On Fri, Feb 23, 2018, at 4:53 PM, Mark via zeromq-dev wrote: > As I mentioned previously the docs on REQ/REP state: > > "If no services are available, then any send operation on the > socket shall block until at least one service becomes available." > > but the send() doesn't block in this situation. As you said earlier > the message is queued and sent async with send() returning to the > caller. > > I also mis-interpreted the docs to imply that when "at least one > service becomes available" that any queued messages would go to that > service, but that's not the case as the round-robin decision is only > made once on the call to send() - not during the async sending > process. > > Anyhoo, it's all good now that I know better.
Yeah one thing that got me when I started out with ZeroMQ is understanding that queues only exist in the context of known peers, and that a zmq socket doesn't have a master queue or anything that exists in the absence of known peers. This is why writing to a socket that is binding but has no peers will block. I say "known peers" rather than "peer connections" because you get a queue once you attempt to connect to a peer, even if that connection is not yet established. Justin _______________________________________________ zeromq-dev mailing list firstname.lastname@example.org https://lists.zeromq.org/mailman/listinfo/zeromq-dev