> I'm trying to rrd-ify the number of times a string occurs in an apache
> access.log file.  I thought COUNTER would be good.  The logfile is
> rotated nightly, so counts go to zero, but not really because the
> "counter" overflowed.  For example:
> 
[...]
> 
> The graph shows a HUGE spike at the time when the counter goes to
> zero.  It very much looks like the delta is 2^32.
> 

Perhaps it helps a lot to insert an U value at night.
Add this to your logrotate script, just after the logs are rotated:

      rrdtool update foo.rrd N:U:U:U:U

This will (AFAIK) do things right:

    rrdtool update foo.rrd --template A:B:C:D 935477400:7006:1:1015:4
    rrdtool update foo.rrd --template A:B:C:D 935477700:7056:1:1017:6
[1] rrdtool update foo.rrd --template A:B:C:D 935478000:66:0:0:0 
    rrdtool update foo.rrd --template A:B:C:D 935478300:172:0:1:0

    rrdtool update foo.rrd --template A:B:C:D 935477400:7006:1:1015:4
    rrdtool update foo.rrd --template A:B:C:D 935477700:7056:1:1017:6
    rrdtool update foo.rrd N:U:U:U:U
[2] rrdtool update foo.rrd --template A:B:C:D 935478000:66:0:0:0
    rrdtool update foo.rrd --template A:B:C:D 935478300:172:0:1:0


[1] The delta is 66-7056 == -6990 ---> add 2^32
[2] The delta is 66-U    == U     ---> no spike


Regards,
Alex

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