ALERT AlertmanagerConfigInconsistent
  IF   count_values by (service) ("config_hash", alertmanager_config_hash)
     / on(service) group_left
       label_replace(prometheus_operator_alertmanager_spec_replicas, "service", "alertmanager-$1", "alertmanager", "(.*)") != 1
  FOR 5m
  LABELS {
    severity = "critical"
  }
  ANNOTATIONS {
    summary = "Alertmanager configurations are inconsistent",
    description = "The configuration of the instances of the Alertmanager cluster `{{$labels.service}}` are out of sync."
  }

ALERT AlertmanagerDownOrMissing
  IF   label_replace(prometheus_operator_alertmanager_spec_replicas, "job", "alertmanager-$1", "alertmanager", "(.*)")
     / on(job) group_right
       sum by(job) (up) != 1
  FOR 5m
  LABELS {
    severity = "warning"
  }
  ANNOTATIONS {
    summary = "Alertmanager down or not discovered",
    description = "An unexpected number of Alertmanagers are scraped or Alertmanagers disappeared from discovery."
  }

ALERT FailedReload
  IF alertmanager_config_last_reload_successful == 0
  FOR 10m
  LABELS {
    severity = "warning"
  }
  ANNOTATIONS {
    summary = "Alertmanager configuration reload has failed",
    description = "Reloading Alertmanager's configuration has failed for {{ $labels.namespace }}/{{ $labels.pod}}."
  }