Cross-namespace Ingress via External Name

cross-ns-ingress.yml

---
# Deployment to serve backend requests
apiVersion: apps/v1
kind: Deployment
metadata:
  name: healthz
  namespace: default
  labels:
    app: healthz
spec:
  replicas: 5
  selector:
    matchLabels:
      app: healthz
  template:
    metadata:
      labels:
        app: healthz
    spec:
      containers:
        - name: healthz
          image: server:latest
          ports:
            - containerPort: 80
          readinessProbe:
            httpGet:
              path: /healthz
              port: 80
            initialDelaySeconds: 1
            periodSeconds: 5
          livenessProbe:
            httpGet:
              path: /livez
              port: 80
            initialDelaySeconds: 1
            periodSeconds: 5
---
# Real service accepting requests in default namespace
apiVersion: v1
kind: Service
metadata:
  name: healthz-svc
  namespace: default
spec:
  ports:
    - port: 80
      targetPort: 80
      protocol: TCP
  selector:
    app: healthz
---
# Dummy service in same namespace as ingress object
# Redirects to "real" service in some other namespace
# Required because cross-ns references are not possible for ingress
apiVersion: v1
kind: Service
metadata:
  name: healthcheck
  namespace: external
spec:
  type: ExternalName
  externalName: healthz-svc.healthz.svc.cluster.local
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80
  clusterIP: ""
---
# External facing ingress object
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: healthz
  namespace: external
  annotations:
    kubernetes.io/ingress.class: external
    nginx.ingress.kubernetes.io/ssl-redirect: "false"
spec:
  rules:
    - host: "*.cloudapp.azure.com"
      http: &health
        paths:
          - path: /healthz
            backend:
              serviceName: healthz
              servicePort: 80
    - host: "*.trafficmanager.net"
      http: *health
---