Today I received the error “server reached MaxRequestWorkers setting” and was a little confused as I had never heard of this setting before.
Apache 2.4 No Longer Uses MaxClients
I recently upgraded to Apache 2.4 due to several performance and stability improvements. However, I still am not familiar with all changes and still need to read up on it. One of the key settings that has changed was known as MaxClients. Whenever too many people visit your site / server, the number of MaxClients defines how many can access a resource the same time. By default 150 people can access an Apache server at the same time.
The full error reads something like this in your error_log
[mpm_prefork:error] [pid 1729] AH00161: server reached MaxRequestWorkers setting, consider raising the MaxRequestWorkers setting
Control Panel WHM
If you use WHM/Cpanel, you will find an option called Apache configuration in the sidebar. Open the subitem Global Configuration and you can change MaxClients or MaxRequestWorkers.
In Our Wiki
For more information read our Webmaster Wiki article on MaxClients