[rrd-developers] Update ex post?
Thorsten von Eicken
tve at voneicken.com
Tue Aug 24 17:32:37 CEST 2010
> So, what's the approach those tools are using (I've never looked at any
> of those [nor have I looked *for* any ;-)])?
Something I wrote quite a while ago is a resampling tool, that would
construct a new RRD using data from an old one, and for each CDP looks
into the old one to get the best data match, and interpolate or combine
values. I used this heavily in a former life to change existing RRDs
full of data when we changed the amount of data we stored in each RRD. I
haven't maintained this and it's rrdtool 1.2 vintage, ca. 2005.
What I'm looking for now is the ability to splice RRDs together. The use
case is replacing a server, for example, we replace www1 by www1-new
and, after the fact, I'd like to splice the graphs together at the time
we cut over service. Operating in the cloud we do this a lot. In this
case I don't mind a discontinuity at the splice point, in fact, I would
probably add a DS or something to mark the splice point so I can draw a
vertical line on graphs.
The splicing could also be very useful for restoring data. E.g., if a
monitoring server dies we can quickly replace it with a new one, but
that doesn't have any data. So all the RRDs start out empty and record
new data coming in. When we get the data from the failed one restored,
we'd like to splice the old and new together.
I'm not expecting someone else to build the above and it's still a
little out on the roadmap here. I have a bunch of other exciting stuff
to contribute to rrdtool in the pipeline... I just wanted to chime in :-).
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