Multi-stage Docker build with Poetry and venv

Do not disable virtualenv creation. Virtualenvs serve a purpose in Docker builds, because they provide an elegant way to leverage multi-stage builds. In a nutshell, your build stage installs everything into the virtualenv, and the final stage just copies the virtualenv over into a small image.

Use poetry export and install your pinned requirements first, before copying your code. This will allow you to use the Docker build cache, and never reinstall dependencies just because you changed a line in your code.

Do not use poetry install to install your code, because it will perform an editable install. Instead, use poetry build to build a wheel, and then pip-install that into your virtualenv. (Thanks to PEP 517, this whole process could also be performed with a simple pip install ., but due to build isolation you would end up installing another copy of Poetry.)

Here's an example Dockerfile installing a Flask app into an Alpine image, with a dependency on Postgres. This example uses an entrypoint script to activate the virtualenv. But generally, you should be fine without an entrypoint script because you can simply reference the Python binary at /venv/bin/python in your CMD instruction.

Dockerfile

FROM python:3.7.6-alpine3.11 as base

ENV PYTHONFAULTHANDLER=1 \
    PYTHONHASHSEED=random \
    PYTHONUNBUFFERED=1

WORKDIR /app

FROM base as builder

ENV PIP_DEFAULT_TIMEOUT=100 \
    PIP_DISABLE_PIP_VERSION_CHECK=1 \
    PIP_NO_CACHE_DIR=1 \
    POETRY_VERSION=1.0.5

RUN apk add --no-cache gcc libffi-dev musl-dev postgresql-dev
RUN pip install "poetry==$POETRY_VERSION"
RUN python -m venv /venv

COPY pyproject.toml poetry.lock ./
RUN poetry export -f requirements.txt | /venv/bin/pip install -r /dev/stdin

COPY . .
RUN poetry build && /venv/bin/pip install dist/*.whl

FROM base as final

RUN apk add --no-cache libffi libpq
COPY --from=builder /venv /venv
COPY docker-entrypoint.sh wsgi.py ./
CMD ["./docker-entrypoint.sh"]

docker-entrypoint.sh

#!/bin/sh

set -e

. /venv/bin/activate

while ! flask db upgrade
do
     echo "Retry..."
     sleep 1
done

exec gunicorn --bind 0.0.0.0:5000 --forwarded-allow-ips='*' wsgi:app

wsgi.py

import your_app

app = your_app.create_app()