Why use WSGI and not just point a web server directly at an application?

• WSGI gives you flexibility. Application developers can swap out web stack components for others. For example, a developer can switch from Green Unicorn to uWSGI without modifying the application or framework that implements WSGI.
• WSGI servers promote scaling. Serving thousands of requests for dynamic content at once is the domain of WSGI servers. WSGI servers handle processing requests from the web server and deciding how to communicate those requests to an application framework's process.

A WSGI middleware component is a Python callable that is itself a WSGI application, but may handle requests by delegating to other WSGI applications. These applications can themselves be WSGI middleware components.

A middleware component can perform such functions as:

• Routing a r...