[PYTHON] Learn how to use Docker through building a Django + MySQL environment

Introduction

After studying ** Ruby ** and ** Rails ** at a programming school, I started touching ** Python ** and ** Django ** for personal interest, but now I'm dealing with ** Django ** The first personal impression I had when I first started was that "** (for implementing features) ** preparation before starting to write code is more difficult than Rails **".

In the future, in order to improve the efficiency of personally creating various apps and moving hands to put into practice new lessons, it is necessary to get used to the environment construction work itself, as well as ** functions. I felt that it was necessary to prepare myself to be able to concentrate on implementing and practicing what I learned **, so I decided to learn about container technology (handling).

The purpose of this article (group) is ** to learn how to use Docker through Django + MySQL environment construction **, and ** to create a Django project template that you can reuse for yourself * *is.

By following the meaning of each description as carefully as possible, I would like to aim to acquire reproducible knowledge even when dealing with different languages / frameworks. It is a memorandum by Docker beginners, but please keep in touch if you like.

Execution environment

Usage environment

- MacOS catalina 10.15.6
- Docker 19.03.8
    (- docker-desktop for Mac 2.2.0.3)
- pyenv 1.2.20

Environment to build

- Python 3.7.7
- Django 3.0.8
- MySQL 5.7.31

table of contents

1. ** Prepare virtual environment using venv ** Use venv to prepare a specific version of Python environment. It also creates a Django project.

2. ** Consider the description of Dockerfile ** Think about ** Docker image ** through the description in the Dockerfile.

3. ** Consider the description of docker-compose.yml ** Create docker-compose.yml and learn about ** Docker container ** through Django and the MySQL settings that connect it.

4. ** Edit the configuration file and execute docker-compose up ** Make various settings on the Django side and execute $ docker-compose up.

5. ** Adjust container launch timing between dependent services ** In the previous process, ** under certain conditions, the MySQL container may not launch before the Django container and the connection may fail **. We aim to solve the problem by creating a dedicated Python file **.

6. ** Development work ** All you have to do is focus on your development work, making changes as the situation demands.

Source code

The source code of the main related files is summarized here in advance. The description contents of each file will be explained in ** Articles by process ** mentioned above.

Dockerfile

FROM python:3.7
ENV PYTHONUNBUFFERED 1

RUN mkdir /code
WORKDIR /code

COPY requirements.txt /code/
RUN pip install --upgrade pip
RUN pip install -r requirements.txt

COPY . /code/

EXPOSE 8000

docker-compose.yml

version: "3"
services:
    web:
        container_name: djst_django
        build: .
        restart: always
        command: >
            bash -c "
                pip install -r requirements.txt &&
                python config/wait_for_db.py &&
                python manage.py runserver 0.0.0.0:8000
            "
        working_dir: /code
        ports: 
            - 172.0.0.1:8000:8000
        volumes:
            - .:/code
        depends_on:
            - db
    db:
        container_name: djst_mysql
        image: mysql:5.7
        restart: always
        environment: 
            MYSQL_DATABASE: $DB_NAME
            MYSQL_USER: $DB_USER
            MYSQL_PASSWORD: $DB_PASSWORD
            MYSQL_ROOT_PASSWORD: $DB_ROOT_PASSWORD
            MYSQL_TCP_PORT: 3306
            TZ: 'Asia/Tokyo'
        volumes: 
            - ./mysql/data:/var/lib/mysql/
            - ./mysql/my.cnf:/etc/mysql/conf.d/my.cnf
        ports: 
            - 3306:3306

config/wait_for_db.py

import os
import MySQLdb
from time import sleep
from pathlib import Path

os.chdir(Path(__file__).parent)
from local_settings import DB_NAME, DB_USER, DB_PASSWORD


count_to_try = 0
LIMIT_OF_COUNT = 20 #Adjust the value as needed


def check_connection(count, limit):
    """
    docker-Compose up Runtime function for time adjustment.
    """
    try:
        conn = MySQLdb.connect(
            unix_socket = "/var/run/mysqld/mysqld.sock",
            user=DB_USER,
            passwd=DB_PASSWORD,
            host="db",
            port=3306,
            db=DB_NAME,
        )
    except MySQLdb._exceptions.OperationalError as e:
        count += 1
        print("Waiting for MySQL... (", count, "/ 20 )")
        sleep(3)
        if count < limit:
            check_connection(count, limit)
        else:
            print(e)
            print("Failed to connect mySQL.")
    else:
        print("Connected!\n")
        conn.close()
        exit()


if __name__ == "__main__":
    check_connection(count_to_try, LIMIT_OF_COUNT)

If you have any suggestions, I would appreciate it if you could comment. I look forward to working with you.