It's all pretty clear to me now after I read RFC and found relationship between that and refresh_pattern usage.
Thank you.
On Fri, Sep 1, 2017 at 4:46 PM, Amos Jeffries <squid3@xxxxxxxxxxxxx> wrote:
On 02/09/17 00:18, Alexander Lazarev wrote:
Well. looks like squid using heuristics after all:
2017/09/01 14:49:12.296 kid2| 22,3| refresh.cc(291) refreshCheck: checking freshness of 'http://mydomain.zone/1.txt'
2017/09/01 14:49:12.296 kid2| 22,3| refresh.cc(312) refreshCheck: Matched '<none> 0 20%% 259200'
2017/09/01 14:49:12.296 kid2| 22,3| refresh.cc(314) refreshCheck: age: 65955
2017/09/01 14:49:12.296 kid2| 22,3| refresh.cc(316) refreshCheck: check_time: Fri, 01 Sep 2017 11:49:12 GMT
2017/09/01 14:49:12.296 kid2| 22,3| refresh.cc(318) refreshCheck: entry->timestamp: Thu, 31 Aug 2017 17:29:57 GMT
2017/09/01 14:49:12.296 kid2| 22,3| refresh.cc(179) refreshStaleness: No explicit expiry given, using heuristics to determine freshness
2017/09/01 14:49:12.296 kid2| 22,3| refresh.cc(198) refreshStaleness: Last modified 5524975 sec before we cached it, L-M factor 20.00% = 1104995 sec freshness lifetime
2017/09/01 14:49:12.296 kid2| 22,3| refresh.cc(205) refreshStaleness: FRESH: age 65955 <= stale_age 1104995
2017/09/01 14:49:12.296 kid2| 22,3| refresh.cc(338) refreshCheck: Staleness = -1
2017/09/01 14:49:12.296 kid2| 22,3| refresh.cc(461) refreshCheck: Object isn't stale..
2017/09/01 14:49:12.296 kid2| 22,3| refresh.cc(470) refreshCheck: returning FRESH_LMFACTOR_RULE
It's a shame there's no warning header, like "https://tools.ietf.org/html/rfc7234#section-5.5.4 " suggests.
There should be when that cached response becomes 24 hrs old. That log says Squid only received the object ~18 hrs ago, so the cached *response* has not been around for 24hrs yet even though the *content* it refers to on the server is older.
Content on a server being old is no particular cause for alarm if it gets cached a few seconds/hrs/mins on a proxy.
Though note that Warning headers about heuristics being used are an OPTIONAL, so it is also not a problem if they are absent.
Guess, I need to set refresh_pattern's max option to minimal value.
Any particular reason you are worried about all this?
Heuristic freshness is normal and usually perfectly fine. A proxy making heuristic decisions is only a problem if it is ignoring server or client instructions about the content cacheability. Also, a reverse-proxy as an agent of the server effectively has permission to ignore things the client wants - though it is usually a good idea to do a background revalidation if the client insists strongly on new content (eg. reload-into-ims option), because that tends to mean there is some problem with what it got earlier [maybe whats in the cache].
On Thu, Aug 31, 2017 at 8:26 PM, Alexander Lazarev wrote:
Thank you for reply!
I still don't understand what's happening.
I create file 1.txt with a little bit of text data. Request it with
curl. Web-server returns it without any cache related headers to
squid, squid returns it to me. Getting it with curl one more time,
squid serves it straight from cache without validation(no entries in
log on origin server).
I create one more file 2.txt with some data. Do same things, same
headers in response. Second response from squid is from cache but
validated from origin server(i see 304 in origin server logs).
What could be wrong?
Nothing wrong. Both sequences are valid and normal. The difference could just be a timing variation as small as a nanosecond in what operations are performed relative to each other - with heuristics based on 0.2 of a recently created objects age HTTP's 1 second in timing resolution is both very course and very sensitive to rounding limits.
Amos
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