[Web-SIG] WSGI 2.0

[Manlio Perillo]

Phillip J. Eby ha scritto:
> At 05:14 PM 10/5/2007 +0200, Manlio Perillo wrote:
>> Phillip J. Eby ha scritto:
>> > At 12:41 PM 10/5/2007 +0200, Manlio Perillo wrote:
>> >> Phillip J. Eby ha scritto:
>> >> > In other words, those flags were to support legacy frameworks 
>> detecting
>> >> > that they were in an incompatible hosting environment.  However, 
>> IIUC,
>> >> > there is no such existing framework that could meaningfully use the
>> >> flag
>> >> > you're proposing, that has any real chance of being portable to
>> >> > different WSGI environments.
>> >>
>> >> This is true, but I continue to think that it is worth adding that 
>> flag.
>> >> Asynchronous support is available in Nginx mod_wsgi, and in the future
>> >> someone can implement a WSGI gateway for lighttpd.
>> >
>> > Right now, the definition of the flag is not sufficiently defined 
>> for my
>> > taste.  You have only proposed that it be set to indicate that
>> > interleaved execution is possible -- but it is *always* possible to 
>> have
>> > interleaved execution in WSGI 1.0, so the only reason to add the 
>> flag to
>> > WSGI 2.0 would be so a server could promise NOT to interleave
>> > execution.  And what good is that?
>> >
>>
>> Ok, here is more useful definition.
>>
>> If wsgi.asynchronous evaluates to true, then the WSGI application *will*
>> be executed into the server main process cycle and thus the application
>> execution *will* be interleaved (since this is the only way to support
>> multiple concurrent requests).
> 
> I still don't see how this is *useful*.  What will the application *do* 
> with this information?
> 

As an example (not tested) SQLAlchemy can implements a 
RequestSingletonPool, that is the equivalend of ThreadSingetonPool.

In this case the pool will checkout a connection using the 
environ['wsgi.request_id'] identifier (unique for each request), instead 
of thread.get_ident.

So, a WSGI application *needs* to know if the application is 
multithreaded or asynchronous to select the right connection pool.



Regards   Manlio Perillo