Deploying a minimal flask app in docker - server connection issues

Question

I have an app who\'s only dependency is flask, which runs fine outside docker and binds to the default port 5000. Here is the full source:

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Answer 1

You need to modify the host to 0.0.0.0 in the docker file. This is a minimal example

# Example of Dockerfile

FROM python:3.8.5-alpine3.12

WORKDIR /app

EXPOSE 5000
ENV FLASK_APP=app.py

COPY . /app
RUN pip install -r requirements.txt

ENTRYPOINT [ "flask"]
CMD [ "run", "--host", "0.0.0.0" ]

and the file app.py is

# app.py
from flask import Flask

app = Flask(__name__)

@app.route("/")
def home():
    return "Hello world"


if __name__ == "__main__":
    app.run()

Then compile with

docker build . -t deploy_flask

and run with

docker run -p 5000:5000 -t -i deploy_flask:latest

You can check the response with curl http://127.0.0.1:5000/ -v