[rrd-users] Graph like functionality when fetching data

[Philip Molter]

The RRD manpage for rrdgraph says this:

  Apart from generating graphs, it can also extract numerical reports.

Is this referring to the GPRINT instructions or, is there an ability
to fetch the data from graph DEFs and CDEFs?  What I'm really
looking for is the ability to specify to 'rrdtool fetch' the files
and DSs that I want to pull data from, and have it combine that
data in new and interesting ways (like I can do with the graphing
methods).

Right now, for example, if I have three interfaces (in separate
RRD files) and I want to know my total traffic for those three
interfaces, I can specify the three DEFs in the files, specify a
bunch of CDEFs, and then graph the data.  I can even go so far as
to get the MAX, MIN, AVG, etc. values of particular CDEFs, and
print them onto the graph using GPRINT.

If I want these values, though, for a printed report or something,
how do I get them?  The fetch function seems to only take one RRD,
and you can't do any data manipulation of the data it gets back.
If I want to get combined traffic data, I have to do that work
myself, including any data reorganization that may be necessary
(especially if they're on different step intervals).  I would think
that since the ability to do this type of manipulation is already
in the code for the graphing function, that the fetching functions
should also have access to it, but I can't find it anywhere.

Is this built-in, and if not, has anyone written a utility that
allows this to be done?

* Philip Molter
* DataFoundry.net
* http://www.datafoundry.net/
* philip at datafoundry.net

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