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From Graham Leggett <minf...@sharp.fm>
Subject Re: re-do of proxy request body handling - ready for review
Date Wed, 02 Feb 2005 21:38:57 GMT
Justin Erenkrantz wrote:

> I don't understand the purpose of serving incomplete files from a cache. 
> Can you please elaborate on what you think mod_cache should do?  -- justin

Since the early days of mod_proxy, there has been a race condition in 
the caching code which has been carried over to mod_cache.

After an URL has been invalidated, and before the new version of that 
URL has been downloaded completely from the backend server, any attempts 
by other clients to fetch the same URL are passed to the backend server 
directly. This results in the load spike on the backend server briefly 
while the replacement cache file is downloaded.

If mod_cache was taught to serve a being-cached URL directly from the 
cache (shadowing the real download), there would be no need for parallel 
connections to the backend server while the file is being cached, and no 
load spike.

Regards,
Graham
--

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