[Twisted-Python] Advice on Writing a Custom Twisted Stackless Reactor

Andrew Francis andrewfr_ice at yahoo.com
Thu Jan 11 16:46:17 EST 2007

Date: Wed, 10 Jan 2007 18:32:43 -0500
From: Jean-Paul Calderone <exarkun at divmod.com>
To: Twisted general discussion
<twisted-python at twistedmatrix.com>

<20070110233243.11447.1076809328.divmod.quotient.12503 at ohm>
Content-Type: text/plain; format=flowed

>Okay.  I see that you're writing stackless
>using TSR.  I'm not sure what the point of this is. 
>Can you explain the functionality that's gained by
>doing this, rather than using something like what's
in >Chris Armstrong's sandbox in threadless.py?

Thank you Jean-Paul for your response. My goal is to
write a custom Twisted reactor for Stackless Python.
Although I have had success writing programmes that
use deferred (for client HTTP calls) and HTTP request
handlers, I have had problems doing both
simultaneously in one programme.

Some context : I am prototyping WS-BPEL (Web services
Business Process Execution Language) processors. In
the WS-BPEL language, it is possible for some
process's "threads" to act as a server and other
"threads" to act as a client simultaneously. 

The problem that I have found is that when Twisted
blocks waiting for a server request, Stackless will
also block, hence no progress on other tasklets that
could execute. I thought I got around this problem by
using task.LoopingCall/() that would issue a
stackless.schedule() at regular intervals. However
this approach turns out to be problematic. I thought I
could solve the problem by placing Twisted in a thread
but no. The main problem with placing Twisted in a
thread is that I seem to lose the deferred (and I
don't believe I am getting deadlock).

>Can you explain the functionality that's gained by
>doing this, 

1. I solve my problem in a clean fashion. 

2. If I write a custom Stackless Reactor, then I have
a solution that conforms to the way Twisted does
stuff. I think would make it easier for others to use
my stuff.

>rather than using something like what's in Chris
>Armstrong's sandbox in threadless.py? 

Chris's approach looks like the approach I currently

>Threaded select reactor actually isn't the same kind
>of reactor as the rest of these, since it isn't
>intended to be used via the normal reactor API (ie,

Right now I am using Twisted 2.4 with Stackless 2.4.3.

For now, I would like to build on top of

Back to my original question, given my previous
example's "main loop", do I simply use interleave() to
get my processor to call Twisted?


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