How do I mimic the route handling?
I'm not sure what is the purpose of this, now in Drupal 8 Guzzle is available to creating external and internal request.

$this-&gt;httpClient-&gt;get($href)-&gt;getBody(TRUE);


The httpClient is a service in Drupal 8  api.drupal.org/api/drupal/core%21core.services.yml/service/http_client/8

you need inject this service in your class.

if you need read the Route properties like callback, permissions, etc. you need use the routeProvider service.

https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Routing%21RouteProvider.php/class/RouteProvider/8

maybe more information about that problem help us to understand what is the best way to porting for Drupal 8

UPDATE:

Thinking a little more, you want to make a sub-request?

something like https://gist.github.com/dmouse/4976461875a27689d155