[Twisted-Python] Re: Callback blocked in event loop

[Ed Suominen]

> On Fri, 10 Nov 2006 15:24:51 +0000 (GMT), Matt P wrote:
>>> Events may be raised in the server, as a twisted.pb call to 
>>> fireEvent on the server and also come in on a separate thread (from
>>> a JMS message queue) and get posted onto the DefferedQueue for 
>>> events.
>>> 
>>> If events are raised in the server, remote listeners get their 
>>> pb.Referenceable callback immediately. It works as I would like.
>>> 
>>> [snip]
>>> 
>>> So, only in the case where teh DeferredQueue.put(...) is called 
>>> from another thread do I have the problem. I can't see why the 
>>> blocking. Does this behaviour make sense to anyone!?
> 
> DeferredQueue isn't threadsafe.  Instead of calling put() directly from
> a non-reactor thread, call it with reactor.callFromThread:
> 
>     reactor.callFromThread(q.put, value)
> 
> Jean-Paul

Matt, this is exactly the sort of thing for which I wrote the taskqueue
module that is patiently awaiting review in ticket #1768
(http://twistedmatrix.com/trac/ticket/1768).

It is a critical part of my sAsync project ("SQLAlchemy done
asynchronously"). You can check out the latest version as used in that
project at:

http://foss.eepatents.com/sAsync/browser/trunk/sasync/taskqueue.py.

The part that would appear to be of particular interested to you is the
ThreadQueue subclass of TaskQueue.

Best regards,
Ed Suominen