Why my Haproxy stats GUI limit sessions in backend sticks to 20000?

Question

My loadbalancer's GUI shows that it's backend has a limit of 20.000 sessions, no matter the maxconn parameter I set in global or in the backend sections.

When running a test, the max parameter in Sessions exceeds the limit.

Any idea how to solve it or if it's even a problem?

HAProxy version: 2.2.11-1ppa1~bionic 2021/03/18

Answer 1

Nothing complex but slightly tricky, the number in the backend session limit is fullconn,

Adding fullconn to your backend will change that limit on the stats page just in case.

backend my-backend
        fullconn 200000

However, if fullconn is not set, it sums up all the session limit values for frontends that route to this backend, divided by 10. And there is lot more in the official documentation explained.

Reference documentation