[Twisted-Python] Implementing an event manager in twisted

[glyph at divmod.com]

On 12:26 am, daedalus at eigenmagic.com wrote:
>I have had an idea to implement an event manager to glue a few 
>different
>system components together, and I am wondering which pieces of twisted
>would be best suited to the task, or even if I should attempt it at 
>all.

Nothing about what you're suggesting sounds dangerous or weird.  In 
fact, it really sounds like what Twisted is already :).  If you want to 
write a layer over it to provide higher-level events, that's fine; most 
Twisted applications do something of the sort.  The one thing I'd 
caution you against is attempting to make something at the same level of 
abstraction as Twisted by building on top of Twisted.  That would just 
add complexity and overhead without any benefit.  So here are some 
things you've described which sound, to me, exactly like what Twisted 
already does:
>I have a desire to provide scheduler functionality (at time x, take
>action y).

This sounds like reactor.callLater().  (Or if you're talking about 
persistent scheduling, axiom's IScheduler.schedule).
>Data is received from an external entity by a listener.

This sounds like IProtocol's dataReceived method.
>A program polls for data, succeeds and notifies the event manager of 
>the
>data that was polled. The event manager notifies a 'poll storage' 
>object
>that stores the data in the database. It could also notify other 
>things.

In python, "notifying things" is just calling functions or methods; in 
the most advanced case, it's still just calling functions or methods 
which have been placed into a list.  Twisted has lots of such lists, and 
it doesn't seem worthwhile to me to unify them into a central structure.

If it does make sense to you to unify them, you might want to look at 
Louie: http://pylouie.org/ .  I've never used it and I don't really get 
what it's for, but several folks that I know seem to like it a lot for 
gluing events together.
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