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From Marco Emilio Poleggi <>
Subject Re: [users@httpd] CacheGcInterval and CacheForceCompletion directives in mod_cache Apache 2.0
Date Mon, 11 Apr 2005 16:32:43 GMT
Joshua Slive wrote:
> On Apr 8, 2005 10:37 AM, Marco Emilio Poleggi <> wrote:
>>Hi all,
>>I'm testing a reverse caching proxy configuration with Apache 2.0.46. I need to
>>use the directives:
> Personally, I wouldn't dare use the cache in 2.0.46.  It has been
> much-repaired in recent versions, and I'm told it works best in the
> development version (2.1).
>> CacheGcInterval
>> CacheForceCompletion
>>which are marked as "currently not implemented" on the mod_[disk_]cache
>>documentation page ( Yet it
>>seems these options are widely used.
> Widely used where?  mod_disk_cache does not have garbage collection. 
> In recent version, there is a program supplied that can be run from
> cron to do this job.
>>Also, I would test a two-tier cache, with "small" objects in main (heap) memory
>>through  mod_mem_cache and the other "big" objects on disk through
>>mod_disk_cache. All objects are static and coming from a back-end server. Since
>>main memory caching is a delicate issue (O.S. caching always lying under...),
>>has anybody had bad experience with heap memory caching?
> I don't think apache would support determining the cache based on size.
> Joshua.

Thank you for your advice, Joshua.

I will try some more recent version. But, frankly, I'm quite surprised that a
caching system lacks a garbage collector: indeed, such a cache is not very useful!

However, I'm trying the the GC helper *htcacheclean* bundled with Apache 2.1,
which was pretty hard to find. This link provides no hint on how to retrieve it

so, I had to search the CVS repository: the source is found inside
'htppd-2.1/support'. The problem here is that you have to build the helper with
a full Apache source environment, so, if you move the resulting executable to
another machine it won't work (quoting the starting comments in it:

  # This wrapper script should never be moved out of the build directory.
  # If it is, it will not operate correctly.

). In fact, htcacheclean is a shell wrapper for a sort of dynamically
re-compiled program against some internal Apache's libraries (I hope not to tell
nonsenses). This is problematic when you have to deploy it over many machines
wherein Apache is installed as a pre-built package...
Does anybody know if there is a way to have a stand-alone and static build of
Also, does anybody know if there exists something else more portable?
I cannot fall back to Apache 1.3 due to distribution maintenance reasons.


Marco Emilio


Marco Emilio Poleggi
CERN IT/FIO             e-mail:
CH-1211 Geneva 23        phone: +41 22 767 8847
Switzerland             office: 31.1-014

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