Open Stack

Hi Daniel,


> -----Original Message-----
> From: Daniel P. Berrange [mailto:berrange at redhat.com]
> Sent: 22 September 2014 12:24
> To: OpenStack Development Mailing List (not for usage questions)
> Subject: Re: [openstack-dev] [Nova] - do we need .start and .end
> notifications in all cases ?
> 
> On Mon, Sep 22, 2014 at 11:03:02AM +0000, Day, Phil wrote:
> > Hi Folks,
> >
> > I'd like to get some opinions on the use of pairs of notification
> > messages for simple events.   I get that for complex operations on
> > an instance (create, rebuild, etc) a start and end message are useful
> > to help instrument progress and how long the operations took. However
> > we also use this pattern for things like aggregate creation, which is
> > just a single DB operation - and it strikes me as kind of overkill and
> > probably not all that useful to any external system compared to a
> > single event ".create" event after the DB operation.
> 
> A start + end pair is not solely useful for timing, but also potentially detecting
> if it completed successfully. eg if you receive an end event notification you
> know it has completed. That said, if this is a use case we want to target, then
> ideally we'd have a third notification for this failure case, so consumers don't
> have to wait & timeout to detect error.
> 

I'm just a tad worried that this sounds like its starting to use notification as a replacement for logging.    If we did this for every CRUD operation on an object don't we risk flooding the notification system.