Some variables that were intendet to be used were in fact not used (e.g.
allTargets) but that will be needed as soon as we have a second non-dev
host in our nixfiles.
I didn't notice this was missing in #5 until after deploying it. Since
the ports on the monitoring-network-interface (ens10) were not open,
scraping would fail and thus generate alerts.
The goal is to create a monitoring setup where each server monitors
itself when it comes failing systemd services, disk or RAM filling up,
…. In addition each prometheus will monitor remote prometheus and
alertmanager instances for signs of failure (e.g. being unreachable,
errors in notification delivery, dropping alerts).
A lot of metrics (especially histograms from prometheus or alertmanager)
are being dropped before ingestion to disk save on space and memory.
Depending on how many servers we may or may not have in the future this
could probably use some kind of overhaul since we rightnow have n^2
monitoring peer relationships (not even speaking of possible duplicated
alerts).
