Kubernetes Ingress to External Service?

Say I have a service that isn't hosted on Kubernetes. I also have an ingress controller and cert-manager set up on my kubernetes cluster.

Because it's so much simpler and easy to use kubernetes ingress to control access to services, I wanted to have a kubernetes ingress that points to a non-kubernetes service.

For example, I have a service that's hosted at https://10.0.40.1:5678 (ssl required, but self signed certificate) and want to access at service.example.com.

You can do it by manual creation of Service and Endpoint objects for your external server.

Objects will looks like that:

apiVersion: v1
kind: Service
metadata:
  name: external-ip
spec:
  ports:
  - name: app
    port: 80
    protocol: TCP
    targetPort: 5678
  clusterIP: None
  type: ClusterIP
---
apiVersion: v1
kind: Endpoints
metadata:
  name: external-ip
subsets:
- addresses:
  - ip: 10.0.40.1
  ports:
  - name: app
    port: 5678
    protocol: TCP

Also, it is possible to use an EndpointSlice object instead of Endpoints.

Then, you can create an Ingress object which will point to Service external-ip with port 80:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: external-service
spec:
  rules:
  - host: service.example.com
    http:
      paths:
      - backend:
          serviceName: external-ip
          servicePort: 80
        path: /