[zeromq-dev] Pub-Sub and HWM

Emmanuel TAUREL taurel at esrf.fr
Thu Nov 10 13:13:10 CET 2011


Hello everybody,

I would like to  have a confirmation of my understanding of the HWM 
usage with the pub/sub framework.

I see four cases when for one reason or another the subscriber is not 
able to read messages:

1 - There is a HWM of let's say 1000 on both publisher and subscriber
Messages are queued on the subscriber side until the HWM is reached 
(1000 messages) then another 1000 messages are
queued on the publisher side and finally the publisher drops messages 
(not sending them on the wire)

2 - There is a HWM of 1000 but only on the subscriber side
1000 messages will be queued on the subscriber side and them messages 
will be dropped by the subscriber. Messages are sent on the wire
in this case

3 - There is a HWM of 1000 only on the publisher side
1000 messages will be queued on the publisher side and following 
messages will be dropped by the publisher. Messages therefore will not 
be sent
on the wire

4 - No HWM at all
Subscriber will need more and more memory to queue all messages.

Is the above correct?

Thank's for your answer

Emmanuel




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