[Web-SIG] WSGI 2.0

[Phillip J. Eby]

At 05:54 PM 10/4/2007 +0200, Manlio Perillo wrote:
>Phillip J. Eby ha scritto:
> > At 04:48 PM 10/4/2007 +0200, Manlio Perillo wrote:
> >> Phillip J. Eby ha scritto:
> >> > It's always the case that a WSGI application can be paused after it
> >> > yields data, even in WSGI 1.0.
> >>
> >> I was not aware of this.
> >> It may cause some problems to a unaware WSGI application the fact that a
> >> new "handler" is started "interleaved" with the previous ones.
> >
> > It may... but the only applications that should be yielding anything are
> > ones that are sending large files, doing server push, or explicitly
> > *desire* to be interleaved in such fashion.
> >
>
>But they have no way to know if the server supports this,

If it's a WSGI-compliant server, it supports this by 
definition.  It's just that synchronous servers don't pause before 
requesting the next iteration.


>  and existing
>WSGI implementations does not interleave the iteration, as far as I know.

Nothing in the spec stops them from doing so - indeed, they're 
*encouraged* to do so:

http://www.python.org/dev/peps/pep-0333/#middleware-handling-of-block-boundaries

"""This requirement ensures that asynchronous applications and 
servers can conspire to reduce the number of threads that are 
required to run a given number of application instances simultaneously."""

Notice that the only way this sentence works is if you are 
interleaving applications.

That being said, the PEP really needs an explicit discussion of the 
execution model.