[rrd-users] How to specify max change in DS:GAUGE ?

Alex van den Bogaerdt alex at ergens.op.het.net
Sun Nov 25 15:05:31 CET 2007

On Sun, Nov 25, 2007 at 02:58:11PM +0100, Niklas Abt wrote:
> Hi!
> I'm plotting the temperature reported by a (slightly faulty) temp
> sensor.
> The Sensor would sometimes report a temp that's about 30° higher than the
> average measurement (...40, 75, 41,..)
> I can't simply put a max-limit to the datasource, since the temperature
> might rise to 80°. Since the temperature changes slowly, a rate-limit
> would be fine (like: next value must be within +/-10 of previous value).
> How do I do that with a GAUGE-datasource?

I don't think you can do this within RRDtool.

Try a wrapper script which looks at the previous value (using rrdtool
fetch) and compares to the value you're going to submit.

By the way: Why do you trust 40 and 41, and how do you determine that
in case of ( 75, 41, ... ) it is 75 that has to go?

In other words, what happens if 75 happens to be the first measurement
in a series when you (or rrdtool) starts to compare?

Alex van den Bogaerdt

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