from twisted.spread import pb
class MasterDuckPond(pb.Cacheable):
    def __init__(self, ducks):
        self.observers = []
        self.ducks = ducks
    def count(self):
        print("I have [%d] ducks" % len(self.ducks))
    def addDuck(self, duck):
        self.ducks.append(duck)
        for o in self.observers:
            o.callRemote("addDuck", duck)
    def removeDuck(self, duck):
        self.ducks.remove(duck)
        for o in self.observers:
            o.callRemote("removeDuck", duck)
    def getStateToCacheAndObserveFor(self, perspective, observer):
        self.observers.append(observer)
        # you should ignore pb.Cacheable-specific state, like self.observers
        return self.ducks  # in this case, just a list of ducks
    def stoppedObserving(self, perspective, observer):
        self.observers.remove(observer)
class SlaveDuckPond(pb.RemoteCache):
    # This is a cache of a remote MasterDuckPond
    def count(self):
        return len(self.cacheducks)
    def getDucks(self):
        return self.cacheducks
    def setCopyableState(self, state):
        print(" cache - sitting, er, setting ducks")
        self.cacheducks = state
    def observe_addDuck(self, newDuck):
        print(" cache - addDuck")
        self.cacheducks.append(newDuck)
    def observe_removeDuck(self, deadDuck):
        print(" cache - removeDuck")
        self.cacheducks.remove(deadDuck)
pb.setUnjellyableForClass(MasterDuckPond, SlaveDuckPond)