[rrd-users] mrtg + rrdcached

Steven Hartland killing at multiplay.co.uk
Tue Feb 2 10:50:16 CET 2010

----- Original Message ----- 
From: "Tobias Oetiker" <tobi at oetiker.ch>
>> I tried getting mrtg to work with rrdcached but it uses updatev
>> in the rrdtool v1.2+ code path so it doesn't work. Looking through
>> the code it seemed like there was no reason why if we forced the
>> old 1.1 path it wouldn't work just fine.
> except for the rrdtool fetch which is necessary to figure out of
> alarms have to be raised which would force rrdcachd to flush the
> cache on every round ... but if you do NOT use alarms, then things
> should work fine.

Hmm, we don't use alarms but there doesn't seem to be any condition
on the fetch, so its only processed if there are threshold checks
are defined.

Are you saying that the call to threshcheck and the info / fetch
block under the comment:
# get the rrdtool-processed values back from rrdtool
in mrtg could be skipped if no threshold checks are defined?

The following is the stats from our rrdcached which has been running
now ~ 30hours, it does seem to indicate there are a very large number
of possibly unneeded flushes happening, do you think this is down
to the mrtg fetch?

9 Statistics follow
QueueLength: 0
UpdatesReceived: 9156170
FlushesReceived: 1083366
UpdatesWritten: 1475662
DataSetsWritten: 9103092
TreeNodesNumber: 4153
TreeDepth: 15
JournalBytes: 0
JournalRotate: 0


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