Get a particular message from ZMQ Sub Queue

Question

I have a python messaging application that uses ZMQ. Each object has a PUB and a SUB queue, and they connect to each other. In some particular cases I want to wait for a particular message in the SUB queue, leaving the ones that I am not interested for later processing.

Right now, I am getting all messages and queuing those I am not interested in a Python Queue, until I found the one I am waiting for. But his means that in each processing routing I need to check first in the Python Queue for old messages. Is there a better way?

Answer 1

A zmq publisher doesn't do any queueing... it drops messages when there isn't a SUB available to receive those messages.

The better way in your situation would be to create a generic sub who only will subscribe to certain messages of interest. That way you can spin up all of the different SUBs (even within one thread and using a zmq poller) and they will all process messages as they come from the PUB....

This is what the PUB/SUB pattern is primarily used for. Subs only subscribe to messages of interest, thus eliminating the need to cycle through a queue of messages at every loop looking for messages of interest.