[libvirt] [RFC] Publishing utilisation on mDNS

[Daniel P. Berrange]

On Wed, May 14, 2008 at 11:13:40PM +0200, Stefan de Konink wrote:
> On Wed, 14 May 2008, Daniel P. Berrange wrote:
> 
> > > I might even go further and publish all resource statistics over mDNS.
> > > Maybe people have ideas about this too, securitywise i'm not really
> > > interested in the implications since I'm publishing it on a management
> > > LAN.
> >
> > This is already a solved problem - any resource monitoring system can
> > publish this kind of information. Rich Jones has already written libvirt
> > plugins for both collectd and nagios to publish VM information, and so
> > there's no need to re-invent this in libvirtd itself, nor abuse Avahi/mDNS
> > service discovery for this purpose
> >
> >   http://collectd.org/documentation/manpages/collectd.conf.5.shtml#plugin_libvirt
> >   http://et.redhat.com/~rjones/nagios-virt/
> 
> I'm currently implementing resource balancing between hosts. So one way or
> the other I want to receive or pull from the active hosts in the network
> their active states. And migrate host from heavy used machines to unused
> ones. Also, bias new started VMs to an unused machine.
> 
> I see the collectd plugin takes the opposite approach which need to
> specify information while this is unknown for my statistics management.

I don't know what you mean here ?  Collectd will push out information for
all guests. It can be configured to sned it in a variety of ways, and if 
none of the existing data transports are suitable it has extensive plugin
capabilities. mDNS is also a push protocol, so there's really no difference
between what you could do with mDNS vs collectd at your receiving end. 

> If I'm reinventing the wheel because ovirt does this already or something
> like it... please tell me.

Well oVirt is a closed-loop system - it has a standardized host OS image
for nodes running VMs, and a matched admin host to receive - oVirt isn't
intended to provide generic services for everyone wanting to us libvirt.
Its just one of many apps built ontop of libvirt. As it hapens oVirt 
currently uses collectd to send resource & guest utilization data to its
management server. We may or may not keep doing this, or change to a 
diffferent resource collection daemon that uses the AMPQ message bus..

Dan.
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