JDBC Communications link failure with mysql docker container

Question

When my java spring application tries to connect to the database I get the following:

Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.

The connection url in the spring application is as follows:

jdbc:mysql://mysqldbserver:3306/supersede_orchestrator_spring?useSSL=false&autoReconnect=true&failOverReadOnly=false&maxReconnects=10

where mysqldbserver is the service name from the docker-compose config:

version : '3'
services:
  springappserver:
    build:
      context: .
      dockerfile: web.dockerfile
    ports:
      - "8081:8080"
    networks:
      - mt-network
    volumes:
      - .:/vol/development
    depends_on:
      - mysqldbserver
  mysqldbserver:
    build:
      context: .
      dockerfile: db.dockerfile
    ports:
      - "13306:3306"
    networks:
      - mt-network
    environment:
      MYSQL_DATABASE: supersede_orchestrator_spring
      MYSQL_USER: supersede_orch
      MYSQL_PASSWORD: ****
      MYSQL_ROOT_PASSWORD: ****
    container_name: orchestrator_mysqldbserver
networks:
  mt-network:
    driver: bridge

In the mysql docker container I already adjusted the bind-address to 0.0.0.0. The privileges of the supersede_orch user are set to %. When I connect to the springappserver docker container, I can reach the database via telnet mysqldbserver 3306 and I can also connect to the database on the command line from the spring docker container: mysql -h mysqldbserver -u supersede_orch -p. Though the java spring application fails to connect to the DB running on the other docker container.

The web.dockerfile looks as follows:

FROM java:8-jre

VOLUME /tmp
ADD build/libs/feedback_orchestrator-2.0.0.jar app.jar

RUN apt-get update
RUN apt-get install mysql-client -y
RUN apt-get install libmysql-java -y

RUN bash -c 'touch /app.jar'

ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom -Djava.net.preferIPv4Stack=true","-jar","/app.jar"]

So, I tried to make sure that java uses IP4 to resolve mysqldbserver (I also used the corresponding IP address for mysqldbserver which also failed).

Finally docker images -a:

42db4e656e6e        orchestrator_springappserver   "java '-Djava.secu..."   16 minutes ago      Up 16 minutes             0.0.0.0:8081->8080/tcp    orchestrator_springappserver_1
e2b0b5cc15ac        orchestrator_mysqldbserver     "docker-entrypoint..."   2 hours ago         Up About an hour          0.0.0.0:13306->3306/tcp   orchestrator_mysqldbserver

Do you have any idea what the problem could be? Thank you!

Answer 1

The above configuration is correct. I was just stupid enough to forget rebuilding the jar. So, the jdbc url was not updated. It works now perfectly.