[rrd-users] Returning nan values

Matthew M. Boedicker matthewm at boedicker.org
Thu Jun 19 19:45:02 CEST 2008

If your update statement is:


it's trying to update with the string N:+user+:+nice+:+sys+:+idle+ every time
and not putting in the actual numbers.

It should be something like:

rrdtool.update('cpu.rrd',"N:%s:%s:%s:%s" % (user, nice, sys, idle))

Are you checking for errors after update? I would think it would say something
if you are trying to update with values like "+user+".

On Thu, Jun 19, 2008 at 01:36:55PM -0400, Emily Chouinard wrote:
> So I've got my code all done but my update function doesn't work. I want 
> to take the values from the /proc/stat file and update my rrd with them 
> but when I do an rrdtool fetch cpu.rrd AVERAGE and several interations I 
> get:
>  fetch cpu.rrd AVERAGE
>                            user                nice                 
> sys               idle
> 1213810500: nan nan nan nan
> 1213810800: nan nan nan nan
> 1213811100: nan nan nan nan
> (but that is just a small glip of all the nan values I get) I was 
> wondering if my update function was correct, my rrd is created properly 
> using
> rrdtool.create('cpu.rrd',
>      'DS:user:DERIVE:30:0:U',
>      'DS:nice:DERIVE:30:0:U',
>      'DS:sys:DERIVE:30:0:U',
>      'DS:idle:DERIVE:30:0:U',
>      'RRA:AVERAGE:0.5:1:576',
>      'RRA:AVERAGE:0.5:6:672',
>      'RRA:AVERAGE:0.5:24:732',
>      'RRA:AVERAGE:0.5:144:1460')
> and then I run a loop to extract the data from a file
>  infile= open('/proc/stat', 'r')
>     #for x in range(0,1):
>     line = infile.readline()
>     if line.startswith('cpu'):
>     info = line.split()   
>     user = info[1]
>     nice = info[2]    
>     sys = info[3]
>     idle = info[4]
> and then I try to update these values from user, nice sys and idle into 
> my rrd with
> rrdtool.update('cpu.rrd','N:+user+:+nice+:+sys+:+idle+')
> but it only gives my nan values, any suggestions on why this is?
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