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From "Tom White (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3675) Provide more flexibility in the way tasks are run
Date Mon, 04 Aug 2008 21:00:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3675?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12619703#action_12619703
] 

Tom White commented on HADOOP-3675:
-----------------------------------

Deveraj, This approach looks good to me. One of the challenges is to handle the user logs,
which are managed using the shell (since HADOOP-1553). If the JVM is reused for more tasks,
how does the shell redirection know about this? If the JVM handled the logging (by redirecting
System.out and System.err), then it would be fine, but the reason it was moved to the shell
was because of performance (see numbers in HADOOP-1553).

> Provide more flexibility in the way tasks are run
> -------------------------------------------------
>
>                 Key: HADOOP-3675
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3675
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: mapred
>            Reporter: Brice Arnould
>            Assignee: Brice Arnould
>            Priority: Minor
>         Attachments: TaskWrapper_v0.patch, userBasedInsulator.sh
>
>
> *The aim*
> With [HADOOP-3421] speaking about sharing a cluster among more than one organization
(so potentially with non-cooperative users), and posts on the ML speaking about virtualization
and the ability to re-use the TaskTracker's VM to run new tasks, it could be useful for admins
to choose the way TaskRunners run their children. 
> More specifically, it could be useful to provide a way to imprison a Task in its working
directory, or in a virtual machine.
> In some cases, reusing the VM might be useful, since it seems that this feature is really
wanted ([HADOOP-249]).
> *Concretely*
> What I propose is a new class, called called SeperateVMTaskWrapper which contains the
current logic for running tasks in another JVM. This class extends another, called TaskWrapper,
which could be inherited to provide new ways of running tasks.
> As part of this issue I would also like to provide two other TaskWrappers : the first
would run the tasks as Thread of the TaskRunner's VM (if it is possible without too much changes),
the second would use a fixed pool of local unix accounts to insulate tasks from each others
(so potentially non-cooperating users will be hable to share a cluster, as described in [HADOOP-3421]).

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