Why does Google Cloud show an error when using ClusterIP

Question

In my gcloud console it shows the following error for my defined ingresses:

Error during sync: error while evaluating the ingress spec: service "monitoring/kube-prometheus" is type "ClusterIP", expected "NodePort" or "LoadBalancer"

I am using traefik as reverse proxy (instead of nginx) and therefore I define an ingress using a ClusterIP. As far as I understand the process all traffic is proxied through the traefik service (which has a Loadbalancer ingress defined) and therefore all my other ingresses SHOULD actually have a ClusterIP instead of NodePort or Loadbalancer?

Question:

So why does Google Cloud warn me that it expected a NodePort or LoadBalancer?

Answer 1

I don't know why that error happens, because it seems (to me) to be a valid configuration. But to clear the error, you can switch your service to a named NodePort. Then switch your ingress to use the port name instead of the number. For example:

Service:

apiVersion: v1 kind: Service metadata:   name: testapp spec:   ports:   - name: testapp-http # ADD THIS     port: 80     protocol: TCP     targetPort: 80   selector:     app: testapp   type: NodePort 

Ingress:

apiVersion: extensions/v1beta1 kind: Ingress metadata:   name: testapp spec:   rules:   - host: hostname.goes.here     http:       paths:       - backend:           serviceName: testapp           # USE THE PORT NAME FROM THE SERVICE INSTEAD OF THE PORT NUMBER           servicePort: testapp-http         path: / 

Update:

This is the explanation I received from Google.

Since services by default are ClusterIP [1] and this type of service is meant to be accessible from inside the cluster. It can be accessed from outside when kube-proxy is used, not meant to be directly accessed with an ingress.

As a suggestion, I personally find this article [2] good for understanding the difference between these types of services.

[1] https://kubernetes.io/docs/concepts/services-networking/service/#publishing-services-service-types

[2] https://medium.com/google-cloud/kubernetes-nodeport-vs-loadbalancer-vs-ingress-when-should-i-use-what-922f010849e0