I decided to learn more about Terraform and see if I could replicate what I did manually in the console, using Terraform. I set up two VMs, one that was publicly accessible and one that was not and had to be accessed through the first VM. These two VMs are almost identical, apart from the firewall rules.
In the interest of being DRY, I thought I'd create a module, so that I don't have to repeat all the options for the two VMs and just specify the differences. Since I wasn't sure about how to create a module, I checked the documentation and found the following:
When to write a module
[...]
We do not recommend writing modules that are just thin wrappers around single other resource types. If you have trouble finding a name for your module that isn't the same as the main resource type inside it, that may be a sign that your module is not creating any new abstraction and so the module is adding unnecessary complexity. Just use the resource type directly in the calling module instead.
Source: https://www.terraform.io/docs/modules/index.html#when-to-write-a-module
It makes sense to me that publishing a module that is just a wrapper around a single resource may not be that useful, but for internal use in your configuration, it seems like a useful tool to make your configuration DRY. If 9 out of 10 arguments are the same for all of your VMs, why wouldn't you create a module to hide the 9 common arguments from the main configuration and not repeat them?
As I am new to Terraform, I just want to make sure that I am not teaching myself bad practices.