server load balancing script

Question

I have a server (Ubuntu) that servers several domains and runs a series of cron scripts. However the load on the server cannot be predicted therefore I cannot set the right amount of load in the cron scripts.

However the scripts that run in cron are overloading from time to time and generate a huge load in both CPU and memory causing several services of the server to stop (such as mail server for example).

The question is: how can I write a script that runs the routines that are now in cron only when the server load is below a minimum threshold? Is there any application that does this under Linux?

Thank you for your time!

Answer 1

You can check the monit system management. You can add this into your configuration file:

   # Monitoring the apache2 web services.
    # It will check process apache2 with given pid file.
    # If process name or pidfile path is wrong then monit will
    # give the error of failed. tough apache2 is running.
    check process apache2 with pidfile /var/run/apache2.pid
     start program = "/etc/init.d/apache2 start"
     stop program  = "/etc/init.d/apache2 stop"
     # Admin will notify by mail if below of the condition satisfied.
     if cpu is greater than 60% for 2 cycles then alert
     if cpu > 80% for 5 cycles then restart
     if totalmem > 200.0 MB for 5 cycles then restart
     if children > 250 then restart
     if loadavg(5min) greater than 10 for 8 cycles then stop
     if 3 restarts within 5 cycles then timeout
     group server

It is a good tool and you can search how to execute your own script when a condition satisfied.