On 12/10/17 19:43, EdouardM wrote:
Amos,
here is an example:
http://au.download.windowsupdate.com/d/msdownload/update/software/updt/2017/09/windows10.0-kb4023814-x86_f07f9708c76807b1b19545521f17d6e2fefdd627.cab
HTTP/1.1 200 OK
Cache-Control: public,max-age=172800
Content-Length: 6150968
Content-Type: application/vnd.ms-cab-compressed
Last-Modified: Wed, 27 Sep 2017 21:16:36 GMT
Accept-Ranges: bytes
ETag: "09295e6d537d31:0"
Server: Microsoft-IIS/8.5
X-Powered-By: ASP.NET
X-CID: 7
X-CCC: IN
X-MSEdge-Ref: Ref A: 7A93444FAE0B4491BE72E049496DEC25 Ref B: BOM02EDGE0119
Ref C: 2017-10-12T06:36:40Z
X-MSEdge-Ref-OriginShield: Ref A: C8FD899B17694B8AA6641257C2636B9B Ref B:
BOM01EDGE0318 Ref C: 2017-10-11T14:02:56Z
Date: Thu, 12 Oct 2017 06:36:40 GMT
Length: 6150968 (5.9M) [application/vnd.ms-cab-compressed]
does it mean the object will be valid for 2 days (max-age=172800) only, then
the Squid will download a fresh copy from internet even if we set the
refresh_pattern to 1 month ?
CC:max-age=172800 means it can be served unconditionally from cache for
172800 seconds from Date: Thu, 12 Oct 2017 06:36:40 GMT.
After Sat, 14 Oct 2017 06:36:40 GMT (Date + CC:max-age) it is stale and
needs revalidating before any use. The headers from the revalidation
response will alter the above headers to provide new values for Date and
maybe other bits.
Altering Date naturally alters the base time for the max-age freshness
calculation. So it should be served unconditionally for the next 48hrs
from time of revalidation. Rinse and repeat. **
refresh_pattern is irrelevant here because all the necessary algorithm
parameters for exact expiry (Date and CC:max-age) are provided by that
server.
** NP: that is what should happen anyway, modulo bugs in Squid
calculations or admin configuration settings to force other behaviour.
Amos
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