[Web-SIG] WSGI and async Servers

[exarkun at twistedmatrix.com]

On 04:40 pm, armin.ronacher at active-4.com wrote:
>Hi,
>
>For this topic I would love to remember everybody that the web is
>currently changing and will even more change in the future which will
>probably also mean that a lot of what we're doing currently might not 
>be
>common practise in the near future.
>
>WSGI is currently not doing to well for asyncronous applications, so
>people claim.  I don't know where this is coming from, probably because
>everybody still thinks our data storages are traditional databases. 
>But
>we really have to wake up from that idea and start at least
>*considering* asynchronous designs when it comes to WSGI.
>
>Tornado appeared recently and from a technical perspective, it's a step
>backwards.  It's not supporting all of HTTP and it's clearly not
>supporting WSGI in any way beyond the very basics.  But the interesting
>point is, that this does not matter for many applications.  Even for an
>application that was never designed to be non-blocking that just
>recently dropped MySQL for most of the data, Tornado is a huge
>performance improvement (personal experience).
>
>Why would it be good to encourage async applications on top of WSGI?
>Because people would otherwise come up with their own implementations
>that are incompatible to each other.  Maybe that should not go into 
>WSGI
>but a AWSGI or whatever, but I'm pretty sure we should at least 
>consider
>it and ask people that use asynchronous applications/servers what the
>issues with WSGI are.

At PyCon, there was some discussion about what changes could be made to 
the WSGI spec to extend it to support asynchronous applications.  I 
probably have some notes, and I think I even sent them to the list at 
the time.  Perhaps those with an interest in async WSGI could take a 
look at those and weigh in on the merits of the conclusions reached.

A number of other people also posted to a thread which covered more of 
the WSGI ideas discussed at PyCon.  The top of that thread is here:

  http://www.mail-archive.com/web-sig@python.org/msg02569.html

I posted an example of what an asynchronous WSGI application might look 
like here:

  http://www.mail-archive.com/web-sig@python.org/msg02582.html

(it looks like I forgot to do anything relating to start_response there 
- I don't remember if this was intentional or not).

I think there was also some talk about how it would be desirable to 
support asynchronous response header generation.

Jean-Paul