[rrd-users] Debugging graph smoothing or bad data samples? interpolation bug?

[Kevin P. Foote]

OK, that's pretty slick. I didn't know cacti could do that.. :-)


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thanks
  kevin.foote

On Tue, 17 Nov 2009, Marc MERLIN wrote:

-> On Tue, Nov 17, 2009 at 10:25:48PM +0100, Tobias Oetiker wrote:
-> > Hi Marc,
-> > 
-> > Today Marc MERLIN wrote:
-> > 
-> > > On Tue, Nov 17, 2009 at 06:50:40AM +0100, Tobias Oetiker wrote:
-> > > > Hi Marc,
-> > > >
-> > > > > Does that make any sense to you?
-> > > >
-> > > > not entirely, I can only say that irregular data arrival times are
-> > > > rrdtools forte ... have you tried to write the data into a logfile
-> > > > (including the timestamp) and then recreate the phaenomenon by hand ?
-> > >
-> > > I have all the data in a logfile already, this is where I read it from :)
-> > > (script writes to logfile, cacti polls logfile from cron and feeds to
-> > > rrdtool).
-> > >
-> > > I have another script that will dump the entire logfile, generate a log list
-> > > of rrdtool update statements and I can recreate the entire rrd from scratch
-> > > after erasing it and replaying all the events.
-> > 
-> > ah ... in that case it is clear ... sometimes, you have one update
-> > in the file and sometimes two by the time cacti comes around ...a
-> > very bad case of jitter ... you should realy make it so that cacti
-> > can trigger the data accqusition ...
-> 
-> Mmmh, I see what you mean. Yes, now that I think about it, in a bad case
-> scenario, the cacti poller could hit a race condition and get the next sample
-> one period early, and see the same sample again.
-> 
-> That must be what happened, thanks for pointing it out to me.
-> 
-> On Tue, Nov 17, 2009 at 04:33:47PM -0500, Kevin P. Foote wrote:
-> > Alternative in line w/Tobi.. scrap cacti (unless you really use it for
-> > other things) and move to using your (obvious) scriptability to update
-> > the RRD on your interval. Then graph with something like drraw which 
-> > focuses on the graph not the acquisition of the data AND the graph.
-> 
-> So, I do use cacti for being able to generate graphs on the fly and zoom
-> in/out with a few mouse clicks. It's quite nice for that.
-> See:
-> http://marc.merlins.org/perso/solar/2009-11.html#Brand-One-Powermeter_-Solar-and-Power-Monitoring-with-Cacti-and-Real-Time-PG_E-Time-of-Use-price-calculation
-> All the graphs that you see, you can select a range with the mouse and zoom
-> in or zoom out with right mouse click.
-> 
-> All that said, cacti has an option not to update the rrd itself and let me
-> do it myself. This is likely the road I'll take to fix this race condition
-> problem.
-> 
-> Thanks for the answers,
-> Marc
-> -- 
-> "A mouse is a device used to point at the xterm you want to type in" - A.S.R.
-> Microsoft is to operating systems & security ....
->                                       .... what McDonalds is to gourmet cooking
-> Home page: http://marc.merlins.org/  
->