Re: negative_dns_ttl in STABLE5 [related patch]

From: Charles Bruneteau <>
Date: Tue, 19 Oct 1999 15:17:46 +0200

Henrik Nordstrom wrote:
> Charles Bruneteau wrote:
> > > "Pragma: no-cache" invalidates both object and DNS caches.
> >
> > Are you certain of this Henrik ?
> I was.. but it doesn't.
> My memory said it was the intention once upon a time, but a closer look
> at the source shows that it does not quite work the way I remembered.
> Only negative cached DNS entries get released on reload (and only if
> Squid has the object cached..)
> Attached is a small patch fixing two issues related to this:
> a) Have PURGE also purge the IP-cache from any (valid or not) DNS entry.

When does a PURGE occur ? Does it only depend on ttls from squid.conf ? With a
-k reconfigure ?

> b) Release negatively cached DNS entries on reload regardless if Squid
> has the reloaded object in cache or not.

> Having reload to invalidate seemingly valid DNS entries is perhaps not a
> so great idea. The amount of reloads is quite large, DNS servers usually
> overloaded, and changes in DNS is fairly rare with common practice that
> such changes takes time to propagate.

Concerning reloads are you talking only about "Pragma: no-cache" header ? Is it
so common ? I mean it's only there when a user ask for it (Shift-reload on
Netscape for example). Is an If-modified-since a reload ?

> The two changes above make the operation somewhat cleaner: makes users
> able to quickly get rid of intermettent DNS errors if they insist, and
> allows the administrator to manually purge specific DNS entries if so
> required.


Received on Tue Oct 19 1999 - 07:49:33 MDT

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