ALERT NodeExporterDown
  IF absent(up{job="node-exporter"} == 1)
  FOR 10m
  LABELS {
    severity = "warning"
  }
  ANNOTATIONS {
    summary = "node-exporter cannot be scraped",
    description = "Prometheus could not scrape a node-exporter for more than 10m, or node-exporters have disappeared from discovery.",
  }