On 5/04/20 2:53 am, Alex Rousskov wrote: > On 4/3/20 4:55 PM, zrm wrote: >> 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? > >> squid to apt: >> --------- >> X-Cache: MISS from tproxy >> X-Cache-Lookup: MISS from tproxy:3130 > >> squid to wget: >> --------- >> X-Cache: MISS from tproxy >> X-Cache-Lookup: MISS from tproxy:3130 > > The headers you have posted tell us that the object was not in Squid > cache when apt and wget transactions started. Since wget was started > after apt, we can speculate that apt transaction did not cache the > object. This is consistent with your observations. I saw nothing in the > posted headers that would explain the difference between apt and wget > outcomes. > > Unfortunately, you did not show the headers for the case where the > object actually got cached by Squid. You can probably do that by > repeating the wget transaction twice. I would also repeat the apt > transaction twice after that. It would also be interesting to see the > wget-apt and apt-wget sequences. In summary, I would do > wget-wget-apt-apt-wget-wget. Sleep for 10+ seconds between each > transaction to reduce chances of overlapping cache operations. > > BTW, you probably do not need to make ALL,2 logs pretty -- we can figure > out what happens based on Squid messages if you submit one transaction > at a time and disclose transaction sequence. You can just post (a link > to) raw (or sanitized) logs. Compress them if they are too big. > > Before sharing the logs, please double check that the problem you want > to address was reproduced during the test. > > >> Last-Modified: Sat, 15 Jun 2019 17:46:35 GMT >> ETag: "1389dc-58b605823fa6e" >> Cache-Control: public, max-age=2592000 >> Content-Length: 1280476 >> Age: 4248100 > > FWIW: The object is 4'248'100 seconds old. The object max-age is > 2'592'000 seconds. Your Squid is probably using an internal max-age of > 259'200 seconds, so Squid will require cache hit revalidation during > subsequent transactions after Squid caches the object (if it caches it). > >
One thing to notice as well is that the object delivered by the upstream caches expired over 19 days before these tests took place: > Cache-Control: public, max-age=2592000 > Age: 4248100 The request from Squid in both transactions was to receive content no longer than 3 days old. The other caches ignored that requirement and served old content from their storage, apparently without even checking an origin whether it was stale. Amos _______________________________________________ squid-users mailing list squid-users@lists.squid-cache.org http://lists.squid-cache.org/listinfo/squid-users
