Text attribute on etcd records prevents CNAME records from resolving

[lholota]

What happened:
I am using external-dns with etcd and coredns with the records defined using a CRD below (I have observed the same behaviour while using a Traefik IngressRoute). I have created two records:

• A record example2.mydomain.com with value 1.1.1.1
• CNAME record example1.mydomain.com pointing to example2.mydomain.com

I can resolve the example2.mydomain.com using an nslookup or dig fine. But when I try to resolve example1.mydomain.com I get the following error:

*** Can't find example1.mydomain.com: No answer

What you expected to happen:

The record was expected to be resolved to 1.1.1.1

How to reproduce it (as minimally and precisely as possible):

I have debugged this issue very extensively and the problem is the text attribute in the etcd records' json. The --registry=txt is the default value in the provided helm chart and it's unfortunately not documented anywhere that this does not work in combination with the coredns provider.

The txt provider adds the text attribute to the records and even though it doesn't break everything (I was still able to resolve the A record example2.mydomain.com) it does break the CNAME lookup.

Anything else we need to know?:
I am not sure whether this is just a documentation problem and the TXT registry simply shouldn't be used or whether using the TXT registry in combination with coredns is a valid usecase and I have discovered a bug. If it's the latter I am more than happy to assist with testing and/or investigation of the bug.

Environment:

• External-DNS version: Docker image = registry.k8s.io/external-dns/external-dns:v0.15.0
• DNS provider: coredns
• Others:
  • Stack installed by the provided helm chart into a Talos cluster (v1.8.3).