[rrd-users] only getting nan values

[Simon Hobson]

Jim Sher <rrdtool at blyzz.com> wrote:

> RRD creating scripts here: (NOTE! I've been chopping and changing the scripts since yesterday when I composed the original email I sent earlier to see if I could jiggle something loose :-) - no luck so far)
> 
> #! /bin/bash
> 
> rrdtool create data.rrd \
> --step '60' \
> 'DS:datadown:COUNTER:120:0:U' \
> 'DS:dataup:COUNTER:120:0:U' \

So here you have a heartbeat of only 120 seconds - that means if two updates are 121 seconds apart then you'll get unknown values stored. The problem here is that we don't know if you've changed this - if you were using this value when collecting every 5 minutes then you'd be 100% guaranteed to get no data !

> rrdtool create load.rrd --start N --step 300 \
> DS:load:GAUGE:1200:0.0:4.0 \

OK, here you've got 20 minutes. As long as you've collected data for at least 10 minutes then you should have something stored.




> As for rrdtool fetch, I can't seem to get the syntax to get any results right :-(

From one of my systems :
$ rrdtool fetch load.rrd AVERAGE -s 1464339000 -r 1800
                      load_1min           load_5min          load_15min

1464339600: 2.3333333333e-03 6.6666666667e-04 0.0000000000e+00
1464341400: 1.2000000000e-02 6.0055555556e-03 3.3333333333e-04
1464343200: -nan -nan -nan

$ rrdtool info load.rrd 
filename = "load.rrd"
rrd_version = "0003"
step = 300
last_update = 1464342015
header_size = 3632
ds[load_1min].index = 0
ds[load_1min].type = "GAUGE"
...
rra[0].cf = "AVERAGE"
rra[0].rows = 576
rra[0].cur_row = 227
rra[0].pdp_per_row = 1
...
rra[2].cf = "AVERAGE"
rra[2].rows = 672
rra[2].cur_row = 91
rra[2].pdp_per_row = 6
...

This fetches data from the AVERAGE cf for resolution 1800s (6x300), and only showing the last few values for brevity. Note that you can only fetch what is stored, you can't fetch arbitrary data consolidated on the fly like you can with rrdgraph.