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From Niklas Edmundsson <ni...@acc.umu.se>
Subject Re: mod_cache responsibilities vs mod_xxx_cache provider responsibilities
Date Thu, 14 Sep 2006 08:19:02 GMT
On Thu, 14 Sep 2006, Graham Leggett wrote:

> Niklas Edmundsson wrote:
>
>> Will it be possible to do away with "one file for headers and one file for 
>> body" in mod_disk_cache with this scheme?
>
> This definitely has lots of advantages - however HTTP/1.1 requires that it be 
> possible to modify the headers on a cached entry independently of the cached 
> body. As long as this is catered for, it should be fine.

Our patch allows for this, the body is simply stored at an offset with 
some logic to detect headers larger than the offset and cope with that 
too (albeit this introduces a risk for bad data being sent to the 
client due to the lockless design, so you really want to avoid this by 
having the offset large enough).

Since seek():ing and writing to an offset doesn't occupy disk space in 
normal unix filesystems there isn't a problem in having the data at a 
rather large offset, but I don't know how non-unix behaves in this 
regard.

/Nikke
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  Niklas Edmundsson, Admin @ {acc,hpc2n}.umu.se      |     nikke@acc.umu.se
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