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

Nikhil Komawar nik.komawar at gmail.com
Wed May 18 15:03:45 UTC 2016

On 5/18/16 2:15 AM, Clint Byrum 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> wrote:
>>>> 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' boolean
>>> 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 which
>>> 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

You have only conveniently picked up one things I've said in my email,
why not choose the other parts of resolving those assumptions correctly.
Please do not phrase me when the propaganda is orthogonal to what I

> that nobody's using that, or that they'll just adapt, is not really a
> great way to establish a relationship with the users.

It's not that assumption that users are not using it:

The very _assumption_ people who are using it is that glance v1 is ok to
be public facing API which was never designed to be one. So, that's the
assumption you need to take into account and not the one you like to
pick. That's the part where I talk about being engaged missing in your

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