[zeromq-dev] Timing issues

Lindley French lindleyf at gmail.com
Wed Jan 15 17:20:07 CET 2014

I have a test case in which I'm communicating between two threads using zmq
sockets. The fact that the sockets are in the same process is an artifact
of the test, not the real use-case, so I have a TCP connection between them.

What I'm observing is that a lot of the time, it takes ~100 milliseconds
between delivery of a message to the sending socket and arrival of that
message on the receiving socket. Other times (less frequently) it is a
matter of microseconds. I imagine this must be due to some kernel or thread
scheduling weirdness, but I can't rule out that it might be due to
something in 0MQ.

If I follow the TCP socket write with one or more UDP writes using
Boost.Asio, the 100 millisecond delay invariably occurs for the ZMQ TCP
message but the UDP messages arrive almost instantly (before the TCP

My design requires that the TCP message arrive before *most* of the UDP
messages. It's fine if some come through first----UDP is faster after all,
that's why I'm using it----but this big of a delay is more than I counted
on, and it's concerning. I don't know if it would apply across a real
network or if it's an artifact of testing in a single process.

Any insights?
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