----- Original Message -----
From: "Oved Ourfalli" <ovedo@redhat.com> To: "Doron Fediuck" <dfediuck@redhat.com> Cc: engine-devel@ovirt.org, arch@ovirt.org Sent: Sunday, February 24, 2013 3:01:19 PM Subject: Re: [Engine-devel] REST API calls from
----- Original Message -----
From: "Doron Fediuck" <dfediuck@redhat.com> To: "Michael Pasternak" <mpastern@redhat.com> Cc: "Oved Ourfalli" <ovedo@redhat.com>, engine-devel@ovirt.org, arch@ovirt.org Sent: Sunday, February 24, 2013 1:20:12 PM Subject: Re: [Engine-devel] REST API calls from
----- Original Message -----
From: "Michael Pasternak" <mpastern@redhat.com> To: "Oved Ourfalli" <ovedo@redhat.com> Cc: engine-devel@ovirt.org, arch@ovirt.org Sent: Sunday, February 24, 2013 9:47:28 AM Subject: Re: [Engine-devel] REST API calls from
On 02/24/2013 09:05 AM, Oved Ourfalli wrote:
----- Original Message -----
From: "Doron Fediuck" <dfediuck@redhat.com> To: "Michael Pasternak" <mpastern@redhat.com> Cc: engine-devel@ovirt.org, arch@ovirt.org Sent: Thursday, February 21, 2013 6:54:59 PM Subject: Re: [Engine-devel] REST API calls from
----- Original Message -----
From: "Michael Pasternak" <mpastern@redhat.com> To: "Doron Fediuck" <dfediuck@redhat.com> Cc: engine-devel@ovirt.org, arch@ovirt.org Sent: Wednesday, February 20, 2013 2:56:59 PM Subject: Re: [Engine-devel] REST API calls from
On 02/14/2013 11:20 AM, Doron Fediuck wrote: > > > ----- Original Message ----- >> From: "Michael Pasternak" <mpastern@redhat.com> >> To: "Libor Spevak" <lspevak@redhat.com> >> Cc: engine-devel@ovirt.org, arch@ovirt.org >> Sent: Wednesday, February 13, 2013 12:55:36 PM >> Subject: Re: [Engine-devel] REST API calls from the GUI >> >> >> Hi Libor, >> >> This issue came across in one of the conversations i had >> with >> UX >> folks, but since we didn't end >> up with any conclusion/road map (nor discussed it properly >> to >> hear >> other thoughts), this is a perfect >> place to start this discussion, >> >> Intuitively REST is a way to go with GWT AJAX calls >> --------------------------------------------------- >> >> pros >> ==== >> >> - api data objects can be reused by generating java classes >> (using >> jaxb) from the rest schema [1] >> - no backend logic will be duplicated as api abstracts the >> backend >> exposing RESTful collection/resources to operate on >> - development against api is "easy" as api describes itself >> in >> RSDL >> [2] >> >> cons >> ==== >> >> - implementing transport layer (HTTP) under GWT >> - implementing own j2xml/json/yaml/... marshalling layer >> - implementing own error handling mechanism >> - implementing REST callback mechanism (in GWT) >> - constant maintenance of the data objects generated from >> the >> api >> - painful for Java developers >> >> Java-SDK >> -------- >> >> pros >> ==== >> >> - abstracts transport layer (leaving developer in standard >> Java >> api) >> - typesafe code (no need to mess with XML bulks) >> - has own data objects to work with >> - abstracts authentication/authorization >> (kerberos/cookie/session/etc.) >> - since SDK is auto-generated, it can be easily extended >> with >> required >> features to support UI (such as callback infrastructure >> for >> instance) >> >> cons >> ==== >> >> - has to be converted in to Javascript (not sure what the >> impacts >> are >> in terms of AJAX calls/etc.) >> - probably much more cons that we're not aware of and will >> have >> to >> figure out with POC >> >> >> thoughts? >> >> [1] http[s]://server[:port]/api?schema >> [2] http[s]://server[:port]/api?rsdl >> > > Although started as a UI request, there are other needs who > wish > to use API calls with a different transport. For example a > backend > hook which gets a REST entry point it can use to fetch for > additional > data, or perform actions. In this case I'd expect an > internal > connection > rather than creating additional connections. > How would you resolve it generically enough in this context?
Doron,
I believe your approach a bit different, UX folks seeking for a convenient way of communicating with ovirt public api, e.g closing api<->GUI gap, and theirs alternatives where native HTTP layer or Java-SDK based framework, while what you need is in-process channel to communicate with the engine itself,
i understanding your will of using stable api for this (RESTapi), but not sure that doing this via JavaSDK is a good way to go simply because SDK is designed to operate in a client-space, while what you need is a server-space bridge for that.
Michael, true but... Thinking about it differently both UI and hooks needs a client. The underlying protocols should be abstracted. This is something which will serve other functions as well.
I'm not sure we would need a new abstraction here. Both UI plugins and engine plugins need some API to do basic operations, and have access to different properties in the engine.
+1, that's exactly what i've suggested to begin with.
The only issue is that UI plugins and engine plugins shave different expectations from performance point of view. If UI is willing to wait for a refresh that may take too long for engine plugins, which would prefer to get the information as soon as possible without going into various communication layers which are not always needed. So again- a simple solution which enables transports layers to be replaced may serve more than one functionality in a better way.
Let's start with the simple solution. We don't know yet who will the plugins, how would they be used, and whether using the SDK will be a bottleneck of any kind. If the proposed solution is to support different transport layers while still using the SDK, then it is an extension we can always do in the future, if we find it of high benefit. (btw, regardless of that, the API/SDK is now faster than in the past, as we support REST sessions, which removes the need to re-authenticate upon each API request).
Oved, we have pretty good idea on how it will be used and what will create performance hits. Otherwise we wouldn't have had this thread.
In the UI plguins implementation, we gave this API, and in addition created a REST session to be used in order to do more sophisticated operations. I think we should probably do the same for engine plugins, giving the basic API, and giving a REST session for more advanced operations. The engine plugin may also have another 3rd party application it interacts with, and it would be able to share this session with it, allowing it to perform different operations on the engine. It would obviously be easy to do that using the Java SDK in the engine side, without creating a new layer of abstraction.
true, but the thing is that java-sdk designed to work with rest-api, and what Doron is trying to do is saving round-trip of engine->sdk->api->engine by enabling extra layer in sdk that will work not via HTTP, but natively with RESTeasy (REST framework we using in api), the disadvantages of such design are:
1. working with java-sdk via JNI (walking out from container to client application - sdk) 2. hacking RESTeasy by: 2.1 working with underlying (not public/backward compatible) interfaces & using JNI as well 2.2 most likely maintaining code working with RESTeasy on every new (RESTeasy) release by reverse engineering new changes/behaviour of this framework 2.3 making assumptions on code invocations to emulate GET/POST/PUT/DELETE HTTP calls 2.4 still having round-trip engine->sdk->RESTeasy->engine
therefore i think that having own private API in engine for that is a much better solution.
I assume the 3rd party application will use either the Java SDK, or another one, according the platform it is built upon, and in the "worst case", will interact directly with the API.
> >> On 02/12/2013 06:13 PM, Libor Spevak wrote: >>> Hi, >>> >>> I would like to ask, if there have been discussions about >>> an >>> option >>> to call REST API services directly from the Frontend (GWT >>> layer)? >>> GWT compiles Java frontend-side to >>> Javascript, calls to backend services are performed >>> "transparently" >>> by the framework using AJAX support. But, there is still a >>> need >>> to >>> have a special set of data objects >>> and the server-side logic can duplicate. >>> >>> Java REST API SDK enables to build "thick" client. The >>> calls >>> are >>> realized using e.g. Apache HttClient and supported >>> libraries. >>> I >>> think the requirements of GWT can be a >>> little bit different, but something overlaps. >>> >>> I found several links about REST API support from GWT, so >>> there >>> is >>> something for inspiration... >>> >>> - http://www.spiffyui.org/ >>> - http://www.zackgrossbart.com/hackito/gwt-rest/ >>> - http://code.google.com/p/gwt-rest/ >>> - http://restygwt.fusesource.org/ >>> >>> But, do you think it would be useful and what drawbacks >>> can >>> occur >>> (authentication, authorization, response times, need to >>> support >>> larger set of services, painful >>> refactoring, ...)? >>> >>> Regards, >>> Libor >>>