Yeah, you need a way to throttle back the publisher. Have the many nodes tell the publisher to slow down if they detect too high of a drop rate. Your publisher can then decide whether to throttle for the slowest client, or for the fastest client. Also, pub/sub may not be the right way to do this for 1:many if the value of 'many' is very high, because each message you send will be sent 1:1 to each subscriber, slowing them all down. Some kind of tree based fanout may work better.
-- Marcin On Fri, Mar 3, 2017 at 12:49 PM, Justin Karneges <[email protected]> wrote: > And what if there are no subscribers? Publishing should block? > > It sounds like your goal is some kind of sensible flow control (I'm not > sure what else an "at least 1 subscriber can read" use-case really is). My > advice is to publish at a fixed rate, for example by sleeping between > publishes. > > I do wish ZMQ_RATE worked for all PUB sockets and not just PGM-based. > > On Fri, Mar 3, 2017, at 12:31 PM, Francesco wrote: > > 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 > > > > > > *_______________________________________________* > zeromq-dev mailing list > [email protected] > https://lists.zeromq.org/mailman/listinfo/zeromq-dev > > > > _______________________________________________ > zeromq-dev mailing list > [email protected] > https://lists.zeromq.org/mailman/listinfo/zeromq-dev >
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