10893:
-------------------------------------
The patch no longer applies after HADOOP-9902, and since that only went into
trunk we'll need a separate patch for branch-2.
I tried to kick the tires on the latest patch but the client classloader never
activated even though I set HADOOP_USE_CLIENT_CLASSLOADER=true. That's because
the following code will always return false:
{code}
boolean useClientClassLoader() {
return Boolean.getBoolean(System.getenv(HADOOP_USE_CLIENT_CLASSLOADER));
}
{code}
getBoolean looks up the value of the specified system property, whereas
parseBoolean tries to parse the given string as a boolean.
Other comments are minor or nits:
In hadoop-config.sh "The system classes are A comma-separated list" s/b "The
system classes are a comma-separated list".
It would be nice if TestMain, TestSecond, TestThird were a bit less generically
named since they are for a very specific test, e.g.: ClassLoaderCheckAppMain,
ClassLoaderCheckAppSecond, ClassLoaderCheckAppThird, etc.. Not a must-fix
though, rather thinking people may wonder what the names mean when they run
across them in the source since TestMain sounds pretty generic.
> 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, 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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