How to create a template using terraform loop

Question

I want to create CFT using terraform template_file by loping based on a list variable(email_addresses). Below are the variables and template I am trying to generate.

variables:-

emails_addresses = ["sample-1@gmail.com", "sample-2@gmail.com"]
sns_arn = "arn:aws:sns:us-east-1:xxxxxx:xxxx"
protocol = "email"

Expecting template:

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Resources": {
        "sample-1": {
            "Type": "AWS::SNS::Subscription",
            "Properties": {
                "Endpoint": "sample-1@gmail.com",
                "Protocol": "email",
                "TopicArn": "arn:aws:sns:us-east-1:xxxx:xxxxx"
            }
        },
        "sample-2": {
            "Type": "AWS::SNS::Subscription",
            "Properties": {
                "Endpoint": "sample-2@gmil.com",
                "Protocol": "email",
                "TopicArn": "arn:aws:sns:us-east-1:xxx:xxxx"
            }
        }
    }
}

The resource name in CFT can be some random string but it should be the same per mail in case of multiple plans/apply.

Answer 1

This one is a bit tricky due to json. Also I would use templatefile instead of template_file as you can pass lists into it.

variable "emails_addresses" {
  default = ["sample-1@gmail.com", "sample-2@gmail.com"]
}

variable "sns_arn" {
  default = "arn:aws:sns:us-east-1:xxxxxx:xxxx"
}

variable "protocol" {
  default = "email"
}

output "test" {
   value = templatefile("./email-sns-stack.json.tpl", {
     emails_addresses = var.emails_addresses,
     sns_arn = var.sns_arn,
     protocol = var.protocol  
   })
 }

where email-sns-stack.json.tpl is:

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Resources": ${jsonencode(
        {for email_address in emails_addresses: 
        split("@",email_address)[0] => {
          Type = "AWS::SNS::Subscription"
          Properties = {
                "Endpoint" = email_address
                "Protocol" = protocol
                "TopicArn" = sns_arn          
          }
        }})}
}

The output, after pretty json formatting for readability:

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Resources": {
    "sample-1": {
      "Properties": {
        "Endpoint": "sample-1@gmail.com",
        "Protocol": "email",
        "TopicArn": "arn:aws:sns:us-east-1:xxxxxx:xxxx"
      },
      "Type": "AWS::SNS::Subscription"
    },
    "sample-2": {
      "Properties": {
        "Endpoint": "sample-2@gmail.com",
        "Protocol": "email",
        "TopicArn": "arn:aws:sns:us-east-1:xxxxxx:xxxx"
      },
      "Type": "AWS::SNS::Subscription"
    }
  }
}