[GordonS]

AFAIK all the well-known proxies/load balancer support automatic failure in one way or another - Caddy, Nginx, Traefik, HAProxy.

I prefer Caddy myself, for it's simplicity. On load balancing, it can detect when an upstream server isn't working, and remove it from the list of upstream until it's working again. Sometimes you want control of this, for example for OS updates - Caddy has an admin API you can use to remove a server from upstreams and wait until all connections are drained, then you can perform the updates and add the server back again. Then do the same for other upstream servers.

(I haven't actually used the Caddy admin API in production yet, but plan to soon).