# PostgreSQL 告警規則
# 監控資料庫連線、效能、磁碟空間等
apiVersion: monitoring.coreos.com/v1
kind: PrometheusRule
metadata:
  name: postgres-alerting-rules
  namespace: monitoring
  labels:
    release: prometheus
    app: kube-prometheus-stack
spec:
  groups:
    - name: postgresql.alerts
      rules:
        # 資料庫連線數過高
        - alert: PostgresConnectionsHigh
          expr: pg_stat_activity_count > 80
          for: 5m
          labels:
            severity: warning
            environment: "{{ $labels.kubernetes_namespace }}"
          annotations:
            summary: "PostgreSQL 連線數過高"
            description: "PostgreSQL 連線數達到 {{ $value }} (閾值 80)"
            runbook: "檢查是否有連線洩漏或需要調整 max_connections"

        # 資料庫連線數接近上限
        - alert: PostgresConnectionsCritical
          expr: pg_stat_activity_count > 95
          for: 2m
          labels:
            severity: critical
            environment: "{{ $labels.kubernetes_namespace }}"
          annotations:
            summary: "PostgreSQL 連線數接近上限"
            description: "PostgreSQL 連線數達到 {{ $value }} (閾值 95)，即將耗盡"
            runbook: "立即檢查並結束閒置連線"

        # 資料庫停機
        - alert: PostgresDown
          expr: pg_up == 0
          for: 1m
          labels:
            severity: critical
            environment: "{{ $labels.kubernetes_namespace }}"
          annotations:
            summary: "PostgreSQL 資料庫停機"
            description: "無法連接到 PostgreSQL 資料庫"
            runbook: "立即檢查 momo-postgres Pod 狀態"

        # 慢查詢過多
        - alert: PostgresSlowQueries
          expr: rate(pg_stat_activity_max_tx_duration{state="active"}[5m]) > 5
          for: 10m
          labels:
            severity: warning
            environment: "{{ $labels.kubernetes_namespace }}"
          annotations:
            summary: "PostgreSQL 慢查詢過多"
            description: "過去 5 分鐘有持續的慢查詢，最長事務時間: {{ $value }}s"
            runbook: "檢查 pg_stat_activity 找出慢查詢並優化"

        # 資料庫大小超過閾值
        - alert: PostgresDatabaseSizeLarge
          expr: pg_database_size_bytes{datname="momo_analytics"} > 5368709120
          for: 5m
          labels:
            severity: warning
            environment: "{{ $labels.kubernetes_namespace }}"
          annotations:
            summary: "PostgreSQL 資料庫大小超過 5GB"
            description: "資料庫 momo_analytics 大小: {{ humanize $value }}"
            runbook: "考慮清理舊資料或擴充磁碟空間"

        # 資料庫空間使用過高
        - alert: PostgresDatabaseSizeCritical
          expr: pg_database_size_bytes{datname="momo_analytics"} > 8589934592
          for: 5m
          labels:
            severity: critical
            environment: "{{ $labels.kubernetes_namespace }}"
          annotations:
            summary: "PostgreSQL 資料庫大小超過 8GB"
            description: "資料庫 momo_analytics 大小: {{ humanize $value }}，空間即將耗盡"
            runbook: "立即清理資料或擴充磁碟空間"

        # 等待鎖定過長
        - alert: PostgresLockWaiting
          expr: pg_locks_count{mode="ExclusiveLock"} > 10
          for: 5m
          labels:
            severity: warning
            environment: "{{ $labels.kubernetes_namespace }}"
          annotations:
            summary: "PostgreSQL 鎖定等待過多"
            description: "有 {{ $value }} 個排他鎖定，可能有阻塞"
            runbook: "檢查 pg_locks 找出阻塞的查詢"

        # 複製延遲 (如有 Replica)
        - alert: PostgresReplicationLag
          expr: pg_replication_lag > 60
          for: 5m
          labels:
            severity: warning
            environment: "{{ $labels.kubernetes_namespace }}"
          annotations:
            summary: "PostgreSQL 複製延遲"
            description: "複製延遲: {{ $value }}s"
            runbook: "檢查網路和 Replica 狀態"

        # 死鎖發生
        - alert: PostgresDeadlocks
          expr: rate(pg_stat_database_deadlocks{datname="momo_analytics"}[5m]) > 0
          for: 1m
          labels:
            severity: warning
            environment: "{{ $labels.kubernetes_namespace }}"
          annotations:
            summary: "PostgreSQL 發生死鎖"
            description: "資料庫 momo_analytics 發生死鎖"
            runbook: "檢查應用程式的交易邏輯"

        # 表膨脹 (Dead Tuples 過多)
        - alert: PostgresTableBloat
          expr: pg_stat_user_tables_n_dead_tup > 100000
          for: 30m
          labels:
            severity: warning
            environment: "{{ $labels.kubernetes_namespace }}"
          annotations:
            summary: "PostgreSQL 表膨脹"
            description: "表 {{ $labels.relname }} 有 {{ $value }} 個死亡元組"
            runbook: "執行 VACUUM ANALYZE {{ $labels.relname }}"