Better handling of multiple loops within 1 resource with Terraform - loops

Question

I'm trying to create multiple CNAME resources based on multiple A record resources and am struggling to find a way to achieve this.
I currently have the following in my variable.tfvars file:
hostnames = [
"webserver1",
"webserver2"
]
domain = domain.com
subdomain_addresses = [
"www-1",
"www-2",
"www-3"
]
I have the following output from my ec2 instance module which is based off the length of var.hostnames: (in this instance there will be 2 private IPs)
output "server_ip_addresses" {
value = aws_instance.this.*.private_ip
}
I currently have the following in my resource.tf file:
resource "aws_route53_record" "instance_record" {
for_each = toset(var.hostnames)
zone_id = data.aws_route53_zone.route53_zone.zone_id
name = "${each.value}.${var.domain}"
type = "A"
ttl = "300"
records = module.ec2_instance.server_ip_addresses
}
resource "aws_route53_record" "webservice_records" {
for_each = toset(var.subdomain_addresses)
zone_id = data.aws_route53_zone.route53_zone.zone_id
name = "${each.value}.${var.domain}"
type = "CNAME"
ttl = "300"
records = [values(aws_route53_record.instance_record)[*].name]
}
What I need is a way to have the webservice_records resource create a subdomain for each entry in var.subdomain_addresses but associate each subdomain with each aws_route53_record.instance_record.name output.
So for example instance_record creates the following A records:
webserver1.domain.com = 10.1.1.18
webserver2.domain.com = 10.1.1.19
and webservice_records creates the following CNAMEs:
www-1.domain.com = webserver1.domain.com, webserver2.domain.com
www-2.domain.com = webserver1.domain.com, webserver2.domain.com
www-3.domain.com = webserver1.domain.com, webserver2.domain.com
I am currently getting the following error:
╷
│ Error: Incorrect attribute value type
│
│ on resource.tf line 62, in resource "aws_route53_record" "webservice_records":
│ 62: records = [values(aws_route53_record.instance_record)[*].name]
│ ├────────────────
│ │ aws_route53_record.instance_record is object with 2 attributes
│
│ Inappropriate value for attribute "records": element 0: string required.
╵
Does someone have a better idea of how this can be achieved?

Answer 1

you can use the setproduct function to achieve that output like below:
so it would be like something like this to create a map:
locals {
hostnames = [
"webserver1",
"webserver2"
]
domain = "domain.com"
subdomain_addresses = [
"www-1",
"www-2",
"www-3"
]
webserver_list = [ for web_list in setproduct(local.hostnames, [local.domain]) : join(".",web_list) ]
cname_map = {for sub_domain in local.subdomain_addresses: sub_domain => local.webserver_list}
}
resource "aws_route53_record" "cnames" {
for_each = local.cname_map
zone_id = data.aws_route53_zone.route53_zone.zone_id
name = each.key
type = "CNAME"
ttl = "300"
records = each.value
}
cname_map looks like this:
cname_map= {
www-1 = [
"webserver1.domain.com",
"webserver2.domain.com",
]
www-2 = [
"webserver1.domain.com",
"webserver2.domain.com",
]
www-3 = [
"webserver1.domain.com",
"webserver2.domain.com",
]
}