HCL Language - 18 - Environment Variables in HCL

Environment Variables in HCL

HCL (HashiCorp Configuration Language) is known for its flexibility and extensibility, allowing developers and operators to define infrastructure configurations. One of the powerful features of HCL is its ability to work with environment variables, making it easier to manage configuration settings that may vary between environments or should not be hard-coded into your Terraform scripts. In this guide, we’ll explore the use of environment variables in HCL.

Understanding Environment Variables

Environment variables are dynamic values that can be set outside of your HCL code. They are commonly used to store configuration details, such as database connection strings, API keys, or any data that should remain secret or change across different deployment environments (e.g., development, staging, production).

Using Environment Variables in HCL

HCL allows you to reference environment variables directly within your configurations. This feature is particularly valuable when dealing with sensitive information that should not be exposed in your codebase.


variable "database_url" {
  type = string
  default = var.ENV["DATABASE_URL"]
}

resource "example_resource" "example" {
  name = "my-resource"
  url  = var.database_url
}

In this example, the “DATABASE_URL” environment variable is accessed using var.ENV["DATABASE_URL"]. This approach allows you to set the value of “DATABASE_URL” outside of your HCL code, making it easy to switch between different databases or environments.

Environment Variables in Terraform Configuration

Terraform also provides a built-in mechanism for reading environment variables. You can access environment variables using the Terraform.workspace attribute, which represents the current workspace in use.


provider "aws" {
  region = "us-east-1"
}

resource "aws_s3_bucket" "example" {
  bucket = "${Terraform.workspace}-my-bucket"
}

In this example, the name of the S3 bucket incorporates the current workspace using ${Terraform.workspace}. This can be useful for creating isolated resources per environment.

Secure Handling of Environment Variables

It’s essential to ensure the secure handling of environment variables, especially when dealing with sensitive data. Use appropriate mechanisms to store and manage secrets, such as HashiCorp Vault or cloud-based secret management services.

Benefits of Using Environment Variables

Leveraging environment variables in HCL offers several advantages:

Security: Sensitive data, like API keys and database credentials, can be kept secure and separate from your code.
Portability: Your configurations become more portable, as they rely on external values that can change between environments.
Consistency: You can maintain consistency in your configurations while accommodating differences in various deployment environments.

Summary

Environment variables in HCL provide a powerful way to manage and secure sensitive configuration data. By referencing these variables within your Terraform code, you can build flexible, consistent, and secure infrastructure configurations that adapt to different environments and use cases.

HCL Language – 18 – Environment Variables in HCL