Re: [munin-users] graphs with day-over-day in percentages

[manuel a. <al...@gm...>]

On 28/02/11 14:47, Steve Schnepp wrote:
> On Mon, Feb 28, 2011 at 14:26, manuel aldana <al...@gm... 
> <mailto:al...@gm...>> wrote:
>
>     I am sure natively this can be done with RRD (simply extract last days
>     value and compare)
>
>
> Actually, I'm quite curious about how to do this with only CDEF in RRD.
> I don't think you can retrieve values at arbitrary time, only the 
> previous computed one via PREV like described in [1].
> And therefore you cannot have a timeshifted RRD.
>
> I'm afraid then that you have to take care of your plugin history in 
> the plugin.
>
> [1] http://oss.oetiker.ch/rrdtool/doc/rrdgraph_rpn.en.html
>
> -- 
> Steve Schnepp
> http://blog.pwkf.org/

Yes, it seems not to be possible with CDEF, but fetch would do it (hour 
interval):
===
rrdtool fetch file.rrd AVERAGE -r 3600

The doing some scripting (with awk, bash, python etc.) and then 
parameters is stdout last and 24th-last line.

But I wonder whether it is possible to access the rrd file by variable 
inside the plugin script... Doing hardcode filepath would be very fragile.


-- 
  manuel aldana
  al...@gm...
  software-engineering blog: http://www.aldana-online.de