[zeromq-dev] High water mark notification for publisher

[Edwin Amsler]

Hey folks,

I brought up this problem a few months back, but had to move onto more 
pressing things at the time.

It was mentioned that under the hood, the PUB-SUB system had individual 
outgoing queues, each with their own water mark counters. What happens 
to a message when all queues are full? It would be ideal to know if the 
message I pass in will be dropped by all queues due to the high water 
mark. I don't think it was implemented then, but it would certainly 
solve my particular problem of over-tasking the publishing side.

I have example code here:
http://pastebin.com/gjfuNdNF

The idea would be that if that ZeroMQ's publisher has no room in the 
internal buffers, that I would be notified the message wasn't sent. In 
the test application, I would then be able to wait before trying again. 
This way the application code which publishes messages isn't creating 
needless work which is secretly thrown away.

Thoughts?