Templating K8s manifest files leveraging ytt

app.yaml

#@ load("@ytt:data", "data")
---
#@ def labels(comp):
app.kubernetes.io/part-of: #@ data.values.app.name
app.kubernetes.io/version: #@ data.values.app.version
app.kubernetes.io/instance: #@ "{}-{}".format(data.values.app.name, data.values.env.name)
app.kubernetes.io/component: #@ comp
#@ end
---
#@ def namespace():
#@  return "{}-{}".format(data.values.app.name, data.values.env.name)
#@ end
---
apiVersion: v1
kind: Namespace
metadata:
  name: #@ namespace()
  labels: #@ labels("app")
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app
  namespace: #@ namespace()
  labels: #@ labels("app")
spec:
  replicas: #@ data.values.app.replicas
  selector:
    matchLabels: #@ labels("app")
  template:
    metadata:
      labels: #@ labels("app")
    spec:
      containers:
      - image: ghcr.io/alexandreroman/spring-on-k8s
        name: app
        resources:
          limits:
            memory: 1Gi
        ports:
        - containerPort: 8080
        livenessProbe:
          httpGet:
            port: 8080
            path: /actuator/health/liveness
        readinessProbe:
          httpGet:
            port: 8080
            path: /actuator/health/readiness
---
apiVersion: v1
kind: Service
metadata:
  name: app
  namespace: #@ namespace()
  labels: #@ labels("app")
spec:
  type: ClusterIP
  ports:
  - port: 8080
    protocol: TCP
    targetPort: 8080
  selector: #@ labels("app")
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: app
  namespace: #@ namespace()
  labels: #@ labels("app")
spec:
  rules:
  - host: #@ "springonk8s.{}".format(data.values.env.domain)
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: app
            port:
              number: 8080

values.yaml

#@data/values
---
env:
  name: staging
  domain: staging.corp

app:
  name: spring-on-k8s
  version: 1.0.0
  replicas: 1