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From: "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: kernel.org mirroring (Re: [GIT PULL] MMC update)
Date: Fri, 08 Dec 2006 15:49:19 -0800
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References: <Pine.LNX.4.64.0612020835110.3476@woody.osdl.org>	 <Pine.LNX.4.64.0612071052560.3615@woody.osdl.org>	 <457868AA.2030605@zytor.com> <20061207193012.GA84678@dspnet.fr.eu.org>	 <4578722E.9030402@zytor.com> <4579611F.5010303@dawes.za.net>	 <45798FE2.9040502@zytor.com>	 <Pine.LNX.4.64.0612080830380.3516@woody.osdl.org>	 <457998C8.3050601@garzik.org>	 <Pine.LNX.4.64.0612081453430.3516@woody.osdl.org> <f2b55d220612081546u1ffa98e5q75be55d31da82a2f@mail.gmail.com>
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Cc: Linus Torvalds <torvalds@osdl.org>, Jeff Garzik <jeff@garzik.org>,
	Rogan Dawes <discard@dawes.za.net>,
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To: "Michael K. Edwards" <medwards.linux@gmail.com>
Sender: git-owner@vger.kernel.org

Michael K. Edwards wrote:
> On 12/8/06, Linus Torvalds <torvalds@osdl.org> wrote:
>> You can't have a cache architecture where the client just does a "get",
>> like memcached does. You need to have a "read-for-fill" operation ...
> 
> In Squid 2.6:
>    collapsed_forwarding on
>    refresh_stale_window <seconds>
> (apply the latter only to stanzas where you want "readahead" of
> about-to-expire cache entries)
> 
> Brief design description at 
> http://devel.squid-cache.org/collapsed_forwarding/.
> 
> (I didn't write this code, everything I know about squid leaked
> through the Google-shaped pinhole in my tinfoil hat, etc.  But if you
> go this way I'd like to be in the loop to understand the scalability
> issues around netfilter-assisted transparent proxying.)
> 

There is another thing that probably will be required, and I'm not sure 
if something in front of Apache (like Squid) rather than behind it can 
easily deal with: on timeout, the process needs to continue in order to 
feed the cache.  Otherwise, you're still in a failure scenario as soon 
as timeout happens.