Kiran Pawar's Blog

Terraform Day 6: Terraform Functions Part: 1

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Kiran Pawar
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This Blog demonstrates the efficient use of Terraform functions to manage infrastructure as code without duplicating resources. The focus is on creating modular, scalable, and maintainable Terraform configurations.

Overview

In this project, we will utilize Terraform functions and techniques to create a cloud infrastructure with multiple instances and subnets efficiently. We aim to minimize duplication in our code by using various Terraform functionalities such as count, for_each, locals, and dynamic blocks.

Key Objectives

  • Clone the repository.

  • Streamline Terraform configuration files by removing unnecessary variables and resources.

  • Implement best practices for variable management and resource creation.

Repository Structure

  • main.tf: Main configuration file containing resource definitions.

  • variables.tf: File for variable definitions.

  • terraform.tfvars: File for variable values.

  • locals.tf: File for local variables.

  • subnet.tf: File dedicated to managing subnet resources.

  • routing_table.tf: File for route table configurations.

  • sg.tf: File for security group configurations.

Step-by-Step Tasks

1. Clone Repository

Start by cloning the repository to your local environment.

2. Clean Up Terraform Files

variables.tf

  • Remove:

    • Access Key and Secret Key

    • AMI

    • Internet Gateway (IGW)

    • All CIDR and Subnet entries

  • Keep:

    • Availability Zones (AZs)

    • Environment (ENV)

  • Define Variables:

    • Create a variable for Public_cidr_block to manage the creation of 6 subnets (3 private and 3 public).

    • Define Private_cidr_block.

terraform.tfvars

  • Copy all relevant variables from variables.tf and paste them into terraform.tfvars.

  • Remove routing table configurations to let them inherit the VPC name.

3. Modify main.tf

  • Remove Access Key and Secret Key entries.

  • Paste remote backend configuration.

  • Update VPC Tags: Instead of passing values for each tag, utilize locals for common tag values.

4. Create locals.tf

  • Define local variables for common tag values.

  • Access local variables in the VPC configuration using the appropriate syntax.

5. Update Subnet Configurations

Public Subnets

  • Remove additional public subnets (subnet 2 and 3).

  • Use count = 3 to create the necessary number of public subnets.

  • Utilize the element function to reference specific CIDR blocks based on the count index.

Private Subnets

  • Rename resources to reflect they are private.

  • Adjust tags accordingly.

6. Route Tables Configuration

  • Define separate route tables for public and private subnets.

  • Comment Out route table associations temporarily.

  • Use terraform plan to preview subnet configurations.

7. Organize Subnets into subnet.tf

  • Move all subnet resources to subnet.tf.

  • Use count.index + 1 to manage subnet indexing dynamically.

8. Create routing_table.tf

  • Move all route table blocks to this file.

  • Address subnet ID issues by ensuring the correct variable references.

  • Introduce Splat syntax for managing multiple subnet associations.

9. Dynamic Security Group Management

sg.tf

  • Copy necessary configurations from main.tf into sg.tf.

  • Add ports 443 and 22 to the security group.

  • Implement dynamic ingress rules by creating a service_ports variable.

  • Populate this variable with values for multiple ports: ["80", "8080", "443", "8443", "22", "3306", "1433"].

10. Finalization

  • Run terraform fmt to format the configuration files.

  • Execute terraform plan and terraform apply to validate and deploy the infrastructure.

  • Check inbound and outbound rules to ensure proper configuration.

Conclusion

By following these steps and utilizing Terraform functions, we can efficiently manage our cloud infrastructure with minimal duplication and improved scalability. This project serves as a template for creating robust Terraform configurations.