"Object size mismatch" error handling in squid

From: Robert Davy <Robert.Davy@dont-contact.us>
Date: Thu, 23 Apr 1998 10:00:09 +1000 (EST)

On the subject of "Object size mismatch" errors such as:

1998/04/19 00:06:03| storeSwapInHandle: WARNING: Object size mismatch.
1998/04/19 00:06:03| --> 'http://home.microsoft.com/images/ie-static.gif'
1998/04/19 00:06:03| --> Expecting 1199 bytes from file: /cache2/03/20/00014
1998/04/19 00:06:03| --> Only read 14420 bytes

We have had a number of occasions over the years where power blackouts, or
system hangs have caused our campus squid cache indexes to become corrupt.

The unfortunate consequence of this is that inevitably (given the propensity
of students to download pornographic images :-) any corruption results in
a pornographic image being presented in place of what was intended (in this
case a very boring IE gif was replaced with an interesting picture of two
ladies doing something impossible with a baseball bat!)

As a result of these experiences I have come to the conclusion that a warning
is not appropriate here, and any "object size mismatches" should result in
the immediate expulsion of the object from the cache, and a fresh copy
being fetched.

This will help us a lot, as the only real way to remove such corruption from
the cache is clear it completely.

What do you think?? A compile time option would be appropriate if anyone can
think of why this should not be the default behaviour...

Robert Davy                       *  .*            Robert.Davy@anu.edu.au
Network Services                          ph:02 62492978  fax:02 62798120
Australian National University      *       Canberra, ACT 0200, Australia
Received on Wed Apr 22 1998 - 17:09:33 MDT

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