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From "Allen Wittenauer (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-2424) LCE should support non-cgroups, non-secure mode
Date Sun, 17 Aug 2014 22:27:18 GMT

    [ https://issues.apache.org/jira/browse/YARN-2424?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14100153#comment-14100153

Allen Wittenauer commented on YARN-2424:

This fix is all about EOU and operability.  I can certainly understand the desire to run cgroups
without needing local users. But transitioning to security is not a binary process for most
users (or, at least, it doesn't have to be...)

The problem with the current code base is that someone moving to a secure mode now has to
either enable cgroups (which, as pointed out in YARN-1253 is irrelevant for security) or cut
everything over at once.  Enabling LCE prior to enabling security allows for a two step transition
and eases problem determination when doing the security upgrade.  Is that user missing from
the system or is Kerberos failing?  Clearly the issues stemming from the former can be sorted
out without security.  This makes the operations side of the house much easier.

It's also worth pointing out that one of the key benefits of running tasks as the user who
submitted them is that it makes troubleshooting much easier.  When one hops on a node, it
is evident as to which user's tasks one is looking at it, even if those tasks aren't validated
as "that" user.  This is especially important in heavy multi-tenant  scenarios.

But, again, the fix in YARN-1253 caused a regression.  LCE w/out security was supported prior
to Hadoop 2.3 and was definitely used by people.    This change still sets the default to
be LCE w/either one user or security, but now for folks who want the prior behavior, they
can flip a flag and get it.

> LCE should support non-cgroups, non-secure mode
> -----------------------------------------------
>                 Key: YARN-2424
>                 URL: https://issues.apache.org/jira/browse/YARN-2424
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: nodemanager
>    Affects Versions: 2.3.0, 2.4.0, 2.5.0, 2.4.1
>            Reporter: Allen Wittenauer
>            Priority: Blocker
>              Labels: regression
>         Attachments: YARN-2424.patch
> After YARN-1253, LCE no longer works for non-secure, non-cgroup scenarios.  This is a
fairly serious regression, as turning on LCE prior to turning on full-blown security is a
fairly standard procedure.

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