sompol13/learn-terraform-functions

Perform Dynamic Operations with Functions

In this tutorial, you create an EC2 instance running a pre-built webapp. You will:

• use the templatefile function to create a user_data script to dynamically configure an EC2 instance with resource information from your configuration.
• use the lookup function to pass a map output to a variable as an input.
• use the concat function to concatenate and output multiple lists of rules to an AWS Security Group.

Add the templatefile function

• Open the variables.tf file in your editor to find the variables associated you will assign to the name and department keys in your template file.
• Add the user_data attribute to the aws_instance resource block.

Initialize and apply the Terraform configuration

• terraform init
• terraform apply

Map regions to AMIs with lookup

You will use the lookup function to dynamically apply the region-appropriate AMI ID for the EC2 instance.

• Open variables.tf file. Copy and append the aws_amis map variable block below to your variables.tf file.
• In your aws_instance resource, change the ami attribute to your lookup function.
• Copy and append the ami_value output block below to your outputs.tf file. This is to verify the lookup function works as expected.

Edit your region variable and observe the changes

• Run terraform apply with a command-line variable flag changing the region to us-east-2.
• Destroy your infrastructure terraform destroy -var "aws_region=us-east-2"

Use the concat function to output lists of security groups

• Create an SSH key and a security group resource.
• In main.tf, add a new aws_security_group resource. Copy and append the resource block below to your main.tf file.
• Create a new aws_key_pair resource to add your newly created SSH key to the instance.
• Edit your aws_instance web resource to allow this security group and the ssh key.

Add the list of Security Groups to your outputs

• Open the outputs.tf file. The vpc_security_group_ids attribute in your aws_instance resource.
• terraform apply

ssh ubuntu@$(terraform output -raw web_public_ip) -i ssh_key

Note: It may take up to five minutes for your instance to be fully built and configured. If you receive a public key error message, wait a couple minutes before trying again.

Reference

https://learn.hashicorp.com/tutorials/terraform/functions