Docker Compose with Django and Postgres

Introduction

This quick-start guide demonstrates how to use Docker Compose to set up and run a simple Django/PostgreSQL app. This is a docker's official tutorial. Link.

Define the project components

For this project, you need to create a Dockerfile, a Python dependencies file 'requirements.txt', and a docker-compose.yml file. (You can use either a .yml or .yaml extension for this file.)

Create an emplty project directory. You can name this directory something easy for you to remember. This directory is the context for your application image. The directory should only contain resources to build that image.
Create a new file called Dockerfile in your project directory. The Dockerfile defines an application's image content via one or more build commands that configure that image. Once built, you can run the image in a container. For more information on Dockerfile. See the Docker user guide here and the Dockerfile reference here for more information.
Add the following content to the Dockerfile.

FROM python:3
ENV PYTHONUNBUFFERED=1
WORKDIR /code
COPY requirements.txt /code/
RUN pip install -r requirements.txt
COPY . /code/

This Dockerfile stars witha python 3 parent image. The parent image is modified by adding a new code directory. The parent image is further modified by installing Python requirements defined in the requirements.txt file.

Save and close the Dockerfile.
Create a requirements.txt in your project directory. This file is used by the RUN pip install -r requirements.txt command in your Dockerfile.
Add the required software in the file.

Django >=3.0,<4.0
psycopg2-binary>=2.8

Save and close the requirements.txt file.
Create a file called docker-compose.yml in your project directory. The docker-compose.yml file describes the services that make your app. In this example, those services are a web and a database. The compose file also describes which Docker images these services use, how they link together, and any volumes they might need to be mounted inside the containers. Finally, the docker-compose.yml file describes which ports these services expose. See the docker-compose.yml reference for more information on how this file works.
Add the following configuration to the file.

version: "3.9"

services:
    db:
        image: postgres
        environment:
            - POSTGRES_DB=postgres
            - POSTGRES_USER=postgres
            - POSTGRES_PASSWORD=postgres
    web:
        build: .
        command: python manage.py runserver 0.0.0.0:8000
        volumes:
            - .:/code
        ports:
            - "8000:8000"
        depends_on:
            - db

This file defines two services: The db service and the web service.

Note:

This uses the build in development server to run your application on port 8000. Do not use this in a production environment. For more information, see Django documentation here.

Create a Django project

In this step, you create a Django starter project by building the image from build context defined in the previous procedure.

Change to the root of your project directory.
Create the Django project by running the docker-compose run command as follows.

docker-compose run web django-admin startproject composeexample .

This instructs Comose to run django-admin startproject composeexample in a container, using the web service's image and configuration. Because the web image doesn't exist yet, Compose builds it from the current directory, as specified by the build: . line in docker-compose.yml.

Once the web service is built, Compose runs it and executes the django-admin startproject command in the container. This command instructs Django to create a set of files and directories representing a Django project.

After the docker-compose command completes, list the contents of your project.

ls -l

Output will look like:

$ ls -l

drwxr-xr-x 2 root   root   composeexample
-rw-rw-r-- 1 user   user   docker-compose.yml
-rw-rw-r-- 1 user   user   Dockerfile
-rwxr-xr-x 1 root   root   manage.py
-rw-rw-r-- 1 user   user   requirements.txt

If you are running Docker on Linux, the files django-admin created by root. This happens because the container runs as the root user. Change the ownership of the new files.

sudo chown -R $USER:$USER .

If you are running Docker on Mac or Windows, you should already have ownership of all files, including those generated by django-admin. List the files just to verify this.

$ ls -l

total 32
-rw-r--r--  1 user  staff  145 Feb 13 23:00 Dockerfile
drwxr-xr-x  6 user  staff  204 Feb 13 23:07 composeexample
-rw-r--r--  1 user  staff  159 Feb 13 23:02 docker-compose.yml
-rwxr-xr-x  1 user  staff  257 Feb 13 23:07 manage.py
-rw-r--r--  1 user  staff   16 Feb 13 23:01 requirements.txt

Connect the database

In this section, you set up the database connection for Django.

In your project directory, edit the composeexample/settings.py filie.
Replace the DATABASES = ... with the following:

DATABASES={
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': 'postgres',
        'USER': 'postgres',
        'PASSWORD': 'postgres',
        'HOST': 'db',
        'PORT': 5432,
    }
}

These settings are determined by the postgres Docker image specified in docker-compose.yml.

Save and close the file.
Run the docker-compose up command from the top level directory for your project.

$ docker-compose up

djangosample_db_1 is up-to-date
Creating djangosample_web_1 ...
Creating djangosample_web_1 ... done
Attaching to djangosample_db_1, djangosample_web_1
db_1   | The files belonging to this database system will be owned by user "postgres".
db_1   | This user must also own the server process.
db_1   |
db_1   | The database cluster will be initialized with locale "en_US.utf8".
db_1   | The default database encoding has accordingly been set to "UTF8".
db_1   | The default text search configuration will be set to "english".

. . .

web_1  | July 30, 2020 - 18:35:38
web_1  | Django version 3.0.8, using settings 'composeexample.settings'
web_1  | Starting development server at http://0.0.0.0:8000/
web_1  | Quit the server with CONTROL-C.

At this point, your django app should be running at port 8000 on your Docker host. Go to http://localhost:8000 on a web browser to see the Django welcome page.

Note

On certain windows(Windows 10), you might need to edit ALLOWED_HOSTS inside settings.py and add your Docker host name or IP address to the list. For demo purposes, you can set the value to: ALLOWED_HOSTS=['*']. This value is NOT safe for production usage. Refer to the Django documentation for more information.

List running containers. In another terminal window, list the running Docker processes with the docker container ls command.
Shut down services and clean up by using either of these methods:

Stop the application by typing Ctrl+C in the same shell in where you started it:

Gracefully stopping... (press Ctrl+C again to force)
Killing test_web_1 ... done
Killing test_db_1 ... done

Or, for a more elegant shutdown, switch to a different shell, and run docker-compose down from the top level of your Django sample project directory.

$ docker-compose down

Stopping django_web_1 ... done
Stopping django_db_1 ... done
Removing django_web_1 ... done
Removing django_web_run_1 ... done
Removing django_db_1 ... done
Removing network django_default

Once you've shut down the app, you can safely remove the Django project directory (for example, rm -rf django).

elabdesunil / docker-compose-django-postgres