On 31/08/2015 1:06 PM, Julien Danjou wrote:
On Mon, Aug 31 2015, gord chung wrote:
for context, we have an open bug in Ceilometer where the value used to capture
cputime of an instance is being reset whenever the instance is restarted or
shutdown[1]. this seems to be the expected behaviour for libvirt driver[2] but
it conflicts with the fact that the meter is currently defined as 'cumulative'
-- which by definition, should not reset. it seems the correct meter type is a
'gauge'.
Nah, gauge is for things with discrete values, e.g. a number of objects
in Swift.
Cumulative are counters that increase and that can be reset.
The problem is that the API still don't know to detect resets and
normalize the values.
That's what needs fixing. We could fix it with Gnocchi.
i think that's the reason the bug is raised... that's not what
cumulative means. by definition it should increase over each successive
value. it's cumulative from the pov of qemu process but not from
instance pov. judging by how Hyper-V meter is built, it doesn't seem
like Hyper-V's cputime meter would ever reset.
i'm not sure Gnocchi is where we should be fixing this as it really only
(potentially) fixes it for Gnocchi and not for any of the other ways
Ceilometer data can be consumed.
a proposed solution in bug and in a previous thread suggests that a
'delta' meter be built from cputime value libvirt provides which would
better handle the reset scenario. that said, is there another option to
truly have a cumulative meter?
cheers,
--
gord
__________________________________________________________________________
OpenStack Development Mailing List (not for usage questions)
Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe
http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
