concatenate two variables in terraform

Question

i'm trying to create a kubernetes cluster from kops using terraform,following code is a part of infrastructure, i'm trying to create the name concatenate with two variables, and i'm getting illegal char error line two, error happens because im trying to define the name with concatenate variables. is it possible in terraform?

resource "aws_autoscaling_group" "master-kubernetes" {
  name                 = "master-"${var.zone}".masters."${var.cluster_name}""
  launch_configuration = "${aws_launch_configuration.master-kubernetes.id}"
  max_size             = 1
  min_size             = 1
  vpc_zone_identifier  = ["${aws_subnet.subnet-kubernetes.id}"]

Answer 1

Try this:

resource "aws_autoscaling_group" "master-kubernetes" {
  name = "master-${var.zone}.masters.${var.cluster_name}"
  # ... other params ...
}

Answer 2

With latest terraform 0.12.x terraform format doc , you could do better like:

resource "aws_autoscaling_group" "master-kubernetes" {
    name = format("master-%s.masters.%s", var.zone, var.cluster_name)
}

Answer 3

I would say rather concatenating at resource level use the locals first define a variable in locals and then you can utilize it at resource level

Locals declaration

locals {
  rds_instance_name = "${var.env}-${var.rds_name}"
}

Resource Level declaration

resource "aws_db_instance" "default_mssql" {
  count                     = var.db_create ? 1 : 0
  name                      = local.rds_instance_name
........
}

This is as simple as its need to be ....