Article 17: Containerizing Microservices with Docker

1. Objective

Learn how to package microservices into Docker containers for consistent deployment.

2. Key Concepts

• Containers vs Virtual Machines
• Docker image
• Docker container
• Dockerfile

3. Why Containers for Microservices

Benefits:

• Consistent runtime environment
• Fast startup
• Easy scaling
• Works the same locally and in production

4. Docker Basics

Common commands:

docker build -t user-service .
docker run -p 8081:8081 user-service

5. Hands-On: Dockerfile for Spring Boot

FROM eclipse-temurin:17-jdk-alpine
VOLUME /tmp
COPY target/user-service.jar app.jar
ENTRYPOINT ["java","-jar","/app.jar"]

6. Build & Run

mvn clean package
docker build -t user-service .
docker run -p 8081:8081 user-service

7. Common Mistakes

• Using large base images
• Hardcoding configs
• Forgetting exposed ports

8. Interview Notes

• Containers package app + dependencies
• Docker enables immutable deployments

9. Summary

Docker makes microservices portable and reproducible.

10. What’s Next

Run multiple containers together using Docker Compose.