provider/variable sharing in modules

[a14m]

not to convolute the repo with a similar question... but is there a way of abstracting the provider for all the modules defined in a project.

for example, I have this project

├── modules
│   ├── RDS
│   └── VPC
└── stacks
    ├── production
    │   └── main.tf
    └── staging
        └── main.tf

and it works fine...
the problem is with the definition of modules

├── RDS
│   ├── README.md
│   ├── main.tf
│   ├── providers.tf
│   └── variables.tf
└── VPC
    ├── README.md
    ├── main.tf
    ├── providers.tf
    └── variables.tf

the provider in both of these modules are exactly the same

# providers.tf
provider "aws" {
  region = "${var.region}"
  version = "~> 1.26"
}

and the variables in each module are different but they all have the region variable.

# variables.tf
variable "region" {
  default     = "eu-central-1"
  description = "AWS region."
}
# other module dependent variables...

is there a way to define those bits of information on the modules level
so that I end up with something roughly like this

├── modules
│   ├── providers.tf  <<< include the *shared* provider definition block
│   ├── variables.tf  <<< include the *shared* region vaiable definition block
│   ├── RDS
│   │   ├── README.md
│   │   ├── main.tf
│   │   └── variables.tf
│   └── VPC
│       ├── README.md
│       ├── main.tf
│       └── variables.tf

Thanks in advance.

[apparentlymart]

Hi @a14m!

In Terraform 0.11 we refined the ways in which providers pass between modules to better support this situation. As of that release, we recommend that most users put provider blocks only in the root module, with child modules then inheriting the root provider configurations or being passed them explicitly.

In your case then, the provider "aws" block would belong in stacks/production and stacks/staging (the two root modules, presumably) and there would be no provider blocks in the modules at all.

At present this pattern will hit the limitation discussed in #16835, preventing those child modules from declaring which version of the aws provider they need. The next major version of Terraform will include the new syntax discussed in that issue so that the modules will be able to declare their provider version requirements separately from the provider configurations themselves:

# (not yet implemented and details may change before release)

terraform {
  required_providers = {
    aws = "~> 1.26"
  }
}

There is more information on this in the Providers within Modules section of the documentation, including an optional syntax for explicitly passing providers into child modules for situations where the default inheritance behavior is insufficient.

I believe that this (except for the forthcoming change discussed in #16835) covers your use-case. Please let me know if I missed something!

[a14m]

Thanks a lot... this covers the use-case of provider configuration...
as for the shared variable part (I did some research after opening this -sorry for not thoroughly doing the research before opening this issue- ) and I found the following issues where it had been discussed in details and the conclusion
(TL;DR for those who don't want to go through the list/discussions ) sharing variables between modules against terraform clarity/explicity principle.

adding those issues here for future reference:

• We've discussed global variables in the past:
• Allow modules to access global variables #5480
• Variables not passed to module #4585
• Allow Easier Module Repitition #2714
• Global Variable Namespace #1742

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.