[openstack-dev] [tc] [all] [glance] Answers to some questions about Glance

Brian Rosmaita brian.rosmaita at RACKSPACE.COM
Wed May 18 12:44:39 UTC 2016

On 5/18/16, 2:15 AM, "Clint Byrum" <clint at fewbar.com> wrote:

>Excerpts from Robert Collins's message of 2016-05-18 14:57:05 +1200:
>> On 18 May 2016 at 00:54, Brian Rosmaita <brian.rosmaita at rackspace.com>
>> >> Couple of examples:
>> >> 1. switching from "is_public=true" to "visibility=public"
>> >
>> >
>> > This was a major version change in the Images API.  The 'is_public'
>> > is in the original Images v1 API, 'visibility' was introduced with the
>> > Images v2 API in the Folsom release.  You just need an awareness of
>> > version of the API you're talking to.
>> So I realise this is ancient history, but this is really a good
>> example of why Monty has been pushing on 'never break our APIs': API
>> breaks hurt users, major versions or not. Keeping the old attribute as
>> an alias to the new one would have avoided the user pain for a very
>> small amount of code.
>> We are by definition an API - doesn't matter that its HTTP vs Python -
>> when we break compatibility, there's a very long tail of folk that
>> will have to spend time updating their code; 'Microversions' are a
>> good answer to this, as long as we never raise the minimum version we
>> support. glibc does a very similar thing with versioned symbols - and
>> they support things approximately indefinitely.
>+1, realy well said. As Nikhil said, assumptions are bad, and assuming
>that nobody's using that, or that they'll just adapt, is not really a
>great way to establish a relationship with the users.

I agree with the general sentiment, and I sincerely hope that all
OpenStack projects take it to heart.

I also want to note for the record that the Images API really did need a
major version change.


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