[Python] Clean way to limit the subscribers in the Publish & Subscribe model

In the Publish & Subscribe model using autobahn, I would like to limit the number of subscribers for a given @exportSub(...). How do you know the number of subscribers?

(From examples)

class MyTopicService(object):

def __init__(self, allowedTopicIds):
self.allowedTopicIds = allowedTopicIds

@exportSub("", True)
def subscribe(self, topicUriPrefix, topicUriSuffix):
ret = False
print "client wants to subscribe to %s %s. Allowed topic ids:%s" % (topicUriPrefix, topicUriSuffix, self.allowedTopicIds)
try:
if topicUriSuffix in self.allowedTopicIds:
ret = True
print "Subscribing client to topic %s %s" % (topicUriPrefix, topicUriSuffix)
else:
print "Client not allowed to subscribe to topic %s %s" % (topicUriPrefix, topicUriSuffix)
except:
print "illegal topic - skipped subscription"
finally:
return ret

class MyServerProtocol(WampServerProtocol):
def onSessionOpen(self):
self.registerHandlerForPubSub(MyTopicService(my_keys_1), url_1_foo)
self.registerHandlerForPubSub(MyTopicService(my_keys_2), url_2_bar)


I could probably do this using my own WampServerFactory, overriding the onClientSubscribed and onClientUnsubscribed methods and using an internal array variable... But I would like to know if there is a cleaner way...

class MyFactory(WampServerFactory):
def onClientSubscribed(self, *a, **k):
WampServerFactory.onClientSubscribed(self, a, k)
print '=== client subscribed '

def onClientUnsubscribed(self, *a, **k):
WampServerFactory.onClientUnsubscribed(self, a, k)
print '=== client unsubscribed '


Code can be found here.

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