# Complete Kubernetes Application Example
# This file contains all resources needed for a production web application

---
apiVersion: v1
kind: Namespace
metadata:
  name: example-app
  labels:
    name: example-app
    environment: production

---
apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
  namespace: example-app
data:
  APP_ENV: "production"
  LOG_LEVEL: "info"
  PORT: "8080"
  DATABASE_HOST: "postgres.example-app.svc.cluster.local"
  DATABASE_PORT: "5432"
  DATABASE_NAME: "appdb"

---
apiVersion: v1
kind: Secret
metadata:
  name: app-secrets
  namespace: example-app
type: Opaque
stringData:
  DATABASE_PASSWORD: "changeme-use-sealed-secrets"
  API_KEY: "changeme-use-external-secrets"

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: app
  namespace: example-app

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app
  namespace: example-app
  labels:
    app: example-app
    tier: frontend
spec:
  replicas: 3
  revisionHistoryLimit: 10

  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0

  selector:
    matchLabels:
      app: example-app

  template:
    metadata:
      labels:
        app: example-app
        tier: frontend
        version: v1.0.0
      annotations:
        prometheus.io/scrape: "true"
        prometheus.io/port: "8080"
        prometheus.io/path: "/metrics"

    spec:
      serviceAccountName: app

      securityContext:
        runAsNonRoot: true
        runAsUser: 1000
        fsGroup: 2000

      containers:
      - name: app
        image: nginx:1.25-alpine
        imagePullPolicy: IfNotPresent

        ports:
        - name: http
          containerPort: 8080
          protocol: TCP

        envFrom:
        - configMapRef:
            name: app-config
        - secretRef:
            name: app-secrets

        resources:
          requests:
            memory: "256Mi"
            cpu: "250m"
          limits:
            memory: "512Mi"
            cpu: "500m"

        livenessProbe:
          httpGet:
            path: /healthz
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 10
          timeoutSeconds: 5
          failureThreshold: 3

        readinessProbe:
          httpGet:
            path: /ready
            port: 8080
          initialDelaySeconds: 10
          periodSeconds: 5
          timeoutSeconds: 3

        securityContext:
          allowPrivilegeEscalation: false
          readOnlyRootFilesystem: true
          runAsNonRoot: true
          runAsUser: 1000
          capabilities:
            drop:
            - ALL

        volumeMounts:
        - name: tmp
          mountPath: /tmp
        - name: cache
          mountPath: /var/cache/nginx

      volumes:
      - name: tmp
        emptyDir: {}
      - name: cache
        emptyDir: {}

---
apiVersion: v1
kind: Service
metadata:
  name: app
  namespace: example-app
  labels:
    app: example-app
spec:
  type: ClusterIP
  selector:
    app: example-app
  ports:
  - name: http
    port: 80
    targetPort: 8080
    protocol: TCP

---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: app
  namespace: example-app
  annotations:
    kubernetes.io/ingress.class: nginx
    cert-manager.io/cluster-issuer: letsencrypt-prod
    nginx.ingress.kubernetes.io/ssl-redirect: "true"
    nginx.ingress.kubernetes.io/rate-limit: "100"
spec:
  tls:
  - hosts:
    - app.example.com
    secretName: app-tls
  rules:
  - host: app.example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: app
            port:
              number: 80

---
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: app
  namespace: example-app
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: app
  minReplicas: 3
  maxReplicas: 20
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 70
  - type: Resource
    resource:
      name: memory
      target:
        type: Utilization
        averageUtilization: 80

---
apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: app
  namespace: example-app
spec:
  minAvailable: 2
  selector:
    matchLabels:
      app: example-app