Terraform 错误 `Inappropriate value for attribute "vpc_zone_identifier": element 0: string required. `

Question

我遇到了这个错误:
Inappropriate value for attribute "vpc_zone_identifier": element 0: string required.
变量应该是字符串列表，因此元素 0 应该是字符串。

这是代码:

VPC 模块:

resource "aws_subnet" "terraform-pub-sn" {
  count                   = "${length(data.aws_availability_zones.all.names)}"
  vpc_id                  = "${aws_vpc.terraform-vpc.id}"
  cidr_block              = "${element(var.vpc_subnet_cidr, count.index)}"
   availability_zone       = "${data.aws_availability_zones.all.names[count.index]}"
    }

输出:

output "terraform_subnet_ids" {
  value = ["${aws_subnet.terraform-pub-sn.*.id}"]
} 

主文件:

module "auto_scaling_group" {
  source = "./modules/AutoScalingGroup"
  terraform_subnet_ids = ["${module.vpc.terraform_subnet_ids}"]
}

ASG 模块:

variable "terraform_subnet_ids"{}

resource "aws_autoscaling_group" "terraform-asg" {
  vpc_zone_identifier  = ["${var.terraform_subnet_ids}"]

  ...
}

我花了半天时间试图解决这个问题，不知道还要尝试什么以及应该如何定义它。 AFAIK 添加 [] 将使变量成为字符串列表，当它选择元素 0 并返回错误时，该元素在技术上应该是一个字符串，所以不知道问题是什么。也许有一种方法可以即时检查它是什么？

完整的错误在这里:

Error: Incorrect attribute value type

  on modules\AutoScalingGroup\asg.tf line 43, in resource "aws_autoscaling_group" "terraform-asg":
  43:   vpc_zone_identifier  = ["${var.terraform_subnet_ids}"]

Inappropriate value for attribute "vpc_zone_identifier": element 0: string
required.

Answer 1

您的示例之一如下:

output "terraform_subnet_ids" {
  value = ["${aws_subnet.terraform-pub-sn.*.id}"]
}

这包括两个操作: aws_subnet.terraform-pub-sn.*.id returns a list of ids ，然后是 [ ... ] constructs a list from its contents .所以这个表达式正在构造一个列表列表，看起来像这样:

[
  ["subnet-abc123", "subnet-123abc"]
]

在 module block 有一个类似的表达:

  terraform_subnet_ids = ["${module.vpc.terraform_subnet_ids}"]

这也有 [ ... ]，所以它添加了另一个级别的列表:

[
  [
    ["subnet-abc123", "subnet-123abc"]
  ]
]

最后，当您在自动缩放组配置中提及此内容时，我们还有一个 [ ... ]表达:

  vpc_zone_identifier  = ["${var.terraform_subnet_ids}"]

所以到这里的时候，分配给这个参数的值是:

[
  [
    [
      ["subnet-abc123", "subnet-123abc"]
    ]
  ]
]

此列表的元素零是字符串列表的列表，因此 Terraform 报告类型错误。

综上所述，我认为按照您的意图完成这项工作的方法是删除 [ ... ]列出所有这些表达式的构造括号:

output "terraform_subnet_ids" {
  # A list of subnet ids
  value = aws_subnet.terraform-pub-sn.*.id
}

module "auto_scaling_group" {
  source = "./modules/AutoScalingGroup"

  # still a list of subject ids
  terraform_subnet_ids = module.vpc.terraform_subnet_ids
}

variable "terraform_subnet_ids" {
  # Setting an explicit type for your variable can be helpful to
  # catch this sort of problem at the caller, rather than in
  # the usage below. I used set(string) rather than list(string)
  # here because vpc_zone_identifier is an unordered set of subnet
  # ids; list(string) would work too, since Terraform will convert
  # to a set just in time to assign to vpc_zone_identifier.
  type = set(string)
}

resource "aws_autoscaling_group" "terraform-asg" {
  # because of the type declaration above, this is now a set
  # of strings, which is the type this argument is expecting.
  vpc_zone_identifier  = var.terraform_subnet_ids
}