Nginx raises 404 when using format => 'js' - ruby-on-rails

Question

I upload images to my App using Ajax and an Iframe. In Development everything works like a charm. But in production Nginx suddenly raises a 404 error. When I look into the log, the request never hits the Rails app. So I guess it has something to do with my Nginx configuration (maybe gzip compression).
The failing requests is send to "/images.js".
Any ideas on how to solve this? Google couldn't help me...
My Nginx config:
server {
listen 80;
server_name www.myapp.de;
root /var/www/apps/myapp/current/public; # <--- be sure to point to 'public'!
passenger_enabled on;
rails_env production;
# set the rails expires headers: http://craigjolicoeur.com/blog/setting-static-asset-expires-headers-with-nginx-and-passenger
location ~* \.(ico|css|js|gif|jp?g|png)(\?[0-9]+)?$ {
expires max;
break;
}
gzip on;
gzip_http_version 1.0;
gzip_vary on;
gzip_comp_level 6;
gzip_proxied any;
gzip_types text/plain text/html text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript;
# make sure gzip does not lose large gzipped js or css files
# see http://blog.leetsoft.com/2007/7/25/nginx-gzip-ssl
gzip_buffers 16 8k;
# this rewrites all the requests to the maintenance.html
# page if it exists in the doc root. This is for capistrano?^?^?s
# disable web task
if (-f $document_root/system/maintenance.html) {
rewrite ^(.*)$ /system/maintenance.html last;
break;
}
# Set the max size for file uploads to 10Mb
client_max_body_size 10M;
error_page 500 502 503 504 /500.html;
location = /500.html {
root /var/www/apps/myapp/current/public;
}
}

Answer 1

nginx will serve the request for /images.js from your root /var/www/apps/myapp/current/public since it matches
location ~* \.(ico|css|js|gif|jp?g|png)(\?[0-9]+)?$ {
expires max;
break;
}
(the break directive only applies to rewrite rules afaik so it can be removed)
If you want to serve /images.js from rails you need to enable rails for that location.

Answer 2

It's worth noting that any .json requests will get caught if you use the regex above. Add a $ to avoid that.
location ~* \.(ico|css|js$|gif|jp?g|png)(\?[0-9]+)?$ {
expires max;
break;
}

Answer 3

For this purpose I use this location directives:
location ~* ^.+\.(jpg|jpeg|gif|png|css|swf|ico|mov|flv|fla|pdf|zip|rar|doc|xls)$
{
expires 12h;
add_header Cache-Control private;
}
location ~* ^/javascripts.+\.js$
{
expires 12h;
add_header Cache-Control private;
}

Answer 4

I ran into a very similar issue, and put format.json instead of format.js - this made a URL that had a .json extension, but allowed me to not modify my Nginx config.