Remote backend config from multiple backend.conf files

[sevagh]

Hello,

I have a bunch of Terraform configs structured something like this:

├── backend.conf (shared)
├── cluster-1
│   ├── backend.conf
│   ├── terraform.tfvars
└── cluster-2
    ├── backend.conf
    ├── terraform.tfvars

I initialize each of these with terraform init --backend-config=./backend.conf --backend-config=../backend.conf. The root backend.conf contains the meat of it (s3 bucket name, DynamoDB lock table name), and the sub-files have different key values to distinguish the stacks.

Is there any way this translates to Terragrunt?

I.e.:

terragrunt = {
  remote_state {
    backend = "s3"
    config { "${get_tfvars_dir()}/../backend.conf" }
    config { "backend.conf" }
  }
}

(this doesn't work, just a contrived example)

I also tried:

extra_arguments "custom_vars" {
      commands = [
        "init",
      ]

      arguments = [
        "-backend-config=${get_tfvars_dir()}/../backend.conf",
        "-backend-config=backend.conf"
      ]
    }

This didn't help me either.

Any suggestions?

Thanks

[sevagh]

I'm reading through this now which seems relevant: #26

[brikis98]

The support for passing files to -backend-config is fairly new to Terraform and not yet supported by Terragrunt. In fact, there are a bunch of changes that came out with Terraform 0.10.0 that we are trying to figure out how to support in Terragrunt. See #261 for the discussion.

[sevagh]

Thanks for the update. Meanwhile is there a reason this doesn't work?

extra_arguments "custom_vars" {
      commands = [
        "init",
      ]

      arguments = [
        "-backend-config=${get_tfvars_dir()}/../backend.conf",
        "-backend-config=backend.conf"
      ]
    }

If extra_arguments were applied to terraform init (and I'm not sure why it's not being applied - is init a special case? is it a bug?) it's still a compelling reason for our organization to use Terragrunt and avoid typing terraform init -backend-config=../backend.conf -backend-config=../../backend.conf each time.

[brikis98]

Since Terragrunt calls init for you, it doesn't currently let you call it yourself. Changing this behavior is what we're discussing in #261.

[sevagh]

I think I can close this now. Feel free to re-open if it's still relevant.