ruby 34 lines · 2 tabs

Custom middleware for request tracking

Alex Kumar Jan 2026

2 tabs

module Middleware
  class RequestTimer
    def initialize(app)
      @app = app
    end

    def call(env)
      start_time = Time.current

      status, headers, response = @app.call(env)

      duration = ((Time.current - start_time) * 1000).round(2)

      # Add timing header
      headers['X-Response-Time'] = "#{duration}ms"

      # Log slow requests
      if duration > 1000
        Rails.logger.warn("Slow request: #{env['REQUEST_METHOD']} #{env['PATH_INFO']} took #{duration}ms")
      end

      [status, headers, response]
    end
  end
end

module MyApp
  class Application < Rails::Application
    config.load_defaults 6.1

    # Add custom middleware
    config.middleware.use Middleware::RequestTimer
    config.middleware.insert_before Rack::Runtime, Middleware::RequestId
  end
end

2 files · ruby Explain with highlit

Rack middleware sits between the web server and Rails application, providing a hook for cross-cutting concerns like request logging, metrics collection, or custom authentication. I use middleware to inject request IDs, track response times, or enforce security headers before the request reaches controllers. Each middleware is a simple class with a call method that receives the Rack env hash. Middleware can short-circuit the request by returning a response early, or pass control to the next middleware in the stack by calling @app.call(env). Proper middleware ordering matters—authentication should run before authorization, and request logging should wrap the entire stack. I keep middleware focused and single-purpose to maintain clarity.

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