dynamic a resolvers being bypassed if entry is in /etc/hosts

Hello, Caddy v2.8.4 h1:q3pe0wpBj1OcHFZ3n/1nl4V4bxBrYoSoab7rL9BMYNk= installed via homebrew on macOS

I am trying to setup a local reverse proxy that is doing path-based routing on the same domain, and resolving the host to different IP's, depending on the path.

Here is my Caddyfile

{
  debug
  https_port 443
  log {
    level debug
  }
}

my.site.com {
    tls internal
    @fivesight {
        path /mypath*
    }

    reverse_proxy @fivesight {
        dynamic a {
            name my.site.com
            port 443
            refresh 0
                resolvers 127.0.0.1
        }
        transport http {
            tls
            resolvers 127.0.0.1
        tls_insecure_skip_verify
        }
    }

    @other {
        not path /mypath*
    }

    reverse_proxy @other {
        dynamic a {
            name my.site.com
            refresh 0
            port 443
        }
        transport http {
            tls
            tls_insecure_skip_verify
        }
    }
}

I have a DNS server running on 127.0.0.1 that resolves my.site.com to a specific IP. This works properly. 1.1.1.1 isn't the real IP, I just redacted it.

dig @127.0.0.1 my.site.com

; <<>> DiG 9.10.6 <<>> @127.0.0.1 my.site.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 45733
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;my.site.com.       IN  A

;; ANSWER SECTION:
my.site.com.    0   IN  A   1.1.1.1

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Wed Jul 31 11:05:59 EDT 2024
;; MSG SIZE  rcvd: 60

I am testing using the following curl curl https://my.site.com/mypath/ --resolve my.site.com:443:127.0.0.1 -v

If I don't have 127.0.0.1 my.site.com in my /etc/hosts - the setup works perfectly

I get a log showing DNS worked as it should:

2024/07/31 15:04:32.128 DEBUG   http.reverse_proxy.upstreams.a  refreshing A upstreams  {"version": "ip", "name": "my.site.com", "port": "443"}
2024/07/31 15:04:32.492 DEBUG   http.reverse_proxy.upstreams.a  discovered A record {"ip": "1.1.1.1"}

However, once I add 127.0.0.1 my.site.com to my /etc/hosts, Caddy resolves the DNS to 127.0.0.1, rather than using the specified resolver:

2024/07/31 15:07:48.957 DEBUG   http.reverse_proxy.upstreams.a  refreshing A upstreams  {"version": "ip", "name": "my.site.com", "port": "443"}
2024/07/31 15:07:48.957 DEBUG   http.reverse_proxy.upstreams.a  discovered A record {"ip": "127.0.0.1"}

I further verified it's taking the hosts file entry by setting it to 127.0.0.2 in the hosts file, and I get this in the logs:

2024/07/31 16:12:53.809 DEBUG   http.reverse_proxy.upstreams.a  refreshing A upstreams  {"version": "ip", "name": "my.site.com", "port": "443"}
2024/07/31 16:12:53.810 DEBUG   http.reverse_proxy.upstreams.a  discovered A record {"ip": "127.0.0.2"}

caddyserver / caddy

dynamic a resolvers being bypassed if entry is in /etc/hosts #6488