Question

How to include OpenCV when building Flask app from Github using App Platform?

I have tried to build my Flask app from my Github repository using the App Platform UI.

I have managed to build the app, as indicated by the build logs, but I am unable to deploy the app, and the deployment log kept on throwing this particular error:

  • ImportError: libGL.so.1: cannot open shared object file: No such file or directory

I have tried changing the dependency from opencv-python to opencv-python-headless, but to no avail, and after some simple search online, I found that OpenCV is not supported by heroku-python-buildpack, which is the default buildpack used by App Platform to build the app.

I am wondering what are the steps which I can take, or files which I have to add to my Github repository, in order for App Platform to be able to compile OpenCV for use with my Flask app.

Any form of help will be appreciated.


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👋 @Occutracker

Great question, I think this would be a good candidate for using Dockerfile based builds.

I hacked together a sample flask app that uses opencv. Disclaimer I don’t have any Python/Flask experience so this might not be best practice.

flask-opencv-streaming sample

A Dockerfile based build will automatically be detected if the Dockerfile exists in the root of the project. My dockerfile looks like:

FROM ubuntu
RUN apt-get update -y --fix-missing --allow-releaseinfo-change
RUN DEBIAN_FRONTEND=noninteractive apt-get install -y python3.6 python3-pip python3-pip python-dev build-essential libgl1-mesa-glx libsm6 libxext6 libglib2.0-0
RUN mkdir /app
WORKDIR /app
COPY . /app/

RUN pip3 install --upgrade pip
RUN pip3 install flask
RUN pip3 install -r requirements.txt
CMD ["python3", "app.py"]

and my DO app spec looks like:

name: flask-opencv-streaming
region: nyc
services:
- dockerfile_path: Dockerfile
  github:
    branch: master
    deploy_on_push: true
    repo: jonfriesen/flask-opencv-streaming
  http_port: 8080
  instance_count: 1
  instance_size_slug: basic-xs
  name: flask-opencv-streaming
  routes:
  - path: /
  source_dir: /