Category Archives: Terraform

Terragrunt: “plan-all” while Passing Outputs between Modules

PROBLEM

Terragrunt has a feature that allows one module to pass outputs to another module.

For example, if “project-prod” module wants to consume “subfolders” output from “folder” module, it can be done like this in “project-prod” module’s terragrunt.hcl:-

include {
    path = find_in_parent_folders()
}

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

inputs = {
    env_folders = dependency.folder.outputs.subfolders
}

The challenge is when running commands such as plan-all, it will fail with the following error:-

Cannot process module Module [...] because one of its 
dependencies, [...], finished with an error: /my/path/folder/terragrunt.hcl 
is a dependency of /my/path/project-prod/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.

SOLUTION

This error occurs because the generated plan for “folder” module has not been applied yet (ie: the infrastructure does not exist), hence there are no outputs to pass to “project-prod” module to satisfy plan-all.

To fix this, mock outputs can be supplied:-

include {
    path = find_in_parent_folders()
}

dependency "folder" {
    config_path = "../folder"

    mock_outputs = {
        subfolders = {
            "dev" = {
                "id" = "temp-folder-id"
            }
            "prod" = {
                "id" = "temp-folder-id"
            }
            "uat" = {
                "id" = "temp-folder-id"
            }
        }
    }
}

inputs = {
    env_folders = dependency.folder.outputs.subfolders
}

Finally, when running apply-all, it will use the runtime outputs instead of provided mock outputs to build the rest of the infrastructure.

GCP + Terraform: “google: could not find default credentials” Error

PROBLEM

When running any Terraform commands (init, plan, etc) from a different server, the following error is thrown:-

Error: google: could not find default credentials. 
See https://developers.google.com/accounts/docs/application-default-credentials 
for more information.

  on  line 0:
  (source code not available)

SOLUTION

One recommended way is to set up a service account by following the instruction from the above link.

Another way, for developement purpose, is to install Google Cloud SDK and run the following gcloud command, which will generate an Application Default Credentials (ADC) JSON file based on your user account and store it in a location where the SDK can find it automatically:-

gcloud auth application-default login

Terraform: “Error acquiring the state lock” Error

PROBLEM

When running terraform plan, the following error is thrown:-

Acquiring state lock. This may take a few moments...

Error: Error locking state: Error acquiring the state lock: writing "gs://my/bucket/terraform.tfstate/default.tflock" failed: googleapi: Error 412: Precondition Failed, conditionNotMet
Lock Info:
  ID:        1234567890
  Path:      gs://my/bucket/folder/terraform.tfstate/default.tflock
  Operation: migration destination state
  Who:       mike@machine
  Version:   0.12.12
  Created:   2019-10-30 12:44:36.410366 +0000 UTC
  Info:      


Terraform acquires a state lock to protect the state from being written
by multiple users at the same time. Please resolve the issue above and try
again. For most commands, you can disable locking with the "-lock=false"
flag, but this is not recommended.

SOLUTION

One way is to disable locking by passing -lock=false flag.

However, if you are sure the lock isn’t properly released, to perform a force unlock, run this command:

terraform force-unlock [LOCK_ID]

In this case…

terraform force-unlock 1234567890