How to connect a flask container with a mysql container - docker

Question

I have already a mysql container named "mysqlDemoStorage" running, exposing port 3306 to 0.0.0.0:3306. I also have a flask app which provides a login page and table-displaying page. The flask app works quite well in host. The login page connects to "user" table in the mysql container and the table-displaying page connects to another table holding all the data to display.
The docker-compose file I used to create the mysql container is as follows:
version: '3'
services:
mysql:
container_name: mysqlDemoStorage
environment:
MYSQL_ROOT_PASSWORD: "demo"
command:
--character-set-server=utf8
ports:
- 3306:3306
image: "docker.io/mysql:latest"
restart: always
Now I want to dockerize the flask app so that I can still view the app from host. The mysql container detail is as followed:
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c48955b3589e mysql:latest "docker-entrypoint.s…" 13 days ago Up 49 minutes 0.0.0.0:3306->3306/tcp, 33060/tcp mysqlDemoStorage
The dockerfile of the flask app I wrote is as follows:
FROM python:latest
WORKDIR /storage_flask
ADD . /storage_flask
RUN pip install -r requirements.txt
EXPOSE 5000
ENTRYPOINT ["python","run.py"]
The flask image can be successfuly built, but when I run the image, I fail to load the page. One point I think that causes the problem is the init.py file to initiate the flask app, which is as follows:
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_bcrypt import Bcrypt
from flask_login import LoginManager
app = Flask(__name__)
app.config['SECRET_KEY'] = 'aafa4f8047ce31126011638be8530da6'
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://root:demo#localhost:3306/storage'
db = SQLAlchemy(app)
bcrypt = Bcrypt(app)
login_manager = LoginManager(app)
login_manager.login_view = "login"
login_manager.login_message_category = 'info'
from storage_flask import routes
I was thinking passing the IP of the mysql container to the flask container as the config string for DB connection. But I'm not sure how to do it.
Could someone help to solve the problem? Thank you

Answer 1

change this line
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://root:demo#localhost:3306/storage'
to
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://root:demo#mysql:3306/storage'
You also need to make sure that both containers are connected to the same network, for that you need to update your docker-compose file to be something like the below file
version: '3.7'
networks:
my_network_name:
name: my_network_name
external: false
services:
mysql:
container_name: mysqlDemoStorage
environment:
MYSQL_ROOT_PASSWORD: "demo"
command:
--character-set-server=utf8
ports:
- 3306:3306
image: "docker.io/mysql:latest"
restart: always
networks:
- my_network_name
second file
version: '3.7'
networks:
my_network_name:
name: my_network_name
external: true
services:
python_app:
container_name: pythonDemoStorage
ports:
- 5000:5000
image: "Myimage"
restart: always
networks:
- my_network_name