A few gotchas when your Drupal site is being deployed behind caching servers and proxy_pass

This post was written 6 years ago.
Fri, 04 Mar 2011
I recently launched a Drupal based site that forms part of the website for a global company (being a freelancer working through a design agency with an NDA, I can't talk about it any more than that, or stick it on my portfolio unfortunately!). I though i'd make a few notes about some of the issues I had to overcome.

The site itself is hosted on a dedicated VPS, but served to the world through akamai caching servers, which means that everything is cached by default. Therefore in this set-up, the CMS is only available at a different URL, where caching is bypassed. Gotcha no.1 is that cookies set and read via PHP do not work in this scenario*. Fortunately Javascript cookies can still be used.

In addition to the caching, the site is served up as part of a much bigger site /deep/down/in/the/url/structure, so proxy_pass is used (before caching) to rewrite the paths. Gotcha no.2 is that base_path() in drupal picks up the path of the origin server, so I had to add a condition like this in my settings.php (excuse wrapping, really must sort this site out for code samples):-

$base_url = 'http://'.$_SERVER['HTTP_X_FORWARDED_HOST'].'/path/to/my/proxied/site';

The clue to gotcha number 3 is in that last example. $_SERVER['HTTP_HOST'] reports the host of the origin server, rather than the public host, so if it is used anywhere in your code, it may cause issues. I ended up adding a function getHost() that I use to return the appropriate host, depending on where the site is being viewed (once again excuse formatting):-

function getHost(){
$host = $_SERVER['HTTP_HOST'];
return $host;

Gotcha No.4 was image paths in optimised css - both the Drupal-provided CSS caching and some external stuff I had using minify - these both rewrote the image paths to use those from the origin server. This meant that CSS applied images worked in the non-cached editing environment but not on live. I haven't come up with a solution for that one yet, other then to leave some of the stylesheets non-minified.

* maybe there is a solution to this, but assume in this case there is little or no scope to request server config changes.
This post was written 6 years ago, which in internet time is really, really old. This means that what is written above, and the links contained within, may now be obsolete, inaccurate or wildly out of context, so please bear that in mind :)
Tags: drupal / php /