RE: First Cache, Last Proxy

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From: Richard Neal G. Plana
Sent: 26 September 1997 15:43
To: squid-users@nlanr.net
Subject: First Cache, Last Proxy

Is it possible to configure Squid to use a proxy cache of
FirstRestort and
Last Resort? I'm thinking of putting up two proxy caches on our two
upstream links to the Internet (A and B). I want proxy A to choose B
as
its cache of FirstResort. This would mean it would look to proxy B
for a
give object first. If it cannot find it there, it would try to get
the
object from its home site itself. However, if it finds that it cannot
do
that (ie. the line goes down, problem with routes, etc.), it will
turn to
B as proxy of LastResort.

I think you want to have a parent entry for each of A and B, with the
line for A having the option "weight=100" and that for B having "no-
query weight=50 default" (actually the numbers are fairly
meaningless, as long as one is greater than the other). Also turn on
source_ping.

The only problem is that B will be chosen if the ping times out (with
length from neighbor_timeout). Increasing the neighbor_timeout will
cause large delays if the pings are lost (or a firewall filters them)
before they get back to you, so increasing the timeout may not be a
good idea.

If you want to have a mechanism that really does only use B if A is
down, then you'll have to do it externally, with a script that checks
A is okay, and if not does something like swap squid.conf's and kill -
HUP squid. (And swap back and kill -HUP squid when A comes back).

Jonathan L.

Origin, 323 Cambridge Science Park, Cambridge, UK. Tel:+44 (1223)
423355
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Received on Fri Sep 26 1997 - 08:35:34 MDT