# 02 — the workhorse. A Deployment manages a ReplicaSet, which manages
# Pods. You get: declarative scaling, rolling updates, instant rollback
# (`kubectl rollout undo`), and self-healing.
#
#   kubectl apply -f 02-deployment-service.yaml
#   kubectl rollout status deploy/checkout
#   kubectl set image deploy/checkout app=ghcr.io/acme/checkout:v2
#   kubectl rollout undo deploy/checkout          # back to v1, seconds
#   kubectl get endpoints checkout                # which Pods get traffic
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: checkout
  labels:
    app: checkout
spec:
  replicas: 4
  revisionHistoryLimit: 5
  selector:
    matchLabels:
      app: checkout
  strategy:
    type: RollingUpdate
    rollingUpdate:
      # Never drop below full capacity during a deploy; add one at a time.
      maxUnavailable: 0
      maxSurge: 1
  template:
    metadata:
      labels:
        app: checkout
    spec:
      securityContext:
        runAsNonRoot: true
        runAsUser: 10001
        seccompProfile:
          type: RuntimeDefault
      # Spread Pods across nodes/zones so one failure ≠ full outage.
      topologySpreadConstraints:
        - maxSkew: 1
          topologyKey: kubernetes.io/hostname
          whenUnsatisfiable: ScheduleAnyway
          labelSelector:
            matchLabels:
              app: checkout
      containers:
        - name: app
          image: ghcr.io/acme/checkout:v1.4.2
          ports:
            - containerPort: 8080
              name: http
          env:
            - name: POD_NAME
              valueFrom:
                fieldRef:
                  fieldPath: metadata.name
          resources:
            requests:
              cpu: 100m
              memory: 128Mi
            limits:
              cpu: "1"
              memory: 512Mi
          startupProbe:
            httpGet:
              path: /healthz
              port: http
            failureThreshold: 30
            periodSeconds: 2
          livenessProbe:
            httpGet:
              path: /healthz
              port: http
            periodSeconds: 10
          readinessProbe:
            httpGet:
              path: /ready
              port: http
            periodSeconds: 5
          lifecycle:
            preStop:
              exec:
                # Give the load balancer time to stop sending new requests
                # before the process exits — kills 502s during rollout.
                command: ["sh", "-c", "sleep 10"]
          securityContext:
            allowPrivilegeEscalation: false
            readOnlyRootFilesystem: true
            capabilities:
              drop: ["ALL"]
      terminationGracePeriodSeconds: 40
---
apiVersion: v1
kind: Service
metadata:
  name: checkout
  labels:
    app: checkout
spec:
  type: ClusterIP
  selector:
    app: checkout
  ports:
    - name: http
      port: 80
      targetPort: http