How to Investigate PrometheusOperatorReconcile Errors
When you see a PrometheusOperatorReconcile alert in the #lower-priority-alarms channel, it means that the Prometheus Operator is unable to reconcile the state of the Prometheus resources in the cluster.
This means some of the prometheus rules or alerts are having issues and has not applied fine.
Troubleshooting
Check the logs of the Prometheus Operator pod to see if there are any errors:
kubectl logs -n monitoring prometheus-operator-kube-p-operator-<pod-id> -f
If you see any error like below:
level=info ts=2024-02-23T10:31:29.0543824Z caller=rules.go:345
component=prometheusoperator msg="Invalid rule" err="group
\"XXX-elasticache\", rule 1, \"elasticache-enginecpu-utilisation\":
annotation \"message\": template: __alert_elasticache-enginecpu-utilisation:1:
undefined variable \"$clusterId\""
This could stops Prometheus from sending out alerts to certain channels and stops changes/new ones being created. You may also see an alert PrometheusErrorSendingAlertsToSomeAlertmanagers if that was the case.
You will need to fix the erroring PrometheusRule.
If the rule is not configured in cloud-platform-environments repository, find the namespace that rule is applied and get the team slack-channel or the last person who made a change and inform them to fix the rule.