I have a need to set a threshold against a value derived from historic observations.
For example, the 90% of the maximum value for some slow-moving -OTHER- metric over the last 45 days (moving window).
If it were the same metric, then I would think about using Holt-Winters, but in this case, it's a different metric, so I don't think thats an option.
Perhaps I could use getRRDValue with all the right arguments to propery summarizes an aggregation of the right CF for a start = now - (some epoch_seconds), but that would cause that retrieval to happen for every test of the threshold.
More likely I need to run something on a daily basis which does the calculation and stores that somewhere (attribute of the component?) where I can get to it with a here.myAttribute call?
Any suggestions / examples?
TIA!
Richard Evans