Is there a load balancer that can be dynamically configured?

Question

Web servers

Hello. The task is as follows: there is a central node where requests from users come, it is necessary to distribute these requests according to the list of end nodes (servers) for direct processing. The highlight of the task is that you need to be able to dynamically change the list of end nodes (add/remove) without rebooting the central node. So far I'm looking in the direction of nginx upstream, but unfortunately, the dynamic configuration of servers is available only in a paid subscription.
I would be glad for any help in solving this problem, even the direction in which you can dig.

Answer 1

Direction towards HAProxy

Answer 2

Well, nginx can easily reload the config without killing the current connections if necessary cheaply.
Or are you constantly changing?