apache MaxClients and locking up

[John ORourke]

Hi folks,

Not sure if this is mod_perl related but the logic goes I've never had 
this issue on a non-mod_perl server...

I've got a busy server with quite a few problems, but one in particular 
is very odd.

Occasionally the DB gets a bit bogged down and starts taking a while to 
respond (optimisations are being done at the mo), and after a while in 
the error log I get:

[Wed Feb 07 12:35:53 2007] [error] server reached MaxClients setting, 
consider raising the MaxClients setting

and then a whole heap of nothing - I can't tell if the server is still 
accepting new connections at that point as the server accepts 
connections but does nothing, and the system is heavily loaded but still 
responsive at the command line, and it's not using any swap space on 
disk because I tuned the apache/mysql settings properly.

I do have MaxClients set quite low (13) because my httpd process size is 
60-70MB - it's all set up so it never needs to swap.  This is mod_perl 
2.08, Apache 2.2.0 both from Fedora Core 5 packages.  I'm using a 
persistent handler object set up during httpd startup, and caching DBI 
connection objects in that.

Obviously I will be attempting to reduce httpd process size and optimise 
the database but still a strange problem.

I'm wondering if maybe I've caused a race condition somewhere but don't 
really know where to start looking.  I'm thinking I'll put in some 
custom handlers to monitor each request's progress for problems.

cheers
John