chore: add under-utilized alerts

dist/rules/host-and-hardware/node-exporter-under-utilized.yml

@@ -0,0 +1,32 @@
+groups:
+
+- name: NodeExporter
+
+  rules:
+
+    - alert: HostUnderUtilizedOfMemory
+      expr: 'node_memory_MemAvailable_bytes / node_memory_MemTotal_bytes * 100 > 80'
+      for: 7d
+      labels:
+        severity: info
+      annotations:
+        summary: Host memory is under utilized (instance {{ $labels.instance }})
+        description: "Node memory is not fully used (> 80% free). Consider reducing memory space.\n  VALUE = {{ $value }}\n  LABELS = {{ $labels }}"
+
+    - alert: HostUnderUtilizedCpuLoad
+      expr: '100 - (avg by(instance) (rate(node_cpu_seconds_total{mode="idle"}[2m])) * 100) < 20'
+      for: 7d
+      labels:
+        severity: info
+      annotations:
+        summary: Host CPU load is under utilized (instance {{ $labels.instance }})
+        description: "CPU load is < 20%. Consider reducing the number of CPUs.\n  VALUE = {{ $value }}\n  LABELS = {{ $labels }}"
+
+    - alert: HostLotsOfFreeDiskSpace
+      expr: '(node_filesystem_avail_bytes * 100) / node_filesystem_size_bytes > 80 and ON (instance, device, mountpoint) node_filesystem_readonly == 0'
+      for: 7d
+      labels:
+        severity: info
+      annotations:
+        summary: Host lots of free disk space (instance {{ $labels.instance }})
+        description: "Disk space is not fully used (> 80% free). Consider reducing disk space.\n  VALUE = {{ $value }}\n  LABELS = {{ $labels }}"