[openstack-dev] [Nova] adding hooks

Sandy Walsh sandy.walsh at RACKSPACE.COM
Tue Nov 20 16:11:35 UTC 2012


My concern would be how exceptions are handled through hooks? If I have nested hooks should I pass them through or die silently. Decorators are bad in this regard and have already caused headaches in notifications. 

-S
________________________________________
From: Daniel P. Berrange [berrange at redhat.com]
Sent: Tuesday, November 20, 2012 11:57 AM
To: OpenStack Development Mailing List
Subject: Re: [openstack-dev] [Nova] adding hooks

On Tue, Nov 20, 2012 at 10:40:58AM -0500, Russell Bryant wrote:
> Greetings,
>
> There is currently a patch in the review queue for nova that adds hooks.
>
> https://review.openstack.org/#/c/16336/
>
> I like the concept, but I think it could benefit from some design
> discussion.  That's difficult on gerrit and much better suited for the
> mailing list, so here we are.

My thoughts are

 - What is the intended usage of the hooks?
 - What is the usage relationship between hooks & extensions ?
 - What are they expected to be allowed to do / not do ?
 - What guarantees are provided wrt hooks continuing to
   work minor, and major updates ?
 - What internal APIs (if any) should hooks be allowed to
   use ?
 - Is there any way to enforce any rules we make above ?

My overriding desire is that we want to avoid sleep-walking into
a situation where people write all sorts of hooks; these rely
on internal code we consider unstable; we're then forced to maintain
stabilty of internal APIs across major and/or minor updates to avoid
breaking people's hooks.


Daniel
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