[openstack-dev] [nova] nova hooks - document & test or deprecate?

Daniel P. Berrange berrange at redhat.com
Mon Feb 29 17:32:55 UTC 2016

On Mon, Feb 29, 2016 at 12:23:09PM -0500, Andrew Laski wrote:
> On Mon, Feb 29, 2016, at 12:12 PM, Dan Smith wrote:
> > > In our continued quest on being more explicit about plug points it feels
> > > like we should other document the interface (which means creating
> > > stability on the hook parameters) or we should deprecate this construct
> > > as part of a bygone era.
> > > 
> > > I lean on deprecation because it feels like a thing we don't really want
> > > to support going forward, but I can go either way.
> > 
> > Deprecate and remove, please. We've been removing these sorts of things
> > over time, and nova hooks have been ignored in that process. But really,
> > making them more rigid is going to get in the way over time, trying to
> > continue to honor an interface that codifies internals at a certain
> > point in time, and leaving them as-is will just continue to generate
> > issues like the quoted bug.
> > 
> > I don't "lean" on deprecation, I feel strongly that these should go away.
> I've worked on a deployment that uses them heavily and would be impacted
> by their removal. They are a very convenient place to put code that
> should run based on Nova events but I have yet to see a usage that
> couldn't have been implemented by having a service listen to
> notifications and run that same code. However there is no service that
> does this. So the only argument I can see for keeping them is that it's
> more convenient to put that code into Nova rather than implement
> something that listens for notifications. And that's not a convincing
> argument to me.

Yes, that's a prime example of a use case where we should be offering
a formally supportable solution instead of an unreliable hack using

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