[squid-users] Unneeded DNS lookups for cache_peer selection

Hello everyone!

We have a setup with a single parent proxy that shall be used for all
requests. "never_direct allow all" ensures that the parent is not to be
bypassed. Still, every request leads to an extra unnecessary (and
failing) DNS lookup. We enjoyed several complaints because of unwanted
DNS traffic inside a firewalled area. As all results are negative, even
the DNS caching does not really help.

I have traced the problem into peerSelectDnsPaths() in
src/peer_select.cc. It seems that despite the clear fact that only one
cache_peer can ever be selected (and has to be selected), the code still
makes a DNS request for the hostname in the requested URL to find the
best proxy. It would be greatly appreciated if we could suppress these
lookups without loosing DNS access for parent proxy lookup by DNS name.
The lookup does not make any sense to me even with multiple parents, if
the parent selection is never based on the request target host.

The only workaround we have found so far is to specify the parent proxy
by IP address and tell Squid with "dns_nameservers localhost" to use a
not existing DNS server. However, this way we loose the DNS based load
balancing at the parent proxy, which we cannot influence ourselves.

This looks like a similar problem to the one discussed in
http://www.squid-cache.org/mail-archive/squid-users/201309/0364.html

Thanks for a great product,

Amon Ott

-- 
Dr. Amon Ott
m-privacy GmbH           Tel: +49 30 24342334
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