Open Stack

> On 9 Jan 2015, at 5:37 am, Joe Gordon <joe.gordon0 at gmail.com> wrote:
> 
> 
> 
> On Sun, Jan 4, 2015 at 7:08 PM, Andrew Beekhof <abeekhof at redhat.com> wrote:
> 
> > On 9 Dec 2014, at 1:20 am, Roman Dobosz <roman.dobosz at intel.com> wrote:
> >
> > On Wed, 3 Dec 2014 08:44:57 +0100
> > Roman Dobosz <roman.dobosz at intel.com> wrote:
> >
> >> I've just started to work on the topic of detection if host is alive or
> >> not: https://blueprints.launchpad.net/nova/+spec/host-health-monitoring
> >>
> >> I'll appreciate any comments :)
> >
> > I've submitted another blueprint, which is closely bounded with previous one:
> > https://blueprints.launchpad.net/nova/+spec/pacemaker-servicegroup-driver
> >
> > The idea behind those two blueprints is to enable Nova to be aware of host
> > status, not only services that run on such. Bringing Pacemaker as a driver for
> > servicegroup will provide us with two things: fencing and reliable information
> > about host state, therefore we can avoid situations, where some actions will
> > misinterpret information like service state with host state.
> >
> > Comments?
> 
> I would rather move the servicegroup concept to use tooz and put things like Pacemaker in there (https://review.openstack.org/138607)

Perhaps I'm missing something obvious, but from looking at git, its unclear to me how tooz addresses the fencing requirement.

There also seems to be an assumption that all services are completely independent - is that correct?
In practice this is rarely the case (or worse, pushes the 'wait and retry' logic onto the individual services.

Finally, could you clarify what you mean by "put things like Pacemaker in there".  
Presumably "there" is a tooz driver of some kind?  What would that achieve?