How to create multiple resources in a for loop with terraform?

Question

I have looked at several bits of documentation as well as a udemy course on terraform and I do not understand how to do the thing that I want to do. I want to create a for loop and in it I want to create an S3 event notification, create an Sns topic that listens to that notification, create an Sqs queue and then subscribe the queue to the sns topic. It seems like for loops in terraform are not advanced enough to do this. Am I wrong, is there any documentation or examples that explain how to use for loops for this use case?

Thanks in advance.

The iterators are within the scope of the resource, and not outside of it. Given that, it is completely possible to functionally do what you describe. More assistance can be provided with an MCVE of your attempt at this. — Matthew Schuchard
– Matthew Schuchard, Commented Apr 1, 2020 at 20:43
Yes, that's kind of what i was seeing from the docs. I'd like to be able to create resources dynamically in a loop. I saw on another SO post that people have been creating their own wrappers with python to basically generate tf files which is a way to achieve this. — slipperypete
– slipperypete, Commented Apr 1, 2020 at 20:50
terraform.io/docs/configuration/…. Each resource type will be created independently with respective for_each. NOT in a big for loop if it is what you are expecting in which you can create a S3 event, then give it to SNS next to be created in a loop. — mon
– mon, Commented Apr 2, 2020 at 2:12

Prithvi Boinpally · Accepted Answer · 2024-02-28 16:15:50Z

16

The for_each example looks like the following:


variable names {
  type = list(string)
  description = "List of names"
}

resource "aws_example_resource" "bar" {
  for_each = toset(var.names)
  name = each.key
}

This will create N resources (length of names), using the each.key to specify the value to assign to name each time

edited Feb 28, 2024 at 16:15

Prithvi Boinpally

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answered Jul 12, 2022 at 20:23

l33tHax0r

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2 Comments

Nacho Mezzadra Over a year ago

Thanks! in my case it only allowed me to use it like this by having set(string) instead of list(string).

VC2019 Over a year ago

I had a case where I needed to use module with for loop instead of resource shown above. I have multiple services that need ses, the only thing different is the service name and the ses name. To do this in loop, below code is what worked for me.

variable "service_names" {   type = list(string)   description = "List of services"   default = [ "abc", "xyz","sdf","klm"] } module "custom_ses" {   for_each = toset(var.service_names)   source   = "./modules/ses"   name     = "${each.key}_ses" }

mon · Accepted Answer · 2020-04-02 02:31:02Z

An example to create AWS VPC subnets then give them to AWS EC2 instances.

resource "aws_subnet" "public" {
  count = length(var.public_subnet_cidr_blocks)
  vpc_id     = var.vpc_id
  cidr_block = var.public_subnet_cidr_blocks[count.index]
}

resource "aws_instance" "public_ec2" {
  count = length(var.public_subnet_ids)
  subnet_id = var.public_subnet_ids[count.index]
  ami           = var.ami_id
  instance_type = "t2.micro"
  tags = {
    Name = "PublicEC2${count.index}}"
  }
  provisioner "local-exec" {
    command = <<EOF
echo "Public EC2 ${count.index} ID is ${self.id}"
EOF
  }
}

There is no syntax like below to create resources.

[ for name in var.names:
 aws_s3_bucket {...} 
 aws_sns_topic {...}
]

For expression is basically for values, not for creating resources.

for Expressions

A for expression creates a complex type value by transforming another complex type value.

To create multiple resources, as below in the document use for_each or count.

for_each: Multiple Resource Instances Defined By a Map, or Set of Strings

By default, a resource block configures one real infrastructure object. However, sometimes you want to manage several similar objects, such as a fixed pool of compute instances. Terraform has two ways to do this: count and for_each.

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