enable multivalue for headless service in external-dns

[stanislavzaletskyi]

we have running serverless pods, which amount changes dynamically (all has label app=pod):
pod1
pod2
....
pod10

this is my headless service for external-dns

kind: Service
apiVersion: v1
metadata:
  name: pods-svc
  labels:
    app: pods
  annotations:
    external-dns.alpha.kubernetes.io/aws-multi-value-answer: 'true'
    external-dns.alpha.kubernetes.io/endpoints-type: HostIP
    external-dns.alpha.kubernetes.io/hostname: pods.example.com
spec:
  ports:
    - protocol: TCP
      port: 443
      targetPort: 443
  selector:
    app: pod
  clusterIP: None
  clusterIPs:
    - None
  type: ClusterIP

Currently external-dns creates one pods.example.com A record and add all pod's HostIP into it (SimpleRouting):
pods.example.com = [1.1.1.1,2.2.2.2,..... ]

What would you like to be added:
My expectations that external-dns should create multiple A records in AWS Route53:
pods.example.com A record = 1.1.1.1
pods.example.com A record = 2.2.2.2
....

Why is this needed:
With multiple A records we can add healthchecks , failover per record.

[berkeli]

Yeah I was disappointed to find out that this isn't supported. Happy to work on this feature too if maintainers are happy to accept a PR

for context: we have a service with 100s of pods, and only multi-value supports upto 400 ips. Simple record (current implementation) only supports upto 100 ips

[stanislavzaletskyi]

Another issue is that external-dns does not support replicas and when high load k8s level start glitches / delays (even if ext-dns pod is running on dedicated low CPU ec2 ) . So k8s level is not right place to manage AWS R53 resources , better use AWS lambda. To make external-dns prodution usable need

• add replicas
• add multi records creation
• healthcheck creation / updates / removal in AWS
  IMHO: Currently it is risky to use external-dns for apps , which works with money (if wrong AWS R53 records could produce loose money ) and high load.