kubernetes per-port backend selection example

per-port-balancing.yaml

# shows how kubernetes kubeproxy can select backends based on which port of a multi-port service is being accessed
# nginx is only listening on port 80
# kuard is only listening on port 8080
# the partial-ports service exposes both 80 and 8080
# 
# kubectl -n foo run -it --rm --restart=Never --image=curlimages/curl:7.76.1 test1 -- curl partial-ports:80
# and
# kubectl -n foo run -it --rm --restart=Never --image=curlimages/curl:7.76.1 test1 -- curl partial-ports:8080
# both succeed 100% of the time
---
apiVersion: v1
kind: Namespace
metadata:
  name: foo

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-80
  namespace: foo
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx-80
  template:
    metadata:
      labels:
        app: nginx-80
    spec:
      containers:
      - name: nginx
        image: library/nginx:1.19.10
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: nginx-80
  namespace: foo
spec:
  selector:
    app: nginx-80
  ports:
  - port: 80        
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: kuard-8080
  namespace: foo
spec:
  replicas: 1
  selector:
    matchLabels:
      app: kuard-8080
  template:
    metadata:
      labels:
        app: kuard-8080
    spec:
      containers:
      - name: kuard
        image: gcr.io/kuar-demo/kuard-amd64:blue
        ports:
        - containerPort: 8080
---
apiVersion: v1
kind: Service
metadata:
  name: kuard-8080
  namespace: foo
spec:
  selector:
    app: kuard-8080
  ports:
  - port: 8080

---
apiVersion: v1
kind: Service
metadata:
  name: partial-ports
  namespace: foo
spec:
  selector: {}
  ports:
  - port: 80
    name: nginx-80
  - port: 8080
    name: kuard-8080

---
apiVersion: discovery.k8s.io/v1beta1
kind: EndpointSlice
metadata:
  labels:
    kubernetes.io/service-name: partial-ports
  name: partial-ports-nginx-80
  namespace: foo
addressType: IPv4
endpoints:
- addresses:
  - 10.244.0.6  # ip of the nginx pod, hand-crafted at run-time
ports:
- name: nginx-80
  port: 80
  protocol: TCP
---
apiVersion: discovery.k8s.io/v1beta1
kind: EndpointSlice
metadata:
  labels:
    kubernetes.io/service-name: partial-ports
  name: partial-ports-kuard-8080
  namespace: foo
addressType: IPv4
endpoints:
- addresses:
  - 10.244.0.7  # ip of the kuard pod, hand-crafted at run-time
ports:
- name: kuard-8080
  port: 8080
  protocol: TCP