[zeromq-dev] subscribe/unsubscribe refcounting behaviour

[Jon Dyte]

Hi

This is just a general question to the list about the behavior of the 
subscribe/unsubscribe socket option.

Basically it seems that at present if you call subscribe multiple times 
for the same prefix.

zmq::socket_t sm (ctx, ZMQ_SUB);

sm.setsockopt (ZMQ_SUBSCRIBE, "ABC", 3);
sm.setsockopt (ZMQ_SUBSCRIBE, "ABC", 3);
sm.setsockopt (ZMQ_SUBSCRIBE, "ABC", 3);


then  the only way to cancel that subscription is to

sm.setsockopt (ZMQ_SUBSCRIBE, "ABC", 3);
sm.setsockopt (ZMQ_SUBSCRIBE, "ABC", 3);
sm.setsockopt (ZMQ_SUBSCRIBE, "ABC", 3);


the same number of times for the same prefix.

This means that the client has to keep track of how many subscriptions 
it has issued in order to cancel it.


so

1) is everyone aware of this?
2) are they happy with it?

I only ask because I was rather surprised to see that this is the way it 
currently works,
after studying the prefix/matching code recently.

Potentially the extra calls could both return an error to indicate 
already subscribed or unsubscribed?

Thoughts?

Jon