Is microsecond precision available in an iRule?

The clock clicks number is not equal to actual microseconds. You need to take into account the processor frequency, and there may be some inaccuracy due to interrupts, etc. In general, I tell people they can think of it as microseconds but the greater the number (difference between first observation and second observation) the greater the skew from accuracy. Imperical testing over a long period using an external time source (known to be accurate) will help prove the case.

 

 

Write an irule that just does an "HTTP::respond 200 content [clock clicks]" and call it every 60 seconds for several days. You'll see the skew for the box in question. When you have an HA pair, you can't assume the processor frequencies are identical either. So you need to check both boxes.