Containerizing and Deploying Spring Boot Microservices with Docker

## Why Docker for Microservices?

Docker containers package an application with its dependencies, ensuring consistent behavior across development, staging, and production environments. For microservices, Docker provides isolation between services and simplifies deployment.

## Creating Docker Images

A multi-stage Dockerfile keeps images lean:

FROM maven:3.9-eclipse-temurin-21 AS build
WORKDIR /app
COPY pom.xml .
RUN mvn dependency:go-offline
COPY src ./src
RUN mvn package -DskipTests

FROM eclipse-temurin:21-jre-alpine
WORKDIR /app
COPY --from=build /app/target/*.jar app.jar
EXPOSE 8080
ENTRYPOINT ["java", "-jar", "app.jar"]

## Docker Compose for Service Orchestration

Docker Compose defines and runs multi-container applications. For a microservices stack, it manages service dependencies, networking, and startup order.

### Infrastructure Services

- **PostgreSQL**: Persistent data storage - **Redis**: Caching and session management - **Kafka + Zookeeper**: Event streaming - **Eureka**: Service discovery

### Application Services

Each microservice is defined as a Compose service with environment-specific configuration injected through environment variables.

## Nginx Reverse Proxy

Nginx sits in front of the application stack, handling:

- SSL termination - Request routing to the API Gateway - Static file serving - Gzip compression - Rate limiting

## Production Considerations

- Use environment variables for all secrets and configuration - Implement health checks for container orchestration - Set resource limits to prevent any single service from consuming all available resources - Use Docker volumes for persistent data