[Twisted-Python] spawning tasks after reactor?

[Darren Govoni]

It works now. Sorry for the extra post.

On Wed, 2008-12-31 at 15:08 -0500, Darren Govoni wrote:
> Hi,
>   Thanks for that suggestion. It looks very close to what I need. I
> tried doing it _after_ the reactor is run and it did not execute. Here
> is a code snippet.
> 
> def convert_to_pdf(arg):
>    print "converting..."
> 
> def notify_pdf:
>    print "Yay! I'm done"
> 
> ...
> 		d = threads.deferToThread(convert_to_pdf,offset)
> 		d.addCallback(notify_pdf)
> 
> All the examples for threads.deferToThread call reactor.run() after
> configuring all the threads, but this isn't useful in my app.
> 
> If I call reactor.run() and _then_ try to deferToThread, it doesn't
> work. I'm probably missing an argument or something.
> 
> Thanks for any tips. Much appreciated.
> 
> Darren
> 
> On Wed, 2008-12-31 at 11:16 -0500, Jean-Paul Calderone wrote:
> > On Wed, 31 Dec 2008 10:51:38 -0500, Darren Govoni <darren at ontrenet.com> wrote:
> > >Hi Jean-Paul,
> > >  Thank you for those suggestions. I can post some simple code after I
> > >get further. The psuedo code of what I want to do is like this:
> > >every few seconds, check a message queue (I see how this is done):
> > >   if there is a message, spawn a deferred so I don't block:
> > >	# The deferred should immediately call a method in a separate
> > >	# thread (wisted kind) to process the message
> > >	# Allow for 10 or so deferreds to be processing messages
> > >	# in parallel while the reactor continues to receive them
> > >	# but block scheduling the deferred if the pool is maxed
> > >	# out
> > 
> > A Deferred is just a convenient way to keep track of callbacks.  It's
> > not an active thing, so to "spawn" one doesn't make much sense.  Instead,
> > you spawn something else and use a Deferred to keep track of its result.
> > 
> > >
> > >Sorry if this is lacking in detail, i'm trying to test the idea in a
> > >simple way with twisted first. If I set up a deferred before calling
> > >reactor.run(), then of course, it runs, but after reactor.run() I have
> > >to invoke reactor.callLater(...) so its a bit different, but what I'd
> > >like is something like reactor.callNow(...) that doesn't block and
> > >invokes the generator in a thread pool.
> > 
> > You probably want twisted.internet.threads.deferToThreadPool (or the older
> > deferToThread).  From its docstring:
> > 
> >   Call the function C{f} using a thread from the given threadpool and return
> >   the result as a Deferred.
> > 
> > Jean-Paul
> > 
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> 
> 
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