On 4/3/20 16:34, Alex Rousskov wrote:
On 4/3/20 4:26 PM, zrm wrote:
In the first case we get TCP_MISS every time because it isn't caching
the data, in the second case it's only the first time and after that we
get TCP_REFRESH_UNMODIFIED. But how and why is this happening?
Those questions can often be answered by looking at HTTP headers
received and sent by Squid when talking to clients and origin servers.
You can see those headers in basic packet captures or if you set
debug_options to ALL,2.
Alex.
apt to squid:
---------
GET /debian/pool/main/v/vim/vim_8.1.0875-5_amd64.deb HTTP/1.1
Host: deb.debian.org
User-Agent: Debian APT-HTTP/1.3 (1.8.2)
----------
squid to deb.debian.org:
---------
GET /debian/pool/main/v/vim/vim_8.1.0875-5_amd64.deb HTTP/1.1
User-Agent: Debian APT-HTTP/1.3 (1.8.2)
Host: deb.debian.org
Via: 1.1 tproxy (squid/4.6)
X-Forwarded-For: 192.168.111.55
Cache-Control: max-age=259200
Connection: keep-alive
----------
deb.debian.org to squid:
---------
HTTP/1.1 200 OK
Server: Apache
X-Content-Type-Options: nosniff
X-Frame-Options: sameorigin
Referrer-Policy: no-referrer
X-Xss-Protection: 1
Last-Modified: Sat, 15 Jun 2019 17:46:35 GMT
ETag: "1389dc-58b605823fa6e"
X-Clacks-Overhead: GNU Terry Pratchett
Cache-Control: public, max-age=2592000
Content-Type: application/x-debian-package
Via: 1.1 varnish
Content-Length: 1280476
Accept-Ranges: bytes
Date: Fri, 03 Apr 2020 05:28:46 GMT
Via: 1.1 varnish
Age: 4248100
Connection: keep-alive
X-Served-By: cache-ams21028-AMS, cache-wdc5559-WDC
X-Cache: HIT, HIT
X-Cache-Hits: 1, 2
X-Timer: S1585891726.434375,VS0,VE0
----------
squid to apt:
---------
HTTP/1.1 200 OK
Server: Apache
X-Content-Type-Options: nosniff
X-Frame-Options: sameorigin
Referrer-Policy: no-referrer
X-Xss-Protection: 1
Last-Modified: Sat, 15 Jun 2019 17:46:35 GMT
ETag: "1389dc-58b605823fa6e"
X-Clacks-Overhead: GNU Terry Pratchett
Cache-Control: public, max-age=2592000
Content-Type: application/x-debian-package
Content-Length: 1280476
Accept-Ranges: bytes
Date: Fri, 03 Apr 2020 05:28:46 GMT
Age: 4248100
X-Served-By: cache-ams21028-AMS, cache-wdc5559-WDC
X-Cache: HIT, HIT
X-Cache-Hits: 1, 2
X-Timer: S1585891726.434375,VS0,VE0
X-Cache: MISS from tproxy
X-Cache-Lookup: MISS from tproxy:3130
Via: 1.1 varnish, 1.1 varnish, 1.1 tproxy (squid/4.6)
Connection: keep-alive
----------
wget to squid:
---------
GET /debian/pool/main/v/vim/vim_8.1.0875-5_amd64.deb HTTP/1.1
User-Agent: Wget/1.20.1 (linux-gnu)
Accept: */*
Accept-Encoding: identity
Host: deb.debian.org
Connection: Keep-Alive
----------
squid to deb.debian.org:
----------
GET /debian/pool/main/v/vim/vim_8.1.0875-5_amd64.deb HTTP/1.1
User-Agent: Wget/1.20.1 (linux-gnu)
Accept: */*
Accept-Encoding: identity
Host: deb.debian.org
Via: 1.1 tproxy (squid/4.6)
X-Forwarded-For: 192.168.111.55
Cache-Control: max-age=259200
Connection: keep-alive
----------
deb.debian.org to squid:
---------
HTTP/1.1 200 OK
Server: Apache
X-Content-Type-Options: nosniff
X-Frame-Options: sameorigin
Referrer-Policy: no-referrer
X-Xss-Protection: 1
Last-Modified: Sat, 15 Jun 2019 17:46:35 GMT
ETag: "1389dc-58b605823fa6e"
X-Clacks-Overhead: GNU Terry Pratchett
Cache-Control: public, max-age=2592000
Content-Type: application/x-debian-package
Via: 1.1 varnish
Content-Length: 1280476
Accept-Ranges: bytes
Date: Fri, 03 Apr 2020 05:28:49 GMT
Via: 1.1 varnish
Age: 4248102
Connection: keep-alive
X-Served-By: cache-ams21028-AMS, cache-wdc5583-WDC
X-Cache: HIT, HIT
X-Cache-Hits: 1, 1
X-Timer: S1585891729.316362,VS0,VE0
----------
squid to wget:
---------
HTTP/1.1 200 OK
Server: Apache
X-Content-Type-Options: nosniff
X-Frame-Options: sameorigin
Referrer-Policy: no-referrer
X-Xss-Protection: 1
Last-Modified: Sat, 15 Jun 2019 17:46:35 GMT
ETag: "1389dc-58b605823fa6e"
X-Clacks-Overhead: GNU Terry Pratchett
Cache-Control: public, max-age=2592000
Content-Type: application/x-debian-package
Content-Length: 1280476
Accept-Ranges: bytes
Date: Fri, 03 Apr 2020 05:28:49 GMT
Age: 4248102
X-Served-By: cache-ams21028-AMS, cache-wdc5583-WDC
X-Cache: HIT, HIT
X-Cache-Hits: 1, 1
X-Timer: S1585891729.316362,VS0,VE0
X-Cache: MISS from tproxy
X-Cache-Lookup: MISS from tproxy:3130
Via: 1.1 varnish, 1.1 varnish, 1.1 tproxy (squid/4.6)
Connection: keep-alive
----------
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