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From Brian Candler <B.Cand...@pobox.com>
Subject Re: What do you want in HTTPD 2.4/3.0/X/GREEN?
Date Fri, 09 Dec 2005 09:31:18 GMT
On Wed, Dec 07, 2005 at 02:52:44PM -0500, Jim Jagielski wrote:
> Yeah, maybe it's time to re-open this discussion... previously,
> whenever we thought about adding more "functionality" to
> the config file, it was discouraged because it increases the
> complexity of Apache for something that could more easily be
> done via an external process (ie: a script that reads in LDAP
> info and autogens a "normal" httpd.conf file)...

The latter idea doesn't scale particularly well though. e.g. if you have
100,000 virtual hosts then
(a) you have to regenerate the whole config file every time any single one
is changed; and
(b) Apache has to reload the whole 100K vhosts every time it's changed.

The rate at which a reload is requested goes up with the number of virtual
hosts, and the work taken for each reload (in terms of database search and
Apache reconfig) also goes up with the number of virtual hosts. So you have
an N^2 scaling problem, and eventually get bogged down doing reloads and
nothing else.

You could argue the same is true if you're constantly reading configs
dynamically (e.g. mod_rewrite). However then the work is proportional to the
number of requests, not the number of vhosts. In practice, out of 100,000
vhosts, I'd be surprised if 5,000 were actually serving any significant
number of pages. It's amazing how many people pay for web hosting when
nobody looks at their pages :-)

Regards,

Brian.

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