I saw this when adding toolsbeta-prometheus to grafana-cloud:
Grafana-cloud (aka grafana-labs) is hosted on production hardware (cloudmetrics100x.eqiad.wmnet). It has two main datasources:
- graphite-labs, hosted on the same hardward and available publicly. This works now but graphite in general is being phased out.
- Various Prometheus instances hosted on the cloud realm. Since the cloudmetrics hosts can't access production directly, these use the grafana setting to have browser javascript run the Prometheus queries (which is now deprecated upstream).
There's also an another Prometheus instance running on cloudmetrics hardware, but that one is only currently added to grafana.wm.o (not grafana-cloud).