Open Stack

On 29 July 2016 at 19:58, Sean Dague <sean at dague.net> wrote:
> On 07/29/2016 02:29 PM, Jay Pipes wrote:
>> On 07/28/2016 09:02 PM, Devananda van der Veen wrote:
>>> On 07/28/2016 05:40 PM, Brad Morgan wrote:
>>>> I'd like to solicit some advice about potentially implementing
>>>> get_all_bw_counters() in the Ironic virt driver.
>>>>
>>>> https://github.com/openstack/nova/blob/master/nova/virt/driver.py#L438
>>>> Example Implementation:
>>>> https://github.com/openstack/nova/blob/master/nova/virt/xenapi/driver.py#L320
>>>>
>>>>
>>>> I'm ignoring the obvious question about how this data will actually be
>>>> collected/fetched as that's probably it's own topic (involving
>>>> neutron), but I
>>>> have a few questions about the Nova -> Ironic interaction:
>>>>
>>>> Nova
>>>> * Is get_all_bw_counters() going to stick around for the foreseeable
>>>> future? If
>>>> not, what (if anything) is the replacement?
>>
>> I don't think Nova should be in the business of monitoring *any*
>> transient metrics at all.
>>
>> There are many tools out there -- Nagios, collectd, HEKA, Snap, gnocchi,
>> monasca just to name a few -- that can do this work.
>>
>> What action is taken if some threshold is reached is entirely
>> deployment-dependent and not something that Nova should care about. Nova
>> should just expose an API for other services to use to control the guest
>> instances under its management, nothing more.
>
> More importantly... *only* xenapi driver implements this, and it's not
> exposed over the API. In reality that part of the virt driver layer
> should probably be removed.

AFAIK, it is only exposed via notifications:
https://github.com/openstack/nova/blob/562a1fe9996189ddd9cc5c47ab070a498cfce258/nova/notifications/base.py#L276

I think its emitted here:
https://github.com/openstack/nova/blob/562a1fe9996189ddd9cc5c47ab070a498cfce258/nova/compute/manager.py#L5886

Agreed with not adding to the legacy, and not to encourage new users of this.

Long term, it feels like removing this from Nova is the correct thing
to do, but I do worry about not having an obvious direct replacement
yet, and a transition plan. (This also feeds back into being able to
list deleted instances in the API, and DB soft_delete). Its not
trivial.

> Like jay said, there are better tools for collecting this than Nova.

I am out of touch with what folks should use to get this data, and
build a billing system? Ceilometer + something?

It feels like that story has to be solid before we delete this
support. Maybe thats already the case, and I just don't know what that
is yet?

Thanks,
John