Additional websocket connections cause exponential increase in CPU usage about haproxy

[git001]

Any chance to update to the latest version http://www.haproxy.org/bugs/bugs-2.4.22.html or to the 2.8 Version and see if the problem still exists?

[stevenwaterman]

Yes, we actually already started working on updating to see if it would help. We'll update and re-release and let you know what happens. Probably on Monday. Thanks!

[stevenwaterman]

We defined additional servers to reduce the number of active sessions per server. This looked promising but once we rolled out the new WS again, CPU usage went up.

Commented out our stick-table and all associated lines of config. This immediately resolved the problem, dropping CPU down to around 30%, and it stayed there. We're not sure why that had any impact, since the new websocket isn't included in the rate limiting.

We then started to get errors after hitting 100k active connections on one backend, which we assume is nothing to do with haproxy and is instead some missing tweak on the application server, eg file descriptors.

But yeah, I'd be interested if you have any ideas why the stick table lines in the config could cause such a huge increase in CPU usage, from relatively few additional connections