[openstack-dev] [nova][ceilometer] proposal to send bulk hypervisor stats data in periodic notifications

Jason Myers jason at mailthemyers.com
Wed Jun 17 16:06:32 UTC 2015

I was involved in the IRC discussion, but to reiterate here this would
be a wonderful thing to get done. The current polling can be terribly
inefficient, and the ceilo team is already looking into other ways to
reduce the impact of it. I'm looking forward to helping with this.



On Wed, Jun 17, 2015, at 10:52 AM, Matt Riedemann wrote:
> Without getting into the details from the etherpad [1], a few of us in 
> IRC today were talking about how the ceilometer compute-agent polls 
> libvirt directly for guest VM statistics and how ceilometer should 
> really be getting this information from nova via notifications sent from 
> a periodic task in the nova compute manager.
> Nova already has the get_instance_diagnostics virt driver API which is 
> nice in that it has structured versioned instance diagnostic information 
> regardless of virt driver (unlike the v2 os-server-diagnostics API which 
> is a free-form bag of goodies depending on which virt driver is used, 
> which makes it mostly untestable and not portable).  The problem is the 
> get_instance_diagnostics virt driver API is per-instance, so it's not 
> efficient in the case that you want bulk instance data for a given 
> compute host.
> So the idea is to add a new virt driver API to get the bulk data and 
> emit that via a structured versioned payload similar to 
> get_instance_diagnostics but for all instances.
> Eventually the goal is for nova to send what ceilometer is collecting 
> today [2] and then ceilometer can just consume that notification rather 
> than doing the direct hypervisor polling it has today.
> Anyway, this is the high level idea, the details/notes are in the 
> etherpad along with next steps.
> Feel free to chime in now with reasons why this is crazy and will never 
> work and we shouldn't waste our time on it.
> [1] https://etherpad.openstack.org/p/nova-hypervisor-bulk-stats-notify
> [2] 
> http://docs.openstack.org/admin-guide-cloud/content/section_telemetry-compute-meters.html
> -- 
> Thanks,
> Matt Riedemann
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