NaN returned for CPU Usage

[g-m-o-n-e-y]

We're getting check output that's not helpful

check-cpu-usage OK: NaN% CPU usage | cpu_idle=NaN, cpu_system=NaN, cpu_user=+Inf, cpu_nice=NaN, cpu_iowait=NaN, cpu_irq=NaN, cpu_softirq=NaN, cpu_steal=NaN, cpu_guest=NaN, cpu_guestnice=NaN

It seems that the check is not safe from dividing by zero.

[g-m-o-n-e-y]

This may only be a problem on an LXC container...I'll double check

[g-m-o-n-e-y]

The issue seems to be (surprise, surprise) floating-point math. Since startTotal and endTotal are large float64s we lose the precision from a smaller User value. On our server, Idle was so large that adding it with the User removed smaller changes in value. This caused diff to always be 0 which resulted in NaN for values printed.