Program 1 - Terraform Conditions using AWS

If-statements In Terraform, a boolean true is converted to a 1 and a boolean false is converted to a 0. Terraform code is written in a language called HCL, which supports booleans (true and false). If you set count to 1 on a resource, you get one copy of that resource and if you set count to 0, that resource is not created at all.

Content of first.tf

### The module takes three variables as inputs:

variable "service_name" {
  description = "The name of the microservice"
}

variable "ami" {
  description = "The ID of an AMI for the microservice"
}

variable "instance_type" {
  description = "The type of EC2 Instance for the microservice"
}

### To keep the example simple, all the module will do is create a single EC2 Instance and an Elastic IP Address for it:

resource "aws_instance" "example" {
  ami = "${var.ami}"
  instance_type = "${var.instance_type}"
  tags {
    Name = "${var.service_name}"
  }
}
resource "aws_eip" "example" {
  instance = "${aws_instance.example.id}"
}

# Here is an example of how you could use this module to deploy two microservices, a frontend and a backend:

module "frontend" {
  source = "/modules/microservice"
  service_name = "frontend"
  ami = "ami-abcd1234"
  instance_type = "t2.medium"
}
module "backend" {
  source = "/modules/microservice"
  service_name = "backend"
  ami = "ami-efgh5678"
  instance_type = "m4.large"
}

## This works fairly well, except for one problem: while the frontend service is user-facing and needs a public IP address, the backend is not user-facing, and it’s a waste, and perhaps even a security risk, to create a public IP for it. How can you conditionally create the aws_eip resource for some users of the microservice module and not create it for others?

If var.create_ip is true, the module will create one EIP and if var.create_ip is false, the module will create zero EIPs?which is exactly what we want!

Program 2 - Terraform Conditions using AWS

1. In Terraform, a boolean true is converted to a 1 and a boolean false is converted to a 0. Terraform code is written in a language called HCL, which supports booleans (true and false). Terraform doesn’t list boolean as an officially supported type, but many Terraform resources accept booleans (e.g. the aws_instance resource has several boolean parameters, including ebs_optimized, disable_api_termination, monitoring, and source_dest_check), and when you use an unquoted true or false in Terraform code, it treats it as a 1 or 0, respectively.

2. If you set count to 1 on a resource, you get one copy of that resource and if you set count to 0, that resource is not created at all.

# First, you’d add a variable that can be used to specify whether an Elastic IP Address should be created:

variable "create_eip" {
  description = "If set to true, create an EIP for the microservice"
}

# Putting these two ideas together, you can update the microservice module as follows:
resource "aws_eip" "example" {
  count = "${var.create_eip}"
  instance = "${aws_instance.example.id}"
}

# If var.create_ip is true, the module will create one EIP and if var.create_ip is false, the module will create zero EIPs — which is exactly what we want! You can now update your two microservices so that the frontend gets an EIP and the backend does not:


module "frontend" {
  source = "/modules/microservice"
  service_name = "frontend"
  ami = "ami-abcd1234"
  instance_type = "t2.medium"
  create_eip = true
}
module "backend" {
  source = "/modules/microservice"
  service_name = "backend"
  ami = "ami-efgh5678"
  instance_type = "m4.large"
  
  create_eip = false
}