Dokku

Dokku is an open-source Platform-as-a-Service (PaaS) that brings Heroku-style application deployment to your own server. Developers push code with git push and Dokku automatically builds the application, creates a Docker container, configures networking, provisions an SSL certificate, and starts serving traffic.

The build process uses Cloud Native Buildpacks (the same technology behind Heroku) to automatically detect the application type and create an optimized container image. Push a Node.js app and it installs dependencies and starts the server. Push a Python app and it sets up the virtualenv and runs the WSGI server. Push a PHP app and it configures Apache or Nginx with PHP-FPM. No Dockerfile required (though custom Dockerfiles are supported).

Dokku includes a plugin system that provides databases (PostgreSQL, MySQL, Redis, MongoDB), SSL certificates (Let's Encrypt with auto-renewal), custom domains, persistent storage, cron jobs, and more. Each plugin follows a consistent interface, making it easy to provision backing services for applications.

For hosting providers, Dokku enables a platform hosting product on a single VPS. Small agencies use it to host client applications with simple deployment workflows. Developer-focused hosts offer Dokku-powered hosting as an affordable Heroku alternative. The per-application isolation (each app runs in its own container) provides security separation.

Dokku runs on a single server and is designed for small to medium deployments (typically 10-50 applications per server depending on resource usage). For larger scale, providers look at Kubernetes, but Dokku fills the gap for those who want Heroku-like simplicity without Heroku-like pricing or Kubernetes-like complexity.

The entire platform installs with a single bootstrap script and manages itself with a straightforward CLI. Application management, scaling, configuration, and service linking are all done through simple dokku commands.