Open Stack

On 02/18/2015 06:37 PM, Brian Rosmaita wrote:
> Thanks for your comment, Miguel.  Your suggestion is indeed very close
> to the RESTful ideal.
>
> However, I have a question for the entire API-WG.  Our (proposed)
> mission is "To improve the developer experience of API users by
> converging the OpenStack API to a consistent and pragmatic RESTful
> design." [1]  My question is: what is the sense of "pragmatic" in this
> sentence?  I thought it meant that we advise the designers of OpenStack
> APIs to adhere to RESTful design as much as possible, but allow them to
> diverge where appropriate.  The proposed functional call to deactivate
> an image seems to be an appropriate place to deviate from the ideal.
>   Creating a task or action object so that the POST request will create
> a new resource does not seem very pragmatic.  I believe that a necessary
> component of encouraging OpenStack APIs to be consistent is to allow
> some pragmatism.

Hi Brian,

I'm sure you're not surprised by my lack of enthusiasm for the 
"functional" Glance API spec for activating/deactivating an image :)

As for the role of the API WG in this kind of thing, you're absolutely 
correct that the goal of the WG is to improve the developer experience 
of API users with a consistent and pragmatic RESTful design.

I feel the proposed `PUT /images/{image_id}/actions/deactivate` is 
neither consistent (though to be fair, the things this would be 
"consistent" with in the Nova API -- i.e. the os-actions API -- are 
monstrosities IMHO) nor pragmatic.

This kind of thing, IMHO, is not something that belongs in the same REST 
API as the other Glance image API calls. It's purely an administrative 
thing and belongs in a separate API, and doesn't even need to be 
RESTful. The glance-manage command would be more appropriate, with 
direct calls to backend database systems to flip the status to 
activate/deactivate.

If this functionality really does need to be in the main user RESTful 
API, I believe it should follow the existing v2 Glance API's /tasks 
resource model for consistency and design reasons.

That said, I'm only one little voice on the API WG. Happy to hear 
other's views on this topic and go with the majority's view (after 
arguing for my points of course ;)

Best,
-jay

> [1] https://review.openstack.org/#/c/155911/
>
> On 2/18/15, 4:49 PM, "Miguel Grinberg" <miguel.s.grinberg at gmail.com
> <mailto:miguel.s.grinberg at gmail.com>> wrote:
>
>     Out of all the proposals mentioned in this thread, I think Jay's (d)
>     option is what is closer to the REST ideal:
>
>     d) POST /images/{image_id}/tasks with payload:
>         { "action": "deactivate|activate" }
>
>     Even though I don't think this is the perfect solution, I can
>     recognize that at least it tries to be RESTful, unlike the other
>     three options suggested in the first message.
>
>     That said, I'm going to keep insisting that in a REST API state
>     changes are the most important thing, and actions are implicitly
>     derived by the server from these state changes requested by the
>     client. What you are trying to do is to reverse this flow, you want
>     the client to invoke an action, which in turn will cause an implicit
>     state change on the server. This isn't wrong in itself, it's just
>     not the way you do REST.
>
>     Jay's (d) proposal above could be improved by making the task a real
>     resource. Sending a POST request to the /tasks address creates a new
>     task resource, which gets a URI of its own, returned in the Location
>     header. You can then send a GET request to this URI to obtain status
>     info, such as whether the task completed or not. And since tasks are
>     now real resources, they should have a documented representation as
>     well.
>
>     Miguel
>
>     On Wed, Feb 18, 2015 at 1:19 PM, Brian Rosmaita
>     <brian.rosmaita at rackspace.com <mailto:brian.rosmaita at rackspace.com>>
>     wrote:
>
>         On 2/15/15, 2:35 PM, "Jay Pipes" <jaypipes at gmail.com
>         <mailto:jaypipes at gmail.com>> wrote:
>         >On 02/15/2015 01:13 PM, Brian Rosmaita wrote:
>         >> On 2/15/15, 10:10 AM, "Jay Pipes" <jaypipes at gmail.com <mailto:jaypipes at gmail.com>> wrote:
>         >>
>         >>> On 02/15/2015 01:31 AM, Brian Rosmaita wrote:
>         >>>> This is a follow-up to the discussion at the 12 February API-WG
>         >>>> meeting [1] concerning "functional" API in Glance [2].  We made
>         >>>> some progress, but need to close this off so the spec can be
>         >>>> implemented in Kilo.
>         >>>>
>         >>>> I believe this is where we left off: 1. The general consensus was
>         >>>> that POST is the correct verb.
>         >>>
>         >>> Yes, POST is correct (though the resource is wrong).
>         >>>
>         >>>> 2. Did not agree on what to POST.  Three options are in play: (A)
>         >>>> POST /images/{image_id}?action=deactivate POST
>         >>>> /images/{image_id}?action=reactivate
>         >>>>
>         >>>> (B) POST /images/{image_id}/actions with payload describing the
>         >>>> action, e.g., { "action": "deactivate" } { "action": "reactivate"
>         >>>> }
>         >>>>
>         >>>> (C) POST /images/{image_id}/actions/deactivate POST
>         >>>> /images/{image_id}/actions/reactivate
>         >>>
>         >>> d) POST /images/{image_id}/tasks with payload: { "action":
>         >>> "deactivate|activate" }
>         >>>
>         >>> An action isn't created. An action is taken. A task is created. A
>         >>> task contains instructions on what action to take.
>         >>
>         >> The Images API v2 already has tasks (schema available at
>         >> /v2/schemas/tasks ), which are used for long-running asynchronous
>         >> operations (right now, image import and image export).  I think we
>         >> want to keep those distinct from what we're talking about here.
>         >>
>         >> Does something really need to be created for this call?  The idea
>         >> behind the "functional" API was to have a place for things that don't
>         >> fit neatly into the CRUD-centric paradigm.  Option (C) seems like a
>         >> good fit for this.
>         >
>         >Why not just use the existing tasks/ interface, then? :) Seems like a
>         >perfect fit to me.
>
>         The existing tasks/ interface is kind of heavyweight.  It provides a
>         framework for asynchronous operations.  It's really not
>         appropriate for
>         this purpose.
>
>         cheers,
>         brian
>
>
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