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.

Asked By: coucou

||

Source

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

Answered By: lepsch

Answer 2

I managed to achieve flask auto reload in docker using docker-compose with the following config:

version: "3"
services:
  web:
    build: ./web
    entrypoint:
      - flask
      - run
      - --host=0.0.0.0
    environment:
      FLASK_DEBUG: 1
      FLASK_APP: ./app.py
    ports: ['5000:5000']
    volumes: ['./web:/app']

You have to manually specify environment variables and entrypoint in the docker compose file in order to achieve auto reload.

Answered By: Radu Cosnita

Answer 3

Assuming your file structure is the below:

Dockerfile: (note WORKING DIR)

FROM python:3.6.5-slim
RUN mkdir -p /home/project/bottle
WORKDIR /home/project/bottle 
COPY requirements.txt .
RUN pip install --upgrade pip --no-cache-dir -r requirements.txt
COPY . .
CMD ["python", "app.py"]

Docker Compose:

version: '3'

services:
  web:
    container_name: web
    volumes:
      - './web:/home/project/bottle/'  <== Local Folder:WORKDIR
    build: ./web
    ports:
      - "8080:8080"

Answered By: ericgu

Answer 4

This is my example:

version: "3.8"

services:
  local-development:
    build:
      context: .
      dockerfile: Dockerfiles/development.Dockerfile
    ports:
      - "5000:5000"
    volumes:
      - .:/code

from flask import Flask

app = Flask(__name__)


@app.route('/')
def hello_world():
    return "hello world"


if __name__ in "__main__":
    app.run(host="0.0.0.0", port=5000, debug=True)

debug=True enables Flask to change as your code changes.

Docker already plugs into your fs events to change the code "in the container".

Answered By: EnduranceI

Answer 5

If the compose is running different services (app and rq, for instance) you need to set up the volumes on both, or it won’t work.

Answered By: ImanolUr

Auto reloading flask server on Docker

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