How to create multiple instances with multiple subnet ids using terraform? - terraform

Question

I have 2 services test1,test2 and for each service i have to create 6 vm's.This 6 vm's should be placed in 3 subnet id's which created in 3 different zones in a same region
In this services,test1 will be in private subnets and test2 will be in public subnets.So i have to pass that correct subnet id when creating ec2 instances
root module:
provider "aws" {
region = var.region
}
module "ecom-vpc" {
source = "./modules/vpc"
}
module "ecom-public-subnet" {
source = "./modules/subnets/public"
vpc-id = module.ecom-vpc.vpc-id
}
module "ecom-private-subnet" {
source = "./modules/subnets/private"
vpc-id = module.ecom-vpc.vpc-id
}
module "ecom-instances-sg" {
source = "./modules/sg"
vpc-id = module.ecom-vpc.vpc-id
}
module "ecom-vm-instances" {
source = "./modules/vm"
priv-subnet-ids = module.ecom-private-subnet.ecom_private_subnets
pub-subnet-ids = module.ecom-public-subnet.ecom_public_subnets
instances-sg = module.ecom-instances-sg.ecom-inst-sg
}
From child modules - vpc,subnets,ec2
variable "service-names" {
type = list(any)
default = ["ecom-app-TEST1","ecom-app-TEST2"]
}
variable "availability_zones" {
type = map
default = {
ap-south-1a = {
private_subnet = "10.0.1.0/24"
public_subnet = "10.0.4.0/24"
}
ap-south-1b = {
private_subnet = "10.0.2.0/24"
public_subnet = "10.0.5.0/24"
}
ap-south-1c = {
private_subnet = "10.0.3.0/24"
public_subnet = "10.0.6.0/24"
}
}
}
resource "aws_vpc" "ecom-vpc" {
cidr_block = var.ecom-cidr
}
output "vpc-id" {
value = aws_vpc.ecom-vpc.id
}
resource "aws_subnet" "ecom-private" {
for_each = var.availability_zones
vpc_id = var.vpc-id
cidr_block = each.value.private_subnet
availability_zone = each.key
map_public_ip_on_launch = false
tags = {
Name = "${split("-", each.key)[2]}"
Subnet_Type = "private"
}
}
output "ecom_private_subnets" {
value = aws_subnet.ecom-private
}
resource "aws_subnet" "ecom-public" {
for_each = var.availability_zones
vpc_id = var.vpc-id
cidr_block = each.value.public_subnet
availability_zone = each.key
map_public_ip_on_launch = true
tags = {
Name = "${split("-", each.key)[2]}"
Subnet_Type = "public"
}
depends_on = [aws_internet_gateway.igw
]
}
output "ecom_public_subnets" {
value = aws_subnet.ecom-public
}
I'm trying to achieve the same by creating a locals which combines service names,priv,public subnet id's,instance count(2).But the problem is i'm not able to make it because i'm not able to create a unique combination of keys
locals {
service_subnets = {
for pair in setproduct(var.service-names, values(var.priv-subnet-ids),values(var.pub-subnet-ids),range(var.instance_count)) :
"${pair[0]}:${pair[1].availability_zone}-${pair[3]}" => {
service_name = pair[0]
priv-subnet = pair[1]
pub-subnet = pair[2]
}
}
}
resource "aws_instance" "ecom-instances" {
for_each = local.service_subnets
ami = data.aws_ami.ecom.id
instance_type = "t3.micro"
tags = {
Name = each.value.service_name
Service = each.value.service_name
}
vpc_security_group_ids = [var.instances-sg[each.value.service_name].id]
subnet_id = "${split("-", each.value.service_name)[2] == "TEST1" ? each.value.pub-subnet.id : each.value.priv-subnet.id }"
}
I'm getting the below error.
Two different items produced the key "ecom-app-TEST1:ap-south-1c-1" in this 'for' expression. If duplicates are expected, use the ellipsis (...)
│ after the value expression to enable grouping by key.
If i add ... and change it as below then it is converted as tuple and i'm not sure how to get and pass the value from each.value in the aws_instance resource
locals {
service_subnets = {
for pair in setproduct(var.service-names, values(var.priv-subnet-ids),values(var.pub-subnet-ids),range(var.instance_count)) :
"${pair[0]}:${pair[1].availability_zone}-${pair[3]}" => {
service_name = pair[0]
priv-subnet = pair[1]
pub-subnet = pair[2]
}
... }
}
on modules/vm/main.tf line 60, in resource "aws_instance" "ecom-instances":
│ 60: subnet_id = "${split("-", each.value.service_name)[2] == "TEST1" ? each.value.pub-subnet.id : each.value.priv-subnet.id }"
│ ├────────────────
│ │ each.value is tuple with 3 elements
│
│ This value does not have any attributes.
Please Guide me

Answer 1

You could try adding the index to your for loop and making it part of your name, might help you avoid elipsis/tuple conversion.
locals {
service_subnets = {
for index, pair in setproduct(var.service-names, values(var.priv-subnet-ids),values(var.pub-subnet-ids),range(var.instance_count)) :
"${pair[0]}:${pair[1].availability_zone}-${pair[3]}=${index}" => {
service_name = pair[0]
priv-subnet = pair[1]
pub-subnet = pair[2]
}
}
}