[Twisted-web] [Twisted-Python] twisted.web questions

[Allen Bierbaum]

On Mon, Jun 14, 2010 at 6:28 PM, Christopher Armstrong <
radix at twistedmatrix.com> wrote:

> On Mon, Jun 14, 2010 at 5:42 PM, Allen Bierbaum <abierbaum at gmail.com>
> wrote:
> > Something like this:
> >
> >   def _bg_GET(self, request):
> >       # Do something slow
> >       request.write(result)
> >       return request
> >    def render_GET(self, request):
> >       d = deferToThread(self._bg_GET, request)
> >       d.addCallback(lambda r: r.finish())
> >       return NOT_DONE_YET
> >
> > That seems to work, but I would like to
> >    a) not use the deferToThread() and
> >    b) do something that doesn't sacrifice too much performance.
> >
> > At the end of the day, what I would really like is something in
> render_GET
> > that checks the return from calling the internal GET method and if it is
> a
> > deferred it adds a callback to finish the request, if not it simply
> returns
> > the result.  (this would allow me to use deferToThread, inlineCallbacks,
> etc
> > as needed in my get methods)
> >
> > Can you see any issues with doing something like this?  (it seems almost
> too
> > simple so I expect that I must be missing something)
>
> Yeah, don't call request methods (like request.write) from the
> function that gets run in a thread. You should be calling
> request.write in the callback, or with callFromThread in the threaded
> function.
>

Good tip.  Looks like the wsgi wrapper has a nice little helper method to
support this:

http://twistedmatrix.com/trac/browser/tags/releases/twisted-10.0.0//twisted/web/wsgi.py#L257

<http://twistedmatrix.com/trac/browser/tags/releases/twisted-10.0.0//twisted/web/wsgi.py#L257>
Thanks,
Allen
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