Setting Static Asset Expires Headers with nginx and Passenger

On a recent project I launched, I’m using the combination nginx+passenger for my front end my my Ruby on Rails application.

While trying to boost my YSlow score, I was having a bit of difficulty trying to figure out how to set HTTP expires headers on all the static assets served by my app.

Rails will set an internal time stamp on static assets (images, css files, javascript files, etc…) by appending a integer value onto the end of the asset filename

http://mydomain.com/images/asset.png?12345678

My original attempt at getting nginx to set an expires header for these assets had me adding the following location block to my nginx config file:

location ~* \.(ico|css|js|gif|jpe?g|png)\?[0-9]+$ {
    expires max;
    break;
}

The regexp I was using was incorrect however as it didn’t take into account that the ?timestamp might not exist in the URI.

Hongli Lai kindly pointed me in the right direction and showed me the proper regexp that he is using.

location ~* \.(ico|css|js|gif|jpe?g|png)(\?[0-9]+)?$ {
    expires max;
    break;
}