Our apache cluster was not able to serve all the requests so we need to raise MaxClients paramenter on each node. Unfortunatly the new value was exceeding the ServerLimit value so we had to raise it accordingly. Despite this on restart apache was again complaining that MaxClients was exceeding ServerLimit value:

# /etc/init.d/apache2 restart
* Forcing reload of web server (apache2)...
WARNING: MaxClients of 1000 exceeds ServerLimit value of 256 servers,lowering MaxClients to 256. To increase, please see the ServerLimitdirective.

These are the interesting lines in /etc/apache2/apache2.conf.

Can you see something wrong here? It was hard for me to figure out how to fix the problem!

  StartServers            10
  MinSpareServers         10
  MaxSpareServers         20
  MaxClients              1000
  ServerLimit             1000
  MaxRequestsPerChild     0
  

Here the right one.
The point is: ServerLimit must be put before MaxClients directive!

StartServers            10
MinSpareServers         10
MaxSpareServers         20
ServerLimit             1000
MaxClients              1000
MaxRequestsPerChild     0

Hope this help you!

Interesting news this morning, just as the 2009 MySQL Conference is starting. As is being reported all over the place, Oracle has agreed to buy Sun at $9.50 per share, giving them to a ton of great technology (Solaris, ZFS, MySQL, DTrace, etc.).

One one of the biggest threats to Oracle's core database business (at the low end, at least) for a while now has been MySQL. And now they're poised to own MySQL after Sun bought it not long ago. (It seems like yesterday that Oracle bought Innobase.)

As I noted a while back, the MySQL landscape is changing.

This news is sure to make the conference more... interesting.

Oracle, please get the InnoDB team together with the MySQL team and see about GPLing ZFS.

Load2Test by DBA InfoPower is a the best for MySQL load testing - they can record actual MySQL production traffic and replay it in staging multiple ways, like "as is", "load parallelization", "think time reduction", etc and generate performance issues root cause analysis on a spot.

I used it with number of my customers and it takes no time to do load testing and get analytics and root cause analysis back (like gathering slow-log data without any impact on a system and more), compare runs, etc

They are small startup that operates "under the radar". I got introduced to this product through the person who works there - and I really like the tool!!!

Load2Test official page - load2test.com