Multistage docker build with venv error: "ModuleNotFoundError: No module named 'flask'"

[rosario-vandebron]

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Example Code

FROM tiangolo/meinheld-gunicorn:python3.9-alpine3.13-2024-03-11 AS app
ENV PATH="/venv/bin:$PATH"
ENV PYTHONPATH="/venv/bin:$PATH"

ENV PORT 5000

EXPOSE 5000

ENV MODULE_NAME="bmprelive.apps.internal.manage"
ENV GUNICORN_CONF="/app/bmprelive/apps/internal/gunicorn_conf.py"

# copy in Python environment
COPY --from=builder /venv /venv

Description

I am trying to build a multistage docker image starting from tiangolo/meinheld-gunicorn:python3.9-alpine3.13-2024-03-11 . I've installed all my dependencies using pip and virtualenv. After all dependencies are installed I simply do in my dockerfile

FROM tiangolo/meinheld-gunicorn:python3.9-alpine3.13-2024-03-11 AS app
ENV PATH="/venv/bin:$PATH"
ENV PYTHONPATH="/venv/bin:$PATH"

ENV PORT 5000

EXPOSE 5000

ENV MODULE_NAME="bmprelive.apps.internal.manage"
ENV GUNICORN_CONF="/app/bmprelive/apps/internal/gunicorn_conf.py"

# copy in Python environment
COPY --from=builder /venv /venv

but then when I try to run the container I see this error:

File "/app/bmprelive/apps/internal/__init__.py", line 2, in <module>
    from flask import Flask
ModuleNotFoundError: No module named 'flask'
[2024-11-18 21:40:40 +0000] [9] [INFO] Worker exiting (pid: 9)
[2024-11-18 21:40:40 +0000] [10] [ERROR] Exception in worker process
Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/gunicorn/arbiter.py", line 589, in spawn_worker
    worker.init_process()
  File "/usr/local/lib/python3.9/site-packages/gunicorn/workers/base.py", line 134, in init_process
    self.load_wsgi()

Looking at the interpreter used I've noticed that it is using the system python and not the venv one. Further investigation confirmed that gunicorn has been installed globally from your image.

Now the question is: Is there a way to use multistage build along with your image? Is there a way to tell which python interpreter the workers should use ? Or maybe I can do a multistage build without venv but I have no experience with it. Can you help?

Operating System

Linux

Operating System Details

Docker

Python Version

3.9

Additional Context

No response