[rrd-users] Re: Simple plotting with rrdtool, no averaging

[Alex van den Bogaerdt]

A.N.Varady wrote:

> I read through the man pages and the tutorial, and I got only so far in my
> understanding (especially of RRA, I wish there were some example images in Alex
> van den Bogaerdt's tutorial). 

Please, if you have comments on the tutorial provide me with feedback.
It's hard for me to know where people experience difficulties if they
don't tell me.

If you really follow the tutorial, you will have created the graphs.  No
need to create them myself. It would also be very hard to include them in
a pod file.  You may be viewing the html file however that is *not* the
file format used to distribute the tutorial.

The tutorial explains rrdtool fetch; you can use this to troubleshoot.

> My problem is that my graph skips spikes.

Next time please present your information in a ready to go script,
this helps us to help you.  I've rearranged your commands and other
info a bit and now have:

   rrdtool create mailpulse.rrd --start 993736200 \
         DS:latency:GAUGE:600:U:U RRA:AVERAGE:0.1:1:1440
   rrdtool update mailpulse.rrd 993736201:1
   rrdtool update mailpulse.rrd 993736801:0
   rrdtool update mailpulse.rrd 993737401:1
   rrdtool update mailpulse.rrd 993738002:1
   rrdtool update mailpulse.rrd 993738636:36
   rrdtool update mailpulse.rrd 993739201:1
   rrdtool update mailpulse.rrd 993739802:1
   rrdtool update mailpulse.rrd 993740401:1
   rrdtool update mailpulse.rrd 993740481:2
   rrdtool update mailpulse.rrd 993740578:2
   rrdtool update mailpulse.rrd 993740729:1
   rrdtool update mailpulse.rrd 993740789:1
   rrdtool update mailpulse.rrd 993740901:1
   rrdtool update mailpulse.rrd 993741001:1
   rrdtool update mailpulse.rrd 993741057:1
   rrdtool update mailpulse.rrd 993741143:1
   rrdtool fetch mailpulse.rrd --start 993736200 --end 993741300 AVERAGE

Its output:

   [alex at home /tmp]$ ./mailpulse.sh
                     latency
   
    993736200:        NaN
    993736500: 1.6666666667e-03
    993736800: 1.6666666667e-03
    993737100: 9.9833333333e-01
    993737400: 9.9833333333e-01
    993737700: 1.0000000000e+00
    993738000: 1.0000000000e+00
    993738300:        NaN
    993738600:        NaN
    993738900: 1.0000000000e+00
    993739200: 1.0000000000e+00
    993739500: 1.0000000000e+00
    993739800: 1.0000000000e+00
    993740100: 1.0000000000e+00
    993740400: 1.0000000000e+00
    993740700: 1.5900000000e+00
    993741000: 1.0000000000e+00
    993741300:        NaN

So, why are there NaN values in this output and not those high numbers?

The hearbeat is set to 600.  This means an update should occur within
600 seconds.  If this doesn't happen, the input is assumed to be inaccurate
and is thus set to unknown.  Let's review part of your input:

   rrdtool update mailpulse.rrd 993738002:1
   rrdtool update mailpulse.rrd 993738636:36
   rrdtool update mailpulse.rrd 993739201:1

You update 993738636 - 993738002 = 634 seconds apart, this results in
an unknown for both 993738000..993738300 and 993738300..993738600.

I must say 993738600..993738900 set to 1 surprises me, I'd expect this
to be unknown as well, or maybe 36*36/300+1*(300-36)/300 == 5.2

> How can I create a graph which simply plots the data as I have it in my log,
> showing all data elements and not trying to average them?

With RRDtool you can't.  Don't use a hammer to paint and don't use a
screwdriver to hammer nails.  In other words, use the right tool for
the job.  If you really want to display the measured values as they
are, you should be using -for instance- a spreadsheet.  RRDtool works
with rates changing over time.  Its consolidation functions and resampling
of the data are an integral part, you shouldn't use rrdtool if you don't
want to.

HTH
-- 
   __________________________________________________________________
 / alex at slot.hollandcasino.nl                  alex at ergens.op.het.net \
| work                                                         private |
| My employer is capable of speaking therefore I speak only for myself |
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| http://faq.mrtg.org/                                                 |
| http://rrdtool.eu.org  --> tutorial                                  |
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