docker-compose run two instance of mysql - mysql

Question

I want to run two instances of mysql using docker-compose.
I'm running MySQL in a Docker container and I have another Docker container running a python script to access the MySQL database.
One works fine on port 3306. In order to get two working, I thought I would just run the other one on a different port. But when I change it to a different port (e.g. 6603), but when I do, I get the below error:
mysql.connector.errors.InterfaceError: 2003: Can't connect to MySQL server on 'mysql:6603' (111 Connection refused)
I have read every question on s.o. I can find that seems relevant but none of the solutions work. I feel certain the fix will involve changing a line or two of configuration but I've spent many hours on this so far so any help would be greatly appreciated.
The docker-compose script is below (works fine if 6603 is replaced with 3306).
server:
build:
context: ../
dockerfile: Docker/ServerDockerfile
ports:
- "8080:8080"
links:
- mysql:mysql
volumes:
- ../py:/app
tty: true
mysql:
image: mysql
expose:
- "6603"
environment:
MYSQL_ROOT_PASSWORD: password
MYSQL_DATABASE: project
volumes:
- ./MySQL:/docker-entrypoint-initdb.d
- ./MySQL/data:/var/lib/mysql
And it is being accessed like this:
cnx = mysql.connector.connect(user='root', password='password',
host='mysql',
port="6603",
database='project')

Answer 1

Try to specify another port for MySQL by modifying its my.cnf file.

Answer 2

Have eventually found a couple of ways that work. The neatest one is for each app to create a network and connect the containers to it.
If each app uses a different network then mysql can run on 3306 on that Docker network and can be accessed on mysql://3306 from app1 and mysql2://3306 from app2. (Assuming you name you give the mysql service for app 2 is mysql2).
The Docker file with the new lines is below:
server:
build:
context: ../
dockerfile: Docker/ServerDockerfile
ports:
- "8080:8080"
volumes:
- ../py:/app
tty: true
networks:
-net
mysql2:
image: mysql
environment:
MYSQL_ROOT_PASSWORD: password
MYSQL_DATABASE: project
volumes:
- ./MySQL:/docker-entrypoint-initdb.d
- ./MySQL/data:/var/lib/mysql
networks:
-net
networks:
net:
driver: bridge
The Docker file for the second app is identical except the names are different (I put a 2 after each for simplicity).
server2:
build:
context: ../
dockerfile: Docker/ServerDockerfile
ports:
- "8081:8080"
volumes:
- ../py:/app
tty: true
networks:
-net2
mysql2:
image: mysql
environment:
MYSQL_ROOT_PASSWORD: password
MYSQL_DATABASE: project
volumes:
- ./MySQL:/docker-entrypoint-initdb.d
- ./MySQL/data:/var/lib/mysql
networks:
-net2
networks:
net2:
driver: bridge