0x29 - nginx: Adding expiration headers

Today I was confronted with the tas of setting a proper expiration header to asset files. As a reminder: this is the aim:

• when requesting an existing file with an additional timestamp parameter (i.e. "?123") add an expiration header.
• when requesting an existing file without an additional timestamp parameter don't add an expiration header.
• when requesting a non-existing file pass on the request to the passenger application.

After surfing the web for ages I found no working solution. In any case, the following did the trick. Read below for an explanation and how I checked this:

  
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# Server settings. server_name and path should match.
server {
  listen 80;
  server_name server.dev;
  root /Users/me/sites/server/public;
  index index.html index.htm;

  error_page   500 502 503 504  /50x.html;
  location = /50x.html {
    root   html;
  }

  sendfile on;

  location / {
    if (-f $request_filename) { 
        set $file X;
    }

    if ($args ~* ^[0-9]+$) {
        set $file "${file}C";
    }

    # existing and can be kept by the client?
    if ($file = "XC") {
        expires 365d;    
    }

    # Doesn't exist? Go to rails app
    passenger_enabled on;
    rails_env production;
  }
}

This takes the following into account:

1. The location value doesn't include the request query parameter
2. This solution adds expiration headers to all requests where a file exists, not only to the "classical" asset requests.
3. For some reason that I don't understand I had to put the "passenger_enabled" and "rails_env" inside the location block. Otherwise the rails application would never pick up any request with a file extension.

After I was done I found an apparently working configuration with a different (and I must say more elegant) approach in the comment section over at Craig's. It is sad you find the good stuff only after banging your head for hours :)

And this is how I tested it:

1. Get the robots.txt file, it must not contain an "Expires" header:

   
     
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    ~/site> curl -I http://server.dev/robots.txt
    HTTP/1.1 200 OK
    Server: nginx/0.7.61
    ...
   
   

2. Get the robots.txt file, with a time stamp; it must contain an "Expires" header:

   
     
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    ~/site> curl -I http://server.dev/robots.txt?1234
    HTTP/1.1 200 OK
    Server: nginx/0.7.61
    Date: Fri, 13 Nov 2009 00:01:23 GMT
    Last-Modified: Sat, 08 Aug 2009 20:28:57 GMT
    Expires: Sat, 13 Nov 2010 00:01:23 GMT
    ...
   
   

3. Get a dynamically created javascript file; it must not contain an "Expires" header, but must refer to Phusion Passenger in the "Server" header, and this regardless of whether or not a timestamp is set:

   
     
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     ~/sites/whispler> curl -I http://server.dev/xx.js?1234
     ...
     Server: nginx/0.7.61 + Phusion Passenger 2.2.5 (mod_rails/mod_rack)
   
     ~/sites/whispler> curl -I http://server.dev/xx.js
     ...
     Server: nginx/0.7.61 + Phusion Passenger 2.2.5 (mod_rails/mod_rack)