Terraform Apps and Infra 4 - Hands-on CLI

In

CLI to manipulate a Terraform deployment

  • Task

      graph TD
A[Main Terraform code]
B[default workspace]
C[test workspace]
D[default workspace state file is terraform.tfstate]
E[test workspace state file resides in terraform.tfstate.d directorys]
F(terraform.workspace value is default)
G(terraform.workspace value is test)
H(deploys to PRO account)
I(deploys to staging account)

A --> B
B --> D
D --> F
F --> H
A --> C  
C --> E
E --> G
G --> I

  • Terraform code

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    # depending on the workspace, we select different regions
    provider "aws" {
      region = terraform.workspace == "default" ? "us-east-1" : "us-west-2"
    }

    # Get Linux AMI ID using SSM Parameter endpoint in us-east-1
    data "aws_ssm_parameter" "linuxAmi" {
      name = "/aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2"
    }

    # Create and bootstrap EC2 in us-east-1
    resource "aws_instance" "ec2-vm" {
      ami                         = data.aws_ssm_parameter.linuxAmi.value
      instance_type               = "t3.micro"
      associate_public_ip_address = true
      vpc_security_group_ids      = [aws_security_group.sg.id]
      subnet_id                   = aws_subnet.subnet.id
      tags = {
        Name = "${terraform.workspace}-ec2"
      }
    }

  • CLI commands required

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    # WORKSPACES
    # check which workspaces we have. WeAt least we get default
    terraform workspace list
    terraform workspace new test
    # check we have automatically switched to the new one
    terraform workspace list

    # DEPLOY ON TEST WORKSPACE
    terraform init
    # avoid inputing "yes" all the time with auto-approve
    terraform apply --auto-approve 
    # check deployment
    terraform state list

    # DEPLOY ON DEFAULT
    terraform workspace select default
    # check we are indeed on default
    terraform workspace list
    # check state is empty for this workspace
    terraform state list
    terraform init
    # avoid inputing "yes" all the time with auto-approve
    terraform apply --auto-approve 
    # check deployment
    terraform state list
    # check there is a terraform.tfstate.d directory, which contains the test workspace
    ls

    # CLEAN UP TEST
    terraform workspace select test
    terraform workspace destroy --auto-approve
    terraform workspace select default
    terraform workspace delete test

Build and test Terraform module

  • Tasks

      graph LR

subgraph Modules
A[main.tf]
B[variables.tf]
C[outputs.tf]
end

D[main_code.tf]
E(EC2 VM)

B -- variables:inputs --> D
C -- outputs returned by module --> D
D --> E

  • Terraform code

    • Terraform VPC module
      • main.tf
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        # vpc module
        provider "aws" {
          region = var.region
        }

        resource "aws_vpc" "this" {
          cidr_block = "10.0.0.0/16"
        }

        resource "aws_subnet" "this" {
          vpc_id     = aws_vpc.this.id
          cidr_block = "10.0.1.0/24"
        }

        data "aws_ssm_parameter" "this" {
          name = "/aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2"
        }
      • variables.tf
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        variable "region" {
          type    = string
          default = "us-east-1"
        }
      • outputs.tf
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        # critical to exporting values
          output "subnet_id" {
          value = aws_subnet.this.id
        }
        output "ami_id" {
          value = data.aws_ssm_parameter.this.value
        }
    • Terraform project module
      • main.tf
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        variable "main_region" {
          type    = string
          default = "us-east-1"
        }

        provider "aws" {
          region = var.main_region
        }

        # invokes the VPC module
        module "vpc" {
          source = "./modules/vpc"
          region = var.main_region
        }

        resource "aws_instance" "my-instance" {
          ami           = module.vpc.ami_id
          subnet_id     = module.vpc.subnet_id
          instance_type = "t2.micro"
        }
      • outputs.tf
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        output "PrivateIP" {
          description = "Private IP of EC2 instance"
          value       = aws_instance.my-instance.private_ip
        }

  • CLI

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    # check terraform status
    terraform version

    # create project structure
    mkdir terraform_project
    cd terraform_project
    mkdir -p modules/vpc
    cd /home/cloud_user/terraform_project/modules/vpc/

    # main project directory
    cd ~/terraform_project

    # DEPLOY AND TEST
    # format the code in all of your files pre-deployment
    terraform fmt -recursive
    terraform init
    terraform validate
    # review actions that will be performed when you deploy
    terraform plan
    # deploy
    terraform apply --auto-approve
    # check
    terraform state list

    # CLEAN UP
    terraform destroy