In Chapter 1, Developing for Drupal 8, when we outlined a high level example of how Drupal 8 handles a user request in order to turn it into a Response, we touched on the render pipeline. So, let's see what this is about, as there are essentially two render pipelines to speak of--the Symfony render pipeline and the Drupal one.
As you know, Drupal 8 uses many Symfony components, one of which being the HTTPKernel component (http://symfony.com/doc/current/components/http_kernel.html). Its main role is to turn a user request (built from PHP super globals into a Request object) into a standardized response object that gets sent back to the user. These objects are defined in the Symfony HTTP Foundation component (http://symfony.com/components/HttpFoundation) ...
