Hi all, I'm new to ZeroMQ but so far all my experiments with it have been quite positive, so thanks for your great work!
However, one thing that I cannot really sort out is the following: I have written a small sample program where I create a ZMQ_PUB socket and I continuously zmq_msg_send() messages in it, never sleeping. This is simulating what I will do in a larger program where I plan to use ZeroMQ. Such program is a massively-parallel utility that needs to send in a fanout fashion (1 to many) several short messages per second (up to say 1million messages / second). In my scenario I don't care about subscribers joining late or eventually loosing some messages (if the network is slow or the subscriber itself is too slow). I do care however about detecting such conditions where messages are dropped. My problem is the "fast producer" one: this sample program shows that the zmq_msg_send() never returns an error; doing some math such my little utility says that is publishing data at rates up to 400Gbps... the only problem is that the NIC on the computer is a 1Gbps NIC. Of course all subscribers report missing 99% of messages (I put a sequence number in the messages I send). This problem does not appear to be new, some interesting references I found are: http://grokbase.com/t/zeromq/zeromq-dev/11ca11s9b9/pub-sub-pattern-rate-control-and-backpressure (Dec 2011) http://grokbase.com/t/zeromq/zeromq-dev/12797gy703/notify-send-er-that-theyve-hit-the-high-water-mark (Jul 2012) http://grokbase.com/t/zeromq/zeromq-dev/129n2e2sx5/high-water-mark-notification-for-publisher (Sep 2012) I experimented a little bit with ZeroMQ and found that: - ZMQ_RATE is not doing anything - ZMQ_XPUB_NODROP set to 1 works BUT basically ties the publisher to the SLOWEST subscriber: from my experiments it looks like (despite the documentation) the publisher now blocks every time there is just 1 subscriber queue that has hit the HWM as written in some of these posts what I would like to have is a NODROP socket option that allows my publisher to send data as fast as the FASTEST subscriber can handle. So here's my question: is there any way to achieve the above, i.e. block the publisher if ALL subscriber queues hit their HWM ? Thanks a lot for any hint! Francesco
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