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UPGRADE-3.0.md

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Upgrade from v2.x to v3.x

If you have any questions regarding this upgrade process, please consult the examples directory:

If you find a bug, please open an issue with supporting configuration to reproduce.

List of backwards incompatible changes

  • Terraform v0.13.1 is now minimum supported version to take advantage of count and for_each arguments at module level

Variable and output changes

  1. Removed variables:

    • instance_count
    • subnet_ids (only need to use subnet_id now)
    • private_ips (only need to use private_ip now)
    • use_num_suffix
    • num_suffix_format

  2. Renamed variables:

    • tags -> tags_all

  3. Removed outputs:

    • availability_zone
    • placement_group
    • key_name
    • ipv6_addresses
    • private_ip
    • security_groups
    • vpc_security_group_ids
    • subnet_id
    • credit_specification
    • metadata_options
    • root_block_device_volume_ids
    • ebs_block_device_volume_ids
    • volume_tags
    • instance_count

  4. Renamed outputs:

    :info: All outputs used to be lists, and are now singular outputs due to the removal of count

Upgrade State Migrations

Before 2.x Example

module "ec2_upgrade" {
  source  = "terraform-aws-modules/ec2-instance/aws"
  version = "2.21.0"

  instance_count = 3

  name                        = local.name
  ami                         = data.aws_ami.amazon_linux.id
  instance_type               = "c5.large"
  subnet_ids                  = module.vpc.private_subnets
  vpc_security_group_ids      = [module.security_group.security_group_id]
  associate_public_ip_address = true

  tags = local.tags
}

After 3.x Example

locals {
  num_suffix_format = "-%d"
  multiple_instances = {
    0 = {
      num_suffix    = 1
      instance_type = "c5.large"
      subnet_id     = element(module.vpc.private_subnets, 0)
    }
    1 = {
      num_suffix    = 2
      instance_type = "c5.large"
      subnet_id     = element(module.vpc.private_subnets, 1)
    }
    2 = {
      num_suffix    = 3
      instance_type = "c5.large"
      subnet_id     = element(module.vpc.private_subnets, 2)
    }
  }
}

module "ec2_upgrade" {
  source = "../../"

  for_each = local.multiple_instances

  name = format("%s${local.num_suffix_format}", local.name, each.value.num_suffix)

  ami                         = data.aws_ami.amazon_linux.id
  instance_type               = each.value.instance_type
  subnet_id                   = each.value.subnet_id
  vpc_security_group_ids      = [module.security_group.security_group_id]
  associate_public_ip_address = true

  tags = local.tags
}

To migrate from the v2.x version to v3.x version example shown above, the following state move commands can be performed to maintain the current resources without modification:

terraform state mv 'module.ec2_upgrade.aws_instance.this[0]' 'module.ec2_upgrade["0"].aws_instance.this[0]'
terraform state mv 'module.ec2_upgrade.aws_instance.this[1]' 'module.ec2_upgrade["1"].aws_instance.this[0]'
terraform state mv 'module.ec2_upgrade.aws_instance.this[2]' 'module.ec2_upgrade["2"].aws_instance.this[0]'

:info: Notes

  • In the v2.x example we use subnet_ids which is an array of subnets. These are mapped to the respective instance based on their index location; therefore in the v3.x example we are doing a similar index lookup to map back to the existing subnet used for that instance. This would also be the case for private_ips
  • In the v3.x example we have shown how users can continue to use the same naming scheme that is currently in use by the v2.x module. By moving the num_suffix_format into the module name itself inside a format function, users can continue to customize the names generated in a similar manner as that of the v2.x module.