"IF" Conditional Resource Creation in Terraform

In Terraform, you can conditionally create resources based on certain conditions. This is often done using the count parameter along with a conditional expression. Here's how you can implement an "if" statement-like behavior:

Using count for Conditional Creation

The count parameter can be set to either 0 or 1 based on a condition:

resource "aws_instance" "example" {
  count = var.environment == "production" ? 1 : 0

  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"
}

In this example, the EC2 instance will only be created if the environment variable is set to "production".

Checking Environment Variables

You can also use environment variables in your conditions:

variable "create_resource" {
  type    = bool
  default = tobool(coalesce(trimspace(get(jsondecode(nonsensitive(data.aws_ssm_parameter.my_vars.value)), "CREATE_RESOURCE", null)), "false"))
}

resource "aws_s3_bucket" "conditional_bucket" {
  count  = var.create_resource ? 1 : 0
  bucket = "my-conditional-bucket"
}

Here, we're using a more complex setup to read an environment variable from AWS Systems Manager Parameter Store, but you could also use Terraform's built-in terraform.workspace or other environment-specific variables.

Using Maps for Environment-Specific Conditions

You can use maps to store environment-specific conditions:

variable "env_resource_count" {
  type = map(number)
  default = {
    dev  = 0
    test = 1
    prod = 1
  }
}

resource "aws_instance" "example" {
  count = lookup(var.env_resource_count, terraform.workspace, 0)

  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"
}

This approach allows you to specify different counts for different environments.

Remember, when using count, you'll need to refer to your resources using the index syntax, e.g., aws_instance.example[0].