title: How can my PHP script tell whether the server is busy?
body: <p>I want to run a cron job that does cleanup that takes a lot of CPU and Mysql resources. I want it to run only if the server is not relatively busy.</p>
  
  <p>What is the simplest way to determine that from PHP? (for example, is there a query that returns how many queries were done in the last minute? ...) </p>