flask

Python Flask example

Create a new directory for this example (or clone this repository with git clone https://github.com/danial-k/docker-intro.git):

mkdir -p docker-intro/node/app
cd docker-intro/node/app

Setting up development container

Start a Python development container with:

docker run \
-it \
--name flask \
--hostname flask \
--mount type=bind,src=`pwd`,dst=/app \
--publish 3800:5000/tcp \
-w //app \
python:3.7 \
bash

Install flask using Python's package manager:

pip install flask

Create a new index.py file with the following content:

from flask import Flask
application = Flask(__name__)

@application.route("/")
def hello():
    return "Hello, World!"

if __name__ == "__main__":
    application.run(host='0.0.0.0')

To run the application with hot-reload enabled:

FLASK_DEBUG=1 FLASK_APP=index.py flask run -h 0.0.0.0

The application should then be available at http://127.0.0.1:3800.

Building deployment container

To publish the application as a self-contained image, use the Dockerfile for this project (placed outside the app directory). This image will use the production-grade gunicorn WSGI server as opposed to the flask development server.

Create a WSGI entry point file wsgi.py:

from index import application

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

docker build -t flask:1.0.0 .

This will send all files in the current directory to the Docker daemon's build context (excluding paths specified in .dockerignore), then create and tag the image. Once the image has been built, run with:

docker run -p 3810:5000 flask:1.0.0

The application should then be available at http://127.0.0.1:3810