[rrd-users] Strange Graph Problem

Christopher Corke chrisc at nwatechsolutions.com
Wed Feb 9 05:05:00 MET 2005

I'm sure this is something simple, but I'm not seeing it.

I created a new table:

../bin/rrdtool create fs_border_loc.rrd --start N       \
   DS:Requests:COUNTER:600:U:U          \
   DS:CacheHits:COUNTER:600:U:U         \
   RRA:AVERAGE:0.5:1:600                \
   RRA:AVERAGE:0.5:6:700                \
   RRA:AVERAGE:0.5:24:775               \
   RRA:AVERAGE:0.5:288:797              \
   RRA:MAX:0.5:1:600                    \
   RRA:MAX:0.5:6:700                    \
   RRA:MAX:0.5:24:775                   \

Simple, it  only has two counters...

I then graph one DS:

/usr/local/rrdtool-1.0.49/bin/rrdtool graph
         --title="FS_BORDER1_LOC (Requests Received by HTTP)" --start
         --imgformat PNG --width="400" --height="176"           \
        DEF:Requests=fs_border_loc.rrd:Requests:AVERAGE         \
        'GPRINT:Requests:MIN:"%2.1lf"   '                       \
        'GPRINT:Requests:AVERAGE:"%2.1lf"       '                      
        'GPRINT:Requests:MAX:"%2.1lf"   '                       \
        AREA:Requests#F06AA4:                                   \

Now if I understand this correctly, I should see a graph with the
Minimum, Average and Maximum values at the bottom.

After the first update of the table, my graph is blank; and all three
values are NaN...  Which I expect after one sample.

After a couple of updates to  the table, all three values change to
0.5, which doesn't surprise me; after two samples the min, max and
average should be all the same.  What surprises me is the graph, the "Y"
axis on my graph display from 400m to 500m...  And my area and line are
both around 450m.  How is that possible, since my min, max and average
are all 0.5????

I even captured the update commands to see if I was getting bad data in
the table:

/usr/local/rrdtool-1.0.49/bin/rrdtool update
/usr/local/rrdtool-1.0.49/data/fs_border_loc.rrd N:257921:167839
/usr/local/rrdtool-1.0.49/bin/rrdtool update
/usr/local/rrdtool-1.0.49/data/fs_border_loc.rrd N:257924:167842
/usr/local/rrdtool-1.0.49/bin/rrdtool update
/usr/local/rrdtool-1.0.49/data/fs_border_loc.rrd N:257984:167897

Nothing even close to the "Y" axis on my graph....

A "/usr/local/rrdtool-1.0.49/bin/rrdtool fetch fs_border_loc.rrd"
returns everything NaN except the following line:

1107921300:  4.5062982527e-01  4.1541378843e-01

So, how do I end up with such a strange graph???

I included a copy of the "PNG" graph file..



-- Attached file removed by Ecartis and put at URL below --
-- Type: image/png
-- Size: 2k (2379 bytes)
-- URL : http://www.ee.ethz.ch/~slist/p/Requests-day.png

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