"Prometheus server at http://localhost:9090 is configured to only keep 0s of metrics history." When using default config

[jonathan-dev]

I was getting a bunch of these errors:

Warning: `alertmanager_notifications_failed_total[2m]` selector is trying to query Prometheus for 2m worth of metrics, but `prom1` Prometheus server at http://localhost:9090 is configured to only keep 0s of metrics history. (promql/range_query)

This makes sense and all but when the retention time flags are not set on startup prometheus defaults to a retention time of 15days. That is not reflected in the /flags endpoint which then returns the 0s for storage.tsdb.retention.time which is read by this tool (check this issue for details).

Under the /status endpoint the 15d retention time is listed. Maybe this should be used as the time for the retention time since it returns the correct value and using the other one the warnings are misleading.