Modules

Terraform modules are containers for multiple resources that are used together. They promote reusability and maintainability in Terraform configurations. Understanding how to create and use modules is a key skill in Terraform.

What Are Terraform Modules?

1. Purpose of Modules:

   • Modules allow you to package and encapsulate a group of resources and configurations for reuse.
   • They help in organizing complex Terraform configurations into manageable chunks.

2. Types of Modules:

   • Root Module: The main configuration directory is considered a root module.
   • Child Modules: Reusable modules sourced from other directories or remote sources.

Creating a Module

1. Module Structure:

   • A typical module includes main configuration files (main.tf), variables (variables.tf), outputs (outputs.tf), and optionally, documentation (README.md).

2. Defining Resources:

   • Inside the module, define the resources that it manages. For example, a module for an AWS EC2 instance might include resource definitions for the instance, security group, and key pair.

3. Using Variables and Outputs:

   • Use input variables to customize modules.
   • Define output values to return information about the resources in the module.

Using a Module

1. Source a Module:

   • In your root module, reference the child module using the source attribute.
   • The source can be a local path or a remote source, like a Terraform Registry URL or a Git repository.

2. Passing Inputs:

   • Provide values for the module’s input variables.

3. Example Usage:

   module "ec2_instance" {
     source = "./modules/ec2"
     
     instance_type = "t2.micro"
     ami           = "ami-123456"
   }

Best Practices

• Documentation: Document your modules, explaining their purpose, inputs, and outputs.
• Versioning: Use versioned sources for modules, especially when using remote sources, to ensure consistent and predictable usage.
• Testing: Regularly test your modules to ensure they work as expected.