Lab 03: Deployments & Replicas

Objectives

• ✅ Create Deployment manifests with replicas
• ✅ Scale replicas up and down
• ✅ Watch rolling updates in real-time
• ✅ Configure health checks (liveness/readiness)
• ✅ Rollback failed deployments
• ✅ Understand init containers

Prerequisites

• Lab 02 complete
• Minikube running
• ~1.5 hours

Step 1: Create Deployment Manifest

Create api-deployment.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: api-deployment
  labels:
    app: api
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1        # Max extra pods during update
      maxUnavailable: 0  # Zero downtime requirement
  selector:
    matchLabels:
      app: api
  template:
    metadata:
      labels:
        app: api
    spec:
      containers:
      - name: api
        image: YOUR_USERNAME/myapp:1.0.0
        ports:
        - containerPort: 5000
        resources:
          requests:
            memory: "256Mi"
            cpu: "100m"
          limits:
            memory: "512Mi"
            cpu: "500m"
        livenessProbe:
          httpGet:
            path: /health
            port: 5000
          initialDelaySeconds: 10
          periodSeconds: 5
          failureThreshold: 3
        readinessProbe:
          httpGet:
            path: /ready
            port: 5000
          initialDelaySeconds: 5
          periodSeconds: 10
          failureThreshold: 1

Step 2: Deploy & Verify

# Deploy
kubectl apply -f api-deployment.yaml

# Watch replicas being created (in another terminal)
watch kubectl get pods -l app=api

# Verify all 3 running
kubectl get deployment api-deployment
# Expected: 3 desired, 3 current, 3 ready

Step 3: Scale Replicas

# Scale up to 5
kubectl scale deployment api-deployment --replicas=5

# Watch pods launching
watch kubectl get pods

# Scale down to 2
kubectl scale deployment api-deployment --replicas=2

# Back to 3
kubectl scale deployment api-deployment --replicas=3

Step 4: Rolling Update

# Update image (simulate new version)
kubectl set image deployment/api-deployment api=YOUR_USERNAME/myapp:2.0.0

# Watch rolling update in progress
watch kubectl rollout status deployment/api-deployment

# View rollout history
kubectl rollout history deployment/api-deployment

Step 5: Rollback

# Rollback to previous version
kubectl rollout undo deployment/api-deployment

# Verify pods are back to v1.0.0
kubectl get pods -l app=api -o jsonpath='{.items[*].spec.containers[0].image}'

# View revision history
kubectl rollout history deployment/api-deployment --revision=1
kubectl rollout history deployment/api-deployment --revision=2

Validation

# Deployment is running with 3 replicas
kubectl get deployment api-deployment
# DESIRED: 3, CURRENT: 3, READY: 3

# All pods are healthy
kubectl get pods -l app=api
# All STATUS: Running

# Health checks pass
kubectl describe pod <any-pod-name> | grep -A3 "Liveness\|Readiness"

Challenge (Optional)

Implement HPA (Horizontal Pod Autoscaler):

apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: api-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: api-deployment
  minReplicas: 3
  maxReplicas: 10
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 70

Cleanup

kubectl delete deployment api-deployment
kubectl delete hpa api-hpa 2>/dev/null || true

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Next: Lab 04: Services & Discovery