Add Prometheus alerting rules

dist/charts/ping-exporter/files/prometheus.rules

@@ -0,0 +1,16 @@
+    - alert: HighPingLossRatio
+      expr: round(ping_loss_ratio * 100) > 0
+      for: 5m
+      labels:
+        severity: warning
+      annotations:
+        summary: High ping loss ratio for {{ $labels.target }}
+        description: "Ping loss ratio for {{ $labels.target }} is {{ $value }}"
+    - alert: HighPingRtt
+      expr: round(ping_rtt_mean_seconds * 1000, 0.1) > 100
+      for: 5m
+      labels:
+        severity: warning
+      annotations:
+        summary: High ping latency for {{ $labels.target }}
+        description: "Ping latency for {{ $labels.target }} is {{ $value }} seconds"

dist/charts/ping-exporter/templates/prometheusrule.yaml

@@ -0,0 +1,14 @@
+{{- if .Values.prometheusRules.enabled }}
+apiVersion: monitoring.coreos.com/v1
+kind: PrometheusRule
+metadata:
+  labels:
+    prometheus: service-prometheus
+    role: alert-rules
+  name: {{ include "ping_exporter.fullname" . }}
+spec:
+  groups:
+  - name: ping_exporter.rules
+    rules:
+{{ .Files.Get "files/prometheus.rules" }}
+{{- end }}

dist/charts/ping-exporter/values.yaml

@@ -105,3 +105,7 @@ config:
 # Create a serviceMonitor resource to be consumed by Prometheus Operator
 serviceMonitor:
   enabled: false
+
+# Create basic Prometheus alerting rules
+prometheusRules:
+  enabled: false