如何将Terraform通过for_each创建的GCP通知通道应用到告警策略

步骤1：调整告警策略变量结构 #

首先需要在business_metric_alert_policies变量定义中新增notification_channel_names字段，用于存储每个告警策略需要关联的通知通道的display_name列表，变量结构参考：

variable "business_metric_alert_policies" {
  type = list(object({
    display_name           = string
    condition_display_name = string
    filter               = string
    duration             = string
    comparison           = string
    threshold_value      = number
    trigger_count        = number
    alignment_period     = string
    per_series_aligner   = string
    cross_series_reducer = string
    # 新增字段：存储需要关联的通知通道display_name列表
    notification_channel_names = list(string)
  }))
  description = "业务指标告警策略配置列表"
}

赋值变量时，直接填写对应要关联的通知通道名称即可，示例：

business_metric_alert_policies = [
  {
    display_name = "API请求延迟过高告警"
    condition_display_name = "95分位延迟超过500ms"
    filter = "metric.type=\"run.googleapis.com/request_latencies\" resource.type=\"cloud_run_revision\""
    duration = "60s"
    comparison = "COMPARISON_GT"
    threshold_value = 500
    trigger_count = 1
    alignment_period = "60s"
    per_series_aligner = "ALIGN_PERCENTILE_95"
    cross_series_reducer = "REDUCE_PERCENTILE_95"
    # 关联两个已定义的通知通道
    notification_channel_names = ["运维Opsgenie通道", "研发组告警通道"]
  }
]

步骤2：修改告警策略资源中的notification_channels参数 #

因为通知通道资源是通过for_each以display_name为key创建的，所以可以通过for表达式遍历每个告警策略绑定的通道名称，直接取出对应通知通道的资源ID即可，修改后的alert_policy.tf对应字段如下：

resource "google_monitoring_alert_policy" "business_metric_alert_policy" {
  for_each = { for inst in var.business_metric_alert_policies : inst.display_name => inst }
  display_name = each.value.display_name
  combiner = "OR"
  conditions {
    display_name = each.value.condition_display_name
    condition_threshold {
      filter = each.value.filter
      duration = each.value.duration
      comparison = each.value.comparison
      threshold_value = each.value.threshold_value
      trigger {
          count = each.value.trigger_count
      }
      aggregations {
        alignment_period = each.value.alignment_period
        per_series_aligner = each.value.per_series_aligner
        cross_series_reducer = each.value.cross_series_reducer
      }
    }
  }
  # 引用通知通道核心配置
  notification_channels = [for channel_name in each.value.notification_channel_names : google_monitoring_notification_channel.alert_notification_opsgenie_channel[channel_name].id]
}

特殊场景：关联所有已创建的通知通道 #

如果某个告警策略需要关联所有已创建的通知通道，无需逐个配置名称，可直接替换notification_channels配置为：

notification_channels = values(google_monitoring_notification_channel.alert_notification_opsgenie_channel)[*].id

内容的提问来源于stack exchange，提问作者jyostna lalitha