Cannot connect MySQL with Spring Boot in docker-compose

Question

I have the problem when running spring boot with mysql using Docker. It runs well locally without Docker. My dockerfile

FROM maven:3.3-jdk-8-alpine

ENV MAVEN_HOME /usr/lib/mvn
ENV PATH $MAVEN_HOME/bin:$PATH
ENV SPRING_DATASOURCE_URL jdbc:mysql://my-db:3306/registration_springboot?createDatabaseIfNotExist=true

ENV SPRING_DATASOURCE_USERNAME vnphu
ENV SPRING_DATASOURCE_PASSWORD password

docker-compose.yml file

version: '3'
services:
  my-db:
     image: mysql/mysql-server:5.7
     container_name: my-db
     environment:
         MYSQL_USER: vnphu
         MYSQL_DATABASE: registration_springboot
         MYSQL_PASSWORD: password
         MYSQL_ROOT_PASSWORD: password
     ports:
          - '3306-3306'

  web:
    build: .
    working_dir: /app
    volumes:
        - .:/app
        - ~/.m2:/root/.m2
    ports:
        - "8080:8080"
    command: mvn clean spring-boot:run
    depends_on:
        - my-db

The error when run: docker-compose up --build

Caused by: java.net.ConnectException: Connection refused (Connection refused)
web_1    |      at java.net.PlainSocketImpl.socketConnect(Native Method) ~[na:1.8.0_121]
web_1    |      at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[na:1.8.0_121]
web_1    |      at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_121]
web_1    |      at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_121]
web_1    |      at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_121]
web_1    |      at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_121]
web_1    |      at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:155) ~[mysql-connector-java-8.0.19.jar:8.0.19]
web_1    |      at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:65) ~[mysql-connector-java-8.0.19.jar:8.0.19]
web_1    |      ... 115 common frames omitted

Answer 1

web application is trying to connect to my-db which is not yet available(database is still loading) you can use any of the following solutions depending on your preference.

1. Restart-on failure

   modify docker-compose file to

   web: ports: "8080:8080" restart:on-failure

2. sleep

   modify docker-compose file under environment

   web: ports: "8080:8080" environment: -SLEEP_LENGTH=5

3. wait-for-it.sh file

   wait-for-it file

   this approach needs you to modify your Dockerfile as well as docker-compose file

Answer 2

The problem is with my ENV in Dockerfile because I also have an environment variable with the same name in Shell which will take precedence.

ENV SPRING_DATASOURCE_URL jdbc:mysql://my-db:3306/registration_springboot?createDatabaseIfNotExist=true

After adding the variable to environment in the docker-compose.yml, It worked

web:
   environment:
        SPRING_DATASOURCE_URL: jdbc:mysql://my-db:3306/registration_springboot?createDatabaseIfNotExist=true

docker-compose.yml will look up as below order:

1. Compose file
2. Shell environment variables
3. Environment file
4. Dockerfile
5. Variable is not defined

You can refer to this article for more details: https://vsupalov.com/override-docker-compose-dot-env/

Answer 3

Your service and db are not on the same network. Consider defining a network and adding to each of service and db