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List:       squid-users
Subject:    Re: [squid-users] refresh_pattern defaults
From:       Amos Jeffries <squid3 () treenet ! co ! nz>
Date:       2014-03-27 2:49:53
Message-ID: 533391D1.1070105 () treenet ! co ! nz
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On 27/03/2014 3:30 p.m., Thomas wrote:
> Hi guys,
> 
> I've been searching for a while and could not find the answer to the
> 'refresh_pattern' default values if they're NOT defined in the
> configuration. On the config website it mentions "none" which I don't
> understand, because in order to calculate this:
> 
> > > How does Squid decide when to refresh a cached object
> 
> if (EXPIRES) {
> if (EXPIRES <= NOW)
> return STALE
> else
> return FRESH
> }
> if (CLIENT_MAX_AGE)
> if (OBJ_AGE > CLIENT_MAX_AGE)
> return STALE
> if (OBJ_AGE > CONF_MAX)
> return STALE
> if (OBJ_DATE > OBJ_LASTMOD) {
> if (LM_FACTOR < CONF_PERCENT)
> return FRESH
> else
> return STALE
> }
> if (OBJ_AGE <= CONF_MIN)
> return FRESH
> return STALE
> 
> (taken from
> http://wiki.squid-cache.org/SquidFaq/InnerWorkings#How_does_Squid_decide_when_to_refresh_a_cached_object.3F)
>  
> 
> We need the refresh_pattern config values? I'm at a loss, have asked a
> good few linux friends etc using squid for a while with no good reply.

The above algorithm uses the server HTTP response header values as
primary source of input parameters.

The refresh_pattern directive is "just" a way to provide default input
parameters for the algorithm in the event that the server response
omitted any or all of them.

Squid is hard-coded with default algorithm parameters which are expected
to store things for up to 3 days in the event that refresh_pattern is
omitted from the config file entirely AND the server response provides
no values.

Amos


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