🐳Deploying Flask app using Nginx, uWSGI, and Docker

Nginx-uWSGI-Flask

Nginx-uWSGI-Flask is a commonly used server setup for light python web applications or ML applications. Flask, a light web framework, is chained with a web server uWSGI and Nginx as a reverse proxy. Flask is integrated as a callable object for uWSGI to call and run the app. And Nginx and uWSGI communicates via unix socket or tcp port.

             ┌───────────────────────────────────────────────┐
             | server:                                       |
             |                                               |
clients <---------> nginx <---------> uwsgi <--------> flask |
             |                                               |
             └───────────────────────────────────────────────┘

Docker

For easier deployment and migration to different machines or server, let's use Docker. Docker is a container-based platform for building and deploying applications. Docker isolates and virtualizes applications using containers. Unlike virtual machines, containers isolates processes by enabling multiple applications to share the resources of a single instance of the host OS without virtualizing entire operationg system. It is lighter, faster, and efficient than virtual machines. It is possible to create and run containers without Docker, but Docker makes it way easier.

Building a Simple Web Server

Here's how I built the server using Docker on Ubuntu 22.04 LTS I used docker-compose which is a tool for building a multi-container Docker app.

I set nginx to listen to port 5000 and communicate with uwsgi via 5050. Flask will be called by uwsgi as a callable object. Because uwsgi and nginx are executed in different containers, pot 5050 is used instead of unix socket.

             ┌───────────────────────────────────────────────┐
             | server:                                       |
             |                                               |
clients <---------> nginx <---------> uwsgi <--------> flask |
           5000               5050        callable object    |
             └───────────────────────────────────────────────┘

Installing and setting up Docker and Docker-compose

Install docker.

$ sudo apt-get install curl
$ curl -s https://get.docker.com | sudo sh

Add user to the docker group.

$ sudo usermod -aG docker $USER

Install docker-compose.

$ sudo curl -L "https://github.com/docker/compose/releases/download/v2.8.0/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
$ sudo chmod +x /usr/local/bin/docker-compose

File Structure

server
├── docker-compose.yml
├── flask
│ ├── Dockerfile
│ ├── app.py
│ ├── requirements.txt
│ └── uwsgi.ini
└── nginx
    ├── Dockerfile
    └── nginx.conf

./flask

app.py

from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello():
    return "hello docker🐳"
        

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

requirements.txt

flask==2.1.*
click==8.0.*
itsdangerous==2.1.*
jinja2==3.0.*
markupsafe==2.1.*
werkzeug==2.2.*
uwsgi==2.0.*

Dockerfile

FROM python:3

WORKDIR /app

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

CMD ["uwsgi","uwsgi.ini"]

uwsgi.ini

[uwsgi]
wsgi-file = app.py
callable = app
socket = :5050
processes = 2
threads = 2
master = true
vacum = true
chmod-socket = 660
die-on-term = true

./nginx

nginx.conf

server {

	listen 5000;
	
	location / {
		include uwsgi_params;
		uwsgi_pass flask:5050;
	}
}

Dockerfile

FROM nginx

RUN rm /etc/nginx/conf.d/default.conf

COPY nginx.conf /etc/nginx/conf.d/

docker-compose.yml

version: "3.7"

services: 
    flask:
        build: ./flask
        container_name: flask
        restart: always
        environment: 
            - APP_NAME=FlaskTest
        expose:
            - 5050

    nginx:
        build: ./nginx
        container_name: nginx
        restart: always
        ports:
            - "5000:5000"

Build and start containers

$ docker-compose up -d --build

• -d: run containers in the background
• --build: build images before starting containers

Open in browser

Now, let's check if our web server is working properly. Open your server domain or IP with port 5000": http://example.com:5000. Your web server should return hello docker🐳

Links

• github