There has previously been some discussion on this list about the virtues of memory caching versus disk caching. As I recall nobody ever claimed to have observed performance gains using mod_mem_cache. I have myself not bothered to run any load tests in an attempt to measure the benefits of mod_mem_cache. The fact is that you virtual file system has the files in memory anyway, and that using mod_mem_cache you would not benefit from the use of sendfile() as you would for responses cached on the file system.
Wrt to the core dumps I experienced when using mod_mem_cache and mod_disk_cache, the error segmentation violation actually occurred in mod_rewrite, but would only be caused if mod_mem_cache was in use. For some reason it's filed on mod_proxy... http://issues.apache.org/bugzilla/show_bug.cgi?id=35160
-ascs
-----Original Message-----
From: Dan Price [mailto:dp@xxxxxxxxxxx]
Sent: Wednesday, April 26, 2006 8:07 PM
To: users@xxxxxxxxxxxxxxxx
Subject: Re: [users@httpd] Problems with Apache 2.2.0 as a conventional proxy
On Wed 26 Apr 2006 at 12:41PM, Axel-St?phane SMORGRAV wrote:
> I had a similar problem when using both mod_mem_cache and mod_disk cache with Apache 2.0.54. I ended up abandoning mod_mem_cache and never experienced the problem again. I may even have posted a bug report... but back then mod_cache did not get much TLD from developers who were, as I understand it, busy developing mod_cache for Apache 2.1/2.2.
Thanks for the advice. Isn't mod_mem_cache a good idea? Wouldn't it hurt my performance not to have in-memory caching?
But it turns out that I did explored the different module combinations during my initial testing. Turning off mod_mem_cache certainly helped-- but I was still seeing core dumps even without it, and the text/plain vs. text/css problem was a real showstopper-- Apache's architecture makes it nicely guarded against core dumps in child processes, but serving the content incorrectly is just not OK for my users.
Rather than go back to Squid, for now I have switched to using Sun's proxy server, which is free but not Open Source, and which has worked better so far. (I realize that I work for Sun so this sounds like a commercial but part of what I like to do is use and test free and open source software; for those interested, see
http://blogs.sun.com/roller/page/dp?entry=installing_sun_java_system_web)
. I'll reevaluate using Apache for proxying content in the 2.4.0 timeframe, and if I can find some time, I'll keep trying to debug the (several hundred) apache core files I have.
-dp
--
Daniel Price - Solaris Kernel Engineering - dp@xxxxxxxxxxx - blogs.sun.com/dp
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