Terragrunt doesn't get outputs from a imported source

Question

I've been following terragrunt docs and I end up with a structure like the following one:

• services/lb
• services/backend
• vpc

I had set a dependency of vpc in services/lb and in services/backend and it works standalone making terragrunt run-all apply.

Then I tried to move this configuration to infrastructure modules following https://terragrunt.gruntwork.io/docs/getting-started/quick-start/#promote-immutable-versioned-terraform-modules-across-environments and create a new repository with the different stages:

• prod
• stage
• ...

Making this I learned (if I am not missing anything) that when importing a source, terragrunt.hcl dependencies configuration of that source are ignored.

samuel@angel:~/Documents/infrastructure-live/prod$ terragrunt_linux_amd64 run-all apply                                                            
INFO[0000] Stack at /home/samuel/Documents/infrastructure-live/prod:                                                                               
  => Module /home/samuel/Documents/infrastructure-live/prod (excluded: false, dependencies: [])                                                    
  => Module /home/samuel/Documents/infrastructure-live/prod/services/backend (excluded: false, dependencies: [])                                   
  => Module /home/samuel/Documents/infrastructure-live/prod/services/lb (excluded: false, dependencies: [])                                        
  => Module /home/samuel/Documents/infrastructure-live/prod/vpc (excluded: false, dependencies: [])                                                
Are you sure you want to run 'terragrunt apply' in each folder of the stack described above? (y/n) y  

So I add explicit dependency configuration in my infrastructure-live terragrunt modules:

infrastructure-live/prod/vpc/terragrunt.hcl

include {
  path = find_in_parent_folders()
}
terraform {
  extra_arguments "common_vars" {
    commands = get_terraform_commands_that_need_vars()

    arguments = [
      "-var-file=../network.tfvars",
      "-var-file=../region.tfvars"
    ]
  }

  
  source = "git::[email protected]:project/infrastructure-modules.git//vpc"

}

infrastructure-live/prod/backend/terragrunt.hcl

terraform {
  source = "git::[email protected]:project/infrastructure-modules.git//services/backend"
}

include {
  path = find_in_parent_folders()
}

dependency "vpc" {
  config_path = "../../vpc"
}

inputs = {
  backend_vpc_id = dependency.vpc.outputs.backend_vpc_id
}

Dependency information from shell:

INFO[0000] Stack at /home/samuel/Documents/infrastructure-live/prod:
  => Module /home/samuel/Documents/infrastructure-live/prod (excluded: false, dependencies: [])
  => Module /home/samuel/Documents/infrastructure-live/prod/services/backend (excluded: false, dependencies: [/home/samuel/Documents/infrastructure-live/prod/vpc])
  => Module /home/samuel/Documents/infrastructure-live/prod/services/lb (excluded: false, dependencies: [/home/samuel/Documents/infrastructure-live/prod/vpc, /home/samuel/Documents/infrastructure-live/prod/services/backend])
  => Module /home/samuel/Documents/infrastructure-live/prod/vpc (excluded: false, dependencies: []) 

But now it says that the dependency does not have outputs. But they are outputs in the module of the imported source!

ERRO[0061] Module /home/samuel/Documents/infrastructure-live/prod/services/backend has finished with an error: /home/samuel/Documents/infrastructure-live/prod/vpc/terragrunt.hcl is a dependency of /home/samuel/Documents/infrastructure-live/prod/services/backend/terragrunt.hcl but detected no outputs. Either the target module has not been applied yet, or the module has no outputs. If this is expected, set the skip_outputs flag to true on the dependency block.  prefix=[/home/samuel/Documents/infrastructure-live/prod/services/backend]ERRO[0061] Dependency /home/samuel/Documents/infrastructure-live/prod/services/backend of module /home/samuel/Documents/infrastructure-live/prod/services/lb just finished with an error. Module /home/samuel/Documents/infrastructure-live/prod/services/lb will have to return an error too.  prefix=[/home/samuel/Documents/infrastructure-live/prod/services/lb]                                                                                               
ERRO[0061] Module /home/samuel/Documents/infrastructure-live/prod/services/lb has finished with an error: Cannot process module Module /home/samuel/Documents/infrastructure-live/prod/services/lb (excluded: false, dependencies: [/home/samuel/Documents/infrastructure-live/prod/vpc, /home/samuel/Documents/infrastructure-live/prod/services/backend]) because one of its dependencies, Module /home/samuel/Documents/infrastructure-live/prod/services/backend (excluded: false, dependencies: [/home/samuel/Documents/infrastructure-live/prod/vpc]), finished with an error: /home/samuel/Documents/infrastructure-live/prod/vpc/terragrunt.hcl is a dependency of /home/samuel/Documents/infrastructure-live/prod/services/backend/terragrunt.hcl but detected no outputs. Either the target module has not been applied yet, or the module has no outputs. If this is expected, set the skip_outputs flag to true on the dependency block.  prefix=[/home/samuel/Documents/infrastructure-live/prod/services/lb]ERRO[0061] Encountered the following errors:Cannot process module Module /home/samuel/Documents/infrastructure-live/prod/services/lb (excluded: false, dependencies: [/home/samuel/Documents/infrastructure-live/prod/vpc, /home/samuel/Documents/infrastructure-live/prod/services/backend]) because one of its dependencies, Module /home/samuel/Documents/infrastructure-live/prod/services/backend (excluded: false, dependencies: [/home/samuel/Documents/infrastructure-live/prod/vpc]), finished with anerror: /home/samuel/Documents/infrastructure-live/prod/vpc/terragrunt.hcl is a dependency of /home/samuel/Documents/infrastructure-live/prod/services/backend/terragrunt.hcl but detected no outputs. Either the target module has not been applied yet, or the module has no outputs. If this is expected, set the skip_outputs flag to true on the dependency block.                                                                                             
/home/samuel/Documents/infrastructure-live/prod/vpc/terragrunt.hcl is a dependency of /home/samuel/Documents/infrastructure-live/prod/services/backend/terragrunt.hcl but detected no outputs. Either the target module has not been applied yet, or the module has no outputs. If this is expected, set the skip_outputs flag to true on the dependency block.                                                                                                    ERRO[0061] Unable to determine underlying exit code, so Terragrunt will exit with error code 1

This is terragrunt cache for VPC. We can see that outputs.tf exists so vpc has outputs.

Content of outputs.tf

output "backend_vpc_id" {
    value = digitalocean_vpc.backend_vpc.id
    description = "Backend VPC ID"
}

What I am missing? What I have to do to access to the outputs of a imported source?

Thanks a lot for the help.

Answer 1

For those who are still suffering about this issue, you may also try adding a mock_outputs to the dependency and see if it works:

dependency "vpc" {
  config_path = find_in_parent_folders("vpc")

  mock_outputs = {
    vpc_id      = "temp-id"
  }
}

inputs = {
  vpc_id = dependency.vpc.outputs.vpc_id
}

https://terragrunt.gruntwork.io/docs/features/execute-terraform-commands-on-multiple-modules-at-once/#unapplied-dependency-and-mock-outputs