Open Stack

In a recent Nova patch review
(https://review.openstack.org/#/c/18718/2), Sean Dague asked about the
deprecation strategy of configuration options since the patch removes
two config options as they are no longer applicable after the change.
I thought documenting the change (removal of old config options) and
its rationale would be enough but Sean required a more sensible way to
take care of config option change.

One thing I'm thinking about strategy is keeping the deprecated
options for one more release, and changing default value of these
config options to None (but since they are no longer used, it doesn't
matter what value they get).  What's more, in the place where these
config options were used, log a deprecation warning.

I'd like to hear opinions, especially sharing similar experiences
about how to handle such cases from community.

-- 
Regards
Huang Zhiteng