[rrd-developers] Re: Cricket/RRDtool doesn't like restarting devices

[steve rader]

 > From: Bert Driehuis
 > I've had an unrelated cause for spikes that render the charts of the
 > history of my Squid server useless. RRDtool (at least in the way it is
 > called by Cricket, but I believe this to be generally true) cannot cope
 > with a restart of an SNMP agent. COUNTER objects wind up with huge
 > values in this scenario:
 > 
 > Time	Value	PDP Value
 > t	200	0
 > t+1	250	50
 > t+2	300	50
 >  [ agent restarts, counter goes to zero ]
 > t+3	5	4.2e9

I just dealt with this kinda problem yesterday: the cure for
me/nrg is to set the min and max values for each DS... and I
happen to have handy examples laying around...

Try 

  rrdtool create -b 947517820 test.rrd \
    DS:queries:COUNTER:600:U:U \
    RRA:AVERAGE:0.5:1:10 

vs 

  rrdtool create -b 947517820 test.rrd \
    DS:queries:COUNTER:600:0:1000 \
    RRA:AVERAGE:0.5:1:10 

with the data 

  rrdtool update test.rrd -t queries 947517827:26802974
  rrdtool update test.rrd -t queries 947518294:26820088
  rrdtool update test.rrd -t queries 947518614:451
  rrdtool update test.rrd -t queries 947518867:6970
  rrdtool update test.rrd -t queries 947519166:6970

The later doesn't spike because its sets the DS max value.
But it assumes a max rate of 1000 queries/sec.  

If we assume this data is traffic at OC3 rates and set the the
max to 19375000 (1.9e+07 aka 155 mbits/sec) I still get a spike
in the 1+e06 range.  Which makes sense, I think, because 1+e06
is less than 1.9e+07.

But is there a graceful way to handle the example above with
19375000 as the max?? 

later
steve
- - -
systems guy
wiscnet.net

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