A Simple Analogy

Kubernetes is like an operations manager for containers. It schedules work, handles failures, scales up when busy, and ensures everything runs smoothly 24/7.

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Why Kubernetes?

• Orchestration: Manage hundreds of containers
• Self-healing: Restart crashed containers
• Auto-scaling: Scale based on demand
• Rolling updates: Zero-downtime deployments
• Service discovery: Auto DNS for containers

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Basic Deployment

apiVersion: apps/v1
kind: Deployment
metadata:
  name: api-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: api
  template:
    metadata:
      labels:
        app: api
    spec:
      containers:
      - name: api
        image: myregistry.azurecr.io/myapi:latest
        ports:
        - containerPort: 80
        env:
        - name: DATABASE_URL
          valueFrom:
            secretKeyRef:
              name: db-secret
              key: connection-string
        resources:
          requests:
            memory: "256Mi"
            cpu: "100m"
          limits:
            memory: "512Mi"
            cpu: "500m"
        livenessProbe:
          httpGet:
            path: /health
            port: 80
          initialDelaySeconds: 30
          periodSeconds: 10

---

Service for Load Balancing

apiVersion: v1
kind: Service
metadata:
  name: api-service
spec:
  type: LoadBalancer
  selector:
    app: api
  ports:
  - protocol: TCP
    port: 80
    targetPort: 80

---

ConfigMap and Secrets

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  log-level: "info"
  environment: "production"

---
apiVersion: v1
kind: Secret
metadata:
  name: db-secret
type: Opaque
stringData:
  connection-string: "postgresql://user:password@db-service:5432/myapp"
  api-key: "secret-key-here"

---

StatefulSet for Databases

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: postgres
spec:
  serviceName: postgres-service
  replicas: 1
  selector:
    matchLabels:
      app: postgres
  template:
    metadata:
      labels:
        app: postgres
    spec:
      containers:
      - name: postgres
        image: postgres:15
        ports:
        - containerPort: 5432
        volumeMounts:
        - name: postgres-storage
          mountPath: /var/lib/postgresql/data
  volumeClaimTemplates:
  - metadata:
      name: postgres-storage
    spec:
      accessModes: [ "ReadWriteOnce" ]
      resources:
        requests:
          storage: 10Gi

---

Horizontal Pod Autoscaling

apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: api-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: api-deployment
  minReplicas: 2
  maxReplicas: 10
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 70
  - type: Resource
    resource:
      name: memory
      target:
        type: Utilization
        averageUtilization: 80

---

Kubectl Commands

# Apply configuration
kubectl apply -f deployment.yaml

# View pods
kubectl get pods
kubectl describe pod api-deployment-xyz

# View services
kubectl get svc

# Scale manually
kubectl scale deployment api-deployment --replicas=5

# Update image
kubectl set image deployment/api-deployment api=myregistry.azurecr.io/myapi:v2

# Rollback
kubectl rollout undo deployment/api-deployment

# View logs
kubectl logs pod-name
kubectl logs -f pod-name  # Follow logs

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Best Practices

1. Set resource limits: Define CPU and memory
2. Health checks: Liveness and readiness probes
3. Security: Use RBAC and network policies
4. Monitoring: Integrate Prometheus/Grafana
5. GitOps: Store configs in Git

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Related Concepts

• Helm for templating
• Ingress for routing
• Network policies for security
• RBAC for access control

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Summary

Kubernetes automates container orchestration at scale. Define deployments, services, and scaling policies to build resilient, self-healing systems.