Run a Flask application with gunicorn and nginx

instructions.md

This guide assumes:

• You have a VPS (something like DigitalOcean, Linode, etc.)
• You have a Flask application and a basic understanding of command line instructions
• You've got nginx installed and know where your configuration files are

Instructions

1. First, you should install gunicorn on your box or virtualenv with pip:

• source venv/bin/activate (optional, if you're not using virtualenv)
• pip install gunicorn

2. Add a configuration block to your nginx configuration:

Note: change 127.0.0.1:5000 to the port that your flask application is set to run on.

server {
  listen 80;
  server_name example.com;
  
  keepalive_timeout 5;
  
  location / {
    proxy_pass http://127.0.0.1:5000;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
  }

}

3. Restart nginx nginx -s reload

4. Make locations for the gunicorn logs, and start your application:

Note: change 127.0.0.1:5000 to match your nginx block if you used a different port, and change app:app if you've got a different name

• mkdir /var/log/gunicorn/
• gunicorn --access-logfile /var/log/gunicorn/access_log --error-logfile /var/log/gunicorn/error_log --pythonpath /var/www/yourapppath -b 127.0.0.1:5000 app:app

5. Done. Your flask application should be running on the domain you set in the nginx configuration

Notes

• Don't forget to run this with screen or supervisord or some other init daemon so that the application doesn't shut down when you exit the shell. Yes, adding & at the end will keep it running, but it's the least elegant way
• sudo killall -HUP gunicorn gracefully restarts workers if you change any of your python code and want to restart the application
• Feel free to comment with questions or anything else and I can expand on it :)