External-dns: External DNS should create CNAME for External LBs

[neilhwatson]

In AWS most ELBs have multiple public IP addresses. I've noticed the EDNS (installed with Helm) creates just one A record for one of the ELB's IP addresses. Shouldn't it create a CNAME to the ELB's FQDN instead? At the very least it should create one A record for every IP the ELB has.

[ideahitme]

that's exactly what it should do (CNAME/ALIAS pointing to ELB dnsname). Few questions:

1. Which AWS region and Availability zone you are running ExternalDNS in?
2. What is the output of kubectl get <resource_type> <resource_name> -o yaml ?

[neilhwatson]

I see. Very likely I don't understand how ingress and EDNS are supposed to work together. Ingress-nginx creates an ELB, which I assume all inbound service traffic is supposed to use. Configuring a service to be NodePort creates, as you say, an A record that points to a node. As does the default service type of Cluster IP.

A service of LoadBalancer still creates an additional load balancer. It is my understanding that some configuration should create a CNAME to the existing ingress ELB which will forward traffic to the correct node. In this way only one ELB is required.

Is this possible?

[neilhwatson]

This problem is was fixed. The problem was not with EDNS, but with nginx-ingress. To use in AWS with one ELB and external-dns install it this way:

 helm install stable/nginx-ingress --wait \
    --set controller.publishService.enabled=true \
    --set controller.publishService.pathOverride=kube-system/nginx-ingress-controller \
    --namespace=kube-system --name=nginx-ingress

  helm install stable/external-dns --wait \
    --set policy=sync \
    --set source=ingress \
    --namespace=kube-system --name=external-dns