[rrd-users] Why Double Counter Wrap ?

[Christian Mönneckes]

Hi,

Why double counter wrap when update delay >= 1 second ?

an example:

rrdtool create test.rrd \
	--start 1098794644 --step 300 \
	DS:count:COUNTER:450:U:U \
	RRA:LAST:0.5:1:5

update values with 1 second delay:

    # UPDATE TIME: Tue Oct 26 14:45:01 2004
    rrdtool update test1.rrd --template count 1098794701:5000

    # UPDATE TIME: Tue Oct 26 14:50:01 2004
    rrdtool update test.rrd --template count 1098795001:6000

    # UPDATE TIME: Tue Oct 26 14:55:01 2004
    rrdtool update test.rrd --template count 1098795301:100

    # UPDATE TIME: Tue Oct 26 15:00:01 2004
    rrdtool update test.rrd --template count 1098795601:100

    # UPDATE TIME: Tue Oct 26 15:05:01 2004
    rrdtool update test.rrd --template count 1098795901:100


the result is a double counter wrap:

    rrdtool fetch test.rrd LAST
    ...
    1098794700: nan
    1098795000: 3.3333333333e+00
    1098795300: 1.4268816204e+07 # <-- first counter wrap
    1098795600: 4.7721793289e+04 # <-- second counter wrap, Why ???
    1098795900: 0.0000000000e+00
    1098796200: nan


but, update values without delay:

    # UPDATE TIME: Tue Oct 26 14:45:00 2004
    rrdtool update test.rrd --template count 1098794700:5000

    # UPDATE TIME: Tue Oct 26 14:50:00 2004
    rrdtool update test.rrd --template count 1098795000:6000

    # UPDATE TIME: Tue Oct 26 14:55:00 2004
    rrdtool update test.rrd --template count 1098795300:100

    # UPDATE TIME: Tue Oct 26 15:00:00 2004
    rrdtool update test.rrd --template count 1098795600:100

    # UPDATE TIME: Tue Oct 26 15:05:00 2004
    rrdtool update test.rrd --template count 1098795900:100


the result is only one counter wrap:

    rrdtool fetch test.rrd LAST
    ...
    1098794700: nan
    1098795000: 3.3333333333e+00
    1098795300: 1.4316537987e+07 # <-- only one counter wrap
    1098795600: 0.0000000000e+00
    1098795900: 0.0000000000e+00
    1098796200: nan


is the double counter wrap a bug ???

Thanks,

Christian Mönneckes


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