Re: kernel.org mirroring (Re: [GIT PULL] MMC update)

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Linus Torvalds wrote:

On Fri, 8 Dec 2006, Jeff Garzik wrote:
This is a bit cheesy, and completely untested, but since mod_cache never
worked for me either, I bet it works better ;-)

Ok, this doesn't do the locking either, so on cache misses or expiry, you're still going to be that thundering herd.

Well, gdbm does reader/write locking.

You still bit a bit of a thundering herd, though. I suppose I could open the gdbm db for writing before calling the CGI, which would effectively get what you're looking for.


Also, if you want to be nice to clients, I'd seriously suggest that when you hit in the cache, but it's expired (or it's close to expired), you still serve the cached data back, but you set up a thread in the background (with some maximum number of active threads, of course!) that refreshes the cached entry and then you extend the expiration time so that you won't end up doing this "refresh" _again_.

It's kind of silly to have people wait for 20 seconds just because a cache expired five seconds ago. Much nicer to say "ok, we allow a certain grace-period during which we'll do the real lookup, but to make things _look_ really responsive, we still use the old cached value".

True, should work with gitweb data at least.

	Jeff


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