Gunicorn

Gunicorn (Green Unicorn) is a Python WSGI HTTP Server for UNIX that serves your Django application. When using Gunicorn with a Django REST Framework (DRF) project, you can handle HTTP requests efficiently and reliably.
Author

Benedict Thekkel

Installation

pip install gunicorn

Basic Usage

To run your Django application using Gunicorn, navigate to your project’s root directory and use the following command

gunicorn your_project_name.wsgi:application

Replace your_project_name with the name of your Django project.

Configuration Options

Gunicorn provides various options to configure the server:

Binding to a Specific Address and Port

gunicorn --bind 0.0.0.0:8000 your_project_name.wsgi:application

Number of Workers

The number of worker processes for handling requests. More workers can handle more requests concurrently but consume more memory.

gunicorn --workers 3 your_project_name.wsgi:application

Timeout

The maximum number of seconds a worker can spend handling a request before it is killed and restarted.

gunicorn --timeout 30 your_project_name.wsgi:application

Logging

You can specify log files for Gunicorn

gunicorn --access-logfile access.log --error-logfile error.log your_project_name.wsgi:application

Deployment with Systemd

For a production deployment, it’s common to use systemd to manage Gunicorn. Here’s an example of a systemd service file

In file /etc/systemd/system/gunicorn.service

[Unit]
Description=gunicorn daemon
After=network.target

[Service]
User=your_user
Group=www-data
WorkingDirectory=/path/to/your/project
ExecStart=/path/to/your/venv/bin/gunicorn --workers 3 --bind unix:/path/to/your/project/gunicorn.sock your_project_name.wsgi:application

[Install]
WantedBy=multi-user.target
  • Replace your_user with your system username.
  • Replace /path/to/your/project with the path to your Django project.
  • Replace /path/to/your/venv with the path to your virtual environment.

Example

[Unit]
Description=gunicorn daemon
After=network.target

[Service]
User=ubuntu
Group=www-data
WorkingDirectory=/home/ubuntu/django_todo
UMask=007
ExecStartPre=/bin/bash -c 'mkdir -p /home/ubuntu/django_todo && chown ubuntu:www-data /home/ubuntu/django_todo'
ExecStart=/home/ubuntu/django_todo/.venv/bin/gunicorn --access-logfile - --workers 3 --bind unix:/home/ubuntu/django_todo/gunicorn.sock config.wsgi:application

[Install]
WantedBy=multi-user.target

After creating the service file, enable and start the service

sudo systemctl daemon-reload
sudo systemctl enable gunicorn
sudo systemctl start gunicorn

Security Considerations

  • Keep Gunicorn and your Django project dependencies up to date.
  • Use HTTPS for secure communication.
  • Use a firewall to restrict access to the Gunicorn server, allowing only the web server (e.g., Nginx) to communicate with it.

Performance Tuning

  • Number of Workers: Start with (2 x $num_cores) + 1 workers. Monitor and adjust based on your application’s performance and server’s resource availability.
  • Worker Class: Use different worker classes based on your application’s nature, e.g., gevent for async applications.
  • Keep-Alive: Adjust the keep-alive setting for persistent connections, especially in high-traffic scenarios.

Monitoring and Logging

  • Use monitoring tools like New Relic, Datadog, or Prometheus to keep an eye on the performance and health of your application.
  • Log files should be monitored for errors and access patterns.

Common Issues and Troubleshooting

  • 502 Bad Gateway: Often due to Gunicorn not running or configuration issues with the reverse proxy server.
  • Slow Performance: Could be due to insufficient worker processes or server resources. Profiling the application can help identify bottlenecks.
  • Memory Leaks: Regularly monitor memory usage and ensure proper resource management in the application.
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