[zeromq-dev] Pub/Sub scalability over TCP vs epgm/pgm

Mark Delany e2c at papa.emu.st
Mon Apr 9 23:09:30 CEST 2018

> > can have topics around 500 and subscribers could be from 500 to 1000.

> The only way to know is to test it

This is true and also measure your system while testing to identify
potential system bottlenecks. What else is your application doing
besides making zeromq calls? Is there I/O involved?

You say you are getting delays. How large are these? How busy are the
systems when you're getting these delays.

As a general rule, 1,000 or so TCP sockets is no big deal for a modern
Unix/Linux kernel. I would also be surprised if 500 topics causes a
much delay. Even a linear search per message would happen pretty
quickly on a modern CPU. I am assuming that zeromq does better than
linear since topics are exact prefix match there are plenty of
alogrithmic solutions that are far faster than O(n).

A number of vmstat samples will give a general idea of what's going


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