zmq: can multiple threads PUSH in a simple PUSH-PULL pattern

Question

I have two processes: a producer which pushes messages via ZMQ to a consumer in a simple PULL-PUSH point-to-point pattern. The producer has several internal threads that send() via zmq. However, 0MQ's docs suggest not to share sockets between threads.

Must I use a single thread to send?
Assuming there is no strict requirement for keeping the sending order between the threads, doesn't the fact that the socket is a one-directional simplex allow multiple threads to use it without introducing locks?

Answer 1

The easiest thing to do is to create a separate PUSH socket on each of producer's threads and connect all these sockets to a single PULL socket in consumer.

It's explicitly stated in the guide that ZeroMQ sockets must be used on a single thread. I'd say that violating this requirement is not a good idea, even if it seems to work: things may break in the next version of the library or on some specific platform or in some specific load scenario. So, it's just too risky.