i am new on haproxy.
is it possible to create a active-active cluster with 4 node that work simultaneously and answer users requests ?
As with most things in life, Yes… and no…
Could you install 4 HAProxy servers all doing the same thing - yes
Each would have their own IP address and could serve those services. Load balancing could be done by doing a round robin DNS. So far so good.
Can you distribute the load equally - That’s where it is more tricky, the DNS round robin would be roughly equal but not truly even. Putting cloudflare in front and using their load balancing would probably be better.
You could quite easily add pacemaker to the mix and thus have the 4 IP numbers serviced by HAProxy be able to be hosted by any of the actual boxes for high availability.