[openstack-dev] [nova] Backwards incompatible API changes

Christopher Yeoh cbkyeoh at gmail.com
Fri Mar 21 08:49:48 UTC 2014

On Thu, 20 Mar 2014 14:31:43 -0700
Joe Gordon <joe.gordon0 at gmail.com> wrote:

> On Wed, Mar 19, 2014 at 5:54 PM, Christopher Yeoh <cbkyeoh at gmail.com>
> wrote:
> > Hi,
> >
> > So it turns out that we have made a backwards incompatible change to
> > the V2 API in Icehouse. Previously when creating a private flavor
> > access was not automatically given to the tenant, now it is. The
> > documentation has always said that it was, but we lied.
> >
> > https://review.openstack.org/#/c/40811/
> >
> >
> Backwards compatibility was discussed in this patch and the answer
> that we used at the time was:
> "But without this fix the flavor-access mechanism is broken as far as
> I can see, and the extra data returned is still compatible with the
> API definition I think (Its just that an optional list part that was
> always empty before will now have one entry from the start) - so any
> code that uses the API really needs to be able to cope with that part
> of the result."
> In retrospect I don't think that was a strong enough answer.

Yes. I think we've learnt an important lesson here in that its just too
hard to accurately predict how disruptive a backwards incompatible
change is. There needs to be extremely exceptional circumstances for it
to be acceptable.


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