How to set nat_gateway_id in aws_route_table - amazon-web-services

Question

main.tf
module "vpc" {
source = "../modules/aws/vpc"
env_prefix = "prod"
environment = "production"
env_name = "test"
vpc_cidr = "10.1.0.0/16"
public_subnet_cidrs = {
test-prod-nat = {
subnet = "10.1.15.0/24"
name = "test-prod-nat"
az = "ap-northeast-1a"
}
}
}
nat.tf
resource "aws_nat_gateway" "private" {
for_each = var.public_subnet_cidrs
allocation_id = aws_eip.nat_gateway.id
subnet_id = aws_subnet.public[each.key].id
tags = merge(
local.tags,
{
Name = format("%s_%s_%s", var.env_prefix, var.env_name, "nat-gateway")
}
)
lifecycle {
prevent_destroy = false
}
}
route_table.tf
/**
* for private subnet
*/
resource "aws_route_table" "private" {
vpc_id = aws_vpc.dandori.id
tags = merge(
local.tags,
{
Name = format("%s_%s", var.env_prefix, var.env_name)
}
)
route {
cidr_block = "0.0.0.0/0"
nat_gateway_id = [
for v in aws_nat_gateway.private : v.id
]
}
lifecycle {
prevent_destroy = false
}
}
When I run the terraform plan after creating the above tf file, I get the following Error
【Error】
╷
│ Error: Incorrect attribute value type
│
│ on ../modules/aws/vpc/route_table.tf line 55, in resource "aws_route_table" "private":
│ 55: nat_gateway_id = [
│ 56: for v in aws_nat_gateway.private : v.id
│ 57: ]
│ ├────────────────
│ │ aws_nat_gateway.private is object with 1 attribute "test-prod-nat"
│
│ Inappropriate value for attribute "nat_gateway_id": string required.
route_table.tf and nat.tf will be files in the module
I'm trying to set the nat_gateway_id in route_table.tf using the for loop method, but I can't set it correctly as shown in the Error message.
What should I do to solve this problem?
Please give me some advice.

Answer 1

If you want to create a route table for each aws_nat_gateway.private, then it should be:
resource "aws_route_table" "private" {
for_each = aws_nat_gateway.private
vpc_id = aws_vpc.dandori.id
tags = merge(
local.tags,
{
Name = format("%s_%s", var.env_prefix, var.env_name)
}
)
route {
cidr_block = "0.0.0.0/0"
nat_gateway_id = each.value["id"]
}
lifecycle {
prevent_destroy = false
}
}