[squid-users] squid won't return cached even with refresh_pattern extra options override-lastmod override-expire ignore-reload ignore-no-store ignore-private store-stale

[Alex Rousskov]

On 3/24/21 12:48 PM, Miroslaw Malinowski wrote:

> Probably, me missing on something silly or it can't be done but I don't
> know why but squid won't return the cached version even when I turn all
> override options ON in refresh_pattern.

AFAICT, no configuration options that can disable revalidation of
Cache-Control:no-cache responses. refresh_pattern does not have an
(equivalent of) "ignore-no-cache-in-responses" option.

IIRC, older Squids were violating an HTTP MUST by forgetting to
revalidate Cache-Control:no-cache responses, but that was fixed in [1].
Your Squid version has that fix.

[1]
https://github.com/squid-cache/squid/commit/fa83b766a208b27abed8da4c9073cf8784cf10fa


> With debug, I can see the rule is matched and the cache is fresh but
> still in access.log is TCP_REFRESH_MODIFIED

> 2021-03-24T15:04:34	squid	.710 kid1| 11,3| http.cc(982)
> haveParsedReplyHeaders: decided: cache positively and share because

FYI: You are looking at cache.log lines logged _after_ Squid has already
decided to refresh the cached version. If you want to analyze why Squid
decided to refresh the cached version, you should look _before_ Squid
logged the request to the server (and before any FwdState.cc lines). I
have not checked the details, but I bet that your Squid revalidates
because of Cache-Control:no-cache in the response. Look for "YES: Must
revalidate stale object".


HTH,

Alex.

> squid conf:
> refresh_pattern -i <URL> 4320 80% 129600 override-lastmod
> override-expire ignore-reload ignore-no-store ignore-private store-stale
> 
> curl headers:
> curl --insecure --verbose --request GET --url 'URL' >/dev/null
> * TCP_NODELAY set
> * ALPN, offering h2
> * ALPN, offering http/1.1
> * successfully set certificate verify locations:
> *   CAfile: /etc/ssl/certs/ca-certificates.crt
>  CApath: /etc/ssl/certs
> } [5 bytes data]
> * TLSv1.3 (OUT), TLS handshake, Client hello (1):
> } [512 bytes data]
> * TLSv1.3 (IN), TLS handshake, Server hello (2):
> { [122 bytes data]
> * TLSv1.3 (IN), TLS handshake, Encrypted Extensions (8):
> { [6 bytes data]
> * TLSv1.3 (IN), TLS handshake, Certificate (11):
> { [1956 bytes data]
> * TLSv1.3 (IN), TLS handshake, CERT verify (15):
> { [78 bytes data]
> * TLSv1.3 (IN), TLS handshake, Finished (20):
> { [52 bytes data]
> * TLSv1.3 (OUT), TLS change cipher, Change cipher spec (1):
> } [1 bytes data]
> * TLSv1.3 (OUT), TLS handshake, Finished (20):
> } [52 bytes data]
> * SSL connection using TLSv1.3 / TLS_AES_256_GCM_SHA384
> 
>> GET URL HTTP/1.1
>> Host: URL
>> User-Agent: curl/7.68.0
>> Accept: */*
>>
> { [5 bytes data]
> * TLSv1.3 (IN), TLS handshake, Newsession Ticket (4):
> { [217 bytes data]
> * TLSv1.3 (IN), TLS handshake, Newsession Ticket (4):
> { [217 bytes data]
> * old SSL session ID is stale, removing
> { [5 bytes data]
> * Mark bundle as not supporting multiuse
> < HTTP/1.1 200 OK
> < Cache-Control: no-cache
> < Content-Type: application/json
> < X-Cloud-Trace-Context: d3c27833b8b4312ce31a2dbae7e12fd0
> < Date: Wed, 24 Mar 2021 15:04:34 GMT
> < Server: Google Frontend
> < Content-Length: 7950
> < X-Cache: MISS from server
> < X-Cache-Lookup: HIT from server
> < Via: 1.1 server (squid/4.14)
> < Connection: keep-alive
> 
> access log:
> 243 172.16.230.249 TCP_REFRESH_MODIFIED/200 8328 GET URL -
> ORIGINAL_DST/IP application/json
> 
> cache log:
> 2021-03-24T15:04:34	squid	.710 kid1| 11,3| http.cc(982)
> haveParsedReplyHeaders: decided: cache positively and share because
> refresh check returned cacheable; HTTP status 200 e:=p2V/0x34868914670*3	 
> 2021-03-24T15:04:34	squid	.710 kid1| 22,3| refresh.cc(470) refreshCheck:
> returning FRESH_MIN_RULE	 
> 2021-03-24T15:04:34	squid	.710 kid1| 22,3| refresh.cc(455) refreshCheck:
> Object isn't stale..	 
> 2021-03-24T15:04:34	squid	.710 kid1| 22,3| refresh.cc(327) refreshCheck:
> Staleness = -1	 
> 2021-03-24T15:04:34	squid	.710 kid1| 22,3| refresh.cc(199)
> refreshStaleness: FRESH: age (60 sec) is less than configured minimum
> (259200 sec)	 
> 2021-03-24T15:04:34	squid	.710 kid1| 22,3| refresh.cc(166)
> refreshStaleness: No explicit expiry given, using heuristics to
> determine freshness	 
> 2021-03-24T15:04:34	squid	.710 kid1| 22,3| refresh.cc(307) refreshCheck:
> entry->timestamp: Wed, 24 Mar 2021 15:04:34 GMT	 
> 2021-03-24T15:04:34	squid	.710 kid1| 22,3| refresh.cc(305) refreshCheck:
> check_time: Wed, 24 Mar 2021 15:05:34 GMT	 
> 2021-03-24T15:04:34	squid	.710 kid1| 22,3| refresh.cc(303) refreshCheck:
> age: 60	 
> 2021-03-24T15:04:34	squid	.710 kid1| 22,3| refresh.cc(301) refreshCheck:
> Matched 'URL 259200 80%% 7776000'	 
> 2021-03-24T15:04:34	squid	.710 kid1| 22,3| refresh.cc(279) refreshCheck:
> checking freshness of URI: https://URL <https://URL>
> 
> 
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