error R10 when deploying flask app with docker to heroku

Question

my python app runs fine as a local docker container, but when trying to deploy on heroku, i get this error:

Error R10 (Boot timeout) -> Web process failed to bind to $PORT within 60 seconds of launch

if __name__ == '__main__':
    from os import environ
    app.run(host='0.0.0.0', port=environ.get('PORT', 5000))

my dockerfile:

FROM python:3

# set a directory for the app
WORKDIR /usr/src/app

# copy all the files to the container
COPY . .

# install dependencies
RUN pip3 install --no-cache-dir -r requirements.txt

# heroku doesn't need this
# EXPOSE 5000

# run the command
CMD ["python3", "app.py"]

i thought it might have to do with the app being a bit too big for dyno=1 and that i'd have to pay to increase the dynos? but I'm not sure..

thanks in advance!!

Answer 1

The application cannot bind to the Heroku port, nothing to do with the Dyno. Try to cast to int the port before assigning it

 port = int(os.environ.get("PORT", 5000))