Self-invented “how to Terraform” rules

While I’m working on something, anything, I really love to work methodically. If there are no rules in the area, I do my own rules and try not to violate them.

I think the reason is my father. He is the most organised and self-motivated human being I ever know. He always has his own rules/methods. I’m glad he is the influence on work-side of my life. I possibly could go and bear-hug him and say “Thank you” once again if I wasn’t thousands and thousands miles away.

So, I’m playing with Terraform every single day. I’ve created some rules for myself and changed them few times. In the end, I gained enough learning-from-mistakes experience with Terraform to stabilise my self-invented rules. Even the team I was working with liked the list and we made the rules for the team.

Here is the my list of rules while I’m Terraform-ing;

General

• Avoid of creating templates per environment (dev/stg/prod) in subfolders. Try to manage that by passing variables.
• If you need to create same resource or group of resources more than once, must be a module.
• Main template should be in main.tf. No multiple files, no hard to read code.
• Variables should be declared in variables.tf
• Outputs should be in outputs.tf
• A description should be provided for each declared variable.
• Templates must be in `templates` directory on the repo/module root.
• Modules must be consumed from tags. Not from master or any other branch.

Styling

Indentation and styling matters, write easy to read templates.

• Use underscore_case for variables, resource and module names. (Always kebab-case for AWS tag names/values and resource’s name attributes)
• Must use two-space soft tabs.
• Must not use literal tab characters.
• Must not contain trailing whitespace.
• Should leave one empty line between resources.
• Should leave one empty line between attributes and inner blocks (such as tag {}, ebs_block_device {} )
• You read the code more than you PR and merge. Attribute assignments (=) should be aligned for clarity, except inner blocks. Inner blocks should have its own alignment.
• Single line comments: #
• Multi-line comments: /* followed by */
• Always keep depends_on attribute at first line of the resource and leave one empty line after.

Modules

• Repository per module or single repository sub-directory per module.
• Everything is in the root of repository. No sub-directory (If it’s a single repo approach, directory depth must be 1), no complexity, no confusion.
• Keep the modules as much as simple and small.
• Module depth must not be greater than 1.
• Always add README file into a module folder with description, input and output variables, and example of usage.
• Any variable must not have default value.
• Once you tested the module and make sure it works, create a tag with semantic versioning

You can see an example template I wrote in here.

I’m wondering about if you have any list like this or if there is something you didn’t like or a better idea please comment below. Thanks for reading and hope you enjoyed it.

Edit: If you’ve made until here, you might like the following post as well.