Setting outbound 'Expires:' in Squid server's HTTP header

Question

I'm having a problem where items served by my Squid server are being cached by Limelight for too long, sometimes days. It happens when a piece of content has been static for a long time (weeks) and then undergoes numerous changes in a matter of hours.

Limelight gets its content from our Squid server and I'm told that if I can add 'Expires: 15m' in the HTTP header the Squid server sends, Limelight will not cache the image for more than 15 min.

Unfortunately, I can fond no setting in Squid that will allow me to add this to the header.

Here's the HTTP header as presently being sent:

HTTP/1.0 200 OK
Date: Tue, 15 Dec 2009 23:57:33 GMT
Server: nginx/0.5.26
Content-Type: image/jpeg
Content-Length: 83843   
Last-Modified: Tue, 15 Dec 2009 23:52:00 GMT
Accept-Ranges: bytes
Age: 450
X-Cache: HIT from squid01.prod.mydomain
X-Cache-Lookup: HIT from squid01.prod.mydomain:3128
Via: 1.0 squid01.prod.mydomain:3128 (squid/2.6.STABLE14)
Connection: close

Answer 1

You need to set the header on the origin server, not on your Squid box.

See: http://www.mnot.net/cache_docs/#IMP-SERVER