Containerizing Spring Cloud Microservices with Docker and Kubernetes (Part 9)

Why Containerize?

Traditional deployment on physical/virtual machines leads to environment inconsistency, dependency conflicts, resource waste, scaling difficulty, and complex releases. Containerization provides consistent environments, isolation, elastic scaling, and fast deployment.

Docker Image Build

Base Dockerfile

# user-service/Dockerfile
# Multi‑stage build
FROM maven:3.8-openjdk-11 AS builder

WORKDIR /app

# Cache dependencies
COPY pom.xml .
COPY common/pom.xml ./common/
COPY user-service/pom.xml ./user-service/

RUN mvn dependency:go-offline

# Copy source and build
COPY common ./common/
COPY user-service ./user-service/

RUN mvn clean package -pl user-service -am -DskipTests

# Runtime stage
FROM openjdk:11-jre-slim

WORKDIR /app

RUN apt-get update && apt-get install -y curl && rm -rf /var/lib/apt/lists/*

# Create non‑root user
RUN groupadd -r blog && useradd -r -g blog blog

# Copy JAR
COPY --from=builder /app/user-service/target/user-service-*.jar app.jar

# Optional SkyWalking agent
COPY --from=builder /app/skywalking-agent /skywalking-agent

HEALTHCHECK --interval=30s --timeout=3s --start-period=30s --retries=3 \
  CMD curl -f http://localhost:8081/actuator/health || exit 1

USER blog
EXPOSE 8081

ENV JAVA_OPTS="-Xms256m -Xmx512m -XX:+UseG1GC"
ENTRYPOINT ["sh","-c","java $JAVA_OPTS -javaagent:/skywalking-agent/skywalking-agent.jar -jar app.jar"]

Build Commands

# Build image
docker build -t blog/user-service:1.0.0 -f user-service/Dockerfile .

# List image
docker images | grep blog

# Run container
docker run -d --name user-service -p 8081:8081 blog/user-service:1.0.0

# Push to registry
docker tag blog/user-service:1.0.0 your-registry/blog/user-service:1.0.0
docker push your-registry/blog/user-service:1.0.0

Docker‑Compose Orchestration

A complete docker-compose.yml defines networks, volumes, and services for MySQL, Redis, Nacos, user‑service, article‑service, and gateway, with environment variables such as SPRING_PROFILES_ACTIVE=docker and health checks.

One‑Click Startup

# Build and start all services
docker-compose up -d --build

# View logs
docker-compose logs -f

# Scale user service to 3 instances
docker-compose up -d --scale user-service=3

# Stop all services
docker-compose down

# Remove data volumes
docker-compose down -v

Kubernetes Deployment

Namespace and ConfigMap

# namespace.yaml
apiVersion: v1
kind: Namespace
metadata:
  name: blog-system

---
# configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: blog-config
  namespace: blog-system
data:
  application.yml: |
    spring:
      cloud:
        nacos:
          discovery:
            server-addr: nacos:8848

Service Manifests

# user-service-deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: user-service
  namespace: blog-system
  labels:
    app: user-service
spec:
  replicas: 3
  selector:
    matchLabels:
      app: user-service
  template:
    metadata:
      labels:
        app: user-service
    spec:
      containers:
      - name: user-service
        image: blog/user-service:1.0.0
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 8081
        env:
        - name: SPRING_PROFILES_ACTIVE
          value: "k8s"
        - name: NACOS_HOST
          value: "nacos"
        resources:
          requests:
            memory: "256Mi"
            cpu: "200m"
          limits:
            memory: "512Mi"
            cpu: "500m"
        livenessProbe:
          httpGet:
            path: /actuator/health
            port: 8081
          initialDelaySeconds: 60
          periodSeconds: 10
        readinessProbe:
          httpGet:
            path: /actuator/health
            port: 8081
          initialDelaySeconds: 30
          periodSeconds: 5
---
# user-service-service.yaml
apiVersion: v1
kind: Service
metadata:
  name: user-service
  namespace: blog-system
spec:
  selector:
    app: user-service
  ports:
  - port: 8081
    targetPort: 8081
  type: ClusterIP

Gateway Deployment and Service

# gateway-deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: gateway
  namespace: blog-system
spec:
  replicas: 2
  selector:
    matchLabels:
      app: gateway
  template:
    metadata:
      labels:
        app: gateway
    spec:
      containers:
      - name: gateway
        image: blog/gateway:1.0.0
        ports:
        - containerPort: 8080
        env:
        - name: SPRING_PROFILES_ACTIVE
          value: "k8s"
        - name: NACOS_HOST
          value: "nacos"
---
# gateway-service.yaml
apiVersion: v1
kind: Service
metadata:
  name: gateway
  namespace: blog-system
spec:
  selector:
    app: gateway
  ports:
  - port: 8080
    targetPort: 8080
  type: LoadBalancer

Ingress and Autoscaling

# ingress.yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: blog-ingress
  namespace: blog-system
spec:
  ingressClassName: nginx
  rules:
  - host: api.blog.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: gateway
            port:
              number: 8080

# hpa.yaml
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: user-service-hpa
  namespace: blog-system
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: user-service
  minReplicas: 2
  maxReplicas: 10
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 70

Deployment Commands

# Create namespace
kubectl create namespace blog-system

# Apply ConfigMap
kubectl apply -f configmap.yaml

# Deploy services
kubectl apply -f user-service-deployment.yaml
kubectl apply -f user-service-service.yaml
kubectl apply -f gateway-deployment.yaml
kubectl apply -f gateway-service.yaml

# Check status
kubectl get pods -n blog-system
kubectl get svc -n blog-system

# Scale
kubectl scale deployment user-service -n blog-system --replicas=5

# Rolling update
kubectl set image deployment/user-service -n blog-system user-service=blog/user-service:1.0.1
kubectl rollout status deployment/user-service -n blog-system

# Rollback
kubectl rollout undo deployment/user-service -n blog-system

CI/CD Pipeline with GitHub Actions

# .github/workflows/deploy.yml
name: Build and Deploy
on:
  push:
    branches: [main]

jobs:
  build-and-deploy:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        service: [user-service, article-service, gateway]
    steps:
    - uses: actions/checkout@v3
    - name: Set up JDK 11
      uses: actions/setup-java@v3
      with:
        java-version: '11'
        distribution: 'temurin'
    - name: Build with Maven
      run: mvn clean package -pl ${{ matrix.service }} -am -DskipTests
    - name: Build Docker image
      run: |
        docker build -t blog/${{ matrix.service }}:${{ github.sha }} \
          -f ${{ matrix.service }}/Dockerfile .
    - name: Push to Docker Hub
      run: |
        docker push blog/${{ matrix.service }}:${{ github.sha }}
    - name: Deploy to K8s
      run: |
        kubectl set image deployment/${{ matrix.service }} \
          ${{ matrix.service }}=blog/${{ matrix.service }}:${{ github.sha }} \
          -n blog-system

Common Issues and Solutions

Slow container start‑up : add JVM container‑aware options

ENV JAVA_OPTS="-XX:+UseContainerSupport -XX:InitialRAMPercentage=50 -XX:MaxRAMPercentage=75"

.

Service discovery failure : avoid localhost inside containers; use service names (e.g., nacos:8848).

Health‑check failure : give enough start‑up time with initialDelaySeconds: 60 and appropriate periodSeconds.

Log disk exhaustion : configure Logback rolling policy with max-history: 7 and max-size: 100MB.