Adding Hit/Miss header to proxied requests

[Dave Barton]

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?

h6edcgdp6:~ # nginx -v
nginx: nginx version: nginx/1.1.0

HTTP request sent, awaiting response...
  HTTP/1.1 200 OK
  Server: nginx
  Date: Thu, 25 Aug 2011 13:49:34 GMT
  Content-Type: application/octet-stream
  Connection: keep-alive
  Keep-Alive: timeout=1
  Content-Length: 104857600
  Last-Modified: Fri, 02 Oct 2009 15:24:44 GMT
  **X-CCACDN-Mirror-ID: fsedcgdown1**
  **X-CCACDN-Proxy-ID: fsedcgdp1((
  Accept-Ranges: bytes
Length: 104857600 (100M) [application/octet-stream]
Saving to: “/dev/null”

Cheers
-- 
Dave Barton
Senior Infrastructure Architect
Comodo CA Ltd

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