Open Stack

On 02/05/2014 01:50 AM, Jesse Noller wrote:
> 
> On Feb 4, 2014, at 10:31 AM, Sean Dague <sean at dague.net> wrote:
> 
>> On 02/05/2014 01:09 AM, Dean Troyer wrote:
>>> On Tue, Feb 4, 2014 at 9:00 AM, Sean Dague <sean at dague.net
>>> <mailto:sean at dague.net>> wrote:
>>>
>>>    Can you be more specific about what goes wrong here? I'm not entirely
>>>    sure I understand why an old client of arbitrary age needs to be
>>>    supported with new OpenStack. The contract is the API, not the client,
>>>    and an old client that doesn't do version discovery is just a buggy
>>>    client from what I'm concerned. Time to release a new version.
>>>
>>>
>>> Problem 1: API version discovery is not universally considered to be
>>> part of the API and therefore is not defined by most services beyond
>>> them responding to a '/' request with a 300 response and a list of
>>> versions. No two of these responses look alike except where the source
>>> was copied from an existing service.
>>>
>>> Problem 2: Identity is unique in that it is handed a deployment-defined
>>> URL to authenticate and get endpoints for all other services.  Most of
>>> these auth URLs have a version hard-coded in them because the client
>>> didn't do version discovery or negotiation until recently.  This is what
>>> we're talking about here, how to remove the version from this URL and
>>> not break old clients.  We can't.  Not without doing nasty things like
>>> detecting an old client and compensating for it server-side.  So we have
>>> to work out a way for new clients to do discovery even when handed a URL
>>> that has a version in it.
>>>
>>> I've tested a couple of more generalized approaches, and the best
>>> solution I have found so far is to simply special-case the known legacy
>>> behaviour then drop in to the general discovery process. 
>>>
>>>    I also wonder if this is an issue with version discovery implementation.
>>>    It seems like if we think this is going to be affecting multiple
>>>    services before doing an odd hack for keystone, we should actually
>>>    figure out a pattern that works for all services, and figure out why
>>>    this has only just become an issue. Most of the other services have done
>>>
>>>
>>> The services that traditionally embed a version inside the URL followed
>>> by a tenant ID or something get even deeper into parsing the URL to hack
>>> the version.
>>>
>>>    dual APIs at some point over the last 2 years, and this didn't seem to
>>>    trip them up too badly. What happened differently in keystone that made
>>>    this an issue? And what can be learned about how we structure APIs going
>>>    forward.
>>>
>>>
>>> I think the difference is this is the first API we have actually tried
>>> to deprecate and we don't have the option to hide it in an updated SC
>>> endpoint.  The service catalog has hidden a lot of this pain for other
>>> services because the clients generally can use whatever endpoint the SC
>>> gives it.
>>>
>>>
>>> a) Version discovery needs to be rationalized across the services.
>>> We've talked about this at summits before, and proposals have been
>>> written.  And here we are.  We'll do it again in Atlanta, hopefully for
>>> the last time.
>>>
>>> b) Define a common structured endpoint and let the client assemble the
>>> components into the final URL.  If the service catalog had a base URL
>>> for compute, and a list of versions, and the additional bits to be
>>> appended the client could make an intelligent choice and assemble the
>>> endpoint.  It isn't like the client doesn't already have to know how the
>>> REST URLs are constructed.
>>>
>>> b-alt) Stop putting things like tenant IDs in the SC.  This has the same
>>> issue as the auth URL in how to do this without instantly breaking the
>>> existing clients.
>>
>> Ok, much clearer now to me (though I'll still claim jetlag for some bits
>> not sinking in).
>>
>> I think a really important thing to keep in mind is any solution that's
>> implemented client side, is something that all the other OpenStack SDKs
>> are going to have to implement as well. So an ugly hack isn't just
>> python-keystone... and be done. It's also just hoisted doing that ugly
>> hack on the php / go sdk teams, jclouds, deltacloud, etc. Something they
>> may not be aware is going to break them, or their users.
> 
> Do we have official openstack PHP / go SDKs?

Official is a strong word, but we do have stackforge teams active on it:
 * https://github.com/stackforge/openstack-sdk-php
 * https://github.com/stackforge/golang-client

And I think we should should be mindful of their work to make OpenStack
easily accessible from their language communities.

	-Sean

-- 
Sean Dague
Samsung Research America
sean at dague.net / sean.dague at samsung.com
http://dague.net

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