[zeromq-dev] XPUB and unsubscribe notification message count (bug or not?)

Michael Haberler mail17 at mah.priv.at
Tue Nov 12 21:26:58 CET 2013


found the Meerkat article on Pieter's blog with an opaque reference to this behavior: http://hintjens.com/blog:37 (Step 4..)

other than the article says, unsubscribe messages are actually sent, just only on the last unsubscribe; 'on every unsubscribe' would be advantageous over DEALER/ROUTER as suggested by the Census pattern because it would allow to properly track subscriber count even if a client exits abnormally and maybe has no more chance to say so on a DEALER/ROUTER pair. 

Any plans to fix that up? Just need to know so I can do a temporary fix or need to change the pattern.

-m



Am 12.11.2013 um 20:25 schrieb Michael Haberler <mail17 at mah.priv.at>:

> I'm puzzled by the following behaviour (trying to track subscriber count per topic):
> 
> XPUB server, XPUB_VERBOSE set
> server tracks messages received on XPUB socket
> 
> single client:
> client 1: SUB socket, connects to server, subscribes to 'topic' -> server receives subscribe message (\001topic)
> client 1 exits: server receives unsubscribe message (\000topic) -  as expected.
> 
> multiple clients subscribing to same topic:
> 
> client 1: SUB socket, connects to server, subscribes to 'topic' -> server receives subscribe message (\001topic)
> client 2: SUB socket, connects to server, subscribes to 'topic' -> server receives subscribe message (\001topic) 
> client 1 exits: ---> no unsubscribe message received! (I would expect an unsubscribe message here)
> client 2 exits: server receives unsubscribe message (\000topic)
> 
> Same situation with 3 clients: only the last unsubscribe generates a unsubscribe message
> 
> Is this as expected? Am I overlooking something? if not - happy to provide an example to reproduce, versions etc
> 
> thanks in advance
> 
> Michael
> 
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