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Terraform scenarios: how to to Reference Output Variable from Module in Different State Files

👀 Views: 61 đŸ’Ŧ Answers: 1 📅 Created: 2025-07-17
terraform aws remote-state HCL

I'm optimizing some code but Could someone explain I've been banging my head against this for hours. I'm currently working on a Terraform setup where I have a main configuration that uses a module to provision AWS resources. The question arises when I try to reference an output variable from this module in another state file that manages a different set of resources. I have the following module defined in `modules/my_module/main.tf`: ```hcl output "instance_id" { value = aws_instance.my_instance.id } ``` When I call this module in my main configuration, I can see the output being generated correctly: ```hcl module "my_module" { source = "./modules/my_module" ... } output "my_instance_id" { value = module.my_module.instance_id } ``` The scenario arises when I attempt to use this output in a different Terraform configuration that manages a separate set of resources: ```hcl data "terraform_remote_state" "my_module_state" { backend = "s3" config = { bucket = "my-terraform-state-bucket" key = "path/to/my_module/terraform.tfstate" region = "us-west-2" } } resource "aws_lambda_function" "example" { function_name = "my_lambda_function" ... environment { INSTANCE_ID = data.terraform_remote_state.my_module_state.outputs.instance_id } } ``` However, when I run `terraform plan`, I get the following behavior message: ``` behavior: Invalid reference on main.tf line 12, in environment: 12: INSTANCE_ID = data.terraform_remote_state.my_module_state.outputs.instance_id References to attributes must be in the form <RESOURCE_TYPE>.<RESOURCE_NAME>.<ATTRIBUTE>, but "data.terraform_remote_state.my_module_state.outputs.instance_id" does not match this format. ``` I've tried various approaches, including ensuring that the remote state is initialized correctly and verifying the output variable is set in the source module. I even checked the state file manually to confirm that the `instance_id` is present. It seems like I'm missing something crucial in referencing outputs across different state files. Any insights or suggestions on how to address this scenario would be greatly appreciated! Am I missing something obvious? I'm using Hcl 3.11 in this project. Any ideas how to fix this?