Even though that header is probably sent in every request, still some content is getting sent back without a check to the original server, or so it seems, because I commonly see TCP_HIT in the access log.
Henrik Nordstrom wrote:
On Wed, 20 Oct 2004, Jim Nachlin wrote:
1098307846.311 21 127.0.0.1 TCP_REFRESH_HIT/304 220 GET http://192.168.2.75/test-rec.cgi - DIRECT/192.168.2.75 - [Host: 192.168.2.75\r\nUser-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.5) Gecko/20031021\r\nAccept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,image/jpeg,image/gif;q=0.2,*/*;q=0.1\r\nAccept-Language: en-us,en;q=0.5\r\nAccept-Encoding: gzip,deflate\r\nAccept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7\r\nKeep-Alive: 300\r\nProxy-Connection: keep-alive\r\nIf-Modified-Since: Wed, 20 Oct 2004 11:37:46 GMT\r\nCache-Control: max-age=0\r\n] [HTTP/1.1 304 Not Modified\r\nDate: Wed, 20 Oct 2004 21:30:46 GMT\r\nServer: Apache/2.0.49 (Unix)\r\nConnection: close\r\nExpires: Wed, 27 Oct 2004 16:37:46 GMT\r\nCache-control: max-age=6000\r\n\r]
1098307888.934 361 127.0.0.1 TCP_REFRESH_HIT/304 220 GET http://192.168.2.75/test-rec.cgi - DIRECT/192.168.2.75 - [Host: 192.168.2.75\r\nUser-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.5) Gecko/20031021\r\nAccept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,image/jpeg,image/gif;q=0.2,*/*;q=0.1\r\nAccept-Language: en-us,en;q=0.5\r\nAccept-Encoding: gzip,deflate\r\nAccept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7\r\nKeep-Alive: 300\r\nProxy-Connection: keep-alive\r\nIf-Modified-Since: Wed, 20 Oct 2004 11:37:46 GMT\r\nCache-Control: max-age=0\r\n] [HTTP/1.1 304 Not Modified\r\nDate: Wed, 20 Oct 2004 21:31:28 GMT\r\nServer: Apache/2.0.49 (Unix)\r\nConnection: close\r\nExpires: Wed, 27 Oct 2004 16:37:46 GMT\r\nCache-control: max-age=6000\r\n\r]
Both these are forced reloads due to the "Cache-Control: max-age=0" header sent by your client.. this tells Squid that you (the client) does not accept cached content unless it first has been verified fresh. This overrides Expires or any freshness information the earlier server reply may have (RFC 2616 14.9.4 Cache Revalidation and Reload Controls, Specific end-to-end revalidation)
Regards Henrik
