Dockerizing a Django Web Application

Hey there, welcome! In this article, we will discuss the steps that details how to configure Django to run on Docker.

Docker gives you the ability to run your applications within a controlled environment, known as a container, built according to the instructions you define. A container leverages your machine's resources much like a traditional virtual machine (VM). However, containers differ greatly from traditional virtual machines in terms of system resources.

Prerequisites

Before you begin this tutorial, ensure the following is installed to your system:

• Python 3.7 or newer
• Python package manager (pip)
• Docker

Setting Up a Django web application

Let's jump directly to the application that we'll dockerize. We will be creating a Docker image for the django todo app that we have already created.

1. Go to the django_todo_app repository.

2. Fork/Clone

3. Create and activate a virtual environment, check reference link:

   python -m venv env && .\env\Scripts\activate   

4. Install all the required dependencies for the project to run.

   (env) pip install -r requirements.txt

5. To initialize a local test database and get rid of the warnings run:

   python manage.py makemigrations
   python manage.py migrate

6. Run the app to verify that nothing is broken and the app runs without errors.

   (env) python manage.py runserver

Creating a Dockerfile

A Dockerfile is a text file that contains instructions on how the Docker image will be built. A Dockerfile contains the directives below.

• FROM: Sets the base image from which the Docker container will be built.

• WORKDIR: Sets the working directory in the image created.

• RUN: Executes commands in the container.

• COPY: Copies files from the file system into the container.

• CMD: Sets the executable commands within the container.

In the root project directory, create a file with the name Dockerfile with no file extension and add the code below.

# pull the official base image

# for windows containers
# FROM python:3.6.3-windowsservercore-ltsc2016

# for linux containers
FROM python:3.8.3-alpine

# set environment variables
ENV PYTHONUNBUFFERED=1
ENV PYTHONDONTWRITEBYTECODE=1

# set work directory
WORKDIR /code

# install dependencies
COPY requirements.txt /code/
RUN pip install -r requirements.txt

# copy project
COPY . /code/

EXPOSE 8000

CMD ["python", "manage.py", "runserver", "0.0.0.0:8000"]

FROM python:3.8.3-alpine sets the base image from which the Docker container will be created.

ENV PYTHONUNBUFFERED=1 ensures that Python output is logged to the terminal, making it possible to monitor Django logs in realtime.

ENV PYTHONDONTWRITEBYTECODE=1 prevents Python from copying pyc files to the container.

WORKDIR /code sets the working directory inside the container to /code.

COPY requirements.txt /code/ copies the requirements.txt file into the work directory in the container.

RUN pip install -r requirements.txt installs all the required modules for the application to run in the container.

COPY . /code/ copies all the project source code to the working directory in the container.

EXPOSE 8000 exposes port 8000 for access from other applications.

CMD ["python", "manage.py", "runserver", "0.0.0.0:8000"] sets the executable commands in the container.

Note: Create .dockerignore file in the root project directory to reduce the image size by excluding files and folders that aren't needed such as .git, .vscode, and __pycache__.

Building the Docker image

To build the Docker image from the Dockerfile, run the command below.

docker build --tag django_todo_app:latest .

--tag sets the tag for the image, e.g. latest in our image.

. indicates that the Dockerfile is within the current working directory.

To list all the images on your computer, execute the command below.

$ docker images

REPOSITORY        TAG            IMAGE ID       CREATED         SIZE
django_todo_app   latest         7fhgyvbjg1b9   1 hours ago     124MB

Creating and running the Docker Container

To build and run a Docker container from the Docker image we created above, run the command below.

docker run --name django_todo_app -d -p 8000:8000 django_todo_app:latest

--name sets the name of the Docker container.

-d makes the image run in detached mode. The image is capable of running in the background.

-p 8000:8000 maps port 8000 in the Docker container to port 8000 in localhost.

django_todo_app: latest specifies which image is used to build the Docker container.

To list all the running Docker containers, execute the command below.

docker ps

Navigate to http://localhost:8000/ and confirm if the app is running in the container.

Publishing the Docker image to Docker Hub

Docker Hub is a repository of container images that can be used to create Docker containers.

To push docker image to the repository, executes below commands.

docker login

docker tag django_todo_app:latest <Docker ID>/django_todo_app:latest

docker push <Docker ID>/django_todo_app:latest

docker login command logs you into your Docker Hub account on the command line, making it possible to push Docker images to Docker Hub.

docker tag django_todo_app: latest <Docker ID>/django_todo_app: latest command modifies the tag of our local Docker image to include the Docker ID.

docker push <Docker ID>/django_todo_app: latest pushes the image to Docker Hub repository we created earlier.

Visit Docker Hub and create an account if you don't have one.

Conclusion

In this article, we walked through how to containerize a Django web application. I hope this was helpful to you.

You can refer to the official Docker documentation. It explains in depth every thing about Docker you need to know.

You can find the code in the dockerize_django_app repo.

Thanks for reading!