Re: [squid-users] delivering stale content while fetching fresh

tis 2006-09-05 klockan 08:31 +0200 skrev Gregor Reich:

> I checked out squid 2.6 STABLE and I found the feature in question and
> the associated comment in the squid.conf file. Thank you. Please correct
> me, if I'm wrong assuming that:
>
> * refresh_stale_hit makes stale content (within the
> refresh_stale_hit-defined period) to be accessed, while - in this
> moment - the fresh content is fetched from the backend servers to
> be cached

Correct. It means that only one client will wait for the refresh, the
others will get the stale copy.

> * refresh_stale_hit is independent of collapsed_forwarding, i.e. it
> doesn't matter wether collapsed_forw. is enabled or not

Correct.

> * collapsed_forwarding bundles concurrent request for the same URI
> into one; but what means "concurrent"? Within a certain time slot?
> If yes, how long is this time slot?

While Squid is waiting for the response headers from the web server, or
at most 30 seconds. If it takes more than 30 seconds for the server to
answer then the next incoming request will create a new request to the
web server and future clients will collapse into that one..

The drawback of enabling collapsed_forwarding is that concurrent
requests for uncachable content will get delayed a bit until Squid sees
that the response can not be cached (response headers required), at
which point all pending collapsed queries for that URL will all start a
new request each..

Regards
Henrik