Advanced Terraform Modules: Learn how to create and use advanced Terraform modules

Terraform is a powerful tool for managing infrastructure as code, and one of its most useful features is the ability to create and use modules. Modules allow you to abstract away complex infrastructure and reuse code across your Terraform configurations. In this post, we'll explore some advanced techniques for creating and using Terraform modules, including nested modules and reusable modules.

Nested Modules

Nested modules allow you to break down complex infrastructure into smaller, more manageable pieces. For example, you might have a module for a VPC, which contains submodules for subnets, security groups, and route tables. This allows you to reuse the same submodules across different VPCs, and makes it easier to manage and test your infrastructure.

To create a nested module, simply create a new directory for your submodule, and define your resources as you would in a regular Terraform configuration file. Then, in your parent module, reference the submodule using a module block:

module "vpc" {
  source = "./modules/vpc"
  cidr_block = "10.0.0.0/16"
}

module "subnet" {
  source = "./modules/vpc/subnet"
  vpc_id = module.vpc.id
  cidr_block = "10.0.1.0/24"
}

Here, we're referencing a submodule called subnet inside a module called vpc. We're passing in the vpc_id output from the vpc module, which allows us to create a subnet that is associated with the VPC.

Reusable Modules

Reusable modules allow you to create generic infrastructure components that can be reused across different projects or organizations. For example, you might create a module for creating an AWS S3 bucket, which can be reused across different applications.

To create a reusable module, you'll want to define inputs and outputs that can be customized and reused across different projects. For example, here's a module for creating an AWS S3 bucket:

variable "bucket_name" {}

resource "aws_s3_bucket" "bucket" {
  bucket = var.bucket_name
  acl = "private"
}

output "bucket_id" {
  value = aws_s3_bucket.bucket.id
}

Here, we've defined a variable called bucket_name, which allows the user to customize the name of the S3 bucket. We've also defined an output called bucket_id, which allows the user to reference the ID of the S3 bucket in other parts of their configuration.

To use this module in your Terraform configuration, simply reference it using a module block, and pass in the required inputs:

module "s3_bucket" {
  source = "github.com/example/s3-bucket"
  bucket_name = "example-bucket"
}

resource "aws_s3_bucket_object" "example" {
  bucket = module.s3_bucket.bucket_id
  key = "example.txt"
  source = "example.txt"
}

Here, we're referencing a reusable module for creating an S3 bucket, passing in a custom bucket_name. We're also referencing the bucket_id output from the module, which allows us to create an S3 object inside the bucket.

Conclusion

In conclusion, mastering advanced Terraform modules can greatly improve your ability to manage complex infrastructures as code. By using nested modules, you can break down large infrastructure into reusable and manageable pieces. By creating reusable modules, you can create generic infrastructure components that can be easily reused across different projects or organizations. With these techniques, you'll be able to deploy complex infrastructures more efficiently and with greater ease.