Unless there’s some other trickiness going on that I’m unaware of, the routes for the WSGI app are defined at application startup time (by methods called in the WSGI app’s __init__).
--- Ryan Petrello Senior Developer, DreamHost ryan.petre...@dreamhost.com On Dec 13, 2013, at 12:56 PM, Doug Hellmann <doug.hellm...@dreamhost.com> wrote: > > > > On Thu, Dec 12, 2013 at 9:22 PM, Christopher Yeoh <cbky...@gmail.com> wrote: > On Fri, Dec 13, 2013 at 4:12 AM, Jay Pipes <jaypi...@gmail.com> wrote: > On 12/11/2013 11:47 PM, Mike Perez wrote: > On 10:06 Thu 12 Dec , Christopher Yeoh wrote: > On Thu, Dec 12, 2013 at 8:59 AM, Doug Hellmann > <doug.hellm...@dreamhost.com > <mailto:doug.hellm...@dreamhost.com>>wrote: > > > > > On Wed, Dec 11, 2013 at 3:41 PM, Ryan Petrello < > ryan.petre...@dreamhost.com > <mailto:ryan.petre...@dreamhost.com>> > wrote: > > Hello, > > I’ve spent the past week experimenting with using Pecan for > Nova’s > API > and have opened an experimental review: > > > https://review.openstack.org/#/c/61303/6 > > …which implements the `versions` v3 endpoint using pecan (and > paves the > way for other extensions to use pecan). This is a *potential* > > approach > I've considered for gradually moving the V3 API, but I’m open > to other suggestions (and feedback on this approach). I’ve > also got a few open questions/general observations: > > 1. It looks like the Nova v3 API is composed *entirely* of > extensions (including “core” API calls), and that extensions > and their routes are discoverable and extensible via installed > software that registers > itself > via stevedore. This seems to lead to an API that’s composed of > > installed > software, which in my opinion, makes it fairly hard to map out > the > API (as > opposed to how routes are manually defined in other WSGI > frameworks). I > assume at this time, this design decision has already been > solidified for > v3? > > > Yeah, I brought this up at the summit. I am still having some > trouble understanding how we are going to express a stable core > API for compatibility testing if the behavior of the API can be > varied so significantly by deployment decisions. Will we just > list each > "required" > extension, and forbid any extras for a compliant cloud? > > > Maybe the issue is caused by me misunderstanding the term > "extension," which (to me) implies an optional component but is > perhaps reflecting a technical implementation detail instead? > > > Yes and no :-) As Ryan mentions, all API code is a plugin in the V3 > API. However, some must be loaded or the V3 API refuses to start > up. In nova/api/openstack/__init__.py we have > API_V3_CORE_EXTENSIONS which hard codes which extensions must be > loaded and there is no config option to override this (blacklisting > a core plugin will result in the V3 API not starting up). > > So for compatibility testing I think what will probably happen is > that we'll be defining a minimum set (API_V3_CORE_EXTENSIONS) that > must be implemented and clients can rely on that always being > present > on a compliant cloud. But clients can also then query through > /extensions what other functionality (which is backwards compatible > with respect to core) may also be present on that specific cloud. > > This really seems similar to the idea of having a router class, some > controllers and you map them. From my observation at the summit, > calling everything an extension creates confusion. An extension > "extends" something. For example, Chrome has extensions, and they > extend the idea of the core features of a browser. If you want to do > more than back/forward, go to an address, stop, etc, that's an > extension. If you want it to play an audio clip "stop, hammer time" > after clicking the stop button, that's an example of an extension. > > In OpenStack, we use extensions to extend core. Core are the > essential feature(s) of the project. In Cinder for example, core is > volume. In core you can create a volume, delete a volume, attach a > volume, detach a volume, etc. If you want to go beyond that, that's > an extension. If you want to do volume encryption, that's an example > of an extension. > > I'm worried by the discrepancies this will create among the programs. > You mentioned maintainability being a plus for this. I don't think > it'll be great from the deployers perspective when you have one > program that thinks everything is an extension and some of them have > to be enabled that the deployer has to be mindful of, while the rest > of the programs consider all extensions to be optional. > > +1. I agree with most of what Mike says above. The idea that there are core > "extensions" in Nova's v3 API doesn't make a whole lot of sense to me. > > > So would it help if we used the term "plugin" to talk about the framework > that the API is implemented with, > and extensions when talking about things which extend the core API? So the > whole of the API is implemented > using plugins, while the core plugins are not considered to be extensions. > > That distinction does help. > > Are the extensions enabled at startup time, or at runtime when an API call is > made? That is, could 2 different users of the same cloud service instance see > different fields in the value returned from the call because of some runtime > decision made inside either an extension (where the extension might not add > fields for some reason) or a bit of core code (by deciding not to call an > extension at all)? > > Doug > _______________________________________________ > OpenStack-dev mailing list > OpenStack-dev@lists.openstack.org > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev _______________________________________________ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
