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From Graham Leggett <>
Subject Re: mod_disk_cache summarization
Date Fri, 27 Oct 2006 21:33:16 GMT
Niklas Edmundsson wrote:

> Different VHosts meaning different URLs/directories, pointing to the 
> same files...

Hmm... Two thoughts come into my head over this one.

One way to approach this is to treat this as a general problem of how do 
we stop people who download the same file from multiple places (say 
different mirrors via proxy, or different URLs to the backend like you 
have) from downloading multiple copies of the same file hosted at 
different URLs.

Here you might have some kind of regex-like expression, like *.iso, that 
says "all files whose names match this regex, are considered the same 
file". A mechanism might have a small cache of filenames that have 
matched the regex in the past, and that link to actual cached entries in 
the cache.

This would need to be abstracted out into an existing hook (or new one 
if necessary).

A second approach could involve the use of the Etags associated with 
file responses, which in the case of files served off disk (as I 
understand it) are generated based on inode number and various other 
uniquely file specific information.

Therefore in theory two responses with the same Etag are actually the 
same file, and if you've already cached a file with that Etag, then the 
same Etag quick cache scenario described above could provide a shortcut 
to the same file cached at a different URL.


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