[openstack-dev] [Oslo][Designate][Congress] Problem with from_dict overrides and new oslo.context release

Ben Nemec openstack at nemebean.com
Mon Oct 9 17:03:24 UTC 2017


I brought up the fix[1] I proposed for [2] in the Oslo meeting today, 
and it led to some good discussion that we wanted to take to a broader 
audience.  In particular, the projects that are affected by the bug.

The oslo.context change I proposed would essentially obsolete the 
from_dict function in the Context object since it would obligate us to 
support all the keys in to_dict in the constructor.  This unfortunately 
implies some rather rigid constraints on the Context object.  We could 
essentially never remove any parameters from the constructor (which at 
some point we want to do for things like "tenant" that are deprecated 
but still present) or risk breaking if someone passed in parameters from 
an old to_dict call.

The other proposal was to rewrite the existing naive from_dict overrides 
in the affected projects to function more like the from_dict in the base 
class where it explicitly handles only the keys that the constructor 
will recognize.[3]  One benefit of this approach is that it would allow 
the removal of some previous workarounds[4].  This is also cleaner from 
an API perspective as it doesn't impose any new requirements on the 
oslo.context API.  The obvious drawback is that it requires 
project-specific fixes in the affected projects.  We would, of course, 
be happy to help with those fixes though.

So those are the options we've discussed and my thoughts on them. 
Please feel free to weigh in with any other input you may have.  Thanks.


1: https://review.openstack.org/509919
2: https://launchpad.net/bugs/1721432

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