Graphiti / Graphite using Apache with Proxy and BasicAuth requests auth for every URL / request
Solution 1:
I have now solved this problem. It was nothing to do with Apache in the end (per se). Graphiti uses a JavaScript function to make HTTP requests to the Graphite service, which we had set up as a separate vhost, which also had Auth setup (some users prefer to use it directly).
So basically, no user/password were in the URL that graphite was using, and so every one triggered an Auth prompt. To fix it, we just needed to update our templates so that the URL generates with the http://<user>:<password>@<host> syntax.