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

David Kranz dkranz at redhat.com
Thu Mar 20 18:20:42 UTC 2014

On 03/20/2014 11:05 AM, Solly Ross wrote:
> I concur.  I suspect people/organizations who are doing CD *probably* won't mind
> such a change as much as the people who use the versioned releases will mind
> backwards-incompatibility.  Correct me if I'm wrong, but doing CD requires a
> certain willingness to roll with the punches, so to speak, whereas people using
> versioned releases are less likely to be as flexible.
> Best Regards,
> Solly Ross
It looks like there was no existing unit test for what horizon ended up 
doing, where a red-flagging change to the test would have been needed. 
There is obviously also no tempest test. But I hope that folks doing CD 
would not roll with this sort of punch if they find it, but push back 
immediately to revert the change unless it had gone through whatever api 
change review process we come up with. I presume that it simply was not 
noticed since it is perhaps a bit of an obscure api point. Since 
OpenStack currently advertises 6 month cycle releases and stable apis, 
it would be best to revert it IMO.

> ----- Original Message -----
> From: "Thierry Carrez" <thierry at openstack.org>
> To: openstack-dev at lists.openstack.org
> Sent: Thursday, March 20, 2014 6:51:26 AM
> Subject: Re: [openstack-dev] [nova] Backwards incompatible API changes
> Christopher Yeoh wrote:
>> The patch was merged in October (just after Icehouse opened) and so has
>> been used in clouds that do CD for quite a while. After some discussion
>> on IRC I think we'll end up having to leave this backwards incompatible
>> change in there - given there are most likely users who now rely on
>> both sets of behaviour there is no good way to get out of this
>> situation. I've added a note to the Icehouse release notes.
> I still think reverting before release is an option we should consider.
> My point is, yes we broke it back in October for people doing CD (and
> they might by now have gotten used to it), if we let this to release
> we'll then break it for everyone else.
> We put a high emphasis into guaranteeing backward compatibility between
> releases. I think there would be more damage done if we let this sail to
> release, compared to the damage of reverting CD followers to pre-October
> behavior...

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