[[!meta title="Nginx: Use X-Accel with conflicting regular expressions"]]

## Background

At [[!ungleich]] we use [[!nginx]] for [[!rails]] 
hostings of our customers. Nginx is configured to
deliver static files using [[!xaccel]]. 
We also want to have a longer expiry time for static files, 
which is configured seperately in nginx.

## Configuration Options

To support X-Accel, we have added this configuration block into nginx:

    # Support for X-Accel
    location /protected/ {
        internal;
        root   /home/app/app/shared;
    }


To support longer expiry times, we have added this configuration
block:

    location ~* \.(ico|css|js|gif|jpe?g|png)(\?[0-9]+)?$ {
        expires 1y;

        # Need to enable proxying in this location as well
        try_files $uri @unicorn;
    }


## The Problem

Using the configuration as stated above, we encounter the problem that
if an application wants to send a JPEG using X-Accel, the regular
expression block is selected (it has higher priority and matches
the .jpeg ending) and thus the application delivers it, instead of nginx
directly.

## The Solution

Luckily though, [nginx supports giving the prefix based
location block precedence](http://nginx.org/en/docs/http/ngx_http_core_module.html#location):
Instead of using **location /protected/**, we can use **location ^~**. Thus our
previous block can be rephrased to:

    location ^~ /protected/ {
        internal;
        root   /home/app/app/shared;
    }

And now the application can serve JPEG files via X-Accel.


[[!tag hosting nginx rubyonrails ungleich]]