[rrd-developers] Re: [rrd-users] Re: Image clipping/stacking want

Sasha Mikheev sasha at netvision.net.il
Tue Mar 6 11:25:14 MET 2001

On Tue, 6 Mar 2001, Alex van den Bogaerdt wrote:

> Sasha Mikheev wrote:
> > Let me add another vote for separating data processing and retrival from
> > graphing. It would be very nice to get tabular data for complex graphs in
> > rrdtool fetch.
> This would be nice, but we need to make sure the input is suitable for
> rrdtool graph.  If the DEF command works on other datasources than RRDs,
> one side of this is done.  The other side would be writing out processed
> data not to a graph but as text, like PRINT but now the complete series.
I mean only this only for RRD datasource. For example I want to do

rrdtool fetch /tmp/foo DEF:x=foo1.rrd:ds0:AVERAGE \
	DEF:y=foo2.rrd:ds0:AVERAGE \
	CDEF:g1=x,y,+ \

should give me data points for both g1 and g2

Of course it can be done now in perl by fetching datasources and then
doing tranformation in the script...

> > Also my favorite features would be:
> > 
> > 1. Pluggable modules for RPN operations.
> Something like:
> usr(x) --->
> FUNC:myfunc=/usr/local/bin/myfunc
> CDEF:vname=whatever,myfunc
> ?
Yeah. although even static hooks for writing functions would be enough.
Also it would be nice to be able to write consolidation functions. For
example PERCENTILE95. ;)

> > 2. Aggregate operations such as average, percentile etc in CDEF and PRINT
> > It should work like this:
> > foo=CDEF:bar,95,PECENTILE
> > now bar will be a constant series and you will be able to graph it.
> This is *very* similar to the stuff I'm currently working on.  It will
> use variables which you can use in CDEF instructions something like:
> DEF:bytes=...
> CDEF:bits=bytes,8,*
> VDEF:perc=95,bits,PERCENT
> CDEF:high=bits,perc,-,100,LE,INF,UNKN,IF
> AREA:high#FF0000
> AREA:bits#0000FF:bits
> LINE1:perc#FF0000:"95th percentile"

I dont think you need to have a separate VDEF for this. perc can be
considered as function with constant value. 

> cheers,

 Sasha Mikheev                      Linux -- put a penguin in your processor

 Avalon Net Ltd, CTO

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