Dockerfile#
If a deploy_with_docker option is selected when creating your django-cookiecutter, your new Django Cookiecutter Project includes a Dockerfile to build a docker image.
The Docker file is modified from the original adaption Here’s a Production-Ready Dockerfile for Your Python/Django App [1].
See a list of further reading in the FOOTNOTES.
Structure#
The Dockerfile is composed of two main areas to reduce the size of the final production image.
A compile image.
FROM python:3.9-slim-bullseye AS compile-image
A production image.
Once the compile-image has completed its build, the production-image copies only what is required to run a production image.
FROM python:3.9-slim-bullseye AS production-image
Environment Variables#
PYTHONDONTWRITEBYTECODE#
The Python interpreter, by default, writes bytecode (.pyc) files to disk when executing code.
The (.pyc) files should not be checked into source control.
Setting PYTHONDONTWRITEBYTECODE to 1 ensures Python will no longer write bytecode files (.pyc) to disk. Reducing the size of your Docker image.
PYTHONUNBUFFERED#
Setting PYTHONUNBUFFERED to 1 ensures the Python output is sent straight to the terminal, allowing you to see the output of your Django logs in real-time.
Also, if the python application crashes, this ensures no partial output is held in a buffer and never sent to the terminal.
ENV PYTHONDONTWRITEBYTECODE 1
ENV PYTHONUNBUFFERED 1
uWSGI#
WSGI [2] (pronounced wiz-gee) stands for Web Server Gateway Interface, and it’s a specification for the software interface between a web server and a Python application.
uWSGI [3] is a popular web server that implements the WSGI standard.
uwsgi [4] is a binary protocol used by uWSGI and mainly works on TCP.
The following ENV_VARS are for configuring the uWSGI server. These shouldn’t need changing; however, if you wish to customise your Django application further, you can read about uWSGI options [5] or uWSGI HTTP [6].
# Location of your django project wsg.py file.
ENV UWSGI_WSGI_FILE=django_project/wsgi.py
ENV UWSGI_HTTP=:8000 UWSGI_MASTER=1 UWSGI_HTTP_AUTO_CHUNKED=1 UWSGI_HTTP_KEEPALIVE=1 UWSGI_LAZY_APPS=1
ENV UWSGI_WORKERS=2 UWSGI_THREADS=4
ENV UWSGI_STATIC_MAP="/static/=/code/static/" UWSGI_STATIC_EXPIRES_URI="/static/.*\.[a-f0-9]{12,}\.(css|js|png|jpg|jpeg|gif|ico|woff|ttf|otf|svg|scss|map|txt) 315360000"
The Art of Graceful Reloading [7] provides information about reloading your Django application. See Dealing with ultra-lazy apps (like Django) in that article for more details if you are experiencing slow application reloads.
If your django project needs nginx as well for heavy loads see this tutorial Setting up Django and your web server with uWSGI and nginx [8].
nginx [9] (pronounced engine-x) is a free, open-source, high-performance HTTP server, reverse proxy and IMAP/POP3 proxy server.
Run Commands#
User#
By default, Docker containers run as the root user. Running a Docker container as root is insecure in production and increases the ability for a Docker escalation attack [10].
Setting an APP_User reduces the ability for bad actors to do damage, and setting WORKDIR to APP_USER reduces file access permission problems.
ARG APP_USER=django
RUN groupadd -r ${APP_USER} \
&& useradd -m --no-log-init -r -g ${APP_USER} ${APP_USER}
WORKDIR /home/${APP_USER}
Footnotes