Re: [rrd-users] Fetching raw data

On Thu, Mar 20, 2008 at 11:41 PM, Luke Burden <lukeburden@gmail.com> wrote:
> Hi all,
>
> What I'm trying to achieve with RRDTool is quite simple, and I believe
> possible with RRD - I just need you guys to run your eyes over my case and
> point out where my misunderstanding of your code is.
>
> I have a time series, with samples each 1 minute. I want to store this in
> an RRD, and retrieve consolidated values to facilitate a zoomable graph
> front-end. This works a treat, but what I want to do as well as fetching
> consolidated data from the RRD is to be able to pull that original data out
> at full resolution too.
>
> I figured that an RRA:AVERAGE with 1 step and a heartbeat of 60 secs would
> do the trick as long as there were only ever 1 sample updated per 60 second
> period. But I can't get this to work! I thought it might be the AVERAGE
> function doing sneaky things, but LAST and MAX give exactly the same fetch
> results.
>
> I'm creating the graph using:
> rrdtool create subset.rrd -b 1199103570 -s 60 DS:users:GAUGE:60:0:1000000
> RRA:MAX:0.5:1:525600 RRA:LAST:0.9:1:525600 RRA:AVERAGE:0.9:1:525600
>
> Then updating with the following data:
> 1199103601 50283
> 1199103661 50282
> 1199103721 50320
> 1199103781 50365
> 1199103841 50359
> 1199103906 50307
> 1199103961 50332
> 1199104021 50298
> 1199104081 50329
> 1199104141 50307
> 1199104202 50267
>
> Then the following fetches:
> rrdtool fetch subset.rrd AVERAGE -r60 -s1199103590 -e1199104202
> rrdtool fetch subset.rrd LAST -r60 -s1199103590 -e1199104202
> rrdtool fetch subset.rrd MAX -r60 -s1199103590 -e1199104202
>
> Produce:
> 1199103600: 5.0283000000e+04
> 1199103660: 5.0282016667e+04
> 1199103720: 5.0319366667e+04
> 1199103780: 5.0364250000e+04
> 1199103840: 5.0359100000e+04
> 1199103900: nan
> 1199103960: 5.0332000000e+04
> 1199104020: 5.0298566667e+04
> 1199104080: 5.0328483333e+04
> 1199104140: 5.0307366667e+04
> 1199104200: nan
> 1199104260: nan
>
> Clearly there is something going on here which I don't understand. Anyone
> care to explain how I can get at the raw numbers?


I just get the same problem, here is what I found:

Use rrdtool dump to see how rrd store your "raw" sample.
You will not found time stamp 1199103601 1199103661 .....
But instead 1199103600, 1199103660, ....
because rrd use alway rrd on the "step" boundary you have choosed.
Here int(1199103601/60)*60.
And 1199103601, 1199103661 and mayby other will be used to calculate
the value for 1199103660 and store it in the RRD

If you want get the original data you must provide

1199103600 50283
1199103660 50282
1199103720 50320
1199103780 50365

to rrd

Regards

>
> On another issue, are there any plans for RRDTool supporting calendar
> monthly consolidations, or is this best done using daily consolidations and
> some scripts?
>
> Many thanks,
>
> Luke
>
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>
>



--
Alain Spineux
aspineux gmail com
May the sources be with you

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