For Each availability zone within an AWS region - amazon-web-services

Question

I am trying to create a subnet within the availability zones within a region using Terraform. I have the below code and am having some trouble getting my subnet to read into the availability zone for the region. Below is also my error.
data "aws_availability_zones" "azs" {
state = "available"
}
locals {
az_names = data.aws_availability_zones.azs.names
}
resource "aws_vpc" "main" {
for_each = var.environment
cidr_block = var.vpc_cidr
tags = {
Name = var.vpc_tags
}
}
resource "aws_subnet" "public" {
for_each = var.public_sub_cidr
vpc_id = aws_vpc.main[each.key].id
cidr_block = cidrsubnet(var.vpc_cidr, 0, each.value.public_subnet)
availability_zone = local.az_names[each.key]
map_public_ip_on_launch = true
tags = {
Name = "${var.vpc_tags}-PubSubnet"
}
}
Errors
Error: Unsupported attribute
on vpc.tf line 17, in resource "aws_subnet" "public":
17: cidr_block = cidrsubnet(var.vpc_cidr, 0, each.value.public_subnet)
|----------------
| each.value is ""
This value does not have any attributes.
Error: Invalid index
on vpc.tf line 18, in resource "aws_subnet" "public":
18: availability_zone = local.az_names[each.key]
|----------------
| each.key is ""
| local.az_names is list of string with 3 elements
The given key does not identify an element in this collection value: a number
is required.
Any advice on reading from availability zones and also assigning these public subnets would be appreciated.
UPDATE
I made some progress, updated my code to use for each with the "length" of my data resource. See code below and error:
resource "aws_subnet" "public" {
for_each = length(local.az_names)
vpc_id = aws_vpc.tableau[each.key].id
cidr_block = cidrsubnet(var.vpc_cidr, 8, each.value)
availability_zone = local.az_names[each.key]
map_public_ip_on_launch = true
tags = {
Name = "${var.vpc_tags}-PubSubnet"
}
}
Error: Invalid for_each argument
on vpc.tf line 15, in resource "aws_subnet" "public":
15: for_each = length(local.az_names)
The given "for_each" argument value is unsuitable: the "for_each" argument
must be a map, or set of strings, and you have provided a value of type
number.
make: *** [apply] Error 1

Answer 1

Not sure what are you trying to achieve, but this is incorrect:
for_each = length(local.az_names)
it should be:
for_each = toset(local.az_names)
Since local.az_names is set now, you can only use each.key (each.value will be same as each.key). For example:
availability_zone = each.key
The following code creates a subnet in each AZ:
provider "aws" {
# your details
}
data "aws_availability_zones" "azs" {
state = "available"
}
locals {
az_names = data.aws_availability_zones.azs.names
}
variable "vpc_cidr" {
default = "10.0.0.0/16"
}
resource "aws_vpc" "main" {
cidr_block = var.vpc_cidr
}
resource "aws_subnet" "public" {
for_each = {for idx, az_name in local.az_names: idx => az_name}
vpc_id = aws_vpc.main.id
cidr_block = cidrsubnet(var.vpc_cidr, 8, each.key)
availability_zone = local.az_names[each.key]
map_public_ip_on_launch = true
}