This tutorial will guide you through the process of deploying a Flask application on a VPS using Gunicorn as the WSGI server and Nginx as the reverse proxy. We will use pipreqs to manage Python dependencies and set up HTTPS using Let's Encrypt.
Prerequisites
- A Flask application ready to be deployed.
- Access to a VPS (e.g., Ubuntu 20.04).
- A registered domain name.
- Basic knowledge of Linux command line operations.
Step 1: Set Up the VPS
Update and Upgrade the System
sudo apt update
sudo apt upgrade -y
Install Required Packages
Install essential packages for building Python packages and SSL:
sudo apt install -y python3-pip python3-venv nginx curl
Step 2: Clone the Flask Application
Clone Your Git Repository
git clone https://github.com/username/your-flask-app.git
cd your-flask-app
Replace https://github.com/username/your-flask-app.git with the URL of your repository.
Step 3: Set Up the Python Environment
Create and Activate a Virtual Environment
python3 -m venv venv
source venv/bin/activate
Install Dependencies Using pipreqs
First, install pipreqs:
pip install pipreqs
Generate a requirements.txt file based on your project imports:
pipreqs . --force
Then, install the dependencies:
pip install -r requirements.txt
Step 4: Set Up Gunicorn
Install Gunicorn
pip install gunicorn
Test Gunicorn Locally
gunicorn --bind 0.0.0.0:8000 app:app
Replace app:app with your actual Flask application entry point.
Create a Systemd Service for Gunicorn
sudo nano /etc/systemd/system/developerbreeze.service
Paste the following content:
[Unit]
Description=Gunicorn instance to serve Flask application
After=network.target
[Service]
User=www-data
Group=www-data
WorkingDirectory=/path/to/your-flask-app
Environment="PATH=/path/to/your-flask-app/venv/bin"
ExecStart=/path/to/your-flask-app/venv/bin/gunicorn --workers 3 --bind unix:/path/to/your-flask-app/developerbreeze.sock app:app
[Install]
WantedBy=multi-user.target
> Replace /path/to/your-flask-app with your actual project path.
> Replace app:app with your actual Flask app entry point.
Start and Enable the Gunicorn Service
sudo systemctl enable developerbreeze.service
sudo systemctl start developerbreeze.service
sudo systemctl status developerbreeze.service
Step 5: Configure Nginx
Create an Nginx Configuration File
sudo nano /etc/nginx/sites-available/developerbreeze
Paste the following:
# HTTP to HTTPS redirection
server {
listen 80 default_server;
listen [::]:80 default_server;
server_name developerbreeze.com www.developerbreeze.com;
return 301 https://developerbreeze.com$request_uri;
}
# HTTPS Server Block
server {
listen 443 ssl http2;
listen [::]:443 ssl http2;
server_name developerbreeze.com www.developerbreeze.com;
ssl_certificate /etc/letsencrypt/live/developerbreeze.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/developerbreeze.com/privkey.pem;
include /etc/letsencrypt/options-ssl-nginx.conf;
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem;
root /path/to/your-flask-app;
index index.html;
access_log /var/log/nginx/access.log;
error_log /var/log/nginx/error.log;
location / {
include proxy_params;
proxy_pass http://unix:/path/to/your-flask-app/developerbreeze.sock;
}
location /static {
alias /path/to/your-flask-app/static;
}
location /favicon.ico {
alias /path/to/your-flask-app/static/favicon.ico;
}
location ~ /.well-known {
allow all;
}
}
> Replace /path/to/your-flask-app with your actual project path.
Enable the Nginx Site
sudo ln -s /etc/nginx/sites-available/developerbreeze /etc/nginx/sites-enabled/
sudo rm /etc/nginx/sites-enabled/default
Test and Restart Nginx
sudo nginx -t
sudo systemctl restart nginx
Step 6: Set Up SSL with Let's Encrypt
Install Certbot
sudo apt install certbot python3-certbot-nginx
Obtain an SSL Certificate
sudo certbot --nginx -d developerbreeze.com -d www.developerbreeze.com
Follow the prompts to complete the installation.
Verify SSL Renewal
sudo certbot renew --dry-run
Step 7: Verify the Deployment
sudo tail -f /var/log/nginx/access.log
sudo tail -f /var/log/nginx/error.log
sudo journalctl -u developerbreeze.service -f
Conclusion
By following these steps, you have successfully deployed your Flask application using Gunicorn and Nginx, secured with SSL from Let's Encrypt. This setup provides a robust and scalable environment for running your web application.