mysql.connector.errors.DatabaseError: 2003 (HY000): Can't connect to MySQL server on '127.0.0.1' (111)

Question

I am creating a docker file that contains a flask app and mysql. This should run on localhost for now.

The flask app is running and so as the mysql server. I am able to connect to mysql server. The app is not able to connect to db.

Python code connecting

def establish_connection():
    config = {
        'user': 'root',
        'password': 'root',
        'host': '127.0.0.1',
        'port': '3306',
        'database': 'persist'
    }

    cnx: str = mysql.connector.connect(**config)
    print(cnx)
    return cnx

Dockerfile

FROM python:3.7.4-buster
WORKDIR /stocksite
ENV FLASK_APP main.py
ENV FLASK_RUN_HOST 0.0.0.0
EXPOSE 5000 32000 3306
COPY . .
COPY requirements.txt requirements.txt
RUN pip install -r requirements.txt
COPY . .
CMD ["flask", "run"]

docker-compose.yml

version: '3'
services:
  web:
    build: .
    ports:
      - "5000:5000"

  db:
    image: mysql
    container_name: db
    ports:
      - "32000:3306"
    environment:
      MYSQL_ROOT_PASSWORD: root
    volumes:
      - ./data/db:/docker-entrypoint-initdb.d

I receive the below error:

mysql.connector.errors.DatabaseError: 2003 (HY000): Can't connect to MySQL server on '127.0.0.1' (111)

Answer 1

Docker compose services are available to other services using their name. Your db service can be connected to from your web container using db:3306

config = {
    'user': 'root',
    'password': 'root',
    'host': 'db',
    'port': '3306',
    'database': 'persist'
}

Answer 2

In the docker-compose you map the port 3306 of the db inside the container to the port 32000 on the host machine.

In the app you should use port 32000 not 3306 .

def establish_connection():
config = {
    'user': 'root',
    'password': 'root',
    'host': '127.0.0.1',
    'port': '32000',
    'database': 'persist'
}

cnx: str = mysql.connector.connect(**config)
print(cnx)
return cnx