scalable-ubuntu-flask-gunicorn-nginx

Description:

This solution provides scaffolding for a scalable Python Flask web application on Ubuntu 18.04 using Gunicorn and NGINX. The web application also leverages Virtualenv to leverage isolated Python environments.

Deployment:

By executing the setup.sh script (instructions below) you will have a "Hello World" web application which leverages Flask a microframework for Python and Gunicorn acting as a webserver with NGINX serving as a reverse proxy. Upon successful deployment and if port 80 is open to you, going to the server IP in a browser will show you the message "Hello World" in red.

Requirement:

Ubuntu 18.04 server
A user named ubuntu on the Ubuntu Server with sudo privileges

Setup:

SSH onto your server and clone the repo into your /home/ubuntu directory
Go into the setup directory and run the setup.sh script

git clone https://github.com/nethacker/scalable-ubuntu-flask-gunicorn-nginx.git

cd scalable-ubuntu-flask-gunicorn-nginx/setup

bash setup.sh

What is the setup.sh script doing?

Below are the general steps the setup.sh file is executing. Please see the actual setup.sh file in the setup directory for literal commands.

Ubuntu global setup

Updating ubuntu packages
Installing ntpdate and updating time against pool.ntp.org
Installing nptd to maintain time avoiding drift
Installing Python3 dependencies to support virtualenv
Installing NGINX

Ubuntu user setup

Updating .bashrc of the ubuntu user to support virtualenv for development

App dependencies setup

Creating a directory structure for our test application named app01
Leverage virtualenv to install Python3 packages in a virtual environment.
Install gunicorn a webserver, flask a microframework, setproctitle for process friendly name
Copy test application app01 to appropriate location from repo hierarchy
Copy test application app01 gunicorn webserver config to appropriate location from repo hierarchy

Systemd setup

Copy test application app01 systemd bootstrap config to appropriate location from repo hierarchy
Start test application app01 using systemd
Configure test application app01 to start after reboots

NGINX Setup

Copy test application app01 nginx config to appropriate location from repo hierarchy
Delete default nginx config
Enable nginx site and restart nginx

Performance notes:

Gunicorn is configured with 5 workers leveraging threading (2 per worker) each worker can handle 1000 connections. Typical formula is 2 workers per cpu core +1 worker
Gunicorn Timeout value is set to 30 seconds and keepalive is set to 2 seconds
NGINX is set to use 8 buffers and 24K size per buffer when reading a response from the proxied server for a single connection
NGINX is set to 4k buffer size used for headers from the pool
NGINX worker_processes are set to "auto" for detecting number of cores and setting that value