Instead of that complicated minute/day/week/year data retention scheme, why not just randomly replace an entry in a fixed-size store? So the probability of a datum being in the store is inversely proportional to the log of its age.
And it's a one-liner.
I noticed the GitHub description for the repo says "ejabberd monitoring server." Can this be used for non-ejabberd monitoring? I assume the answer is yes given the rest of the documenation. Maybe you can update the description.
Grapherl is realtime scalable stats gathering daemon which can handle high amount of incoming data points (~1 million data points per minute per socket). It also provides a web dashboard that allows the users to visualize graphs for gathered stats.
