Where to run collectstatic when deploying django app to heroku using docker? - django

Question

I am deploying a Django app to Heroku using Docker. When I put RUN manage.py collectstatic --noinput in the Dockerfile, it fails because there is no value set for the environment variable DJANGO_SECRET_KEY. My understanding is that this is because config vars aren't available during build time.
When I run collectstatic as a release command, it works without error, and successfully copies the static files. However, when I hit the app url, it returns a 500 error because the static files can't be found. I believe this is because the release command is run as a dyno on an ephemeral filesystem, and the copied files are therefore not found.
It seems to be a catch-22. Putting collectstatic in the Dockerfile fails because there are no config variables available, but putting it as a release command fails because only file changes from the build phase are saved?
What to do?
Here are my collectstatic settings in settings.py
MIDDLEWARE = [
'django.middleware.security.SecurityMiddleware',
'whitenoise.middleware.WhiteNoiseMiddleware',
...
]
...
STATIC_ROOT = os.path.join(BASE_DIR, 'staticfiles')
STATIC_URL = '/static/'
STATICFILES_DIRS = (
os.path.join(BASE_DIR, 'static'),
)
STATICFILES_STORAGE = 'backend.storage.WhiteNoiseStaticFilesStorage'
Dockerfile
# Pull base image
FROM python:3.7-slim
# Set environment varibles
ENV PYTHONDONTWRITEBYTECODE 1
ENV PYTHONUNBUFFERED 1
# Set work directory
RUN mkdir /code
WORKDIR /code
# Install dependencies
RUN pip install pipenv
COPY Pipfile Pipfile.lock /code/
RUN pipenv install --system
# Copy project
COPY . /code/
## collect static files
RUN mkdir backend/staticfiles
# This fails because DJANGO_SECRET_KEY can't be empty
RUN python manage.py --noinput
heroku.yml
build:
docker:
web: Dockerfile
run:
web: gunicorn backend.config.wsgi:application --bind 0.0.0.0:$PORT

Answer 1

After confirming with Heroku support, this does indeed appear to be a bit of a catch-22.
The solution was to put collectstatic in the Dockerfile so that it runs during build time and the files persist.
We got around not having a secret key config var by setting a default secret key using the get_random_secret_key function from Django.
The run phase uses the secret key from the Heroku config vars, so we aren't actually changing the secret key every time -- the default only applies to the build process. collectstatic doesn't index on the secret key, so this is fine.
In settings.py
from django.core.management.utils import get_random_secret_key
...
SECRET_KEY = os.getenv('DJANGO_SECRET_KEY', default=get_random_secret_key())

Answer 2

I don't use heroku so can't test, but you should be able to run collect static before you run the app;
Dockerfile
# Pull base image
FROM python:3.7-slim
# Set environment varibles
ENV PYTHONDONTWRITEBYTECODE 1
ENV PYTHONUNBUFFERED 1
# Set work directory
WORKDIR /code/
# Install dependencies
RUN pip install pipenv
COPY Pipfile Pipfile.lock .
RUN pipenv install --system
# Copy project
COPY . .
# Collect static files
RUN python manage.py collectstatic --noinput
# run gunicorn
CMD gunicorn hello_django.wsgi:application --bind 0.0.0.0:$PORT
You could also not run collectstatic in your dockerfile, or event run the application because these can be ran by heroku.yml, for example;
build:
docker:
web: Dockerfile
config:
DJANGO_SETTINGS_MODULE: project.settings
run:
web: gunicorn backend.config.wsgi:application --bind 0.0.0.0:$PORT
release:
image: web
command:
- python manage.py collectstatic --noinput
You also shouldn't need to mkdir for your working directory. Just set WORKDIR /code/ early in your dockerfile and after that things will run based on that directory.
There's a decent article on this here; https://testdriven.io/blog/deploying-django-to-heroku-with-docker/

Answer 3

You can prefix commands with dummy environment variables
RUN DJANGO_SECRET_KEY=secret python manage.py collectstatic --no-input