Ingress 是 Kubernetes 中一個進階的服務元件，提供比基本 Service 更多的功能，例如驗證、負載平衡、路由過濾等。但是， Kubernetes 預設是沒有 IngressController 的（我印象中是這樣啦），因此我們需要在使用 Ingress 之前，你需要先手動建立一個 Ingress Controller，並為其配置相應的資源。

因為這次資源有點多，所以我們先建立一個新的 Namespace，這裡命名為 ingress-nginx：

# ingress-namespace.yaml

apiVersion: v1
kind: Namespace
metadata:
  name: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx

然後，使用 Nginx 創建兩個簡單的 Pod 和相應的 Service：

# nginx-pods-and-services.yaml

apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod1
  namespace: default
  labels:
    app: nginx-pod1
spec:
  containers:
    - image: nginx:latest
      name: nginx
      ports:
        - containerPort: 80

---

apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod2
  namespace: default
  labels:
    app: nginx-pod2
spec:
  containers:
    - image: nginx:latest
      name: nginx
      ports:
        - containerPort: 80

---

apiVersion: v1
kind: Service
metadata:
  name: nginx-service-1
spec:
  selector:
    app: nginx-pod1
  ports:
    - protocol: TCP
      port: 8081
      targetPort: 80

---

apiVersion: v1
kind: Service
metadata:
  name: nginx-service-2
spec:
  selector:
    app: nginx-pod2
  ports:
    - protocol: TCP
      port: 8082
      targetPort: 80

接下來，進入 Pod 內修改顯示的內容，通常位置在 /usr/share/nginx/html/index.html：

kubectl exec -it pod nginx-pod1 -- bash

然後建立 Ingress Controller：

# ingress-controller.yaml

# ...（之前的 ConfigMap、ServiceAccount、Role、RoleBinding 的內容）

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-ingress-controller
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: ingress-nginx
      app.kubernetes.io/part-of: ingress-nginx
  template:
    metadata:
      labels:
        app.kubernetes.io/name: ingress-nginx
        app.kubernetes.io/part-of: ingress-nginx
      annotations:
        prometheus.io/port: "10254"
        prometheus.io/scrape: "true"
    spec:
      hostNetwork: true
      terminationGracePeriodSeconds: 300
      serviceAccountName: nginx-ingress-serviceaccount
      nodeSelector:
        kubernetes.io/os: linux
      containers:
        - name: nginx-ingress-controller
          image: quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.33.0
          args:
            - /nginx-ingress-controller
            - --configmap=$(POD_NAMESPACE)/nginx-configuration
            - --tcp-services-configmap=$(POD_NAMESPACE)/tcp-services
            - --udp-services-configmap=$(POD_NAMESPACE)/udp-services
            - --publish-service=$(POD_NAMESPACE)/ingress-nginx
            - --annotations-prefix=nginx.ingress.kubernetes.io
          securityContext:
            allowPrivilegeEscalation: true
            capabilities:
              drop:
                - ALL
              add:
                - NET_BIND_SERVICE
            runAsUser: 101
          env:
            - name: POD_NAME
              valueFrom:
                fieldRef:
                  fieldPath: metadata.name
            - name: POD_NAMESPACE
              valueFrom:
                fieldRef:
                  fieldPath: metadata.namespace
          ports:
            - name: http
              containerPort: 80
              protocol: TCP
            - name: https
              containerPort: 443
              protocol: TCP
          # ...（之後的 livenessProbe、readinessProbe、lifecycle 等的內容）

然後，建立相應的 LimitRange 資源和 Ingress 服務：

# ingress-limits-and-service.yaml

apiVersion: v1
kind: LimitRange
metadata:
  name: ingress-nginx
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
spec:
  limits:
    - min:
        memory: 90Mi
        cpu: 100m
      type: Container

---

apiVersion: v1
kind: Service
metadata:
  name: ingress-nginx
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
spec:
  type: NodePort
  ports:
    - name: http
      port: 80
      targetPort: 80
      protocol: TCP
      nodePort: 30080
    - name: https
      port: 443
      targetPort: 443
      protocol: TCP
      nodePort: 30443
  selector:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx

最後，建立 Ingress 資源，將不同路由映射到不同的後端 Pod：

# ingress-resource.yaml

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: ingress-nginx
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  rules:
    - host: my.example.com # 要轉的域名 -> http://"my.example.com"/pod1
      http:
        paths:
          - path: /pod1 # 自訂的path
            pathType: Prefix
            backend:
              service:
                name: nginx-service-1
                port:
                  number: 8081
          - path: /pod2
            pathType: Prefix
            backend:
              service:
                name: nginx-service-2
                port:
                  number: 8082

這樣，你就可以透過不同的路由進入到不同的後端 Pod 了。