Interface Graph With Additional Data

[zaf]

We have a database containing device and interface names, and the corresponding circuit bandwidth (eg not interface bandwidth, but the available bandwidth of the circuit that the interface is plugged into). We'd like to have our interface graphs have this line plotted. - Note: ifSpeed, or other SNMP values from the device itself, won't reflect the *purchased* circuit bandwidth (eg an STM-1 plugged into a 1Gbps interface), so as I understand, the pre-build Interface with Bandwidth won't help, as that uses ifSpeed.

I've created a cacti data input method to, when given either the "hostname - ifAlias", or the unique (DB) ID, return the current bandwidth (this changes as we reprovision links, so entering this data as a value isn't ideal).

We have scripts which automatically create required graphs for us, using the CLI, but so far I'm having difficulty with creating a graph template that has most of its data (in/out bytes) from a Data Query, and also from another data template.

The current problem I have is when I create the graph (using the web interface for now, auto scripting will come later), it asks for the circuit id (good!), but then doesn't create an actual datasource for the bandwidth. Eg the graph has "None" for the Bandwidth Datasource.

Not really sure what I've missed, or if what I'm doing is possible, so my question is two fold:

a) Can this be done?

b) ..... how?

[gandalf]

This can be done in theory ...
You will have to use a script to fetch the current speed on each polling interval (bad, as a script is way slower than a pure SNMP request).
You will have to modify the data template to provide the data source item for the bandwidth.
You will have to recreate all rrd files as rrdtool is not able to add a data source item to an already existing rrd file (well, recently there have been tools ...)
Well, that's theory.
The _real_ issue is the first one ...
R.