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From Brian Akins <brian.ak...@turner.com>
Subject Re: Possible new cache architecture
Date Mon, 01 May 2006 12:46:14 GMT
Graham Leggett wrote:
>
> The potential danger with this is for race conditions to happen while 
> expiring cache entries. If the data entity expired before the header 
> entity, it potentially could confuse the cache - is the entry cached or 
> not? The headers say yes, data says no.

Nope.  Look at the way the current http cache works. An http "object," 
headers and data, is only valid if both headers and data are valid.

> Each variant should be an independent cached entry, the cache should 
> allow different variants to be cached side by side.

Yes.  Each is distinguished by its key.

>> As far as mod_cache is concerned these are 3 independent entries, but 
>> mod_http_cache knows how to "stitch" them together.
>>
>> mod_cache should *not* be HTTP specific in any way.
> 
> mod_cache need not be HTTP specific, it only needs the ability to cache 
> multiple entities (data, headers) under the same key, 

No.


> In other words, there must be the ability to cache by a key and a subkey.


No. mod_http_cache generates new keys for headers (key.header) data 
(key.data) and each variant (key1.header, key2.header, key1.daya... 
etc.).  As far as the underlying generic cache is concerned, they are 
all independent entries.


-- 
Brian Akins
Lead Systems Engineer
CNN Internet Technologies

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