Am 26.03.2014 14:51, schrieb Aymeric Augustin:
2014-03-26 12:41 GMT+01:00 Victor Stinner <[email protected]
<mailto:[email protected]>>:
I would like to know which WSGI implementations are compatible with
Tulip/asyncio (and maybe also Trollius!).
I've been asked by users for that also already .. like in "can I run
Autobahn/asyncio and WSGI together"? A typical use case would be:
A user posts a form via plain old HTTP to WSGI app. The app does it's
usual stuff, but in addition sends a WebSocket message to notify all
connected clients of some bit of info in the form data posted in real-time.
As far as I understand, WSGI as defined by PEP 3333 is incompatible
with asyncio. The WSGI callable would have to become a coroutine for
asyncio to do something useful and the specification doesn't allow that.
FWIW, Twisted includes a WSGI container that runs the WSGI app bits on a
background thread pool
http://twistedmatrix.com/documents/current/web/howto/web-in-60/wsgi.html
As far as I know, this does not allow to run async. bits in the WSGI app
code. However, what you can do is call the main thread from one of the
background worker threads, and do your async stuff from the main thread
then:
https://github.com/oberstet/scratchbox/blob/master/python/twisted/wsgi/test.py
I am unsure how the other direction would work ..
Then, also FWIW, there is
https://github.com/twisted/klein
which models Flask/Bottle, but directly on top of Twisted Web, which
_does_ allow to do async. stuff
At this point, from what I've seen, authors of web applications tend to
separate their sync and async services because the performance
characteristics are widely different.
As far as I know and judging from past attempts, a PEP adding async
support to WSGI would be met with fierce resistance. (I had started
writing one but I gave up after reading discussions on the topic.)
If a WSGI implementation is not designed for asyncio, is it still
possible to run asyncio tasks in an handler?
Most likely yes, by running the main server loop and the asyncio
event loop in different threads.
Ah, yeah. That's what the Twisted WSGI container does ..
Cheers,
/Tobias
--
Aymeric.
