I was thinking about setting up a monitoring of a Tor-Relay using Telegraf, InfluxDB and Grafana. Although I did read quite some documenation about it already I thought it might be good to check for possible experiences made here before spending (wasting) too much time trying it out myself.

Questions I could not answer yet myself include e.g.

What will be the performance impact of running Telegraf on a Tor-Realy (CPU, disk, I/O,...)?
What happens if the InfluxDB (running on another system) is not reachable (maintenance, outages) - is the data lost or buffered somehow?
I would like to also keep see old/historical data but not as granular as more recent data - is there any way to boild down old data, e.g. to only keep hourly data for data older that a month etc.?

There are an overwhelmingly number of monitoring possibilities (munin, collecd, monit, nyx, RRDtool, Cacti, Monitorix, Nagios, Zabbix,...) out there and one could easily spend days if not weeks with reading and testing. So any kind of shared experiences, hints or tips are more than welcome.