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From Ruediger Pluem <rpl...@apache.org>
Subject Re: store_headers in memcache and diskcache
Date Tue, 05 Feb 2008 22:24:40 GMT


On 02/05/2008 07:45 PM, Dirk-Willem van Gulik wrote:
> Caching experts --  why do memcache and diskcache have seemingly quite
> different caching strategies when it comes to storing the headers ? E.g.
> the cache_object_t * is populated with the status/date/etc data in
> memcache - but not in disk-cache. Is this work in progress or subtle
> design ?

But mod_mem_cache never restores the status (see comment mod_cache.c:288) :-).
I think the difference is because cache_object_t is the data structure that
mod_mem_cache actually stores in the cache to keep this data (in fact a pointer
to the cache_info data) around whereas mod_disk_cache serializes the cache_info from cache_object_t
data and writes it to disk. Once mod_disk_cache reads back the data from the disk it populates
the cache_info field in cache_object_t again with the deserialized data
(see open_entity and file_cache_recall_mydata).

> 
> I am trying to understand (got  a working mod_memcached_cache.c* -- and
> cannot quite get the right VARY behaviour).

As others mentioned mod_mem_cache did not receive the same love as mod_disk_cache.
So I am not quite sure if VARY even works correctly with mod_mem_cache.

Regards

RĂ¼diger


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