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From Dirk-Willem van Gulik <>
Subject Re: dynamically change max client value
Date Mon, 04 Nov 2002 17:35:25 GMT

In my ideal world every config directive would be able to advertize or
register an optional 'has changed' hook. Which, if present, would be
called in context whenever a value is somehow updated (through snmp, a
configd, signal, wathever). If there is no such hook; the old -update- on
graceful restart is the default (though it sure would be nice to have some
values also advertize that they need a full shutdown and restart).

Of course one could also argue for not just a put but also for a 'get'
interface in context :-)


On Mon, 4 Nov 2002, David Burry wrote:

> Recently there has been a little discussion about an API in apache for
> controlling starts, stops, restarts, etc...
> I have an idea that may help me solve a problem I've been having.  The
> problem is in limiting the number of processes that will run on a machine to
> somewhere below where the machine will keel over and die, while still being
> close to the maximum the machine will handle.  The issue is depending on
> what the majority of those processes are doing it changes the maximum number
> a given machine can handle by a few orders of magnitude, so a multi-purpose
> machine that serves, say, static content and cgi scripts (or other things
> that vary greatly in machine resource usage) cannot be properly tuned for
> maximum performance while guaranteeing the machine won't die under heavy
> load.
> The solution I've thought of is... what if Apache had an API that could be
> used to say "no more processes, whatever you have NOW is the max!"  or
> otherwise to dynamically raise or lower the max number (perhaps "oh there's
> too many, reduce a bit")....  You see, an external monitoring system could
> monitor cpu and memory and whatnot and dynamically adjust apache depending
> on what it's doing.....  This kind of system could really increase the
> stability of any large Apache server farm, and help keep large traffic
> spikes from killing apache so bad that nobody gets served anything at all.
> In fact this idea could be extended someday to dynamically change all sorts
> of apache configuration things, but all I really need that I know of right
> now is the max client value...
> What do you all think of this idea?  Does this already exist perhaps?
> Dave

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