[rrd-users] Re: rrdtool - using the rrd for more than graphs - calculating averages for prime shift

Alex van den Bogaerdt alex at ergens.op.het.net
Fri May 30 11:38:23 MEST 2003

On Thu, May 29, 2003 at 10:13:52AM -0400, dmahler at telcordia.com wrote:

> I am trying to use my rrd files to create some new metrics.   not graphs,
> but rather server busy "scores" over time.     the idea is to create sorted
> list, by server grouping, of how busy the servers are.   during prime
> shift.
> I am already collecting cpu statistics into individual rrd files.   I could
> of course create a view over time of the cpu usage by going an rrd graph.
> this is in place.
> But... my thought is to ask rrd: "provide the cpu min, max, average for
> prime shift/weekdays,  for 3 months.  "
> provide all the values into stdout and let me manipulate it in stdin.

> - is this doable?   have others used  rrd data in a non-graphical way?


> - can one use rrdgraph to get the numbers, w/o generating the graph itself?

PRINT, not GPRINT;  Don't use graphing elements and no image is created

> - can you issue one rrd call to get the prime shift numbers only, or (more
> likely) do I have to do this in a loop for each day?

Probably just one call with many DEF/CDEF/PRINTs in it

> = are my mathematic thoughts faulty (averages of averages)?

Averages of rates.  The rates in itself maybe averages but that
doesn't really matter.

step 1:  mask out undesired values  (CDEF with LTIME, UNKN and IF)
step 2:  print the min,average or max value (PRINT)

Prepare a database with example values and practise on that.

If necessary, provide complete, small examples of what RRDtool
does where you think it should do otherwise or where you think
you don't get it.  Small and complete meaning all that is needed
to show the behaviour without trashing the list: A script that
creates a small database with just enough rows for the example,
a script that updates this database with suitable numbers (use
hard timestamps, not "N", a script that extracts the data and
finally your hand-computed results (with reasoning) vs. the
rrdtool generated results.

Much of what looks like rudeness in hacker circles is not intended to give
offence. Rather, it's the product of the direct, cut-through-the-bullshit
communications style that is natural to people who are more concerned about
solving problems than making others feel warm and fuzzy.


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