Incorrect "host not found (authoritative)" - occasional but annoying

We've been running one version or another of squid (and of its
predecessor, Harvest Cache) for a long time, on a relatively small
scale. There's a problem that hits us occasionally: and having
upgraded to the 1.1..22 release, and noting that the problem still
seems to be there, I thought I would mention it on the list and see if
anyone recognises the symptoms.

As far as the user is concerned, they access a URL at a valid host
and get told:

  The following error was encountered:

     DNS name lookup failure

  The system returned:

    DNS Domain 'what.ev.er' is invalid: Host not found (authoritative).

  listing the name of their intended destination.

The cache.log merely records ERR_DNS_FAIL at the corresponding point.

If one waits long enough for squid's DNS caching to time out, and
then re-loads the identical URL, it works just fine.

The thing that's puzzling about this from the point of view of the
user is the assertion that this answer was "authoritative", when in
fact it is entirely untrue. Is there some kind of time-out or other
failure mode in DNS queries that gets erroneously reported as an
authoritative not-found?

I searched the squid-users archive for similar symptoms, but none of
the items that I found seemed to really match what we've been
experiencing.

Incidentally I have the impression that this happens more often when
the cache is relatively idle. So perhaps it wouldn't be seen at sites
that are always active. It's almost looking as if some process (the
squid DNS process?) is going too deeply to sleep ;-)

The system on which squid runs is also a general unix server, running
all kinds of other tasks for our users in this research group. I
don't recall this kind of thing (i.e an authoritative "host not found"
report that was untrue) ever happening in any other kind of DNS lookup
situation here; not when web browsing with the proxy turned off, nor
when doing any other kind of thing (telnet, ftp etc.) from this same
server.

Any suggestions, please?

(The machine is a DEC ALPHA running OSF1 V3.2 62 alpha, for what it's
worth).
Received on Sun Aug 02 1998 - 10:33:32 MDT