Deployments

# 1) Minimal Deployment
apiVersion: apps/v1
kind: Deployment
metadata:
    name:   web
    labels: { app: web }
spec:
    replicas: 3
    selector:
        matchLabels: { app: web }
    template:
        metadata:
            labels: { app: web }
        spec:
            containers:
                - name:  web
                  image: myapp:1.4.2
                  ports: [{ containerPort: 3000 }]
                  env:
                      - name: NODE_ENV
                        value: production
                  resources:
                      requests: { cpu: 100m, memory: 128Mi }
                      limits:   { cpu: 500m, memory: 512Mi }
                  readinessProbe:
                      httpGet: { path: /health, port: 3000 }
                      periodSeconds: 5
                  livenessProbe:
                      httpGet: { path: /health, port: 3000 }
                      initialDelaySeconds: 30
                      periodSeconds: 30

# 2) Rolling update — zero-downtime by default
spec:
    strategy:
        type: RollingUpdate
        rollingUpdate:
            maxUnavailable: 0       # never lose capacity
            maxSurge:       1       # one extra pod during the roll

# 3) Recreate strategy — for stateful apps that can't run both versions
spec:
    strategy:
        type: Recreate

# 4) Apply + watch
kubectl apply -f web.yaml
kubectl rollout status deployment/web --timeout=120s
kubectl get deployments,replicasets,pods

# 5) Update the image — declarative or imperative
kubectl set image deployment/web web=myapp:1.4.3
# OR change the YAML and re-apply
# Rollout begins automatically.

# 6) Rollback if something broke
kubectl rollout history deployment/web
kubectl rollout undo    deployment/web                # back one revision
kubectl rollout undo    deployment/web --to-revision=3
kubectl rollout pause   deployment/web                # freeze mid-rollout
kubectl rollout resume  deployment/web

# 7) Scale
kubectl scale deployment/web --replicas=10

# 8) Pair with a HorizontalPodAutoscaler
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata: { name: web-hpa }
spec:
    scaleTargetRef: { apiVersion: apps/v1, kind: Deployment, name: web }
    minReplicas: 3
    maxReplicas: 50
    metrics:
        - type: Resource
          resource: { name: cpu, target: { type: Utilization, averageUtilization: 70 } }

# 9) Disruption budget — protect availability during node drains
apiVersion: policy/v1
kind: PodDisruptionBudget
metadata: { name: web-pdb }
spec:
    minAvailable: 2
    selector: { matchLabels: { app: web } }

# 10) Best practices
#   • Set requests + limits — predictable scheduling + OOM safety
#   • Readiness probe gates traffic; liveness restarts hung pods
#   • Image tag → SHA digest in prod for immutable rollouts
#   • Pair PDB with HPA so autoscale-down doesn't violate availability

apiVersion: apps/v1
kind: Deployment
metadata: { name: api }
spec:
    replicas: 3
    selector: { matchLabels: { app: api } }
    template:
        metadata: { labels: { app: api } }
        spec: { containers: [{ name: api, image: api:1.0 }] }