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Date: Wed, 2 Jul 2008 05:59:45 -0700 (PDT)
From: "Steve Loughran (JIRA)" <jira@apache.org>
To: core-dev@hadoop.apache.org
Subject: [jira] Commented: (HADOOP-3675) Provide more flexibility in the way
 tasks are run
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    [ https://issues.apache.org/jira/browse/HADOOP-3675?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12609910#action_12609910 ] 

Steve Loughran commented on HADOOP-3675:
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An in-VM task runner should always run the task in a new security manager (or at least try to set a new security manager, and fail gracefully if it can't, in case someone else is running Hadoop under a new Security Manager already). The SM could block calls to System.exit()

The reason for doing this from the outset is if you leave it out, it sets up expectations that are hard to change later on. The rule should be in-VM == under a security manager. 

> 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
>
>
> *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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