[rrd-users] rrdtool fetch return values

[Frank Harper]

When I fetch values using the following code:

my ($time,$step,$names,$data) = RRDs::fetch($filePath,"AVERAGE",
       "--start","now",
       "--end","now");

Two data points are returned:

Start:       Tue Mar 14 09:00:00 2000 (953020800)
Step size:   300 seconds
DS names:    ds0, ds1, ds2, ds3, ds4, ds5
Data points: 2
Tue Mar 14 09:00:00 2000 (953020800) av=6178.09084612431
Tue Mar 14 09:05:00 2000 (953021100) av=NaN

Will fetch always return an extra NaN data point? I'm thinking about future
versions of RRDtool. Also what about when I use other values for --start and
--end?

If the NaN is always present as the last data point , I'll just throw it away.

Frank Harper wrote:

> Steve, thanks for your positive feedback.
>
> I'm glad to see you agree that the amount of "unknown" information, is
> important.
>
> The basic assumption that I'm making here, is that when information for a data
> source is unavailable that means there is a service outage for the
> corresponding network node/application. Of course that might not be true for a
> variety of reasons, but I hope the approximation will be useful in managing
> our networks.
>
> I'm in the process of writing scripts that will provide this information. They
> use rrdtool directly, so, with a little work, they should work with any of the
> rrdtool front ends. I'm currently using cricket, so that's what the first
> version will work with for sure.
>
> My basic idea is to have a script update an rrd containing availability
> information for a set of data sources at regular intervals (1 day default). I
> will record two availability numbers: working hours and 24h/7.
>
> A cgi will then use this information to provide the following HTML reports:
>
> Textual statistics, over a certain time period, for all data sources in the
> availability rrd, sorted by availability (ascending). This should tell us
> where reliability may need improvement.
>
> Graphics for one data source in the availability rrd, over a certain time
> period. This will show us what the trend is for a particular data source.
>
> When all this is working, I'll send it to Tobi to be included in the contrib
> directory.
>
> steve rader wrote:
>
> >  > From: Frank Harper
> >  > I want a textual report containing availability statistics for some my
> >  > RRD datasources. Now, it seems to me like this would be a pretty common
> >  > thing to do. But strangely enough, I haven't found anything available
> >  > that looks like it would fit the bill.
> >  >
> >  > Did I miss a publicly available tool/contribution that would do this?
> >  > Or is this something so trivial that everybody just rolls their own?
> >  > Or maybe this isn't even a good idea (please tell me why not)?
> >
> > Frank,
> >
> > This is a good idea: I'm thinking I'll write a perl script
> > for NRG that would produce a plain text report of (NRG) data
> > collection failure over some arbitrary reporting interval
> > (default one day.)
> >
> > So then cron could send this report every night to provide a
> > terse report of "monitoring availability" over the last day.
> >
> > Is that what you're thinkin' of?
> >
> > If so, maybe send me an example of how you'd like the report
> > and I'll cook something up.
> >
> > If not, tell us more about what you mean by "textual report
> > containing availability statistics".
> >
> > steve
> > - - -
> > systems & network guy
> > high energy physics
> > university of wisconsin
>
> --
> Frank Harper, TURBOMECA network manager
> e-mail: Frank.Harper at turbomeca.fr
> Tel: +33-559-12-52-18
> Fax: +33-559-12-51-50
>
> --
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--
Frank Harper, TURBOMECA network manager
e-mail: Frank.Harper at turbomeca.fr
Tel: +33-559-12-52-18
Fax: +33-559-12-51-50



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