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Re: Refresh pattern issue in squid 3.1.20

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On 2015-12-31 22:35, Eliezer Croitoru wrote:
On 31/12/2015 00:48, SaRaVanAn wrote:
Hi, All,
I tired suggested refresh pattern, still i was getting TCP_HIT/MEM_HIT.
It's not getting refreshed after 10 minutes.


*Conf*
refresh_pattern -i ^http://[a-z\-\_\.A-Z0-9]+\.wsj\.(net|net|com|edu)/ 10
200% 10 override-expire override-lastmod reload-into-ims ignore-reload


It is not being refreshed because it does not need to be.

Basically the refresh_pattern overrides can only *extend* caching, or delay revalidation, not shorten it. If the origin says an object is fresh for X amount of time it is expensive (by all metrics; bandwidth, request latency, disk I/O delay, CPU cycles) to discard it earlier than that.

override-expires forces the 'min' value to apply. It is a *minimum* freshness time. If the Expires header or CC:max-age are present and already saying a value larger, then it has no effect.
 - this is what you are seeing SaRaVanAn.

If there were no Expires or CC:max-age, then the max limit would be applied and with a value of "10" it does what you want to happen.

- notice how none of the override-* are relevant to doing what you want, and the Expires/CC:max-age override is just preventing some dynamic content from updating as fast as the origin claims it will be changing.


override-lastmod forces the 'min' limit to be used if the Last-Modified header (lmfactor) algorithm calculates a short caching time. - it also can only extend freshness time *up* to the min-value, not reduce it. If the algorithm produces a longer caching time that will be used.



I am not sure but you are maybe hitting bug 4389 which I have just
recently filed:
http://bugs.squid-cache.org/show_bug.cgi?id=4389


The CC:no-cache control is not present in the responses redbot shows me. So not that one.

Amos

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