python - Auto reloading flask server on Docker

Question

I want my flask server to detect changes in code and reload automatically. I'm running this on docker container. Whenever I change something, I have to build and up again the container. I have no idea where's wrong. This is my first time using flask.

Here's my tree

├── docker-compose.yml
└── web
    ├── Dockerfile
    ├── app.py
    ├── crawler.py
    └── requirements.txt

and code(app.py)

from flask import Flask 
import requests
app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello Flask!!'

if __name__ == '__main__':
    app.run(debug = True, host = '0.0.0.0')

and docker-compose

version: '2'
services:

  web:
    build: ./web
    ports:
     - "5000:5000"
    volumes:
     - ./web:/code

Please give me some advice. Thank you in advance.

Answer 1

Flask supports code reload when in debug mode as you've already done. The problem is that the application is running on a container and this isolates it from the real source code you are developing. Anyway, you can share the source between the running container and the host with volumes on your docker-compose.yaml like this:

Here is the docker-compose.yaml

version: "3"
services:
  web:
    build: ./web
    ports: ['5000:5000']
    volumes: ['./web:/app']

And here the Dockerfile:

FROM python:alpine

EXPOSE 5000

WORKDIR app

COPY * /app/

RUN pip install -r requirements.txt

CMD python app.py