创建Azure ServiceBus主题订阅时遇Terraform索引无效错误求助

问题场景 #

配置Azure ServiceBus主题订阅时触发以下错误：

Error: Invalid index
│
│   on .terraform\modules\servicebus\modules\servicebus\main.tf line 103, in resource "azurerm_servicebus_subscription" "subscription":
│  103:   for_each            = { for sb in var.topic_list : "${sb[\"subscription\"]}" => sb }
│
│ The given key does not identify an element in this collection value.
╵
╷
│ Error: Invalid index
│
│   on .terraform\modules\servicebus\modules\servicebus\main.tf line 103, in resource "azurerm_servicebus_subscription" "subscription":
│  103:   for_each            = { for sb in var.topic_list : "${sb[\"subscription\"]}" => sb }
│
│ The given key does not identify an element in this collection value.

涉及代码及输入如下：

原模块代码 #

resource "azurerm_servicebus_subscription" "subscription" {
  for_each            = { for sb in var.topic_list : "${sb[\"subscription\"]}" => sb }
  name                = each.value[\"subscription\"]
  topic_id            = azurerm_servicebus_topic.topics[\"${each.value.name}\"].id
  max_delivery_count  = var.max_delivery_count
}

原variable.tf #

variable "topic_list" {
  type = list(object({
    name                    = string
    max_size_in_megabytes   = string
  }))
  default     = []
}

输入值 #

topic_list: 
  - name: "topicair"
    max_size_in_megabytes: "5120"
    subscriptions: 
      - subscription: subscription1
      - subscription: subscription2
      - subscription: subscription3
  - name: "topicwint"
    max_size_in_megabytes: "81920"
    subscriptions: 
      - subscription: subscriptiontop1
      - subscription: subscriptiontop2
      - subscription: subscriptiontop3

错误原因 #

1. 变量类型定义不完整：variable "topic_list"的object类型未声明subscriptions字段，但输入值中包含该字段，导致Terraform无法识别该属性。
2. for_each遍历逻辑错误：当前代码试图直接从var.topic_list的每个元素中取subscription字段，但该字段实际存在于每个topic的subscriptions列表中，而非topic本身，因此触发"Invalid index"错误。

修复方案 #

1. 修正变量类型定义 #

更新variable.tf，补充subscriptions字段的类型声明：

variable "topic_list" {
  type = list(object({
    name                    = string
    max_size_in_megabytes   = string
    subscriptions           = list(object({
      subscription = string
    }))
  }))
  default     = []
}

2. 修正订阅资源的遍历逻辑 #

使用flatten函数将所有topic下的订阅展平为一维列表，并生成唯一的键（避免订阅名称重复时冲突）：

resource "azurerm_servicebus_subscription" "subscription" {
  for_each = {
    for sub in flatten([
      for topic in var.topic_list : [
        for s in topic.subscriptions : merge(s, { topic_name = topic.name })
      ]
    ]) : "${sub.topic_name}-${sub.subscription}" => sub
  }

  name                = each.value.subscription
  topic_id            = azurerm_servicebus_topic.topics[each.value.topic_name].id
  max_delivery_count  = var.max_delivery_count
}

说明 #

• flatten函数将嵌套的subscriptions列表转换为一维列表，每个元素包含订阅名称和所属topic名称。
• 使用${sub.topic_name}-${sub.subscription}作为for_each的键，确保每个订阅实例的唯一性，即使不同topic下有同名订阅也不会冲突。

内容的提问来源于stack exchange，提问作者pks