Rack là gì? Rails liên quan đến Rack như thế nào?

Rack là interface chuẩn giữa Ruby web framework và web server (Puma, Unicorn, Passenger). Mọi Rack app là một object có method call(env) trả về [status, headers, body].

Rails là một Rack application — khi Puma nhận request, nó gọi Rails app qua Rack interface.

# config.ru — entry point Rack
require_relative "config/environment"
run Rails.application

Middleware stack: Rails dùng Rack middleware chaining — mỗi middleware wrap request/response (logging, CSRF check, session, gzip compression, ...). Xem bằng rails middleware.

Hiểu Rack giúp debug middleware, viết custom middleware, và tích hợp với các Rack-compatible library như Warden (Devise dùng bên dưới).

Rack is a standard interface between Ruby web frameworks and web servers (Puma, Unicorn, Passenger). Every Rack app is an object with a call(env) method that returns [status, headers, body].

Rails is a Rack application — when Puma receives a request it calls the Rails app via the Rack interface.

# config.ru — Rack entry point
require_relative "config/environment"
run Rails.application

Middleware stack: Rails uses Rack middleware chaining — each middleware wraps the request/response (logging, CSRF check, session, gzip, ...). Inspect with rails middleware.

Understanding Rack helps debug middleware, write custom middleware, and integrate Rack-compatible libraries like Warden (used under the hood by Devise).