amazon-web-services - Terraform:在应用之前无法确定数据源上的长度()？

Question

我正在尝试动态声明多个 aws_nat_gateway通过 aws_subnet_ids 检索公共(public)子网列表来获取数据源数据源。但是，当我尝试设置 count 时参数等于子网 ID 的长度，我收到错误消息 The "count" value depends on resource attributes that cannot be determined until apply... .

这几乎与 example in their documentation 直接矛盾。 !。我该如何解决？他们的文件有错吗？

我正在使用 Terraform v0.12。

data "aws_vpc" "environment_vpc" {
  id = var.vpc_id
}

data "aws_subnet_ids" "public_subnet_ids" {
  vpc_id = data.aws_vpc.environment_vpc.id
  tags = {
    Tier = "public"
  }
  depends_on = [data.aws_vpc.environment_vpc]
}

data "aws_nat_gateway" "nat_gateway" {
  count      = length(data.aws_subnet_ids.public_subnet_ids.ids)  # <= Error
  subnet_id  = data.aws_subnet_ids.public_subnet_ids.ids.*[count.index]
  depends_on = [data.aws_subnet_ids.public_subnet_ids]
}

我希望能够成功应用此模板，但出现以下错误:

Error: Invalid count argument

  on ../src/variables.tf line 78, in data "aws_nat_gateway" "nat_gateway":
  78:   count      = "${length(data.aws_subnet_ids.public_subnet_ids.ids)}"

The "count" value depends on resource attributes that cannot be determined
until apply, so Terraform cannot predict how many instances will be created.
To work around this, use the -target argument to first apply only the
resources that the count depends on.

Answer 1

似乎您正在尝试获取尚未创建或无法确定的子网，terraform cmd 输出建议您添加 -target 标志以创建 VPC 和子网或先执行其他任务，之后，您将应用 nat_gateway 资源。我建议您使用 AZ 列表而不是子网 ID，我将在下面添加一个简单的示例。

variable "vpc_azs_list" {
  default = [
    "us-east-1d",
    "us-east-1e"
  ]
}

resource "aws_nat_gateway" "nat" {
  count         = var.enable_nat_gateways ? length(var.azs_list) : 0
  allocation_id = "xxxxxxxxx"
  subnet_id     = "xxxxxxxxx"
  depends_on = [
    aws_internet_gateway.main,
    aws_eip.nat_eip,
  ]
  tags = {
    "Name"       = "nat-gateway-name"
    "costCenter" = "xxxxxxxxx"
    "owner"      = "xxxxxxxxx"
  }
}

我希望对您和其他用户有用。