On 2/29/2016 11:23 AM, 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.

So I agree with moving forward on deprecation and think that
notifications provide a suitable replacement for the functionality
provided.



--Dan

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Forgive my ignorance or for playing devil's advocate, but wouldn't the main difference between notifications and hooks be that notifications are asynchronous and hooks aren't? In the case of how Rdo was using it, they are adding things to the injected_files list before the instance is created in the compute API. You couldn't do that with notifications as far as I know.

--

Thanks,

Matt Riedemann


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