child_modules_depth_limit.md

Terraform modules childs limits

We've all seen a root module with a child module that also has a child module.

TL;DR

As IAC guild we recommand that you have no more than 2 levels in your module hierarchy.

Limit the depth of the your modules' tree

We do not recommand to have a module tree that is too deep.

Why?

• Debugging
  • It is hard to understand what is going on in the code -> the more child modules there are, the more difficult it will be to debug
• Maintainability
  • Upgrade a root, child or grandchild modules may have an impact on the whole module tree (providers / terraform versions for instance)

Recommandation

We recommand to have a module tree that is no more than 2 levels deep like the following tree:

Ok 👍

├── root_module # <- Level 0
│   ├── child_module_1 # <- Level 1
│   │   ├── grandchild_module_1 # <- Level 2
│   ├── child_module_2 # <- Level 1

Not recommanded 👎

├── root_module # <- Level 0
│   ├── child_module_1 # <- Level 1
│   │   ├── grandchild_module_1 # <- Level 2
│   │   │   ├── grand_grandchild_module_1 # <- Level 3
│   ├── child_module_2 # <- Level 1