Re: [Xen-devel] xl remus - Invoking scripts from xl

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2013-07-18 at 11:53 +0100, George Dunlap wrote:
> On Wed, Jul 17, 2013 at 5:39 PM, Shriram Rajagopalan <rshriram@xxxxxxxxx> 
> wrote:
> > On Wed, Jul 17, 2013 at 9:57 AM, Ian Campbell <Ian.Campbell@xxxxxxxxxx>
> > wrote:
> >>
> >> On Sun, 2013-07-14 at 10:13 -0500, Shriram Rajagopalan wrote:
> >>
> >> > I can use xenstore too but I don't want to pollute xenstore entries
> >> > unless absolutely necessary.
> >>
> >> Ultimately it may be that the script is running in a different domain
> >> (e.g. a driver domain) so xenstore may be the best way.
> >>
> >> Can you enumerate what would be going in there? It may be
> >> that /libxl/<domid> or even /tools/remus/<domid> might be an appropriate
> >> home for it.
> >>
> >
> > driver domains is something that I didnt think about. interesting idea
> > though.
> >
> > basically, if I were to use xenstore as a communication medium between
> > the script & xl-remus, things that xl would need as return values from the
> > script
> > (via xenstore) are the ifb devices that map to each of the vifs belonging to
> > the guest,
> > so that plug qdiscs can be installed on all of them.
> 
> Just to check, are you making a distinction here between xl and libxl?
>  Ideally the important functionality to do Remus would be in libxl, so
> that any toolstack could impliment it.  xl is meant to represent an
> example toolstack one might build; it in theory one should be able to
> implement Remus using libvirt or xapi without significant effort.

Right, and that's why I would prefer to avoid a dependency on Python.
Since I think at least some of these projects will see it as an
additional barrier.

On the other hand if its just an implementation detail of a remus
specific script which libxl happens to call out to when asked then I
suppose it is up to the Remus folks whether they find this acceptable.

Ian.



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