cgroup stanza a proposal

[Serge Hallyn]

Quoting Stéphane Graber (stgraber at ubuntu.com):
> On Thu, Nov 21, 2013 at 12:26:19PM -0800, Steve Langasek wrote:
> > Hi Stéphane,
> > 
> > On Wed, Nov 20, 2013 at 02:23:59PM -0500, Stéphane Graber wrote:
> > Is upstart responsible for destroying the cgroup, or is this done by the
> > cgroup manager?
> 
> My initial thought was that Upstart would take care of it, so once it
> thinks all jobs using a given cgroup are stopped, it'll ask the manager
> to destroy the cgroup.
> 
> Serge mentioned that the cgroup manager may also be set as a release
> agent which would let it automatically remove cgroups when the last task

Yeah and I'm pretty sure we do not want to use release agents.
I'm not even sure they will continue to be supported long-term
(would have to check the roadmap).

> exits, but I don't think we should use that capability with upstart as
> it'd mean restarting a job would tear down the cgroup and set it up
> again, which may not be what all our users want (if for whatever reason
> they have changed the restrictions after the job started).

I think what we really want is for removal of the cgroups to be
a part of post-stop.

-serge