CODEWITHSUNDEEP
pythontwisted
David
David

Reputation: 18261

Inter-service messaging/bus for twisted

Is there an in-twisted mechanism for passing messages in-process service to another? I wrote up a prototype bus that looks like 

    from collections import defaultdict
    channels = defaultdict(list)

    def registerSingle(name, callback):
        """
            Similar to register but ensures only one callback is register to a channel
            @todo change Exception to something more appropriate

            :name str A reasonably coherent name for a callback channel
            :callback callable Either a bound method or just a function
        """
        global channels
        if len(channels[name]) > 0:
            raise Exception("Tried to register %s but already has %s registered" % ( name, channels) )
        channels[name].append(callback)

    def register(name, callback):
        """
            Binds a callback to a named channel

            :name str A reasonably coherent name for a callback channel
            :callback callable Either a bound method or just a function
        """
        global channels
        channels[name].append(callback)


    def call(name, *args, **kwargs):
        """
            Applies the provided arguments to any and all callbacks for a specified channel

            :name str A reasonably coherent name for a callback channel
        """
        for callback in channels[name]:
            callback(*args, **kwargs)

To be used like

foo.py

from Application.data import bus

def doSomething(fooArg):
    print "Hello from Foo, you sent " , fooArg

bus.register("foo.doSomething", doSomething)

bar.py

 from Application.data import bus

 bus.call("foo.doSomething", "A simple string")

That's a really simple example as the primary use case is to share a common in memory data store. Initially I tried using a singleton but ran into too many problems when trying to cover it with unit-tests. I then tried passing a reference to the data store everywhere but felt that I was tying my application up to be 100% dependent on the data store never changing.

My only concern with the data.bus idea is that it's basically just an over glorified global variable. So my question, is there some sort of service bus or messaging system inside of twisted to allow for passing arbitrary messages between different resources inside of a twisted application or is my data.bus idea as good as it gets for a solution?

Upvotes: 2

Views: 375

Answers (1)

andrew cooke
andrew cooke

Reputation: 46862

it sounds like you want a "blackboard" or "tuple space" for python (i don't see how twisted changes things?)? if so, here's one - http://pypi.python.org/pypi/linda/0.5.1

Upvotes: 1

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