Acquia GeoIP Country variation

This is a tiny module for Acquia clients that have GeoIP support installed on their load balancers. It changes Drupal's Vary response header to include the X-Geo-Country header. The effect of this is that the visitors of your site will get cached responses for only the country they are visiting from.

Drupal 7 one-liner

Although the code is super tiny, if you want to avoid installing a module you can put this in your settings.php file and achieve exactly the same thing:

drupal_add_http_header("Vary", "X-Geo-Country", TRUE);