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On Fri, Oct 3, 2014 at 11:18 AM, Chris Friesen
<chris.friesen at windriver.com> wrote:
> On 10/03/2014 11:38 AM, Chris Dent wrote:
>>
>> On Fri, 3 Oct 2014, Joe Gordon wrote:
>
>
>>>> Many of those services expect[1] to be able to send notifications (or
>>>> be polled by) ceilometer[2]. We've got an ongoing thread about the need
>>>> to contractualize notifications. Are those contracts (or the desire
>>>> for them) a form of dependency? Should they be?
>>>>
>>>
>>> So in the case of notifications, I think that is a Ceilometer CAN-USE
>>> Nova
>>> THROUGH notifications
>>
>>
>> Your statement here is part of the reason I asked. I think it is
>> possible to argue that the dependency has the opposite order: Nova might
>> like to use Ceilometer to keep metrics via notifications or perhaps:
>> Nova CAN-USE Ceilometer FOR telemetry THROUGH notifications and polling.
>>
>> This is perhaps not the strict technological representation of the
>> dependency, but it represents the sort of pseudo-social
>> relationships between projects: Nova desires for Ceilometer (or at
>> least something doing telemetry) to exist.
>
>
> This may be quibbling, but I would suggest that it is the end-user that may
> want something doing telemetry to exist.
>
> Nova proper doesn't really care about telemetry.  Nova exports telemetry
> because end-users want the information to be available for use by other
> services.  Nova itself doesn't actually make use of it or call out to
> services that make use of it.

Yup.

> Now something like Heat really depends on telemetry.  It wants to know if an
> instance didn't kick the watchdog timer, or if the webserver keeps crashing,
> or other information provided by telemetry.
>

Now that is a really good point. /me tosses up a pull request for that change.