docker-compose for services in Spring Boot - Mini Project: Build & Apply

docker-compose for services

📖 Scenario: You are building a simple Spring Boot application that needs to run alongside a database service. To make it easy to start both services together, you will use docker-compose to define and run these services.

🎯 Goal: Create a docker-compose.yml file that defines two services: a Spring Boot app and a PostgreSQL database. The Spring Boot app should connect to the database service using the correct hostname and port.

📋 What You'll Learn

Define a service named app using the Spring Boot Docker image springboot-app:latest

Define a service named db using the official PostgreSQL image postgres:15

Set environment variables for the db service: POSTGRES_USER as user, POSTGRES_PASSWORD as password, and POSTGRES_DB as mydb

Expose port 5432 on the db service

Configure the app service to depend on db

Set environment variables for the app service to connect to the database host db and port 5432

💡 Why This Matters

🌍 Real World

Docker Compose is widely used to run multi-service applications locally or in development environments. It simplifies starting and stopping related services together.

💼 Career

Understanding docker-compose is essential for developers and DevOps engineers to manage containerized applications efficiently, especially when working with microservices or databases.

1

Create the basic docker-compose structure

Create a file named docker-compose.yml and start with the version "3.8" and an empty services section.

Spring Boot

version: "3.8"
services:
  # Your services will go here

Need a hint?

Start your docker-compose.yml with the version and services keys.

2

Add the database service configuration

Under services, add a service named db using the image postgres:15. Set environment variables POSTGRES_USER to user, POSTGRES_PASSWORD to password, and POSTGRES_DB to mydb. Expose port 5432 on the host.

Spring Boot

version: "3.8"
services:
  db:
    # Add image, environment, and ports here

Need a hint?

Use the official PostgreSQL image and set the environment variables exactly as specified.

3

Add the Spring Boot app service with dependency

Add a service named app using the image springboot-app:latest. Make it depend on the db service using depends_on. Set environment variables SPRING_DATASOURCE_URL to jdbc:postgresql://db:5432/mydb, SPRING_DATASOURCE_USERNAME to user, and SPRING_DATASOURCE_PASSWORD to password.

Spring Boot

version: "3.8"
services:
  db:
    image: postgres:15
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: password
      POSTGRES_DB: mydb
    ports:
      - "5432:5432"
  app:
    # Add image, depends_on, and environment here

Need a hint?

Use depends_on to ensure the app waits for the database. Set the Spring datasource environment variables to connect to the db service.

4

Complete the docker-compose file with network and restart policy

Add a restart policy with value always to the app service. Also, define a network named app-network and connect both app and db services to this network.

Spring Boot

version: "3.8"
services:
  db:
    image: postgres:15
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: password
      POSTGRES_DB: mydb
    ports:
      - "5432:5432"
    networks:
      - app-network
  app:
    image: springboot-app:latest
    depends_on:
      - db
    environment:
      SPRING_DATASOURCE_URL: jdbc:postgresql://db:5432/mydb
      SPRING_DATASOURCE_USERNAME: user
      SPRING_DATASOURCE_PASSWORD: password
    networks:
      - app-network
    # Add restart policy here

networks:
  app-network:
    driver: bridge

Need a hint?

Use the restart key under app and define the app-network at the bottom with driver bridge. Connect both services to this network.