[prometheus] add sample probe and rule

prometheus-monitoring/probe.yaml

@@ -0,0 +1,16 @@
+kind: Probe
+apiVersion: monitoring.coreos.com/v1
+metadata:
+  name: ungleich-ch
+  namespace: monitoring
+spec:
+  interval: 60s
+  module: http_2xx
+  prober:
+    url: blackbox-exporter:19115
+  targets:
+    staticConfig:
+      static:
+      - https://ungleich.ch
+      - https://monitoring.place7.ungleich.ch
+      - https://google.com

prometheus-monitoring/prometheus-rule.yaml

@@ -0,0 +1,20 @@
+apiVersion: monitoring.coreos.com/v1
+kind: PrometheusRule
+metadata:
+  creationTimestamp: null
+  labels:
+    prometheus: k8s
+    role: alert-rules
+  name: prometheus-example-rules
+spec:
+  groups:
+  - name: ./example.rules
+    rules:
+    - alert: RAMUsage
+      expr: (node_memory_MemAvailable_bytes / node_memory_MemTotal_bytes) < 0.25
+      for: 5m
+      labels:
+        severity: info
+      annotations:
+        summary: "Server {{ $labels.instance }} has a less than 25% RAM available"
+        description: "Server {{ $labels.instance }} has only {{ $value }}% of its total amount of RAM available!"