I'm a newbie to rrdtool so I'm hoping I'm just doing something stupid.
Right now, it seems that boolean operators in CDEF have a delay in computation.
I'm using rrdgraph (tried both using RRDP under perl and rrd.cgi) to print
values for current bandwidth, average bandwidth, currently if the bandwidth is
greater than zero, and on average if the bandwidth is greater than zero. Here's
the graph command:
graph dummy.png -s end-86400 -e now-600 --step 120
DEF:BwIn1=bw.rrd:ds0:AVERAGE:step=120:end=now-600:start=end=86400
CDEF:bitsin=BwIn1,8,*
CDEF:bb=BwIn1,0,GT
"PRINT:bitsin:AVERAGE: Avg in %4.1lf %Sbps"
"PRINT:bitsin:LAST: Curr In %4.1lf %Sbps"
"PRINT:bb:AVERAGE: Avg > 0 %3.6lf"
"PRINT:bb:LAST: Curr > 0 %3.6lf"
The rrd step size is 120. I seem to get two different outputs:
Half the time, I get the following, as expected:
Avg in 100.4 Mbps
Curr In 162.3 Mbps
Avg > 0 1.000000
Curr > 0 1.000000
The other half the time, I get the following:
Avg in 100.4 Mbps
Curr In 162.3 Mbps
Avg > 0 0.997230
Curr > 0 0.000000
These two results are definitely linked to step size- they flop from one to
another every 120 seconds.
It seems that the boolean GT command is bumping into unknown values for last
value which is not surprising. But the arithmetic * command doesn't seem to
have the same problem (CF = "LAST").
Also, given the definition of end=now-600, it seems that the last point (which
could be unknown) should not figure in the average calculations. I thought, by
forcing the step size to 120s, rrdtool would use the finest resolution RRA so
the possible unknown last point would cover an interval much less than the 600s
lopped off the end.
Any help would be much appreciated! Thanks!
Sue
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