Improving the Code Reusability with Terraform Module

This is a presentation about my experience of implementing 'effective' automation with Terraform.

You can check out the contents below in presentation.pdf.

Contents

1. Terraform Basic Concept

In this section, I'm gonna explain the definition of provisioning and IaC, known as Infrastrcture as Code.
Then, let's find out what Terraform is, and how it works.

2. Terraform Module

I want to tell my experience why I studied and applied Terraform Module. You may figure it out if you compare the tree structure before, and after applying Terraform Module. Plus, we can configure a backend using S3 and DynamoDB.
Let's see how Terraform manages its state files.

3. Live Demo

Demo is the best practice to understand all these concepts. Let's go on!

Demo Tree Structure & Architecture

In this Demo, you can configure dev and prod environment by reusing network and ec2 modules.

• network module involves vpc, subnet, internet gateway, nat gateway, EIP, and route table
• ec2 module involves key, bastion host, and private ec2 instances

Now, let's go for it!

This demo deploys EC2 instances on a single availability zone in the dev environment, and on multiple availability zones in the prod environment.

• Don't forget to delete all these resources after running this demo❗️ It invloves some resources that are charged.
• What you should do is just changing the values of dev.tfvars and prod.tfvars. Resouce modules will be reused by calling them at the root module.

This is an architecture of this demo.

CLI Commands for Demo

Before running, you should install aws cli(v2) and terraform using homebrew.

• This is how you shorten the 'terraform' command to 'tf'.

  # path
  which terraform
  
  # inject path, using '-s' option for symbolic link
  sudo ln -s ${path}/terraform ${path}/tf

• This demo calls key-pair resource using data block, which means key-pair is provisioned already on console.
  So, if you want to run this demo,
  1. just create your key-pair on console directly
  2. and modify key_name info at the very top of the modules/ec2/main.tf file.

1. (if configuring the backend) First, provision S3 bucket and DynamoDB table in the global folder.

# terraform-demo/global
tf init
tf fmt # check and apply a canonical format
tf validate # verify if configuration files are valid
tf plan --var-file

2. Provision the dev environment

• But if you didn't configure the backend, please annotate the terraform block!

# terraform-demo/root/dev
tf init
tf fmt & tf validate # optional step
tf plan --var-file=dev.tfvars
tf apply --var-file=dev.tfvars -auto-approve

3. Provision the prod environment. Just change the .tfvars file.

# terraform-demo/root/prod
tf init
tf fmt & tf validate # optional step
tf plan --var-file=prod.tfvars
tf apply --var-file=prod.tfvars -auto-approve

4. Remove the resources you provisioned above.

# terraform-demo/root/dev
tf destroy -var-file=dev.tfvars

# terraform-demo/root/prod
tf destroy -var-file=prod.tfvars

References

🖥️ Web : Terraform Docs

📚 Book : Terraform Up&Running by Oreilly

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