How can I make packages installed using Poetry accessible in Docker?

Question

I have a Django REST framework API that I'm trying to run in Docker.The project uses Poetry 1.1.12. When running, I can see that Poetry is installed correctly, and that Poetry installs the packages in my pyproject.toml , including Django. I'm using supervisor to run the API using Daphne, as well as some other tasks (like collecting static files).

However, when supervisor runs the app, I get:

Traceback (most recent call last):
  File "/home/docker/api/manage.py", line 22, in <module>
    main()
  File "/home/docker/api/manage.py", line 13, in main
    raise ImportError(
ImportError: Couldn't import Django. Are you sure it's installed and available on your PYTHONPATH environment variable? Did you forget to activate a virtual environment?
Traceback (most recent call last):
  File "/home/docker/api/manage.py", line 11, in main
    from django.core.management import execute_from_command_line
ModuleNotFoundError: No module named 'django'

Notice how I set POETRY_VIRTUALENVS_CREATE=false and ENV PATH="/root/.local/bin:${PATH}" . According to the poetry installation script, that is the path that needs to be added to PATH.

Here is an abridged versioned of my Dockerfile:

FROM python:3.9-slim-buster
ENV PATH="/root/.local/bin:${PATH}"

RUN apt-get update && apt-get install -y --no-install-recommends \
    ... \
    curl \
    supervisor \
    && curl -sSL 'https://install.python-poetry.org' | python - && poetry --version \
    && apt-get remove -y curl \
    && apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false \
    && apt-get clean -y && rm -rf /var/lib/apt/lists/* \
    && rm -rf /var/lib/apt/lists/*

COPY poetry.lock pyproject.toml /home/docker/api/

WORKDIR /home/docker/api

RUN if [ "$DEBUG" = "false" ] \
    ; then POETRY_VIRTUALENVS_CREATE=false poetry install --no-dev --no-interaction --no-ansi -vvv --extras "production" \
    ; else POETRY_VIRTUALENVS_CREATE=false poetry install --no-interaction --no-ansi -vvv --extras "production" \
    ; fi

COPY . /home/docker/api/
COPY .docker/services/api/files/supervisor.conf /etc/supervisor/conf.d/

CMD ["supervisord", "-n"]

Which is pretty much how I see others doing it. Any ideas?

Answer 1

Could it be because of a missing DJANGO_SETTINGS_MODULE environment variable?

Answer 2

Poetry documents itself as trying very very hard to always run inside a virtual environment. However, a Docker container is itself isolation from other Pythons, and it's normal (and easiest) to install packages in the "system" Python.

There is a poetry export command that can convert Poetry's files to a normal pip requirements.txt file, and from there you can RUN pip install in your Dockerfile. You could use a multi-stage Dockerfile to generate that file without actually including Poetry in your main image.

FROM python:3.9-slim-buster AS poetry
RUN pip install poetry
WORKDIR /app
COPY pyproject.toml poetry.lock .
RUN poetry export -f requirements.txt --output requirements.txt

FROM python:3.9-slim-buster
WORKDIR /app
COPY --from=poetry /app/requirements.txt .
RUN pip install -r requirements.txt
COPY . .
CMD ["./manage.py", "runserver", "0.0.0.0:8000"]

django should show up in the generated requirements.txt file, and since pip install installs it as a "normal" "system" Python package, your application should be able to see it normally, without tweaking environment variables or other settings.