[rrd-users] Re: Filling in NaN's?

Clifton Royston cliftonr at lava.net
Fri Apr 27 03:36:42 MEST 2001

On Thu, Apr 26, 2001 at 09:24:10PM -0400, Adam Rothschild wrote:
> On Thu, Apr 26, 2001 at 02:27:34PM -1000, Clifton Royston wrote:
> > As you can tell, I'm philosophically opposed to this.
> As am I.  There was a very specific and somewhat broken situation
> which required this, unfortunately.  I definitely don't want to come
> across as saying it's a good thing, or encouraging its widespread
> usage.
  Understood.  Every rule requires exceptions...

> >   If you only want smooth looking *graphs*, there's probably a way to
> > do this with some of the CDEF expressions in the grapher, using the
> > "PREV" command.  E.g. assuming orig is the def for your original data
> > source, something like:
> > 
> >   CDEF:smooth=orig,UN,PREV,orig,IF
> > 
> > should give you a graph with flat-lines where the data is unknown, much
> > like MRTG's old behavior.
> Yup, that works; thanks.
> What I'd really like though is a script to perform the necessary
> fondlage on the RRD itself -- or more realistically, export the RRD to
> XML, perform the necessary fondlage there, and then re-build the RRD.
> Has anyone done this before?

Not that I'm aware of.  However, the command sequence of :

  rrdtool dump foo.rrd | massage-xml > temp.xml 
  rrdtool restore temp.xml foo.rrd

makes it pretty much a simple exercise in filter-processing of text
files.  You could almost do it in sed, but a perl script which
remembers the last non-NAN seen and replaces NaNs in the input with
that number should be pretty darn short.

  -- Clifton

 Clifton Royston  --  LavaNet Systems Architect --  cliftonr at lava.net
   WWJD?   "JWRTFM!" - Scott Dorsey (kludge)   "JWG" - Eddie Aikau

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