Override provider configuration

[jmgilman]

Assume I have a root terragrunt.hcl with:

generate "provider" {
  path = "provider.tf"
  if_exists = "overwrite"
  contents = <<EOF
provider "aws" {
  region = "eu-central-1"
}
EOF
}

In a child module, I want to configure a specific IAM role to use, so in terragrunt.hcl:

include "root" {
  path = find_in_parent_folders()
}

And in main.tf:

provider "aws" {
  assume_role {
    role_arn     = "arn:aws:iam::123456789012:role/ROLE_NAME"
  }
}

This won't work because Terraform complains about duplicate provider configurations. How would I override the root configuration to specify a role ARN in this case?

There's a similar question on StackOverflow that has gone unanswered.

---

Tracked in ticket #109744

[denis256]

Hi,
for case of role_arn can be used iam_role field in child HCL file.

In case if different parameters are required to be injected, custom configuration can be loaded through read_terragrunt_config

Full example in https://github.com/denis256/terragrunt-tests/tree/master/discussion-621

# parent terragrunt.hcl
locals {
  provider_conf = read_terragrunt_config("provider.hcl", {inputs = { config = ""}})
}
generate "provider" {
  path = "provider.tf"
  if_exists = "overwrite"
  contents = <<EOF
provider "aws" {
  region = "eu-central-1"
  ${local.provider_conf.inputs.config}
}
EOF
}

# app2/provider.hcl
inputs = {
  config = <<EOF
  #
  # custom provider config
  #
  iam_role = "arn:aws:iam::ACCOUNT_ID:role/ROLE_NAME"
  EOF
}

# app2/terragrunt.hcl
include "root" {
  path = find_in_parent_folders()
}

# app2/provider.tf
# Generated by Terragrunt. Sig: nIlQXj57tbuaRZEa
provider "aws" {
  region = "eu-central-1"
  #
  # custom provider config
  #
  iam_role = "arn:aws:iam::ACCOUNT_ID:role/ROLE_NAME"
}

Most probably exists other approaches too - I shared some ideas