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Working with our recommended Django application configuration

Our recommended Django application configuration is mentioned in:

The Twelve-factor model adopted for these applications places all configuration in environment variables, so that the application can readily be moved to another host or platform, or set up locally for development. The configuration for:

  • security
  • database
  • media
  • static files

settings is handled by a few simple code snippets in settings.py. In each case, the settings will fall back to safe and secure defaults.

Application container​

In both local and cloud environments, the application will run in a web container, using the same image and exactly the same codebase.

Django server​

In cloud environments: the Dockerfile contains a CMD that starts up Django using the production application gateway server.

In the local environment: the command line in docker-compose.yml starts up Django using the runserver, overriding the CMD in the Dockerfile. If the command line is commented out, docker-compose up will use the application gateway server locally instead.

Database​

In cloud environments: the application will use one of our database clusters.

In the local environment: the application will use a container running the same database.

During the build phase: the database falls back to in-memory SQLite, as there is no database available to connect to, and no configuration variables available from the environment in any case.

Security settings​

Debug mode​

In cloud environments: the application will safely fall back to DEBUG = False.

In the local environment: .env-local supplies a DJANGO_DEBUG variable to allow Django to run in debug mode.

Secret key​

In cloud environments: a random SECRET_KEY variable is always provided and will be used.

In the local environment: where no SECRET_KEY environment variable is provided, the application will fall back to a hard-coded key in settings.py.

Allowed hosts​

In cloud environments: DOMAIN and DOMAIN_ALIASES variable are always provided and will be used.

In the local environment: default values are provided via the DOMAIN_ALIASES environment variable in .env-local.

SECURE_SSL_REDIRECT​

Unless explicitly disabled with a SECURE_SSL_REDIRECT = False environment variable, Django's SECURE_SSL_REDIRECT will apply.

Static files​

In cloud environments: the application gateway server and WhiteNoise are used.

In the local environment: static files are served by the Django runserver. When you instead run the application gateway server locally and enforce DEBUG = False, it can be tested with WhiteNoise in the local environment.

Media files​

In cloud environments: file storage and serving is handled by the S3 instance.

In the local environment: the local filesystem is used for storage, and Django's runserver is used to serve media. If a cloud environment's DEFAULT_STORAGE_DSN is applied in the .env-local file, the local server will use the S3 instance instead.

Database migrations​

In its current state, database migrations are not executed automatically in cloud deployments. To run migrations automatically, add a release command: python manage.py migrate. Alternatively you can run the command manually in the cloud environment using SSH.