Add new alert for samples rejected due ti duplicate timestamp (#1148)

Signed-off-by: Sébastien GLON <sebastien.glon@akeneo.com>

assets/prometheus/rules/prometheus.rules.yaml

@@ -90,3 +90,12 @@ groups:
     annotations:
       description: "Prometheus {{ $labels.namespace }}/{{ $labels.pod}} isn't ingesting samples."
       summary: "Prometheus isn't ingesting samples"
+
+  - alert: PrometheusTargetScapesDuplicate
+    expr: increase(prometheus_target_scrapes_sample_duplicate_timestamp_total[5m]) > 0
+    for: 10m
+    labels:
+      severity: warning
+    annotations:
+      description: "{{$labels.namespace}}/{{$labels.pod}} has many samples rejected due to duplicate timestamps but different values"
+      summary: Prometheus has many samples rejected

manifests/prometheus/prometheus-k8s-rules.yaml

@@ -634,3 +634,12 @@ data:
         annotations:
           description: "Prometheus {{ $labels.namespace }}/{{ $labels.pod}} isn't ingesting samples."
           summary: "Prometheus isn't ingesting samples"
+    
+      - alert: PrometheusTargetScapesDuplicate
+        expr: increase(prometheus_target_scrapes_sample_duplicate_timestamp_total[5m]) > 0
+        for: 10m
+        labels:
+          severity: warning
+        annotations:
+          description: "{{$labels.namespace}}/{{$labels.pod}} has many samples rejected due to duplicate timestamps but different values"
+          summary: Prometheus has many samples rejected