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Re: app6 up



On Wed, Apr 23, 2008 at 09:12:19PM -0500, Matt Domsch wrote:
> It's a shame mod_proxy_balancer doesn't grok geoip.  It'd be fun for
> it to default North American users to our US app servers, .EU to
> Telia, with the fallback to use any of the others that are alive...

http://mail-archives.apache.org/mod_mbox/httpd-users/200706.mbox/%3CBAY115-W237A9C5FD8FCA670B034B5B1130 phx gbl%3E

gist is, we're actually proxypassing from the proxy servers to the app
servers.  The problem becomes, we need our US users to magically hit a
US proxy server, and then be proxypassed to a US app server; likewise we
need EU users to magially hit a .EU proxy server and be proxypassed
to a EU app server.

So it's not a mod_proxy_balancer problem as much as it is a DNS
challenge - we want different answers from DNS depending on the user's
location.  And that's always fun...

Instead, we could make proxy*.fp.o do a geoip lookup and then issue a
HTTP redirect to proxy*.us.fp.o for US users, proxy*.eu.fp.o
for EU users etc.  And _then_ let the balancer kick in.  Still, you'll
have potentially high latency on that first lookup before the
redirect.  For mirrorlist, it's not worth it; the app answers quickly
enough to any request that the whole process is overshadowed by the
TCP connection setup time and transfer latency, not app processing.
For apps with more "think time" though, it's something to consider.

-- 
Matt Domsch
Linux Technology Strategist, Dell Office of the CTO
linux.dell.com & www.dell.com/linux


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