使用Python连接到Docker容器中的MySQL

Question

I am using pony.orm to connect to mysqldb using a python code:

db.bind(provider='mysql', user=username, password=password, host='0.0.0.0', database=database)

And when I write the docker compose file:

  db:
    image: mariadb
    ports:
      - "3308:3306"
    environment:
      MYSQL_DATABASE: db
      MYSQL_USER: root
      MYSQL_ROOT_PASSWORD: ''

How can I pass the hostname to the python program by giving a value (in environment:) in the docker-compose.yml file ?

If I pass the value there can I access the value through os.environ['PARAM'] in the Python code?

Answer 1

Because you've named your service db in the docker-compose.yaml , you can use that as the host , provided you are on the same network:

db.bind(provider='mysql', user=username, password=password, host='db', database=database)

To ensure you are on that network, in your docker-compose.yaml , at the bottom, you'll want:

networks:
  default:
    external:
      name: <your-network>

And you'll need to create that network before running docker-compose up

docker network create <your-network>

This avoids the need for an environment variable, as the container name will be added to the routing table of the network.

You don't need to define your own network, as docker-compose will handle that for you, but if you prefer to be a bit more explicit, it allows you the flexibility to do so. Normally, you would reserve this for multiple compose solutions that you wanted to join together on a single network, which is not the case here.

It's handled in docker-compose the same way you would do it in vanilla docker :

docker run -d -p 3308:3306 --network <your-network> --name db mariadb
docker run -it --network <your-network> ubuntu bash

# in the shell of the ubuntu container
apt-get update && apt-get install iputils-ping -y
ping -c 5 db

# here you will see the results of ping reaching container db
5 packets transmitted, 5 received, 0% packet loss, time 4093ms

Edit

As a note, per @DavidMaze's comment, the port you will be communicating with is 3306, since that's the port that the container is listening on, not 3308.