fix: Add cpu_credits support for all burstable instance types

[tofupup]

Description

Add a burstable_types data source, and modify the local.is_t_instance_type check to check against this data source, instead of a manually updated list of instance types. This allows the cpu_credits setting to be set for all instance types that support the setting.

Motivation and Context

Current instance type t4g supports burstable CPU credit settings, and it seems likely AWS will add more instance types like this in the future (t5*, etc). Using a data source for this, while it adds a small startup penalty while the data source is queried, will automatically these future changes, as well as the existing instance types.

Fixes #293

Breaking Changes

This should not break backwards compatibility, as existing instance types that support the cpu_credits are supported by the data source.

How Has This Been Tested?

• [x] I have updated at least one of the examples/* to demonstrate and validate my change(s)
• [x] I have tested and validated these changes using one or more of the provided examples/* projects
• [x] I have executed pre-commit run -a on my pull request

Existing t3 test:

❯ terraform plan -target=module.ec2_t3_unlimited | grep -A2 credit_specification
      + credit_specification {
          + cpu_credits = "unlimited"
        }
❯ terraform apply -target=module.ec2_t3_unlimited
ec2_t3_unlimited_id = "i-01525b74f750093e6"
❯ aws --region eu-west-1 ec2 describe-instance-credit-specifications --instance-ids i-01525b74f750093e6
{
    "InstanceCreditSpecifications": [
        {
            "InstanceId": "i-01525b74f750093e6",
            "CpuCredits": "unlimited"
        }
    ]
}

New t4g test:

❯ terraform plan -target=module.ec2_t4g_standard | grep -A2 credit_specification
      + credit_specification {
          + cpu_credits = "standard"
        }
❯ terraform apply -target=module.ec2_t4g_standard
ec2_t4g_standard_id = "i-092e7613313e6c631"
❯ aws --region eu-west-1 ec2 describe-instance-credit-specifications --instance-ids i-092e7613313e6c631
{
    "InstanceCreditSpecifications": [
        {
            "InstanceId": "i-092e7613313e6c631",
            "CpuCredits": "standard"
        }
    ]
}

Create instances, 1 x t3 standard, 1 x t3 unlimited, 1 x t4g standard, 1 x t4g unlimited, 1 x a1 (settings as standard but this instance doesn't support bursting)

Code

data "aws_ssm_parameter" "ubuntu-jammy-arm64" {
    name = "/aws/service/canonical/ubuntu/server/22.04/stable/current/arm64/hvm/ebs-gp2/ami-id"
}

data "aws_ssm_parameter" "ubuntu-jammy-amd64" {
    name = "/aws/service/canonical/ubuntu/server/22.04/stable/current/amd64/hvm/ebs-gp2/ami-id"
}

module "t3_standard_instance" {
  source  = "terraform-aws-modules/ec2-instance/aws"
  version = "4.1.4"

  name = "t3-credit-standard"

  ami                    = data.aws_ssm_parameter.ubuntu-jammy-amd64.value
  instance_type          = "t3.micro"
  monitoring             = false
  cpu_credits            = "standard"

  tags = {
    Credit = "standard"
    InstanceType = "t3.micro"
  }
}

module "t3_unlimited_instance" {
  source  = "terraform-aws-modules/ec2-instance/aws"
  version = "4.1.4"

  name = "t3-credit-unlimited"

  ami                    = data.aws_ssm_parameter.ubuntu-jammy-amd64.value
  instance_type          = "t3.micro"
  monitoring             = false
  cpu_credits            = "unlimited"

  tags = {
    Credit = "unlimited"
    InstanceType = "t3.micro"
  }
}

module "t4g_standard_instance" {
  source  = "terraform-aws-modules/ec2-instance/aws"
  version = "4.1.4"

  name = "t4g-credit-standard"

  ami                    = data.aws_ssm_parameter.ubuntu-jammy-arm64.value
  instance_type          = "t4g.small"
  monitoring             = false
  cpu_credits            = "standard"

  tags = {
    Credit = "standard"
    InstanceType = "t4g.small"
  }
}

module "t4g_unlimited_instance" {
  source  = "terraform-aws-modules/ec2-instance/aws"
  version = "4.1.4"

  name = "t4g-credit-unlimited"

  ami                    = data.aws_ssm_parameter.ubuntu-jammy-arm64.value
  instance_type          = "t4g.small"
  monitoring             = false
  cpu_credits            = "unlimited"

  tags = {
    Credit = "standard"
    InstanceType = "t4g.small"
  }
}

module "a1_standard_instance" {
  source  = "terraform-aws-modules/ec2-instance/aws"
  version = "4.1.4"

  name = "a1-credit-standard"

  ami                    = data.aws_ssm_parameter.ubuntu-jammy-arm64.value
  instance_type          = "a1.medium"
  monitoring             = false
  cpu_credits            = "standard"

  tags = {
    Credit = "standard"
    InstanceType = "a1.medium"
  }
}

output "t3_standard_id" {
  value = module.t3_standard_instance.id
}
output "t3_unlimited_id" {
  value = module.t3_unlimited_instance.id
}
output "t4g_standard_id" {
  value = module.t4g_standard_instance.id
}
output "t4g_unlimited_id" {
  value = module.t4g_unlimited_instance.id
}
output "a1_standard_id" {
  value = module.a1_standard_instance.id
}

Run using current v4.1.4 module, shows t4g with unset credit_specification like a1 type, created instances using default burst specification (unlimited for t4g). t3 is set correctly

❯ terraform plan | egrep -A3 'credit_spec|tags_all'
      + tags_all                             = {
          + "Credit"       = "standard"
          + "InstanceType" = "a1.medium"
          + "Name"         = "a1-credit-standard"
--
      + credit_specification {}

      + ebs_block_device {
          + delete_on_termination = (known after apply)
--
      + tags_all                             = {
          + "Credit"       = "standard"
          + "InstanceType" = "t3.micro"
          + "Name"         = "t3-credit-standard"
--
      + credit_specification {
          + cpu_credits = "standard"
        }

--
      + tags_all                             = {
          + "Credit"       = "unlimited"
          + "InstanceType" = "t3.micro"
          + "Name"         = "t3-credit-unlimited"
--
      + credit_specification {
          + cpu_credits = "unlimited"
        }

--
      + tags_all                             = {
          + "Credit"       = "standard"
          + "InstanceType" = "t4g.small"
          + "Name"         = "t4g-credit-standard"
--
      + credit_specification {}

      + ebs_block_device {
          + delete_on_termination = (known after apply)
--
      + tags_all                             = {
          + "Credit"       = "standard"
          + "InstanceType" = "t4g.small"
          + "Name"         = "t4g-credit-unlimited"
--
      + credit_specification {}

      + ebs_block_device {
          + delete_on_termination = (known after apply)

❯ terraform apply
a1_standard_id = "i-04497a01dd37628fd"
t3_standard_id = "i-0b92ea1a73bf20e43"
t3_unlimited_id = "i-0ae6e2f3afb84316c"
t4g_standard_id = "i-0c4f1e7256d376190"
t4g_unlimited_id = "i-03d861674e1260f90"
# (ORDER BELOW: t3 standard, t3 unlimited, t4g standard, t4g unlimited, a1)
❯ aws ec2 describe-instance-credit-specifications --instance-ids i-0b92ea1a73bf20e43 i-0ae6e2f3afb84316c i-0c4f1e7256d376190 i-03d861674e1260f90 i-04497a01dd37628fd
{
    "InstanceCreditSpecifications": [
        {
            "InstanceId": "i-0b92ea1a73bf20e43",
            "CpuCredits": "standard"
        },
        {
            "InstanceId": "i-0ae6e2f3afb84316c",
            "CpuCredits": "unlimited"
        },
        {
            "InstanceId": "i-0c4f1e7256d376190",
            "CpuCredits": "unlimited"
        },
        {
            "InstanceId": "i-03d861674e1260f90",
            "CpuCredits": "unlimited"
        },
        {
            "InstanceId": "i-04497a01dd37628fd",
            "CpuCredits": "standard"
        }
    ]
}

Replace module source in code to point to fork with changes implemented, shows t4g with set credit_specification, created instances using specified burst setting

❯ grep source main.tf
  source  = "git::https://github.com/tofupup/terraform-aws-ec2-instance.git?ref=5cc414b1979774244087d51dd72a424e5ba1a5ae"
❯ terraform plan | egrep -A3 'credit_spec|tags_all'
      + tags_all                             = {
          + "Credit"       = "standard"
          + "InstanceType" = "a1.medium"
          + "Name"         = "a1-credit-standard"
--
      + credit_specification {}

      + ebs_block_device {
          + delete_on_termination = (known after apply)
--
      + tags_all                             = {
          + "Credit"       = "standard"
          + "InstanceType" = "t3.micro"
          + "Name"         = "t3-credit-standard"
--
      + credit_specification {
          + cpu_credits = "standard"
        }

--
      + tags_all                             = {
          + "Credit"       = "unlimited"
          + "InstanceType" = "t3.micro"
          + "Name"         = "t3-credit-unlimited"
--
      + credit_specification {
          + cpu_credits = "unlimited"
        }

--
      + tags_all                             = {
          + "Credit"       = "standard"
          + "InstanceType" = "t4g.small"
          + "Name"         = "t4g-credit-standard"
--
      + credit_specification {
          + cpu_credits = "standard"
        }

--
      + tags_all                             = {
          + "Credit"       = "standard"
          + "InstanceType" = "t4g.small"
          + "Name"         = "t4g-credit-unlimited"
--
      + credit_specification {
          + cpu_credits = "unlimited"
        }

❯ terraform apply
a1_standard_id = "i-0a67bdc418058132d"
t3_standard_id = "i-06097e933ea3e7a65"
t3_unlimited_id = "i-028140121fa6f73ca"
t4g_standard_id = "i-0db54f86efe99f19e"
t4g_unlimited_id = "i-021c6e761b0ef47e1"
# (ORDER BELOW: t3 standard, t3 unlimited, t4g standard, t4g unlimited, a1)
❯ aws ec2 describe-instance-credit-specifications --instance-ids i-06097e933ea3e7a65 i-028140121fa6f73ca i-0db54f86efe99f19e i-021c6e761b0ef47e1 i-0a67bdc418058132d
{
    "InstanceCreditSpecifications": [
        {
            "InstanceId": "i-06097e933ea3e7a65",
            "CpuCredits": "standard"
        },
        {
            "InstanceId": "i-028140121fa6f73ca",
            "CpuCredits": "unlimited"
        },
        {
            "InstanceId": "i-0db54f86efe99f19e",
            "CpuCredits": "standard"
        },
        {
            "InstanceId": "i-021c6e761b0ef47e1",
            "CpuCredits": "unlimited"
        },
        {
            "InstanceId": "i-0a67bdc418058132d",
            "CpuCredits": "standard"
        }
    ]
}