I may misunderstand this concept:

I have two services (Frontend and API). Both should to use one subdomain (my.domain.com):

• domain.com => for FRONTEND ('hello-world')
• domain.com/api => for API

I have a K8s-cloud running at Hetzner. Hetzner also provides loadbalancers. The cluster was created with Rancher-UI

This is how I configure the loadbalancer Service:

---
apiVersion: "v1"
kind: Service
metadata:
  name: "nginx-hello-world"
  labels:
    app: "hello-world"
  annotations:
    load-balancer.hetzner.cloud/name: lb-development
    load-balancer.hetzner.cloud/hostname: my.domain.com
    load-balancer.hetzner.cloud/protocol: http
spec:
  type: LoadBalancer
  selector:
    app: "hello-world"
  ports:
    - name: "http"
      port: 80
      targetPort: 80

And this is my Deployment for the frontend hello-world:

apiVersion: "apps/v1"
kind: "Deployment"
metadata:
  name: "nginx-hello-world"
  labels:
    app: "hello-world"
spec:
  selector:
    matchLabels:
      app: "hello-world"
  strategy:
    type: "Recreate"
  template:
    metadata:
      labels:
        app: "hello-world"
    spec:
      containers:
        - image: "rancher/hello-world"
          name: "nginx-hello-world"
          imagePullPolicy: "Always"
          ports:
            - containerPort: 80
              name: "http"

The two manifests above are WORKING! I can reach out to 'hello-world' by visiting my.domain.com/

Now I wanna hook my backend API into that setup. I thought I can do this by using an ingress manifest:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  labels:
    app: my-ingress
  name: my-ingress
spec:
  rules:
  - host: my.domain.com
    http:
      paths:
      - backend:
          serviceName: hello-api
          servicePort: 80
        path: "/app"
        pathType: Prefix
      - backend:
          serviceName: hello-world
          servicePort: 80
        path: "/"
        pathType: Prefix

How can I achieve to connect another workload with my.domain.com/api for the API and keep the use of the Hetzner loadbalancer?

I thought I can do that, by simply changing the selector in the Loadbalancer Service to point to my-ingress, but nothing I tried, worked so far.

┌─────────────────┐  ┌──────────────────┐   ┌──────────────────┐
│                 │  │  Ingress         │   │                  │
│ Loadbalancer Svc├─►│my.domain.com/    ├──►│ Frontend deploym.│
│                 │  │my.domain.com/api ├──►│ backend API depl │
└─────────────────┘  └──────────────────┘   └──────────────────┘

PS: it may be interesting: When I deployed Rancher, it has also created a nginx-ingress-controller

Thank you in advance