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NaN returned for CPU Usage #4

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g-m-o-n-e-y opened this issue Dec 6, 2022 · 2 comments · May be fixed by #5
Open

NaN returned for CPU Usage #4

g-m-o-n-e-y opened this issue Dec 6, 2022 · 2 comments · May be fixed by #5

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@g-m-o-n-e-y
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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
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This may only be a problem on an LXC container...I'll double check

@g-m-o-n-e-y
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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.

@g-m-o-n-e-y g-m-o-n-e-y linked a pull request Dec 7, 2022 that will close this issue
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use diffs of individual times to keep from losing (some) precision g-m-o-n-e-y/check-cpu-usage
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@g-m-o-n-e-y