Couldn't resolve host registered by GKE internal lb(ingress)

Question

In GKE clsuter, I can't call with hostname in internal http loadbalancer config. This is generated ingress yaml file.

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  annotations:
    ingress.kubernetes.io/backends: '{"k8s1-d21262da-default-hellorest-backend-service-80-698951b3":"HEALTHY","k8s1-d21262da-kube-system-default-http-backend-80-43d0837a":"HEALTHY"}'
    ingress.kubernetes.io/forwarding-rule: k8s2-fr-h23zc63d-default-hellorest-ingress-i-jxaunyik
    ingress.kubernetes.io/target-proxy: k8s2-tp-h23zc63d-default-hellorest-ingress-i-jxaunyik
    ingress.kubernetes.io/url-map: k8s2-um-h23zc63d-default-hellorest-ingress-i-jxaunyik
    kubernetes.io/ingress.class: gce-internal
  creationTimestamp: "2021-04-08T09:29:50Z"
  finalizers:
  - networking.gke.io/ingress-finalizer-V2
  generation: 1
  managedFields:
  - apiVersion: extensions/v1beta1
    fieldsType: FieldsV1
    fieldsV1:
      f:metadata:
        f:annotations:
          .: {}
          f:kubernetes.io/ingress.class: {}
      f:spec:
        f:rules: {}
    manager: GoogleCloudConsole
    operation: Update
    time: "2021-04-08T09:29:50Z"
  - apiVersion: networking.k8s.io/v1beta1
    fieldsType: FieldsV1
    fieldsV1:
      f:metadata:
        f:annotations:
          f:ingress.kubernetes.io/backends: {}
          f:ingress.kubernetes.io/forwarding-rule: {}
          f:ingress.kubernetes.io/target-proxy: {}
          f:ingress.kubernetes.io/url-map: {}
        f:finalizers:
          .: {}
          v:"networking.gke.io/ingress-finalizer-V2": {}
      f:status:
        f:loadBalancer:
          f:ingress: {}
    manager: glbc
    operation: Update
    time: "2021-04-08T09:30:44Z"
  name: hellorest-ingress-i
  namespace: default
  resourceVersion: "39841"
  selfLink: /apis/extensions/v1beta1/namespaces/default/ingresses/hellorest-ingress-i
  uid: 728a4e1b-8435-4b1e-a378-82665e7a8a6c
spec:
  rules:
  - host: hello
    http:
      paths:
      - backend:
          serviceName: hellorest-backend-service
          servicePort: 80
        pathType: ImplementationSpecific
status:
  loadBalancer:
    ingress:
    - ip: 10.178.100.7

In one of cluster node, service is successfully called with load balncer IP address. But call with hostname does not work.

# success with ip
$ curl http://10.224.13.150/hello
I am hellorest-backend-67fddc48f9-5hnmg(10.220.0.7)

# cannot resolve host
$ curl http://hello/hello
curl: (6) Couldn't resolve host 'hello'

More about test environments.

• GKE Cluster : zonal / private cluster / 1.18.16-gke.302 / 2 nodes / control plane 172.16.0.0/28, global access disabled / http load balancing enabled
• deployed service : hellorest-backend-service / 3 pods / 80 to 8080 tcp forwarding / default namespace / NodePort
• ingress service : hellorest-ingress-i / internal http(s) lb / default namespace / 10.178.100.7 / no problem in health check

Answer 1

As already mentioned in the comments, in order to make it work you need to have a DNS private zone with a record A: hello . That can be done by using a cloud console. Google Cloud Private DNS Zones explains that in more detail:

Google Cloud DNS can now provide:

1. Create private DNS zones to provide DNS name resolution to your private network resources (VMs, load balancers, etc.).

2. Connect a private zone to a single network or multiple networks, giving you flexibility when designing your internal network architectures.

3. Create split-horizon DNS architectures where identical or overlapping zones can coexist between public and private zones in Cloud DNS, or across different GCP networks.

4. Utilize IAM-based, DNS-specific roles to delegate administrative or editor access to manage or view managed private zones.

All the necessary info and examples can be found in the linked article.