openstack team mailing list archive

["Kevin L. Mitchell" <kevin.mitchell@xxxxxxxxxxxxx>]

On Tue, 2012-01-03 at 19:54 +0000, Ewan Mellor wrote:
> I'd love to see openstack-common get off the ground, so I'm all in
> favor of this.
> 
> One question: why do you feel that you need such strong backwards
> compatibility?  If someone makes a change in openstack-common and
> makes simultaneous changes in all OpenStack projects to match, isn’t
> that sufficient?

No "simultaneous" change is ever actually simultaneous.  We see this all
the time with interop between keystone (in particular), nova, and
glance.  Once openstack-common gets into the picture, the interop
problems stand to be significantly worse; if one tiny change is not
backwards compatible, you break *everything* that uses openstack-common.
The good thing, of course, is that it'll be noticed quickly; the bad
thing is that all work gets significantly impeded until the fix(es) go
in.

Speaking from experience: it is possible to preserve N+2 backwards
compatibility while still making major enhancements.  It can be a pain
in the butt sometimes, but it is doable, and, in cases like
openstack-common, I think it is necessary.
-- 
Kevin L. Mitchell <kevin.mitchell@xxxxxxxxxxxxx>