On Thu, May 1, 2008 at 6:09 PM, Daniel Brandt daniel.brandt@gmail.com wrote:

Hello, I'm looking for some advice on how to get started with an asyncore -> Twisted conversion. Being new to twisted I have some trouble getting started (re)designing my system. All ideas are welcome since I'm also doing this to learn.

I am about to convert a message-passing daemon written with asyncore to Twisted, and I have two goals in mind. Code that is easier to maintain and expand, and higher reliability. The last part would probably be achievable while sticking with the present code, but since I keep hearing I really should use Twisted instead, I figured I'd try it out :-).

The daemon listens for connections from different peers. Some peers just leave a message and disconnect, some peers connect as receivers and linger waiting for messages. A message will be given to the daemon by a messenger, and forwarded by the daemon to exactly one of the connected receivers. The daemon keeps a data structure (a dict with identifier: channel, actually) of receivers which it cycles through in a round-robin fashion.

One common strategy in twisted is to keep a list of your connected clients (Protocol instances) as part of the factory. See:

http://twistedmatrix.com/projects/core/documentation/howto/servers.html

So in the dataReceived method on you Protocol, you would do something like:

def dataReceived(self): self.factory.clients.append(self)

There are more scenarios as well; (recievers may send status messages back to the daemon that the daemon logs, some messengers linger waiting for confirmation from a receiver and a few other) but they arees, mostly just variations of the above.

I'm a bit confused about what parts should be in the Protocol and what should be separated away from it. Should I make a specialized Factory or make a Service (or several depending on what type of client connection it is)?

I think generally it is a good idea to have a specialized Factory as this binds global state for you Protocol instances. The server howto linked above describes this pattern quite well.

I realize there is a lot in my description that's open for interpretation, but since I'm mostly after design ideas and good practices, I'm hoping that's OK..

The finger tutorial does a good job of explaining many aspects of twisted, and this might give you some ideas of how to leverage its parts for your application:

http://twistedmatrix.com/projects/core/documentation/howto/tutorial/index.ht...