[jira] Commented: (MAPREDUCE-217) Tasks to run on a different jvm version than the TaskTracker

["Amar Kamat (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-217?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12769911#action_12769911 ] 

Amar Kamat commented on MAPREDUCE-217:
--------------------------------------

Had a discussion with Sharad on this. As he rightly pointed out that giving preference to user defined classpath entries over (tt's) inherited classpath entries can lead to security issues where a malicious user can define its own Task.java or ReduceTask.java. I think we should keep the classpath ordering as is.

bq. At least it also needs to set the new classpath for the native libraries and probably there's more that I'm missing.
Koji, as of today users can add their libraries which is given preference over the inherited ones.

Currently this is what is done
child.jvm : tt.jvm
child.libraries : user-defined-libraries+tt.libraries
child.classpath : tt.classpath+job-jar.classpath+dist-cache-entries+current.wor,dir+user-defined.classpath

Changes are 
child.jvm : user-defined.jvm else tt.jvm
// since user is specifying the jvm, the user is responsible for add the the required libs too


> Tasks to run on a different jvm version than the TaskTracker
> ------------------------------------------------------------
>
>                 Key: MAPREDUCE-217
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-217
>             Project: Hadoop Map/Reduce
>          Issue Type: New Feature
>         Environment: linux
>            Reporter: Koji Noguchi
>            Assignee: Amar Kamat
>         Attachments: mapreduce-217-v1.0.patch
>
>
> We use 32-bit jvm for TaskTrackers. 
> Sometimes our users want to call 64-bit JNI libraries from their tasks.
> This requires tasks to be running on 64-bit jvm.
> On Solaris, you can simply use -d32/-d64 to choose, but on Linux, it's on a completely different package.
> So far, tasks run on the same jvm version as the TaskTracker.
> {noformat}
> // use same jvm as parent
> File jvm =   new File(new File(System.getProperty("java.home"), "bin"), "java");
> {noformat}
> Is it possible to let users provide a java home path 
> or let them choose from a pre-selected list of paths?

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