[zeromq-dev] Only first X messages received with PGM/0MQ c++ setup

Johnny Berentsen johnny.berentsen at gmail.com
Mon Apr 16 18:25:14 CEST 2018


2018-04-16 14:35 GMT+02:00 Luca Boccassi <luca.boccassi at gmail.com>:

> On Mon, 2018-04-16 at 13:54 +0200, Johnny Berentsen wrote:
> > 2018-04-02 15:30 GMT+02:00 Johnny Berentsen <johnny.berentsen at gmail.c
> > om>:
> >
> > > Hi all
> > > <snip initial explanation>
> > >
> >
> > Now I have a vector with size 2500 of std::strings filled with 4096 #
> > characters. Every ten seconds I loop through the vector and send the
> > data
> > over a EPGM socket. If I go full throttle, only the first 1000
> > messages are
> > received, but if I add a usleep(1) after each send, all messages are
> > received.
>
> Default high water mark is 1000 messages, most likely the receiving
> side is too slow to process and so it starts dropping messages
>
>
You're absolutely right. I was put off by the documentation that said:
The default *ZMQ_SNDHWM* value of zero means "no limit".

Shame on me for not trying though :/

I understand that setting the HWM is different depending on the usage
pattern. However, I can't find much information on the different criterias
that should be considered.
I've come up with these:
Typical and max packet size, network restrictions, number of packets,
available memory, CPU

My application will run on a LAN on modern PC's with >=8GiB memory, up to a
few kB's per message and only a burst of a few thousand messages once in a
while. What value is reasonable in such a case?
I also tested with checking the return value of send() but it returned true
regardless of sending or not. Are there other ways of being noticed that
messages have been dropped?

JC
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