I tried getting dns_cluster working with FQDNs, however the discovery always fails when I set a FQDN in the RELEASE_NODE env with the error message Cannot get connection id for node app_name@prod-01.<redacted>.com coming from erlang. When I call Node.connect :"app_name@prod-01.<redacted>.com" manually, it connects and everything works fine.
I have an A record for <redacted>.com with the IP addresses for prod-01 and prod-02, the two machines which connect together, and they have full TCP access to each other. The hostname of both machines is set to their own FQDN, and I created an A record for each of those, too.

The documentation clearly states:

export RELEASE_NODE="myapp@fully-qualified-host-or-ip"

so I assume, a FQDN as node name is supported by dns_cluster.

Replacing the FQDN in RELEASE_NODE with the public IP address, the dns discovery starts working. However I would prefer to use domain names in the config to make the setup more robust in case a machine gets a new IP address.

Am I doing something wrong, or might this be an issue somewhere in the dns_cluster lib? Unfortunately I can't figure out where the Cannot get connection id for node error is coming from.