Middleware

What is Middleware in Ruby on Rails?

Middleware is a layer in the Rails request–response cycle that intercepts incoming requests and outgoing responses. Before a request reaches a controller or before a response is sent back to the browser, it can pass through multiple middleware components.

Each middleware performs a specific task, such as handling sessions, managing cookies, logging requests, or enforcing security rules. Rails uses Rack-based middleware, allowing developers to add, remove, or customize behavior at different points in the request flow.

Why is Middleware Useful?

Middleware allows cross-cutting concerns to be handled in a centralized and reusable way, without cluttering controllers or models.

Benefits include:

• Cleaner and more focused controller logic

• Reusable request and response processing

• Consistent behavior across the entire application

• Easy integration of authentication, logging, and security

• Flexible customization of the request lifecycle

How Middleware Works in Rails?

When a request hits a Rails application, it flows through a stack of middleware before reaching the router and controllers. After the controller generates a response, it travels back through the same middleware stack in reverse order.

Each middleware can inspect, modify, or halt the request or response as needed. The middleware stack is configurable via Rails, allowing applications to insert custom middleware when required.

Example

When a user sends a request to a Rails application, middleware may first check authentication, then load session data, log the request details, and handle cookies before the request reaches the controller.

After the controller processes the request, the response passes back through middleware that may compress the response, add security headers, or store session updates before sending it to the browser.

Where to Use Middleware?

• Authentication and authorization handling

• Request logging and monitoring

• Session and cookie management

• Security headers and rate limiting

• Request throttling and API versioning

In Summary

Middleware in Ruby on Rails provides a powerful way to process requests and responses outside of controllers. By handling cross-cutting concerns in a centralized layer, middleware helps keep Rails applications clean, modular, and easier to maintain.