simple pub/sub

[Adam Tauno Williams]

On Thu, 2010-01-21 at 08:54 -0800, Steve Howell wrote:
> Hi, I'm looking for ideas on building a simple architecture that
> allows a bunch of independent Python processes to exchange data using
> files and perform calculations.
> One Python program would be collecting data from boat instruments on a
> serial port, then writing that info out to a file, and also
> transmitting data to instruments as needed (again through the serial
> port).  It would be the most complex program in terms of having to
> poll file descriptors, or something similar, but I want to limit its
> job to pure communication handling.

This should be pretty easy using multiprocessing.  In OpenGroupware
Coils we have a master process
<http://coils.hg.sourceforge.net/hgweb/coils/coils/file/2c7847ef0527/src/coils-master-service.py> that spins up children (workers, that each provide a distinct service) it opens a Pipe to each child to send messages to the child and a Queue from which it reads [all children (clients) write to the Queue and listen on their Pipe].  Then the master just listens on its pipe and forwards messages from children to other children.

All children are Service objects
<http://coils.hg.sourceforge.net/hgweb/coils/coils/file/2c7847ef0527/src/coils/core/service.py>.  Then implementing a new service [type of worker] is as easy as (our brutally simple pubsub service) <http://coils.hg.sourceforge.net/hgweb/coils/coils/file/2c7847ef0527/src/coils/logic/pubsub/service.py>

Hope that helps.

-- 
OpenGroupware developer: awilliam at whitemice.org
<http://whitemiceconsulting.blogspot.com/>
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