---
groups:
  - name: General system
    rules:
      - record: node_memory_MemAvailable_percentage
        expr: (node_memory_MemAvailable_bytes / node_memory_MemTotal_bytes) * 100
      - record: node_cpu_count
        expr: count without(cpu, mode) (node_cpu_seconds_total{mode="idle"})

      - alert: InstanceDown
        expr: up == 0
        for: 5m
        labels:
          serverity: critical
        annotations:
          summary: "{{ $labels.instance }} down"

      - alert: SystemdServiceFailed
        expr: node_systemd_unit_state{state="failed"} > 0
        for: 5m
        labels:
          serverity: error
        annotations:
          summary: "{{ $labels.name }} on {{ $labels.instance }} crashed"

      - alert: OomKill
        expr: increase(node_vmstat_oom_kill[5m]) > 0 # Scrape interval of 1 minute
        for: 0m
        labels:
          serverity: error
        annotations:
          summary: "OOM kill on {{ $labels.instance }}"

      - alert: VeryLowAvailableMemory
        # Less than 3% available or less than 100KB available memory
        expr: ((node_memory_MemAvailable_percentage < 3) or (node_memory_MemFree_bytes < (1024 * 100)))
        for: 2m
        labels:
          serverity: critical
        annotations:
          summary: "Very low free memory on {{ $labels.instance }}"

      - alert: LowAvailableMemory
        expr: node_memory_MemAvailable_percentage < 10
        for: 5m
        labels:
          serverity: warn
        annotations:
          summary: "Low free memory on {{ $labels.instance }}"

      - alert: ReducedAvailableMemory
        expr: node_memory_MemAvailable_percentage < 20
        # Detect constant high memory usage as a potential sign that the host could maybe need some more memory
        for: 1h
        labels:
          serverity: info
        annotations:
          summary: "Reduced available memory on {{ $labels.instance }}"

      - alert: HighMemoryPressure
        # For at least 5 seconds over the last 2 Minutes, no progress could be made
        # due to memory congestion
        expr: increase(node_pressure_memory_stalled_seconds_total[2m]) >= 5
        labels:
          serverity: error
        annotations:
          summary: "Memory preassure on {{ $labels.instance }}"

      - alert: VeryHighLoad
        expr: ((node_load1 / node_cpu_count) > 1) or ((node_load5 / node_cpu_count) > 0.9)
        for: 5m
        labels:
          serverity: error
        annotations:
          summary: "Very High load on {{ $labels.instance }}"

      - alert: HighLoad
        expr: ((node_load1 / node_cpu_count) > 0.9) or ((node_load5 / node_cpu_count) > 0.8)
        for: 10m
        labels:
          serverity: warn
        annotations:
          summary: "High load on {{ $labels.instance }}"

      - alert: ElevatedLoad
        # Detecting a long-term increased load
        expr: (node_load15 / node_cpu_count) > 0.7
        for: 15m
        labels:
          serverity: info
        annotations:
          summary: "Elevated load15 on {{ $labels.instance }}"

      - alert: LowFreeDiskSpace
        expr:  node_filesystem_readonly == 0 and ON (instance, device, mountpoint) (node_filesystem_avail_bytes * 100) / node_filesystem_size_bytes < 15
        for: 10m
        labels:
          serverity: info
        annotations:
          summary: "{{ $labels.mountpoint }} on {{ $labels.instance }} has less than 15% space left"

      - alert: VeryLowFreeDiskSpace
        expr:  node_filesystem_readonly == 0 and ON (instance, device, mountpoint) (node_filesystem_avail_bytes * 100) / node_filesystem_size_bytes < 5
        for: 3m
        labels:
          serverity: error
        annotations:
          summary: "{{ $labels.mountpoint }} on {{ $labels.instance }} has less than 5% space left"

  - name: Prometheus Alertmanager
    rules:
      - alert: AlertmanagerMissing
        expr: prometheus_notifications_alertmanagers_discovered < 1
        for: 5m
        labels:
          serverity: warn
        annotations:
          summary: "No connected alertmanager on {{ $labels.instance }}"

      - alert: AlertmanagerMissing
        expr: increase(prometheus_notifications_dropped_total[5m]) > 0
        labels:
          serverity: error
        annotations:
          summary: "Dropped alert notifications on {{ $labels.instance }}"

      - alert: FailingAlertmanagerNotifications
        expr: increase(alertmanager_notifications_failed_total[5m]) > 0
        labels:
          serverity: error
        annotations:
          summary: "Failing notifications via {{ $labels.integration }} on {{ $labels.instance }}"

      - alert: FailingRuleEvaluation
        expr: sum by (instance) (increase(prometheus_rule_evaluation_failures_total[5m])) > 0
        labels:
          serverity: warn
        annotations:
          summary: "Failing rule evaluations on {{ $labels.instance }}"