[rrd-developers] followup on invalid data or spikes

[Steve Bishop]

Tobi,

I have tracked this bug some more.   In earlier versions of rrdtool (< 1.0.7) or maybe earlier,
it seemed that these spikes, or invalid data occurred randomly, out of the blue, in
rrd databases that didn't have limits established.  Maybe they still do.

I know these spikes didn't occur
because of erroneous data.  Also, I am fairly certain that the majority of the databases
where these spikes occurred, did not have the "non-byte" boundary counter reset or rollover
issues (I am using the COUNTER database type).

I have reproduced this bug.  I've only been able to document one rrd that has
one piece of invalid data in it.  It will occur whether the rrd has limits established
or not.

Here are the instructions (or commands), I used to reproduce this bug.  It involves
the dump, restore, and tune commands.  So far, I have only been able to reproduce
the bug using the method I describe below.  Nevertheless, I believe that this problem
or bug can manifest itself in other ways.

I am using version 1.0.8 of rrdtool.  I am including the data files I used to reproduce
this problem.  Here is the sequence of shell commands I ran:

rrdtool create my.rrd -b 946843500 -s 300 "DS:load:GAUGE:300:0:5000" "DS:out_oct:COUNTER:300:0:1250000" "DS:drop_oct:COUNTER:300:0:U"
"DS:out_pkts:COUNTER:300:0:25000" "DS:drop_pkts:COUNTER:300:0:U" "RRA:AVERAGE:0.5:1:864" "RRA:AVERAGE:0.5:3:1344" "RRA:AVERAGE:0.5:12:744"
"RRA:AVERAGE:0.5:288:91"

foreach i ( `cat file1`)
    rrdtool update my.rrd $i
end

rrdtool dump my.rrd > db.out
rrdtool restore -r db.out my.rrd
rrdtool tune my.rrd -a out_oct:1250000 -a out_pkts:25000

foreach i ( `cat file2`)
    rrdtool update my.rrd $i
end


Now, examine the rrd at this point, and you will find invalid data:
rrdtool dump my.rrd > db.out
rrdtool restore -r db.out db.xml

out of range found [ds: 3], [value : 1.9991590274e+37]


Steve Bishop
Developer
Verio, Inc.






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