Feature toggles in Terraform

00_basic_toggle.tf

# Terraform converts boolean values to 1 (true) and 0 (false)
# This passed into the count sets the count to 1 or zero effectivly creating or skipping the resource
variable "create_my_group" { default="true" }
variable "name_my_group" { default="my_group" }
variabble "vpc_my_group" { default="vpcid" }

resource "aws_security_group" "my_group" {
  count = "${var.create_my_group}"
  name = "${var.name_my_group}"
  vpc_id = "${var.vpc_id)"
}

01_basic_conditionals_toggle.tf

variable "toggle" { default="false" }
variable "true_val" { default="true_val" }
variable "false_val" { default="false_val" }

output "toggle_result" {
  value = "${ var.toggle ? var.true_val : var.false_val }"
}

02_multi_resource_toggle.tf

variable "toggle_efs" { default="true" }
variable "efs_target_qty" { default=3 }

data "aws_subnet" "data_tier" {
  filter {
    name = "tag:StorageClass"
    values = ["data_storage"]
  }
}

resource "aws_efs_file_system" "data_vol" {
  count = "${ var.toggle_efs ? 1 : 0 }"
}

resource "aws_efs_mount_target" "data_vol_mount" {
  count = "${ var.toggle_efs ? var.efs_target_qty : 0 }"
  file_system_id = "${aws_efs_file_system.data_vol.id}"
  subnet_id      = "${element(data.aws_subnet.data_tier.*.id, count.index)}"
}