Spring Boot + docker-compose + MySQL: Connection refused

Docker compose always starts and stops containers in dependency order, or sequential order in the file if not given. But docker-compose does not guarantee that it will wait till the dependency container is running. You can refer here for further details. So the problem here is that your database is not ready when your spring-mysql container tries to access the database. So, the recommended solution is you could use wait-for-it.sh or similar script to wrap your spring-mysql app starting ENTRYPOINT.

As example if you use wait-for-it.sh your ENTRYPOINT in your Dockerfile should change to following after copying above script to your project root:

ENTRYPOINT ["./wait-for-it.sh", "db:3306", "--", "java", "-jar", "app.jar"]

And two other important thing to consider here is:

• Do not use links they are deprecated you should use user-defined network instead. All services in docker-compose file will be in single user-defined network if you don't explicitly define any network. So you just have to remove the links from compose file.
• You don't need to publish the port for docker container if you only use it inside the user-defined network.

I was facing the same issue and in case you do not want to use any custom scripts, this can easily be resolved using health checks along with depends on. A sample using these is as follows:

services:
  mysql-db:
    image: mysql
    environment:
      - MYSQL_ROOT_PASSWORD=vikas1234
      - MYSQL_USER=vikas
    ports:
      - 3306:3306
    restart: always
    healthcheck:
      test: [ "CMD", "mysqladmin" ,"ping", "-h", "localhost" ]
      timeout: 20s
      retries: 10

  app:
    image: shop-keeper
    container_name: shop-keeper-app
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - 8080:8080
    depends_on:
      mysql-db:
        condition: service_healthy
    environment:
      SPRING_DATASOURCE_URL: jdbc:mysql://mysql-db:3306/shopkeeper?createDatabaseIfNotExist=true
      SPRING_DATASOURCE_USERNAME: root
      SPRING_DATASOURCE_PASSWORD: vikas1234

Your config looks nice, I would just recommend:

• Remove links: db. It has no value in user-defined bridge networking
• Remove port exposing for db unless you want to connect from outside docker-compose - all ports are exposed automatically inside user-defined bridge network.

I think the problem is that database container takes more time to start than web. depends_on just controls the order, but does not guarantee you database readiness. If possible, set several connection attempts or put socket-wait procedure in your web container.