groups:
- name: Hardware alerts
  rules:
  - alert: Node down
    expr: up{job="node_exporter"} == 0
    #     ^ promql
    for: 3m
    labels:
      severity: warning
    annotations:
      title: Node {{ $labels.instance }} is down
      description: Failed to scrape {{ $labels.job }} on {{ $labels.instance }} for more than 3 minutes. Node seems down.