Open Stack

On 2/6/17 5:51 AM, Jordan Pittier wrote:
[super-enormous snip -- Chris, Ken, and Jordan make good points, I
encourage you to read the entire thread; I just want to concentrate on
one point]
> 
> I would say we should make compromise, not solve dilemma. I can live in a
> world where we sometimes allow an API change and sometimes prevent it.
> 
+1000

I agree with Jordan.  We need to look at the context of each specific
case and decide whether a change is OK based on the details.  We've
already got the guideline that says "in general", you shouldn't change
the response code, and we respect that.  The Glance team isn't claiming
that the guideline is incorrect--we're just saying that given the
context of this specific bug (that is, it's been documented for a long
time to return a 204, all other metadefs DELETE calls are documented to
return a 204, all the other metadefs DELETE calls do in fact return a
204, etc.), it makes sense that this case is an exception.

Granting an exception here doesn't mean that the floodgates have opened
for an "anything goes" approach to API changes.  It just means that an
exception is appropriate in this particular case.  I am being a bit
disingenuous there because if an exception is appropriate in this case,
then it will be appropriate in other relevantly similar cases.  But
"relevant similarity" will include the entire context of the case, for
example, whether there was a published API contract, whether the other
similar calls behave as documented, etc.  From 10,000 meters, it looks
like what we're advocating is "It's OK to change a response code".  But
when you look more closely, our claim is that given the details of this
particular bug, it makes sense to fix it in the code and not in the docs.

To summarize, my point is that we shouldn't be worried that this case is
going to set a precedent.  It would be worrisome if it were going to set
a *bad* precedent, but when you look at the details of the situation, I
don't think it will.  So it looks to me, anyway, that a compromise is in
order here.  (In case I'm being too obscure, what I mean is: we should
agree that it's OK for the Glance team to fix this bug in the code with
patch https://review.openstack.org/#/c/420038/.)

cheers,
brian