Once the request has passed through all 20 middleware objects, it then enters the router.
Rack::Head – Removes response body from HEAD requests. Rack::Session::Abstract::Persisted – Session management. ActionDispatch::Cookies – Cookie serialization and encryption. ActiveRecord::Migration::CheckPending – Raises an exception if there are pending migrations. ActionDispatch::Callbacks – Runs callbacks before/after/around each request. ActionDispatch::RemoteIp – Determines the IP address of the client. ActionDispatch::DebugExceptions – Logging and debug info pages for unhandled exceptions. Ruby rack app code#
WebConsole::Middleware – Interactive console for running code on the server. ActionDispatch::ShowExceptions – Makes responses for unhandled exceptions. Sprockets::Rails::QuietAssets – Silences logging on requests for sprockets assets. ActionDispatch::RequestId – Gives each request a unique id. Rack::MethodOverride – Overrides the HTTP request method based on the _method param. Rack::Runtime – Response time measurement. ActiveSupport::Cache::Strategy::LocalCache::Middleware – Response caching. ActionDispatch::Executor – Undocumented ¯\_(ツ)_/¯. ActionDispatch::Static – Responds to requests for static files. Rack::Sendfile – Makes responses from files on disk. Here is an ordered list of all the middleware in the development environment: Rails provides a bunch of middleware that are enabled by default. Modify the response returned from the next app. Modify the env before it is passed to the next app. Rack middleware are app objects that call other app objects. In this case, the next app is an instance of Rack::Sendfile, which indicates that the request is entering the middleware stack. It adds things to the env hash, and then passes it along to the next rack app. The application object is a kind of rack middleware itself. action_dispatch.encrypted_signed_cookie_salt. action_dispatch.show_detailed_exceptions. These values are accessible to all the middleware and controllers. The build_request call merges a bunch of values into the env. Looking inside the default file we find this:ĭef call ( env ) req = build_request env app. Rack apps define their entry point in the file, and Rails is no different. The rack app returns a response, which the web server sends back to the browser. When the web server receives a HTTP request, it converts that request into an env hash, and calls your rack app. This is how Rails, and most other Ruby web frameworks, interact with web servers. In the example above, the response body is an array with a string in it, which is valid. The third element is the body of the response, which can be any object that responds to #each, yielding only strings. The second element is a hash of HTTP headers. The first element is the HTTP status code. The response is represented as a three-element array. It contains all the information about the request, like the HTTP method, the server’s hostname, the URL path, and so on. This hash is referred to as the “request environment,” usually shortened to just “env.” The web request is represented as a hash. The ENV constant is a global built in to Ruby, and contains all the environment variables for the current process. The request env represents a HTTP request. The request env should not be confused with the ENV constant. This method receives the web request as an argument and returns an array as the response. There is only one method that a rack app must implement: the #call method. Class ComplimentApp def call ( env ) ] end end
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