JDBC Communications link failure with Docker Compose - mysql

Question

When my Spring Boot app tries to connect to the MySQL-database, it throws a CommunicationsException:
spring-service_1 | com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
spring-service_1 |
spring-service_1 | The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
As far as I can tell, my docker-compose.yml is correct, as well as my Dockerfile which simply builds and moves the jar. I've tried changing around some application properties, but it always ends up either in this Connection Exception, or the database refusing access after building my jar and using docker-composer up or docker-composer up --build.
The docker-compose.yml:
version: "3"
services:
mysql-service:
image: mysql:5.7
networks:
- spring-boot-mysql-network
volumes:
- C:/Docker/mysql-conf:/etc/mysql/conf.d
- C:/Docker/mysql-data:/var/lib/mysql
restart: always
environment:
- MYSQL_USER=springuser
- MYSQL_PASSWORD=password123
- MYSQL_ROOT_PASSWORD=password123
- MYSQL_DATABASE=springprototype
- MYSQL_ROOT_HOST='%'
spring-service:
build:
context: ./
dockerfile: Dockerfile
ports:
- "4000:4000"
networks:
- spring-boot-mysql-network
depends_on:
- mysql-service
networks:
spring-boot-mysql-network:
driver: bridge
The Dockerfile:
FROM adoptopenjdk:11-jdk-hotspot
ADD target/*.jar app.jar
EXPOSE 4000
ENTRYPOINT ["java", "-jar", "app.jar"]
My Spring Boot app's application.properties:
spring.jpa.hibernate.ddl-auto=update
spring.datasource.url=jdbc:mysql://mysql-service:3306/springprototype
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL57Dialect
server.port=4000
What could be wrong here? Maybe I'm overlooking or forgetting something.

Answer 1

You can simplify the network by removing all the extra definitions and using directly the default network because you only have two services.
version: "3"
services:
mysql-service:
image: mysql:5.7
volumes:
- C:/Docker/mysql-conf:/etc/mysql/conf.d
- C:/Docker/mysql-data:/var/lib/mysql
restart: always
environment:
- MYSQL_USER=springuser
- MYSQL_PASSWORD=password123
- MYSQL_ROOT_PASSWORD=password123
- MYSQL_DATABASE=springprototype
- MYSQL_ROOT_HOST='%'
spring-service:
build:
context: ./
dockerfile: Dockerfile
ports:
- "4000:4000"
depends_on:
- mysql-service