[squid-users] TCP_REFRESH_UNMODIFIEDs are really MISSes

Wed Oct 11 01:50:43 UTC 2017

Dear Colleagues,

When updating several almost identical FreeBSD hosts via a
squid-3.5.27 proxy, I expect to see lots of HITs, because the patches
on the update server should be identical too.

However, I see lots of TCP_REFRESH_UNMODIFIED lines, and only
occasional HIT statuses. Please see the log excerpt at the end of the
message, and the example exchange between client and squid.

 From the squid documentation I figure out that a
TCP_REFRESH_UNMODIFIED status means that there was an IMS request
involved. But I don't understand who made this IMS request: client to
squid or squid to the webserver.

The "fetch" HTTP client the freebsd-update utility uses is rather dumb
and does not send IMS requests (also see below). Could someone please
explain what is happening here?

The HTTP replies from the squid cache to the HTTP client are
"X-Cache-Lookup: MISS from proxy2.sibptus.ru:8080", so these
TCP_REFRESH_UNMODIFIED statuses seem to be really MISSes and I'm not
saving traffic on these updates.

1507630624.673    389 212.73.124.12 TCP_REFRESH_UNMODIFIED/200 572 GET http://update6.freebsd.org/to-10.4-RELEASE/i386/bp/82a25f03517d9d65b3c0af22f77ed9cbe94d09f1af6f4cd835a93b5f191122dc-63836fc812fc7b03a2ad1d2df9c59dde3178e1eaf4d0e32342a8a04a7121ac6d - HIER_DIRECT/198.148.79.66 application/octet-stream
1507630625.067    394 212.73.124.12 TCP_REFRESH_UNMODIFIED/200 574 GET http://update6.freebsd.org/to-10.4-RELEASE/i386/bp/584713682ac3cc86fd2bfb7edbb9030aa48efbf027465ebcce705864310140af-0981c929f128ad067d3c8c577f9c84302523e24548b561edceee28a3357a5007 - HIER_DIRECT/198.148.79.66 application/octet-stream
1507630625.515    448 212.73.124.12 TCP_REFRESH_UNMODIFIED/200 980593 GET http://update6.freebsd.org/to-10.4-RELEASE/i386/bp/1195d725efce75f0db6317f507d8a9514f35613c7466673a86db23100bd6fa77-c4150431df5b14b15546b3db5e30f2bd2c35d6d52812f057dc101fab20847324 - HIER_DIRECT/198.148.79.66 application/octet-stream
1507630625.914    399 212.73.124.12 TCP_REFRESH_UNMODIFIED/200 532 GET http://update6.freebsd.org/to-10.4-RELEASE/i386/bp/aac782643cbfaad218bf72f037624af304d353f2a12fb6a5eeb117cdd6c9bc27-2f6df820f68859d2e86a8f45777a81a7186477048893456f891fd91dae19af3b - HIER_DIRECT/198.148.79.66 application/octet-stream
1507630625.948     33 212.73.124.12 TCP_HIT/200 980593 GET http://update6.freebsd.org/to-10.4-RELEASE/i386/bp/1195d725efce75f0db6317f507d8a9514f35613c7466673a86db23100bd6fa77-c4150431df5b14b15546b3db5e30f2bd2c35d6d52812f057dc101fab20847324 - HIER_NONE/- application/octet-stream
1507630626.354    406 212.73.124.12 TCP_REFRESH_UNMODIFIED/200 531 GET http://update6.freebsd.org/to-10.4-RELEASE/i386/bp/58764b03f019f1aa9e28e24ddb9e74abf323cfc3984bd899accf7b15bb2a6462-6d53fae808e6d79c6c251f6b1fe5e26fbd84e191f84900bcf01931d49855249f - HIER_DIRECT/198.148.79.66 application/octet-stream
1507630626.391     36 212.73.124.12 TCP_HIT/200 980593 GET http://update6.freebsd.org/to-10.4-RELEASE/i386/bp/1195d725efce75f0db6317f507d8a9514f35613c7466673a86db23100bd6fa77-c4150431df5b14b15546b3db5e30f2bd2c35d6d52812f057dc101fab20847324 - HIER_NONE/- application/octet-stream
1507630626.391      0 212.73.124.12 TCP_MEM_HIT/200 527 GET http://update6.freebsd.org/to-10.4-RELEASE/i386/bp/1af4cec823d8b1f42c3b8a58ec0da40bfc2f97efacd92e7758096eba081e08db-2ac8890502bc272d65f2b7dd73fa7def11fa4d3feb2005b82b58ba43747b57e4 - HIER_NONE/- application/octet-stream
1507630626.785    393 212.73.124.12 TCP_REFRESH_UNMODIFIED/200 697 GET http://update6.freebsd.org/to-10.4-RELEASE/i386/bp/6c0eae2981826e2033797003f53aedba9adb7e317c936f6923912e5df2627216-341717a9aa21a95b7f9f83e29ac3de1cac6b9d58700ece767e4ab7cd028105c9 - HIER_DIRECT/198.148.79.66 application/octet-stream
1507630627.184    399 212.73.124.12 TCP_REFRESH_UNMODIFIED/200 1001 GET http://update6.freebsd.org/to-10.4-RELEASE/i386/bp/6f486e6baa2d057fa16d3fa43e666917ab9d045de2e59a7d05ace758c7d03373-653636793fd95f406da85e1375acd38f31b6c39c404b18cd8e0a641a2deb6065 - HIER_DIRECT/198.148.79.66 application/octet-stream
1507630627.577    392 212.73.124.12 TCP_REFRESH_UNMODIFIED/200 674 GET http://update6.freebsd.org/to-10.4-RELEASE/i386/bp/3c78173d804b5299f24199a125b3c52145c7e7680c97debb051d823526ae0579-595c12cd31ef1c4d084c308b7278d28bbb844873da246d88fb02db90f90b88b9 - HIER_DIRECT/198.148.79.66 application/octet-stream
1507630627.967    389 212.73.124.12 TCP_REFRESH_UNMODIFIED/200 1193 GET http://update6.freebsd.org/to-10.4-RELEASE/i386/bp/cc4d2e70a2c12900362eba48bae5fa8388bfd8ed9975246578d5c68fd00fb9b3-74473c002b6e269ddb7b3c385cfff0f43b4fcbf1dcba7f36dac7c7918b19f8a9 - HIER_DIRECT/198.148.79.66 application/octet-stream
1507630628.357    391 212.73.124.12 TCP_REFRESH_UNMODIFIED/200 29745 GET http://update6.freebsd.org/to-10.4-RELEASE/i386/bp/2f0861149594653c2b91faec675aef008728c5ba13b352ca3877714a40bffbd6-e6b495c0d23d7eb5fe43bb07e5a8a71f3bad37844a0e8a121ef2178e5fd6ca4a - HIER_DIRECT/198.148.79.66 application/octet-stream

GET http://update.FreeBSD.org/to-10.4-RELEASE/i386/bp/4b363ee1c1e681fe5a67dd7201062ee1977f1437ce9de7c7bc9c9b84839f10df-6dc4edca0bcab3f4b0ae59d1a2714aeb0df22fce043c8897079ab9914fdafbf4 HTTP/1.1
Host: update.FreeBSD.org
User-Agent: freebsd-update (upgrade, 10.3-RELEASE-p20)
Connection: Keep-Alive

HTTP/1.1 200 OK
Date: Wed, 11 Oct 2017 01:38:16 GMT
Server: Apache/2.2.16 (FreeBSD) mod_ssl/2.2.16 OpenSSL/0.9.8n DAV/2
Last-Modified: Sun, 01 Oct 2017 19:32:05 GMT
ETag: "1f0c0de-951-55a81501e5740"
Accept-Ranges: bytes
Content-Length: 2385
Content-Type: text/plain
X-Cache: MISS from proxy2.sibptus.ru
X-Cache-Lookup: MISS from proxy2.sibptus.ru:8080
Via: 1.1 proxy2.sibptus.ru (squid/3.5.27)
Connection: keep-alive

BSDIFF40.......

-- 
Victor Sudakov,  VAS4-RIPE, VAS47-RIPN
AS43859