Terraform: Command line variables aren't passed to modules

[curtisallen]

Using -var has been a great tool to keep us from committing secrets to git. It doesn't look like -var works when passing modules variables.
Consider this simple terraform config

module "test" {
  source = "[email protected]:terraform-community-modules/tf_aws_rds.git"
  rds_instance_name = "somename"
  rds_allocated_storage="5"
  rds_engine_type="postgres"
  rds_engine_version="9.4.1"
  rds_instance_class="db.m2.small"
  database_name="testdb"
  database_user="test"
  rds_security_group_id="sg-1234"
  subnet_az1="vpc-1234"
  subnet_az2="vpc-1234"
  aws_access_key = "123"
  aws_secret_key = "mysecret"
  aws_region="us-east-1"
}

I would expect to be able to run

terraform get
terraform plan -var "database_password=test"

But I get an error

Errors:

  * 1 error(s) occurred:

* module root: module test: required variable database_password not set

Is this expected behavior?

This approach works as long as I don't use modules.

[jedineeper]

You will need to pass it through to the module, so add

database_password="${var.database_password}"

to the module call.

[curtisallen]

All I needed to do was add a variable definition and this worked thanks!

In case anyone is wondering

variable "database_password" {
     description = "db password"
}

then reference the variable as Jed suggested

module "test" {
  ...
  database_password="${var.database_password}"
}

[steven-vogogo]

Thank you @curtisallen, was using some ansible vaulted ssl certs to inject into terraform on the command line task and adding the variable description fixed it. Could not find this information any where!
This should get documented somewhere in terraform.

[noahwhite]

@curtisallen I have a similar issue where I am not seeing -var being passed to my module. In the module I have a variables.tf with all the variable "" {} definitions. eg:

variables.tf
variable "foo-ami" {
default="12345"
description="foo"
}

The variable is referenced in a resource which is creating an AWS EC2 instance. If I try to override it with something like terraform plan -var 'foo-ami=98765' it fails to do so. I've also tried removing the default from the variable thinking maybe I could only set it once but that fails complaining that the variable is never set further proving that -var is not getting picked up. Since you seem to be doing this, any thoughts would be really appreciated. Thanks!

[curtisallen]

@noahwhite you have to reference the variable in terraform script that calls the module. Just like I mentioned here https://github.com/hashicorp/terraform/issues/2648#issuecomment-119610489

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