Run MySql In A Docker Container With Flask

Miguel Grinberg’s Flask Web Development book Chapter 5 shows how to run Flask with SqlAlchemy and a SQLite database. Because SQLite is included in Python, the settings are simple and easy. This post records the steps on how to run a MySQL database in a docker container with Flask (under a Linux Mint OS or Ubuntu).

Install Docker

The first step is to install docker and pull the MySQL container image. This Docker Curriculum website has a nice Docker tutorial.

curl -fsSL https://get.docker.com -o get-docker.sh
sudo sh get-docker.sh 
sudo usermod -aG docker george  # restart after this step

# those steps installs docker-compose, optional
sudo curl -L "https://github.com/docker/compose/releases/download/\
              1.29.1/docker-compose-$(uname -s)-$(uname -m)"\ 
              -o /usr/local/bin/docker-compose
sudo chmod +x /usr/local/bin/docker-compose 
docker-compose

docker pull mysql:latest
docker images

Run Container

How to start running the MySQL container is a little tricky. After some Google searching, I found that this medium article has nice practical examples. I simply create a bash script start_mysql.sh and bash command source start_mysql.sh will start the container. The script includes a -v volume option which maps a directory on a host to the mysql data directory in the container. So the database data files are saved on the host computer.

# start_mysql.sh file
#!/bin/bash
docker run --name=test-mysql \
    --env="MYSQL_ROOT_PASSWORD=pw" \
    -p 3306:3306 \
    -v /home/george/Code/docker/test-mysql/data:/var/lib/mysql \
    -d  \
    mysql:latest

A second bash script mysql-terminal.sh starts a terminal session which runs mysql client inside the container. It will enter the mysql as a root user.

# mysql-terminal.sh file
#!/bin/bash
docker exec -it test-mysql mysql -uroot -ppw

You can create a new db and a user once you are in the mysql client with those commands.

CREATE DATABASE test_db;
USE test_db;
CREATE USER 'newuser'@'%' IDENTIFIED BY 'pw';
GRANT ALL PRIVILEGES ON test_db.* to 'newuser'@'%';

Connect Flask App

Once you have the docker container running, you can connect a Flask app to it. The first step is to install flask-sqlalchemy, pymysql, and cryptography packages in virtual environment.

. venv/bin/activate
pip install flask-sqlalchemy pymysql cryptography

Note the pymysql and cryptography packages are required. I cannot make it working without those packages.

In the flask app python file, have those db settings.

app.config['SQLALCHEMY_DATABASE_URI'] = \
    'mysql+pymysql://newuser:pw@localhost:3306/test_db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False

Then you can run the flask shell and run those commands to test the db connections.

>>>from hello import db
>>>db.create_all()
>>>db.metadata.tables.keys()  # show table names