Spring Boot unable to communicate with MySQL DB in docker environment

I am trying to run a springboot microservice docker image. It fetches the DB connection properties from a Config server. However it is unable to connect to the container.

Error :

JdbcEnvironmentInitiator - HHH000342: Could not obtain connection to query metadata : 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.

Exception :

at com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
Caused by :
at java.net.PlainSocketImpl.socketConnect(Native Method) ~[na:1.8.0_242]
2020-09-28 11:39:32.782 [ : ] WARN  [task-1] o.h.e.j.s.SqlExceptionHelper - SQL Error: 0, SQLState: 08S01
 1 --- [         task-1] o.h.engine.jdbc.spi.SqlExceptionHelper   : SQL Error: 0, SQLState: 08S01
2020-09-28 11:39:32.791 [ : ] ERROR [task-1] o.h.e.j.s.SqlExceptionHelper - 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.
 1 --- [         task-1] o.h.engine.jdbc.spi.SqlExceptionHelper   : 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.

Properties located at Config Server

shopping-service.datasource.url: jdbc:mysql://A.B.C.D:3306/shoppingCartDB
shopping-service.datasource.username: root
shopping-service.datasource.password: root

A.B.C.D is my docker host IP.

application.yaml

datasource:
    url: ${shopping-service.datasource.url}
    username: ${shopping-service.datasource.username}
    password: ${shopping-service.datasource.password}
    #driver-class-name: com.mysql.jdbc.Driver
  jpa:
    generate-ddl: true
    properties:
      hibernate:
        dialect: org.hibernate.dialect.MySQL8Dialect
        show_sql: true
        ddl-auto: create-drop
  profiles:
    active: dev

I have pulled the MySQL 8.0 docker image from docker hub.

docker pull mysql/mysql-server:8.0
docker run --name=mysql-container -d mysql/mysql-server:8.0

Changed the password to "root".

mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'root';
Query OK, 0 rows affected (0.02 sec)

Created the database :

mysql> create DATABASE shoppingCartDB;
Query OK, 1 row affected (0.00 sec)

mysql> exit

Docker RUN

docker run -p 5000:5000 shoppingms:latest --env shopping-service.configserverurl=http://A.B.C.D:8888 --env shopping-service.eureka.url=http://A.B.C.D:4444/eureka

It is able to fetch the properties from config server. I checked the logs. Error came from this line :

 com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...

In my local environment I am able to use the locally installed MySQL Db with the same connection parameters. However in docker I am getting the exceptions. Where I am going wrong can anyone please help me out.

UPDATE :

After exposing the MySQL container to port 3306, the error stands at now :

2020-09-28 12:07:43.942 [ : ] WARN  [task-1] o.h.e.j.e.i.JdbcEnvironmentInitiator - HHH000342: Could not obtain connection to query metadata : null,  message from server: "Host 'Some-IP' is not allowed to connect to this MySQL server"
     1 --- [         task-1] o.h.e.j.e.i.JdbcEnvironmentInitiator     : HHH000342: Could not obtain connection to query metadata : null,  message from server: "Host 'Some-IP' is not allowed to connect to this MySQL server"

2020-09-28 12:07:49.219 [ : ] WARN  [task-1] o.h.e.j.s.SqlExceptionHelper - SQL Error: 1130, SQLState: HY000
 1 --- [         task-1] o.h.engine.jdbc.spi.SqlExceptionHelper   : SQL Error: 1130, SQLState: HY000
2020-09-28 12:07:49.225 [ : ] ERROR [task-1] o.h.e.j.s.SqlExceptionHelper - null,  message from server: "Host 'Some-IP' is not allowed to connect to this MySQL server"
 1 --- [         task-1] o.h.engine.jdbc.spi.SqlExceptionHelper   : null,  message from server: "Host 'Some-IP' is not allowed to connect to this MySQL server"

I would suggest running a docker compose file to describe your application setup.

As a guide line, this is a compose file for running phpMyAdmin, MySQL 8, tomcat on a given network. I have given a guess at your application requirement:

version: "3.5"
services:
  # Update the below for your application
  app:
    image: shoppingms:latest
    restart: always
    ports:
      - 5000:5000
    links:
      - db:db
    environment: 
      - shopping-service.configserverurl=http://A.B.C.D:8888
      - shopping-service.eureka.url=http://A.B.C.D:4444/eureka
    networks: 
      - appnet
  db:
    image: mysql:8.0
    restart: always
    ports:
        - 3306:3306
    command: --default-authentication-plugin=mysql_native_password
    environment:
        MYSQL_DATABASE: mydb
        MYSQL_USER: user
        MYSQL_PASSWORD: user123
        MYSQL_ROOT_PASSWORD: user123
    volumes:
        - ./sql-init:/docker-entrypoint-initdb.d
        - ./mysql/data:/var/lib/mysql
    networks:
        - appnet
  phpmyadmin:
    image: phpmyadmin/phpmyadmin
    restart: always
    links:
        - db:db
    ports:
        - 8201:80
    environment:
        MYSQL_USER: user
        MYSQL_PASSWORD: user123
        MYSQL_ROOT_PASSWORD: user123
    networks:
        - appnet
  tomcat:
    image: library/tomcat:9
    restart: always
    links:
        - db:db
    ports:
        - 8081:8080
    volumes:
      - ./tomcat/webapps:/usr/local/tomcat/webapps
      - ./tomcat/logs:/usr/local/tomcat/logs
    networks:
        - appnet

networks:
  appnet:
    name: appnet

In this application I was running a externally hosted tomcat server with Spring webapp volumed into the container. There are various ports exposed as well for ease of external access.

You would need configure/tweak your application container as per your requirement.

The Database is exposed on the DNS name db which is what phpMyAdmin uses.

Able to resolve the issue now.

 1. Identify the ip address from docker inspect command.
 2. Create an user for that ip.
 3. Need to alter the new user password.
 4. Grant some privileges to the user.
 5. Exit

Now run your container again, this time it could obtain the connections and successfully create the tables.