Using an upstream header value as a proxy_cache_key

[Maxim Dounin]

Hello!

On Thu, Dec 24, 2009 at 03:28:25PM -0800, Troy Hakala wrote:

> Is it possible to have an upstream server set an HTTP header 
> that can be used as the key in proxy_cache_key? This doesn't 
> work:
> 
>                 proxy_cache_key $upstream_http_x_myheader;
> 
> And neither does this:
> 
>                 set $v $upstream_http_x_myheader;
>                 proxy_cache_key $v;

It won't, as $upstream_* variables are available only after 
request to upstream while cache key must be constructable from 
client request (before request to upstream, to find out if it's 
needed).

Maxim Dounin