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You have a graph that shows a multi provider setup for a domain. Where would routing to either machine happen? As in which ip would you use on the dns side?

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For the public cluster with multiple ingress (caddy) nodes you'd need a load balancer in front of them to properly handle routing and outage of any of them. You'd use the IP of the load balancer on the DNS side.

Note that a DNS A record with multiple IPs doesn't provide failover, only round robin. But you can use the Cloudflare DNS proxy feature as a poor man's LB. Just add 2+ proxied A records (orange cloud) pointing to different machines. If one goes down with a 52x error, Cloudflare automatically fails over to the healthy one.

I looked into this yesterday for making Caddy HA on my Proxmox cluster and stumbled upon keepalivd. It will provide you with a virtual IP and failover but not load balancing so you'd need to still point that at something like HAProxy for that.

Could be something interesting to integrate though.

Not OP, but you could do "simple" dns load balancing between both endpoints.

As I mentioned in the sibling comment, please note that in this case you only get round-robin, not failover. If one of the addresses is down, the DNS record will continue returning it and users will hit a dead end.

A proper load balancer or Cloudflare DNS proxy would handle this.

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