upcoming changes to TTLs.

From: Duane Wessels <wessels>
Date: Sun, 27 Oct 96 22:13:12 -0800

For the next 1.1 beta version I have changed the way Squid handles
object lifetimes. Instead of calculating a TTL when the object
enters the cache, it now checks for "freshness" or "staleness"
when the request is made.

If the object is considered "fresh" then it will be a TCP HIT.

If the object is "stale" then Squid makes the request with an
If-Modified-Since line. The result will be either TCP_REFRESH_HIT (not
modified), TCP_REF_FAIL_HIT (IMS request failed), or TCP_REFRESH_MISS
(new content).

The 'ttl_pattern' config option is replaced with a 'refresh_pattern'
directive. In addition to the regular expression, the refresh_pattern
line takes three parameters: min, max, percent.

If the object age is less than 'min', it is fresh.

If the object expiry time has been reached, it is stale.

If the object age is more than 'max', it is stale.

If it is inbetween, then we check the last-modified factor. If
the LM-factor is less than 'percent' then it is fresh, otherwise
it is stale.

Note that there is no separate option corresponding to
'ttl_force_pattern'. You can override the object's Expires setting
with the 'min' value since it is checked first.

I hope this makes sense and provides enough flexibility. I'm
sure y'all will let me know otherwise.. :-)

Duane W.
Received on Sun Oct 27 1996 - 22:13:13 MST

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