Ionel Maries Cristian ha scritto:
This is a very interesting initiative.
However there are few problems:
- there is no support for chunked input - that would require having
support for readline in the first place, also, it should be the
gateway's business decoding the chunked input.
Unfortunately Nginx does not yet support chunked input, so I can't help
here.
- the original wsgi spec somewhat has some support for streaming and
asynchronicity [*1]
Right, and in fact I have used this for the implementation of some
extensions in the WSGI module for Nginx.
- i don't see how removing the write callable will help (i don't see a
issue having the server providing a stringio.write as the write callable
for synchronous apps)
To summarize: the main problem with the write callable is that after you
call it control is not returned to the WSGI gateway.
With an asynchronous server it is a problem since if you write a lot of
data the server may not be able to send it to the client.
This is not a problem if the application returns a generator, since the
gateway can suspend the execution until the socket is ready to send data.
With the write callable this is not possible,
In my implementation of WSGI for Nginx I provide two separate
implementation of the write callable:
- put the socket temporary in synchronous mode
(this is WSGI compliant but it is very bad for Nginx)
- buffer all the written data until control is returned to the
gateway (this is *not* WSGI compliant)
However if you use greenlets, then implementing the write callable is
not a problem.
- passing nonstring values though middleware will make using/porting
existing wsgi middleware hairy (suppose you have a middleware that
applies some filter to the appiter - you'll have your code full of
isinstance nastiness)
Yes, this should be avoided.
Also, have you looked at the existing gateway implementations with
asynchronous support?
There are a bunch of them:
http://trac.wiretooth.com/public/wiki/asycwsgi
http://chiral.j4cbo.com/trac
http://wiki.secondlife.com/wiki/Eventlet
my own shot at the problem: http://code.google.com/p/cogen/
and manlio's mod_wsgi for nginx
(I may be missing some)
However there is absolutely no unity in handling the wsgi.input (or
equivalent)
The wsgi.input can be handled with ngx.poll:
c = ngx.connection_wrapper(wsgi.input)
...
ngx.poll_register(c, WSGI_POLLIN)
...
ngx.poll(1000)
Unfortunately I can not test if this is implementable.
I have some doubts.
> [...]
Manlio Perillo
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