[Observium] problem with overall traffic view

hello,

I found a little problem (maybe not a bug, but I think is not so good).

if I use "overall_traffic" aggregation (ie for peering) observium make a graph with stacking the traffic from all the ports with a description starting with a label (ie "peering:"), and it works ok.

but if I modify a port (ie dismiss a peering, removing also the "peering:" label from the router interface) observium remove all the pregress traffic the old interface did from the 'peering' graph, so you lose part of the old stats :-(

isn't it possible to have the overall_traffic collected in a dedicated rrd, use the sum of labelled interfaces for new data and use the rrd data for the old data in order to have a real historic data even if I change a port?

thanks