[rrd-users] Strange GAUGE values when parsing MySQL output

Arthur Meeks Meeks arthur.meeks.luppu at gmail.com
Tue Aug 11 21:28:50 CEST 2009

2009/8/11 Marc Powell <marc at ena.com>

Hi Marc,
Thanks a lot fot the reply

> I think you mean to say 'm', as in milli, not 'M' as in Mega. They're
> several orders of magnitude different. For example, the first value
> above is of course '.16333333', not 1,633,333.3333.

Ups, you're correct, but either way, the value is wrong, as I'd never get
1.6 or .16 values, just 1 or 2, nothing in between.

> > I've read that the common problem here is using COUNTER instead of
> > GAUGE, but as you can see, I'm using GAUGE to draw exactly, 0, 1, 2
> > etc..
> Using GAUGE helps but you're not as much as you believe. Internally to
> RRDtool, they're still rates that fall into very specific interval
> buckets. If you want the exact values out that you put in, you must
> input the value on an even rrd STEP from the rrd START.
> If you are not inputing the values with a timestamp that falls exactly
> on a step (bucket) from the start time, RRDtool will adjust the value
> based on how early or late you are from the bucket time. If you input
> early, the value will be increased. If you input late, the value will
> be decreased.

I would like to input the values with a timestamp, as the piece of log I
posted in my first email shows, but I'm not sure if I understood this
correctly (I'm a newbie in rrdtool :-) ), you mean I should change the
--start 1? But, in favour of what?

> > The problem disappear when the value got from the MySQL is something
> > like: 3989
> > Then the graph shows 3K, 3.5K, 4K etc in the vertical margin, which
> > is correct. But I don't understand why a value like: "1" is shown as
> > 100M in the graph.
> The value was input very much head of the step time?

Probably not, the script runs every 30 seconds and it took about a second to
generate the graph.

Again, thanks a lot, Marc

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