☁️ DevOps & Cloud

"Automate everything. If you do it twice, script it."

Modern DevOps practices for deploying, scaling, and maintaining production applications.

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🐳 Docker

Dockerfile Best Practices

# Multi-stage build for smaller images
FROM eclipse-temurin:21-jdk AS build
WORKDIR /app
COPY pom.xml .
COPY src ./src
RUN ./mvnw clean package -DskipTests

FROM eclipse-temurin:21-jre
WORKDIR /app
COPY --from=build /app/target/*.jar app.jar

# Non-root user for security
RUN addgroup --system app && adduser --system --group app
USER app

EXPOSE 8080
HEALTHCHECK --interval=30s --timeout=3s \
  CMD curl -f http://localhost:8080/actuator/health || exit 1

ENTRYPOINT ["java", "-jar", "app.jar"]

Docker Compose

# docker-compose.yml
version: '3.8'

services:
  app:
    build: .
    ports:
      - "8080:8080"
    environment:
      - SPRING_DATASOURCE_URL=jdbc:postgresql://db:5432/myapp
      - SPRING_REDIS_HOST=cache
    depends_on:
      db:
        condition: service_healthy
      cache:
        condition: service_started
    networks:
      - backend

  db:
    image: postgres:16
    environment:
      POSTGRES_DB: myapp
      POSTGRES_USER: user
      POSTGRES_PASSWORD: password
    volumes:
      - postgres_data:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U user -d myapp"]
      interval: 10s
      timeout: 5s
      retries: 5
    networks:
      - backend

  cache:
    image: redis:7-alpine
    networks:
      - backend

volumes:
  postgres_data:

networks:
  backend:

Essential Commands

# Build and run
docker build -t myapp:latest .
docker run -d -p 8080:8080 --name myapp myapp:latest

# Compose operations
docker compose up -d
docker compose logs -f app
docker compose down -v

# Debugging
docker exec -it myapp /bin/sh
docker logs --tail 100 -f myapp
docker stats

---

☸️ Kubernetes

Core Concepts

Deployment Example

# deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
  labels:
    app: myapp
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - name: myapp
        image: myapp:latest
        ports:
        - containerPort: 8080
        resources:
          requests:
            memory: "256Mi"
            cpu: "250m"
          limits:
            memory: "512Mi"
            cpu: "500m"
        livenessProbe:
          httpGet:
            path: /actuator/health
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 10
        readinessProbe:
          httpGet:
            path: /actuator/health/readiness
            port: 8080
          initialDelaySeconds: 5
          periodSeconds: 5
---
apiVersion: v1
kind: Service
metadata:
  name: myapp-service
spec:
  selector:
    app: myapp
  ports:
  - port: 80
    targetPort: 8080
  type: LoadBalancer

Kubectl Commands

# Cluster info
kubectl cluster-info
kubectl get nodes

# Deployments
kubectl apply -f deployment.yaml
kubectl get pods -w
kubectl describe pod myapp-xxx

# Scaling
kubectl scale deployment myapp --replicas=5

# Debugging
kubectl logs myapp-xxx -f
kubectl exec -it myapp-xxx -- /bin/sh
kubectl port-forward svc/myapp-service 8080:80

# Rolling updates
kubectl set image deployment/myapp myapp=myapp:v2
kubectl rollout status deployment/myapp
kubectl rollout undo deployment/myapp

---

🔄 CI/CD with GitHub Actions

Complete Workflow

# .github/workflows/deploy.yml
name: Build and Deploy

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]

env:
  REGISTRY: ghcr.io
  IMAGE_NAME: ${{ github.repository }}

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      
      - name: Set up JDK 21
        uses: actions/setup-java@v4
        with:
          java-version: '21'
          distribution: 'temurin'
          cache: maven
      
      - name: Run tests
        run: ./mvnw verify

  build:
    needs: test
    runs-on: ubuntu-latest
    if: github.ref == 'refs/heads/main'
    
    steps:
      - uses: actions/checkout@v4
      
      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3
      
      - name: Login to Container Registry
        uses: docker/login-action@v3
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}
      
      - name: Build and push
        uses: docker/build-push-action@v5
        with:
          context: .
          push: true
          tags: |
            ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:latest
            ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.sha }}
          cache-from: type=gha
          cache-to: type=gha,mode=max

  deploy:
    needs: build
    runs-on: ubuntu-latest
    environment: production
    
    steps:
      - name: Deploy to Kubernetes
        uses: azure/k8s-deploy@v4
        with:
          manifests: k8s/
          images: |
            ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.sha }}

---

☁️ Cloud Platforms

AWS Services Overview

Service	Purpose	Alternative
EC2	Virtual servers	GCP Compute Engine
S3	Object storage	GCP Cloud Storage
RDS	Managed databases	GCP Cloud SQL
Lambda	Serverless functions	GCP Cloud Functions
EKS	Managed Kubernetes	GCP GKE
CloudWatch	Monitoring	GCP Cloud Monitoring
SQS/SNS	Messaging	GCP Pub/Sub

AWS CLI Examples

# S3 operations
aws s3 cp file.txt s3://mybucket/
aws s3 sync ./dist s3://mybucket/static/

# ECR (Container Registry)
aws ecr get-login-password | docker login --username AWS --password-stdin <account>.dkr.ecr.<region>.amazonaws.com
docker tag myapp:latest <account>.dkr.ecr.<region>.amazonaws.com/myapp:latest
docker push <account>.dkr.ecr.<region>.amazonaws.com/myapp:latest

# ECS / EKS
aws ecs update-service --cluster mycluster --service myapp --force-new-deployment
aws eks update-kubeconfig --name mycluster --region us-east-1

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📊 Monitoring & Observability

The Three Pillars

Pillar	Purpose	Tools
Logs	Event records	ELK Stack, Loki, CloudWatch Logs
Metrics	Measurements	Prometheus, Datadog, CloudWatch
Traces	Request flow	Jaeger, Zipkin, X-Ray

# Prometheus scrape config
scrape_configs:
  - job_name: 'spring-app'
    metrics_path: '/actuator/prometheus'
    static_configs:
      - targets: ['app:8080']

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📝 Detailed Topics

• Docker Networking
• Kubernetes RBAC
• Helm Charts
• Infrastructure as Code (Terraform)
• Security Best Practices

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DevOps Principles

1. Infrastructure as Code - Version control everything
2. Immutable infrastructure - Replace, don't patch
3. Automate deployments - Reduce human error
4. Monitor everything - Know before users complain
5. Fail forward - Quick rollbacks, blameless postmortems