Hi, I am planning to develop an application that will query a number of services at given intervals, and Twisted seems like a very nice platform to do so. However, because of little previous experience with Twisted, especially with building proper applications, using interfaces and using plugins, I could really need some pointers to get me started.
In the following I will try to explain in broad terms what the application will do, and humbly ask for input on how I may structure it using factories, protocols etc.: 1. A number of more-or-less similar server applications (5-10) have a number of concurrent instances/servers (1-30) each. 2. I need to acquire the status of each instance at given intervals. These will typically range from every 20 seconds to every 3 minutes, and depend on the which service the instance is based on. 3. A list of the server instances shall be acquired via an XML-query every few minutes to pick up on new or removed instances. 4. An executable already exists which can be used to status-poll almost all services using different parameters. I will be calling it from my application to do the polling instead of recreating it in Python. 5. I need to be able to create my own polling-protocol for at least one of the service types which is incompatible with the executable. 6. Some services can not only be polled at intervals, but additionally stream information that I am interested in listening to. 7. At a later point in time, I wish to be able to communicate with IRC, MSN and other services/protocols using the queried and streamed data. My initial general thought is the following: 1. Design a class for each server application, where all classes implement the same interface. The class defines how to deal with server instances of its corresponding server application type. Classes are created as Twisted-plugins. 2. For each new server instance that is discovered, create an object which contains a timer and polls the server at specific intervals, writing the result to a globally accessible data structure. 3. For server instances that stream data continuously in addition to being polled at regular intervals, create a separate object which listens to the server. I believe I should somehow have a global data structure which contains references to all the server instance objects, regardless of type, and allows them to store data. This is sort of like the factory does for protocols, except in my case I don't think I can use a regular factory since I need both clients (to poll at intervals) and servers (to listen to streaming data). I suppose I could use a ClientFactory for the pollers and a Factory for the stream-listeners, and let them have a common data-store? But is it possible to use a single ClientFactory to spawn all poller-objects regardless of server type? Or do I need one ClientFactory for each server type? Do I perhaps need one ClientFactory per server instance? Or should I just ignore factories all together since it is primarily the timer and asyncronicity of Twisted I need? I am quite certain there is a correct twistified way of handling this sort of problem. I am just not sure what it is, and would sincerely welcome all feedback on how this should be done. Feel free to point to examples of applications that are similar to what I sketched above, and tell me to study the code :) Cheers, Einar _______________________________________________ Twisted-Python mailing list Twisted-Python@twistedmatrix.com http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python
