如何在Terraform变量的默认值中引用资源?

Question

我有一个来自AWS上网络平台实现的子网和vpc id的输出。tfstate存储在s3 example/networking/terraform.tfstate.

public_subnets = [
"subnet-0c1ed9933fxxxxxf",
"subnet-0ee61aaa65xxxx3",
"subnet-0b9bcf251ebxxxxx54",
]
vpc_id = "vpc-085b3d740xxxxxx"

我不想手动将输出vpc或子网放在tf代码中，而是动态调用它。但是在

下面抛出这个错误

| Error: Variables not allowed
│ 
│   on main.tf line 28, in variable "target_vpc":
│   28:   default     = "${data.terraform_remote_state.vpc.outputs.vpc_id}"
│ 
│ Variables may not be used here.
╵
╷
│ Error: Variables not allowed
│ 
│   on main.tf line 34, in variable "target_subnet":
│   34:   default     = "${data.terraform_remote_state.subnet.outputs.public_subnets[1]}"
│ 
│ Variables may not be used here.

代码:

provider "aws" {
region = "eu-west-1"
}
data "terraform_remote_state" "vpc" {
backend = "s3"
config = {
bucket = "example-comp"
key    = "comp/networking/terraform.tfstate"
region = "eu-west-1"
}
}
data "terraform_remote_state" "subnet" {
backend = "s3"
config = {
bucket = "example-comp"
key    = "comp/networking/terraform.tfstate"
region = "eu-west-1"
}
} 
variable "target_vpc" { 
default     = "${data.terraform_remote_state.vpc.outputs.vpc_id}"
description = "Project Default VPC: aws acct as default"
}
variable "target_subnet" { 
default     = "${data.terraform_remote_state.subnet.outputs.public_subnets[1]}"
description = "Project Default VPC SN: eu-west-1"
}
variable "aws_ami" {
type = string
default = "ami-0b850cf02cc00fdc8"
}
variable "server_type" {
type = string
default = "t2.micro"
}   
variable "target_keypairs" {
type = string
default     = "EC2 Tutorial"
description = "Project default keys:"
}   
variable "project" {
default = "example-comp"
}
terraform {
required_version = ">= 0.12.31"
backend "s3" {
bucket = "example-comp"
key    = "comp/simple-instance/terraform.tfstate"
region = "eu-west-1"
}
}
resource "aws_security_group" "dm_sg_res" {
name        = "${var.project}-server-sg"
description = "multiple firewall rules"
vpc_id      = var.target_vpc
ingress {
from_port   = 22
to_port     = 22
protocol    = "tcp"
cidr_blocks = ["0.0.0.0/0"]
}
ingress {
from_port   = 80
to_port     = 80
protocol    = "tcp"
cidr_blocks = ["0.0.0.0/0"]
}
ingress {
from_port   = 3000
to_port     = 3000
protocol    = "tcp"
cidr_blocks = ["0.0.0.0/0"]
}
egress {
from_port   = 0
to_port     = 0
protocol    = "-1"
cidr_blocks = ["0.0.0.0/0"]
}
}
resource "aws_instance" "server_inst_res" {
ami                    = var.aws_ami
instance_type          = var.server_type
vpc_security_group_ids = [aws_security_group.dm_sg_res.id]
key_name               = var.target_keypairs
subnet_id              = var.target_subnet
connection {
type        = "ssh"
user        = "centos"
private_key = "${file("EC2Tutorial.pem")}"
timeout     = "3m"
host        = "${self.public_ip}"
}
provisioner "remote-exec" {
inline = [
"sudo yum update -y",
"sudo yum install git wget vim unzip -y",
"sudo setenforce 0"
]
}
provisioner "local-exec" {
command = "ANSIBLE_HOST_KEY_CHECKING=false ansible-playbook -u centos -i '${self.public_ip},' --private-key 'EC2Tutorial.pem' site.yaml"
}
tags = {
Name = "${var.project}-server"
}
}
output "pub_ip" {
value = ["${aws_instance.server_inst_res.public_ip}"]
}

Answer 1

您正在引用variable的默认值的数据资源，这是不允许的(请参阅关于输入变量的Terraform文档):

variable "target_vpc" {
default = data.terraform_remote_state.vpc.outputs.vpc_id
}

应该使用local变量作为中间变量:

locals {
target_vpc = var.target_vpc == null ? data.terraform_remote_state.vpc.outputs.vpc_id : var.target_vpc
}
variable "target_vpc" {
default = null
}

在其他资源中引用VPC时，使用local.target_vpc，不使用var.target_vpc。