Gemmy wrote:
I have a question about the "Date" in response header.
As I know, the "Date" should be the just time when the server response
the request. But If I request through squid2.6 as a cache server, I get
the right "Date" only the first time! Squid return the same
"Date"/"Expires"...after the second request.
I guess that squid might return the headers exist in the cache file. I
strings one file and see text as follows:
http://tech.china.com/zh_cn/mobile/market/11025044/20080102/images/2008010209212895055100.jpg
HTTP/1.1 200 OK
Server: nginx/0.7.62
Date: Fri, 03 Sep 2010 12:40:54 GMT
Content-Type: image/jpeg
Content-Length: 47072
Last-Modified: Wed, 02 Jan 2008 01:15:06 GMT
Connection: keep-alive
Expires: Fri, 03 Sep 2010 13:10:54 GMT
Cache-Control: max-age=1800
Accept-Ranges: bytes
But when I test a url through a CDN's cache, I see the "Date" changes
every test.
wget -S http://images7.moonbasa.com/ProductImg/Middle/WX10010090M01.jpg
-O /dev/null
--22:00:09-- http://images7.moonbasa.com/ProductImg/Middle/WX10010090M01.jpg
Resolving images7.moonbasa.com... 123.183.210.173
Connecting to images7.moonbasa.com|123.183.210.173|:80... connected.
HTTP request sent, awaiting response...
HTTP/1.1 200 OK
Server: DnionOS/1.0
Date: Fri, 03 Sep 2010 14:00:22 GMT
Content-Type: image/jpeg
Connection: keep-alive
Cache-Control: max-age=31104000
Content-Length: 13726
Last-Modified: Mon, 23 Aug 2010 09:06:04 GMT
Accept-Ranges: bytes
ETag: "2074f569a242cb1:1b20"
Vary: Accept-Encoding
X-Powered-By: ASP.NET
X-Cache: MISS from CT-SHBA-177-211.fastcdn.com
Age: 12119
X-Cache: HIT from CT-QHD-210-146.fastcdn.com
Length: 13726 (13K) [image/jpeg]
Is there anything wrong?
Other than their omitting Via: header. Not really.
One of the privileges of being a CDN / reverse-proxy is being an
authoritive source for the data. Which means the Date is allowed to be
set at the time they leave the CDN.
It's also possible the CDN is re-validating on every request and sending
you the revised Date from the origin server. Squid tries hard to avoid this.
Amos
--
Please be using
Current Stable Squid 2.7.STABLE9 or 3.1.7
Beta testers wanted for 3.2.0.1
