oam/examples/kubernetes/create an admission webhook/resources.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: webhook
  namespace: test
  labels:
    app: webhook
spec:
  selector:
    matchLabels:
      app: webhook
  template:
    metadata:
      namespace: test
      labels:
        app: webhook
    spec:
      containers:
      - name: webhook
        image: webhook
        imagePullPolicy: Never  # only needed locally
        ports:
        - containerPort: 8443
        volumeMounts:
        - mountPath: /cert
          name: cert
      volumes:
      - name: cert
        secret:
          secretName: webhook
---
apiVersion: v1
kind: Service
metadata:
  name: webhook
  namespace: test
spec:
  selector:
    app: webhook
  ports:
    - protocol: TCP
      port: 443
      targetPort: 8443
---
apiVersion: admissionregistration.k8s.io/v1beta1
kind: ValidatingWebhookConfiguration
metadata:
  name: webhook-validate
  namespace: test
webhooks:
  - name: test.example.com
    failurePolicy: Fail
    clientConfig:
      service:
        name: webhook
        namespace: test
        path: /validate
    rules:
      - apiGroups: [""]
        resources:
          - "pods"
        apiVersions:
          - "*"
        operations:
          - CREATE
---
apiVersion: admissionregistration.k8s.io/v1beta1
kind: MutatingWebhookConfiguration
metadata:
  name: webhook-mutate
  namespace: test
  labels:
    component: mutating-controller
webhooks:
  - name: test.example.com
    failurePolicy: Fail
    clientConfig:
      service:
        name: webhook
        namespace: test
        path: /mutate
    rules:
      - apiGroups: [""]
        resources:
          - "pods"
        apiVersions:
          - "*"
        operations:
          - CREATE