Puma is a concurrent HTTP server for Ruby applications that implements the Rack interface. It operates as a clustered web server, using a combination of worker processes and threads to handle multiple simultaneous web connections via TCP ports or UNIX domain sockets.
The server features a master-worker process model that utilizes multiple CPU cores and employs copy-on-write preloading to reduce memory usage. It supports zero-downtime restarts through socket-handover capabilities, allowing application updates without dropping pending network requests.
The project includes a token-authenticated control interface for production administration, dynamic thread pool scaling to manage request volume, and a plugin architecture for exporting server metrics to external monitoring tools. It also provides built-in support for SSL/TLS connection security and server lifecycle hooks for executing custom logic during boot and shutdown.
