block_device_mappings does not support different types together (e.g. EBS and ephemeral)

[Evisort-Dave]

Description

As the type of the block_device_mappings is currently set to list(any), this prevents you from being able to specify e.g. an EBS volume (which requires an ebs {} configuration block), as well as an instance store volume (which requires the virtual_name attribute), as the object structure of each list item will not match and this will fail Terraform's type checking.

Versions

• Module version [Required]: terraform-aws-modules/autoscaling/aws 6.7.1

• Terraform version: 1.0.11

• Provider version(s):

• provider registry.terraform.io/hashicorp/aws v4.49.0

Reproduction Code [Required]

  block_device_mappings = [
    {
      # Root EBS volume
      device_name = "/dev/xvda"
      ebs = {
        delete_on_termination = true
        encrypted = true
        volume_size = 40
        volume_type = "gp2"
      }
    },
    {
      # Local instance store
      device_name = "/dev/xvdb"
      virtual_name = "ephemeral0"
    }
  ]

Steps to reproduce the behavior:

Create an ASG with the above block_device_mappings config.

Expected behavior

The configuration allows me to specify a launch template with both an EBS volume and an instance store volume on the same instance.

Actual behavior

The above configuration will fail with the error all list elements must have the same type.

Additional context

I'm not able to find a workaround here, as I can't make the elements match by e.g. adding virtual_name = null to the EBS element, as it won't match the string type of the second element, and if I set it to a blank string, the provider crashes.

Any ideas?

[bryantbiggs]

There is no effect on having an ephemeral instance store listed in the block device mappings. Either they are present based on the instance type or they are not. To utilize, you will need to mount them, typically through user data

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