PrometheusDuplicateTimestamps #

Find the Prometheus Pod that concerns this.

$ kubectl -n <namespace> get pod
prometheus-k8s-0                       2/2     Running   1          122m
prometheus-k8s-1                       2/2     Running   1          122m

Look at the logs of each of them, there should be a log line such as:

$ kubectl -n <namespace> logs prometheus-k8s-0
level=warn ts=2021-01-04T15:08:55.613Z caller=scrape.go:1372 component="scrape manager" scrape_pool=default/main-ingress-nginx-controller/0 target=http://10.0.7.3:10254/metrics msg="Error on ingesting samples with different value but same timestamp" num_dropped=16

Now there is a judgement call to make, this could be the result of:

Faulty configuration, which could be resolved by removing the offending ServiceMonitor or PodMonitor object, which can be identified through the scrape_pool label in the log line, which is in the format of <namespace>/<service-monitor-name>/<endpoint-id>.
The target is reporting faulty data, sometimes this can be resolved by restarting the target, or it might need to be fixed in code of the offending application.