Module

Summary

A Terraform module is a set of Terraform configuration files in a single directory that can be considered its own standalone Terraform project.

• it can therefore...
  • contain its own resources, data sources, locals, etc.
  • take variables (ie. inputs on a per-module basis)

What are they for?

Modules are useful as they allow us to define a reusable block of Terraform code of which we can have many instances in our main Terraform project.

• even a single directory with a single .tf file is considered a module.

A convention is to use a common prefix for resources from a single module

A Terraform module is similar to the concept of a package (e.g. npm package), providing many of the same benefits.

• As a result, any non-trivial real-world Terraform configuration would use modules.

Example:

module "work_queue" {
    source = "./directory-of-module"
    variable_name = "passed_in_value"
}

Returning values from modules (output)

Most modules return values to make them easier to use.

• to reference those values, use module.<module_identifier>.<output_name>

It is possible to return a whole resource from a module.

• This allows us to return all of the fields from the resource that we created

Remote modules

Modules can be specified with a URL pointing to a remote git repo, designating them as remote modulues.

• these modules get cloned to .terraform/modules/, which is similar to node_modules/ in Node.js

Remote modules should be specified with a git tag to peg a specific version

• ex. github.com/Tycholiz/my-terraform-module?ref=0.0.1

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Backlinks

• Terraform
• Terragrunt