[Web-SIG] Fwd: Collating follow-up on the future of WSGI

Benoit Chesneau bchesneau at gmail.com
Thu Jan 21 00:12:51 EST 2016

---------- Forwarded message ---------
From: Benoit Chesneau <bchesneau at gmail.com>
Date: Thu, 21 Jan 2016 at 06:12
Subject: Re: [Web-SIG] Collating follow-up on the future of WSGI
To: Graham Dumpleton <graham.dumpleton at gmail.com>

I am not speaking about websockets. You could use it for SSE, or some apps
could use the Upgrade header to upgrade from http to their own protocol
etc... The only discussion i saw about websockets are about the addition of
an async api or an external api. I am not describing that. I am speaking
about providing a low level abstraction like wsgi.input but adding to it
the support of output. (I was referring to wsgi.multithread...). This low
level interface would allow anyone to provide its own
implementation(server) or usage (application) still acting as a *gateway* .

Also who are "we"? I am starting to think the discussion is already done
and only obscure details like the content_length or headers encoding should
be discussed. The RAW_SOCKET have been added on demand of the gunicorn
users. Such thing also exist in things like cherrypy if I remember. A lot
of code around have been created over it. So before deciding it's
unworkable or whatever I strongly invite you to consider it as an addition
to the environ. And since some servers need to pass the data differently I
then suggest a Resource object on which you can read and write and
eventually poll. This is not a websocket but more a proxy ressource to the
client connexion. I will come back asap with a small spec.

I also propose a second addition to the protocol that formalize the
addition of extensions to the protocol by the servers if they want to.
Having for example something like "`wsg.extensions` . Such addition would
help anyone to experiment changes over the wsgi before making such changes
in the specification by itself possibly.

I think we have a good opportunity to extend the WSGI specification to
allow the users to take over the new challenges on the web without forcing
them to use a concurrency mode or skip completely the WSGI spec. The
interest I see in WSGI is its simplicity and low level interface allowing
users to build whatever they want over it. The different workers and their
support of different concurrency models and framework in gunicorn let me
think it is possible. Are the participants of this thread ready to discuss

- benoît

On Wed, 20 Jan 2016 at 23:37, Graham Dumpleton <graham.dumpleton at gmail.com>

> On 21 Jan 2016, at 9:27 AM, Benoit Chesneau <bchesneau at gmail.com> wrote:
> again. any server can do such implementation if we create a new Resource
> abstraction. This abstraction would expose a common api to read and write.
> The implementation would be specific to the server.
> If you mean not exposing the raw socket and having a separate high level
> API for implementing something like WebSocket this was already talked
> about. The suggestion was that it should not be a part of WSGI. Develop
> that API independently with no link to WSGI. The idea of upgrading from
> WSGI to a different API isn’t practical for various WSGI servers as it
> isn’t possible to unwind the state of the connection path created to get to
> point of handling the WSGI application. The better scenario is that the
> switch to an alternate WebSocket API is handled completely within the web
> server however it needs to handle it, when it needs to handle it, and not
> be reliant on going into a WSGI application which then says, oh, I actually
> need that to be WebSocket.
> Now like we have wsgi.thread I would instead suggest to add a system of
> capability or extension like in smtp, imap, ... so the servers that
> implement a specific extension can legally published it. Would it work for
> you?
> Since there is nothing in WSGI environ called wsgi.thread now I have no
> idea what you are really suggesting here.
> Graham
> benoit
> On Wed, 20 Jan 2016 at 21:28, Graham Dumpleton <graham.dumpleton at gmail.com>
> wrote:
>> On 21 Jan 2016, at 2:48 AM, Benoit Chesneau <bchesneau at gmail.com> wrote:
>> On Wed, Jan 20, 2016 at 1:57 AM Robert Collins <robertc at robertcollins.net>
>> wrote:
>>> On 20 January 2016 at 12:04, Benoit Chesneau <bchesneau at gmail.com>
>>> wrote:
>>> >
>>> > not at all. But I made the assumption that the wsgi server maintained a
>>> > thread directly or not where the python application is running .
>>> >
>>> > In any case there is some sort of wrapping done in the same
>>> thread/process
>>> > where the python application is running. And then nothing stop to give
>>> the
>>> > socket away to the application and tell to the server to stop to
>>> communicate
>>> > with it.
>>> What socket?
>>> Data could be being passed by shm, for instance.
>>> -Rob
>> While shared memory would be quite a bad idea, then why not. I still
>> don't see why having a way to upgrade the connection can't be done.
>> Call it I/O resource or Socket, the issue is the same. At the end nothing
>> stop the server to pass the control to the app. If we forget the socket
>> (which is btw the simplest design) then the server could stop to control
>> the I/O resource when the application ask it to do it. At some point either
>> a garbage collection or a basic resource return/claim flow could be used to
>> definitely free the resource.
>> The thing behind that is that it would allow the WSGI spec to only focus
>> on providing a strict gateway workflow without forcing the application to
>> adopt a concurrency model aync or not.
>> No one has said you cannot do it. because though it is only able to be
>> implemented in a subset of WSGI servers/adapters, then it doesn’t seem
>> appropriate that it be a part of the core WSGI specification.
>> This is the role of a WSGI extension as found at:
>>     http://wsgi.readthedocs.org/en/latest/specifications.html
>> So go talk to the authors of uWSGI, and the other couple of packages
>> available for trying to plug these into some of the pure Python based WSGI
>> servers and come to an agreement between yourselves as to a standard way of
>> doing it and the extension specification can be added to the wsgi.org
>>  site.
>> Graham
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