[openstack-dev] [nova] Host maintenance notification

Chris Friesen chris.friesen at windriver.com
Mon Apr 6 19:07:18 UTC 2015

On 04/06/2015 12:52 PM, Matthew Treinish wrote:
> On Mon, Apr 06, 2015 at 01:17:20PM -0500, Matt Riedemann wrote:
>> On 4/6/2015 9:46 AM, Chris Friesen wrote:
>>> On 04/06/2015 07:56 AM, Ed Leafe wrote:
>>>> On Apr 6, 2015, at 1:21 AM, Chris Friesen <chris.friesen at windriver.com>
>>>> wrote:
>>>>>> Please feel free to add a blueprint in Launchpad. I don't see this as
>>>>>> needing a full spec, really. It shouldn't be more than a few lines of
>>>>>> code to send a new notification message.
>>>>> Wouldn't a new notification message count as an API change?  Or are we
>>>>> saying that it's such a small API change that any discussion can
>>>>> happen in
>>>>> the blueprint?
>>>> I don't think that the notification system is the same as the API. It is
>>>> something that you can subscribe to or not, and is distinct from the API.
>>> It's certainly not the same as the REST API.  I think an argument could
>>> be made that the notification system is part of the API, where API is
>>> defined more generally as "something that expresses a software component
>>> in terms of its operations, inputs, outputs, and underlying types".
>>> If we don't exercise any control over the contents of the notifications
>>> messages, that would make it difficult for consumers of the
>>> notifications to do anything interesting with them.  At a minimum it
>>> might make sense to do something like REST API microversions, with a
>>> version number and a place to look up what changed with each version.
>> The events and their payloads are listed in the wiki here [1].
>> In the past people have added new notifications with just bug reports, I'm
>> not sure a new spec is required for a host going into maintenance mode (as
>> long as it's new and not changing something).
> Yeah, in it's current state without real versioning on notifications I think
> just adding it with a bug is fine. If nova actually had a versioning mechanism
> and made stability guarantees on notifications it would be a different story.

I'm fine either way...just wanted to be sure the decision was made consciously.


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