如何在从 IPAM 获取下一个可用的 CIDR 时阻止 terraform 中的数据在每次运行时刷新

Question

我正在尝试通过从 IPAM 获取下一个可用的 CIDR 来自动创建 VPC。但是每次运行 Terraform 都会在我使用数据时获得一个新的 CIDR 块。我尝试将 CIDR 存储在参数存储区中，但只要运行 terraform 甚至不更改 terraform 代码，它仍然会被覆盖？

有人可以帮忙吗？

#Preview next CIDR from pool 
data "aws_vpc_ipam_preview_next_cidr" "previewed_cidr" {
 ipam_pool_id   = data.aws_vpc_ipam_pool.ipv4_ipam_pool.id
 netmask_length = var.vpc_mask_length["standard"]
}

resource "aws_ssm_parameter" "vpc_cidr" {
 name  = "/test/custom-fields/vpc_cidr"
 type  = "String"
 value = data.aws_vpc_ipam_preview_next_cidr.previewed_cidr.cidr
}

#Calculate subnet cidrs from previewed IPAM CIDR

locals {
 partition           = cidrsubnets(data.aws_vpc_ipam_preview_next_cidr.previewed_cidr.cidr, 1, 1)
 private_subnets     = cidrsubnets(local.partition[0], 2, 2, 2)
}

module "vpc" {
 source  = "terraform-aws-modules/vpc/aws"
 version = "3.19.0"
 name             = "dev-vpc"
 cidr             = aws_ssm_parameter.vpc_cidr.value
 azs              = formatlist("${data.aws_region.current.name}%s", ["a", "b", "c"])
 private_subnets. = local.private_subnets
}

resource "aws_vpc_ipam_pool_cidr_allocation" "ipam_allocation" {
 ipam_pool_id = data.aws_vpc_ipam_pool.ipv4_ipam_pool.id
 cidr         = data.aws_vpc_ipam_preview_next_cidr.previewed_cidr.cidr
 description  = "test-vpc"
}

尝试的解决方法：

选项1：

我也尝试过 aws_vpc_ipam_preview_next_cidr 资源，但 vpc 模块不接受它作为输入并抛出以下错误“计数”值取决于在应用之前无法确定的资源属性，但资源属性已经应用。

resource "aws_vpc_ipam_preview_next_cidr" "previewed_cidr" {
 
 ipam_pool_id   = data.aws_vpc_ipam_pool.ipv4_ipam_pool.id
 netmask_length = var.vpc_mask_length["standard"]
}

选项2：

我也读过生命周期，不幸的是我不能在模块或数据上使用它们，它只支持资源。我试过下面的代码，但也没有运气。

resource "aws_vpc_ipam_pool_cidr_allocation" "ipam_allocation" {
  ipam_pool_id = data.aws_vpc_ipam_pool.ipv4_ipam_pool.id
  cidr         = data.aws_vpc_ipam_preview_next_cidr.previewed_cidr.cidr
  description  = "test-vpc"
  lifecycle {
      ignore_changes = [cidr]
    }
}