Adding Hit/Miss header to proxied requests

[Maxim Dounin]

Hello!

On Thu, Aug 25, 2011 at 03:56:34PM +0100, Dave Barton wrote:

> Hi,
> 
> We're using a pretty simple setup of ipvsadm balancing between 6 nginx
> caching-proxies with 3 nginx backend servers configured.
> 
> When the request hits the proxy, I add a header to show which proxy
> serviced the request. Similarly the backend servers add a header to
> their response to show which one served the traffic.
> 
> Because we're anycasting the service at three locations, this
> information is very useful for troubleshooting!
> 
> Anyway, what I want to do now is add a header to show whether a response
> was served from cache or from the backend. Having been through the
> documentation I'm not currently able to see how this could be done.
> Anyone able to offer any advice?

add_header X-Cached $upstream_cache_status;

http://wiki.nginx.org/HttpHeadersModule#add_header
http://wiki.nginx.org/HttpUpstreamModule#.24upstream_cache_status

Maxim Dounin