Tricky Caching reverse Proxy - different User agents to be watched

[Ryan Malayter]

On Mon, May 10, 2010 at 2:41 AM, musa <nginx-forum at nginx.us> wrote:
> Well, in this case (realy small page, short caching time) it doesnt matter when it caches for each user-agent.

The user-agent string contains a lot more than just the browser
version, unfortunately. It can also includes the versions of various
browser plug-ins, add-ons, etc., which means you are caching a
different version of each page for IE8 users with one version of .NET
or another.

For example, here's a full user-agent string pulled from our logs:
Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0;
SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729;
Media Center PC 6.0; InfoPath.2)

To eliminate unnecessary requests to the back-end as well as
duplicated cache entries, it might be best to use the nginx map module
to "normalize" the User-Agent to just a few values:
http://wiki.nginx.org/NginxHttpMapModule

For example (syntax not tested, just a guess based on documentation):

map $http_user_agent $shortua {
   default          anybrowser;
   *iPhone*       iPhone;
   *Blackberry*   bb;
   *IEMobile*   winmoble;
   "*Windows Phone*"  winmobile;
}

proxy_cache_key "$scheme$proxy_host$uri$is_args$args $shortua";

-- 
RPM