[collectd] Hit counter in threshold

Sebastian Harl sh at tokkee.org
Sun Jul 12 11:04:26 CEST 2009


["fixed" top-posting ...]

On Sun, Jul 12, 2009 at 10:01:54AM +0200, Mariusz Gronczewski wrote:
> 2009/7/12 Peter Bray <pdb_ml at yahoo.com.au>:
> >>  1) hysteresis, i. e. something like this:
> >>     -- 8< --
> >>       if (value > (threshold + epsilon))
> >>         status = bad
> >>       else if (value < (threshold - epsilon))
> >>         status = good
> >>       return status
> >>     -- >8 --
> >>     This, used right, should provide modest flapping protection.
> >
> > Just a small comment, hysteresis as used in the satellite control
> > systems I've worked with over the last eight years, means N samples
> > above/below a threshold to trigger the condition.

Which is basically what Andrés called a "hit counter" (see the beginning
of this thread.)

> > Others may have a different understanding of hysteresis but I thought I
> > mention this understanding as naming is so important to understanding.

Thanks for pointing that out - making sure to get the disambiguation
right is an important thing to do.

> Generally hysteresis have wide meaning

According to Wikipedia [1], "hysteresis" is a very generic term,
describing a system whose state is dependent on input _and_ the current
state. So, imho, we should try to find more specific terms for each
implemented hysteresis "algorithm" that's included in collectd. Does
anybody know of common terms used in (other) monitoring software? If
there are reasonable terms available that are in common use, we should
try to stick to those as well.

> tho both definitions are useful in practice (for example above one
> would be good for temp, "turn off alarm when its 5 degrees below MAX",
> and "trigger if 3 samples over" would be great for CPU or load avg
> meter)



PS: Pretty please, do not use top-posting [2]. I've seen a lot of that
    on this list recently and, imho, it really breaks the readability of
    threads, especially, if it's mixed with inline replies or bottom
    posting. Thanks!

[1] http://en.wikipedia.org/wiki/Hysteresis
[2] http://en.wikipedia.org/wiki/Posting_style#Top-posting

Sebastian "tokkee" Harl +++ GnuPG-ID: 0x8501C7FC +++ http://tokkee.org/

Those who would give up Essential Liberty to purchase a little Temporary
Safety, deserve neither Liberty nor Safety.         -- Benjamin Franklin

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