feat: Add EKS Fargate support (#1067)

Co-authored-by: Simon Gurcke <simon@gurcke.de>
Co-authored-by: Daniel Piddock <33028589+dpiddockcmp@users.noreply.github.com>

README.md

@@ -187,8 +187,11 @@ MIT Licensed. See [LICENSE](https://github.com/terraform-aws-modules/terraform-a
 | cluster\_version | Kubernetes version to use for the EKS cluster. | `string` | n/a | yes |
 | config\_output\_path | Where to save the Kubectl config file (if `write_kubeconfig = true`). Assumed to be a directory if the value ends with a forward slash `/`. | `string` | `"./"` | no |
 | create\_eks | Controls if EKS resources should be created (it affects almost all resources) | `bool` | `true` | no |
+| create\_fargate\_pod\_execution\_role | Controls if the EKS Fargate pod execution IAM role should be created. | `bool` | `true` | no |
 | eks\_oidc\_root\_ca\_thumbprint | Thumbprint of Root CA for EKS OIDC, Valid until 2037 | `string` | `"9e99a48a9960b14926bb7f3b02e22da2b0ab7280"` | no |
 | enable\_irsa | Whether to create OpenID Connect Provider for EKS to enable IRSA | `bool` | `false` | no |
+| fargate\_pod\_execution\_role\_name | The IAM Role that provides permissions for the EKS Fargate Profile. | `string` | `null` | no |
+| fargate\_profiles | Fargate profiles to create. See `fargate_profile` keys section in fargate submodule's README.md for more details | `any` | `{}` | no |
 | iam\_path | If provided, all IAM roles will be created on this path. | `string` | `"/"` | no |
 | kubeconfig\_aws\_authenticator\_additional\_args | Any additional arguments to pass to the authenticator such as the role to assume. e.g. ["-r", "MyEksRole"]. | `list(string)` | `[]` | no |
 | kubeconfig\_aws\_authenticator\_command | Command to use to fetch AWS EKS credentials. | `string` | `"aws-iam-authenticator"` | no |
@@ -243,6 +246,10 @@ MIT Licensed. See [LICENSE](https://github.com/terraform-aws-modules/terraform-a
 | cluster\_security\_group\_id | Security group ID attached to the EKS cluster. On 1.14 or later, this is the 'Additional security groups' in the EKS console. |
 | cluster\_version | The Kubernetes server version for the EKS cluster. |
 | config\_map\_aws\_auth | A kubernetes configuration to authenticate to this EKS cluster. |
+| fargate\_iam\_role\_arn | IAM role ARN for EKS Fargate pods |
+| fargate\_iam\_role\_name | IAM role name for EKS Fargate pods |
+| fargate\_profile\_arns | Amazon Resource Name (ARN) of the EKS Fargate Profiles. |
+| fargate\_profile\_ids | EKS Cluster name and EKS Fargate Profile names separated by a colon (:). |
 | kubeconfig | kubectl config file contents for this EKS cluster. |
 | kubeconfig\_filename | The filename of the generated kubectl config. |
 | node\_groups | Outputs from EKS node groups. Map of maps, keyed by var.node\_groups keys |

aws_auth.tf

@@ -43,18 +43,20 @@ locals {
       local.auth_launch_template_worker_roles,
       local.auth_worker_roles,
       module.node_groups.aws_auth_roles,
+      module.fargate.aws_auth_roles,
     ) :
     {
       # Work around https://github.com/kubernetes-sigs/aws-iam-authenticator/issues/153
       # Strip the leading slash off so that Terraform doesn't think it's a regex
       rolearn  = replace(role["worker_role_arn"], replace(var.iam_path, "/^//", ""), "")
-      username = "system:node:{{EC2PrivateDNSName}}"
+      username = role["platform"] == "fargate" ? "system:node:{{SessionName}}" : "system:node:{{EC2PrivateDNSName}}"
       groups = tolist(concat(
         [
           "system:bootstrappers",
           "system:nodes",
         ],
-        role["platform"] == "windows" ? ["eks:kube-proxy-windows"] : []
+        role["platform"] == "windows" ? ["eks:kube-proxy-windows"] : [],
+        role["platform"] == "fargate" ? ["system:node-proxier"] : [],
       ))
     }
   ]

examples/fargate/main.tf

@@ -0,0 +1,112 @@
+terraform {
+  required_version = ">= 0.12.6"
+}
+
+provider "aws" {
+  version = ">= 2.28.1"
+  region  = var.region
+}
+
+provider "random" {
+  version = "~> 2.1"
+}
+
+provider "local" {
+  version = "~> 1.2"
+}
+
+provider "null" {
+  version = "~> 2.1"
+}
+
+provider "template" {
+  version = "~> 2.1"
+}
+
+data "aws_eks_cluster" "cluster" {
+  name = module.eks.cluster_id
+}
+
+data "aws_eks_cluster_auth" "cluster" {
+  name = module.eks.cluster_id
+}
+
+provider "kubernetes" {
+  host                   = data.aws_eks_cluster.cluster.endpoint
+  cluster_ca_certificate = base64decode(data.aws_eks_cluster.cluster.certificate_authority.0.data)
+  token                  = data.aws_eks_cluster_auth.cluster.token
+  load_config_file       = false
+  version                = "~> 1.11"
+}
+
+data "aws_availability_zones" "available" {
+}
+
+locals {
+  cluster_name = "test-eks-${random_string.suffix.result}"
+}
+
+resource "random_string" "suffix" {
+  length  = 8
+  special = false
+}
+
+module "vpc" {
+  source  = "terraform-aws-modules/vpc/aws"
+  version = "2.47.0"
+
+  name                 = "test-vpc"
+  cidr                 = "172.16.0.0/16"
+  azs                  = data.aws_availability_zones.available.names
+  private_subnets      = ["172.16.1.0/24", "172.16.2.0/24", "172.16.3.0/24"]
+  public_subnets       = ["172.16.4.0/24", "172.16.5.0/24", "172.16.6.0/24"]
+  enable_nat_gateway   = true
+  single_nat_gateway   = true
+  enable_dns_hostnames = true
+
+  public_subnet_tags = {
+    "kubernetes.io/cluster/${local.cluster_name}" = "shared"
+    "kubernetes.io/role/elb"                      = "1"
+  }
+
+  private_subnet_tags = {
+    "kubernetes.io/cluster/${local.cluster_name}" = "shared"
+    "kubernetes.io/role/internal-elb"             = "1"
+  }
+}
+
+module "eks" {
+  source          = "../.."
+  cluster_name    = local.cluster_name
+  cluster_version = "1.17"
+  subnets         = module.vpc.private_subnets
+
+  tags = {
+    Environment = "test"
+    GithubRepo  = "terraform-aws-eks"
+    GithubOrg   = "terraform-aws-modules"
+  }
+
+  vpc_id = module.vpc.vpc_id
+
+  fargate_profiles = {
+    example = {
+      namespace = "default"
+
+      # Kubernetes labels for selection
+      # labels = {
+      #   Environment = "test"
+      #   GithubRepo  = "terraform-aws-eks"
+      #   GithubOrg   = "terraform-aws-modules"
+      # }
+
+      tags = {
+        Owner = "test"
+      }
+    }
+  }
+
+  map_roles    = var.map_roles
+  map_users    = var.map_users
+  map_accounts = var.map_accounts
+}

examples/fargate/outputs.tf

@@ -0,0 +1,29 @@
+output "cluster_endpoint" {
+  description = "Endpoint for EKS control plane."
+  value       = module.eks.cluster_endpoint
+}
+
+output "cluster_security_group_id" {
+  description = "Security group ids attached to the cluster control plane."
+  value       = module.eks.cluster_security_group_id
+}
+
+output "kubectl_config" {
+  description = "kubectl config as generated by the module."
+  value       = module.eks.kubeconfig
+}
+
+output "config_map_aws_auth" {
+  description = "A kubernetes configuration to authenticate to this EKS cluster."
+  value       = module.eks.config_map_aws_auth
+}
+
+output "region" {
+  description = "AWS region."
+  value       = var.region
+}
+
+output "fargate_profile_arns" {
+  description = "Outputs from node groups"
+  value       = module.eks.fargate_profile_arns
+}

examples/fargate/variables.tf

@@ -0,0 +1,52 @@
+variable "region" {
+  default = "us-west-2"
+}
+
+variable "map_accounts" {
+  description = "Additional AWS account numbers to add to the aws-auth configmap."
+  type        = list(string)
+
+  default = [
+    "777777777777",
+    "888888888888",
+  ]
+}
+
+variable "map_roles" {
+  description = "Additional IAM roles to add to the aws-auth configmap."
+  type = list(object({
+    rolearn  = string
+    username = string
+    groups   = list(string)
+  }))
+
+  default = [
+    {
+      rolearn  = "arn:aws:iam::66666666666:role/role1"
+      username = "role1"
+      groups   = ["system:masters"]
+    },
+  ]
+}
+
+variable "map_users" {
+  description = "Additional IAM users to add to the aws-auth configmap."
+  type = list(object({
+    userarn  = string
+    username = string
+    groups   = list(string)
+  }))
+
+  default = [
+    {
+      userarn  = "arn:aws:iam::66666666666:user/user1"
+      username = "user1"
+      groups   = ["system:masters"]
+    },
+    {
+      userarn  = "arn:aws:iam::66666666666:user/user2"
+      username = "user2"
+      groups   = ["system:masters"]
+    },
+  ]
+}

fargate.tf

@@ -0,0 +1,22 @@
+module "fargate" {
+  source                            = "./modules/fargate"
+  cluster_name                      = coalescelist(aws_eks_cluster.this[*].name, [""])[0]
+  create_eks                        = var.create_eks
+  create_fargate_pod_execution_role = var.create_fargate_pod_execution_role
+  fargate_pod_execution_role_name   = var.fargate_pod_execution_role_name
+  fargate_profiles                  = var.fargate_profiles
+  iam_path                          = var.iam_path
+  iam_policy_arn_prefix             = local.policy_arn_prefix
+  subnets                           = var.subnets
+  tags                              = var.tags
+
+  # Hack to ensure ordering of resource creation.
+  # This is a homemade `depends_on` https://discuss.hashicorp.com/t/tips-howto-implement-module-depends-on-emulation/2305/2
+  # Do not create node_groups before other resources are ready and removes race conditions
+  # Ensure these resources are created before "unlocking" the data source.
+  # Will be removed in Terraform 0.13
+  eks_depends_on = [
+    aws_eks_cluster.this,
+    kubernetes_config_map.aws_auth,
+  ]
+}

modules/fargate/README.md

@@ -0,0 +1,54 @@
+# eks `fargate` submodule
+
+Helper submodule to create and manage resources related to `aws_eks_fargate_profile`.
+
+## Assumptions
+* Designed for use by the parent module and not directly by end users
+
+## `fargate_profile` keys
+`fargate_profile` is a map of maps. Key of first level will be used as unique value for `for_each` resources and in the `aws_eks_fargate_profile` name. Inner map can take the below values.
+
+| Name | Description | Type | Default | Required |
+|------|-------------|------|---------|:--------:|
+| name | Fargate profile name | `string` | Auto generated in the following format `[cluster_name]-fargate-[fargate_profile_map_key]`| no |
+| namespace | Kubernetes namespace for selection | `string` | n/a | yes |
+| labels | Key-value map of Kubernetes labels for selection | `map(string)` | `{}` | no |
+| tags | Key-value map of resource tags. Will be merged with root module tags. | `map(string)` | `var.tags` | no |
+
+<!-- BEGINNING OF PRE-COMMIT-TERRAFORM DOCS HOOK -->
+## Requirements
+
+No requirements.
+
+## Providers
+
+| Name | Version |
+|------|---------|
+| aws | n/a |
+
+## Inputs
+
+| Name | Description | Type | Default | Required |
+|------|-------------|------|---------|:--------:|
+| cluster\_name | Name of the EKS cluster. | `string` | n/a | yes |
+| create\_eks | Controls if EKS resources should be created (it affects almost all resources) | `bool` | `true` | no |
+| create\_fargate\_pod\_execution\_role | Controls if the the IAM Role that provides permissions for the EKS Fargate Profile should be created. | `bool` | `true` | no |
+| eks\_depends\_on | List of references to other resources this submodule depends on. | `any` | `null` | no |
+| fargate\_pod\_execution\_role\_name | The IAM Role that provides permissions for the EKS Fargate Profile. | `string` | `null` | no |
+| fargate\_profiles | Fargate profiles to create. See `fargate_profile` keys section in README.md for more details | `any` | `{}` | no |
+| iam\_path | IAM roles will be created on this path. | `string` | `"/"` | no |
+| iam\_policy\_arn\_prefix | IAM policy prefix with the correct AWS partition. | `string` | n/a | yes |
+| subnets | A list of subnets for the EKS Fargate profiles. | `list(string)` | `[]` | no |
+| tags | A map of tags to add to all resources. | `map(string)` | `{}` | no |
+
+## Outputs
+
+| Name | Description |
+|------|-------------|
+| aws\_auth\_roles | Roles for use in aws-auth ConfigMap |
+| fargate\_profile\_arns | Amazon Resource Name (ARN) of the EKS Fargate Profiles. |
+| fargate\_profile\_ids | EKS Cluster name and EKS Fargate Profile names separated by a colon (:). |
+| iam\_role\_arn | IAM role ARN for EKS Fargate pods |
+| iam\_role\_name | IAM role name for EKS Fargate pods |
+
+<!-- END OF PRE-COMMIT-TERRAFORM DOCS HOOK -->

modules/fargate/data.tf

@@ -0,0 +1,17 @@
+data "aws_iam_policy_document" "eks_fargate_pod_assume_role" {
+  count = local.create_eks && var.create_fargate_pod_execution_role ? 1 : 0
+  statement {
+    effect  = "Allow"
+    actions = ["sts:AssumeRole"]
+
+    principals {
+      type        = "Service"
+      identifiers = ["eks-fargate-pods.amazonaws.com"]
+    }
+  }
+}
+
+data "aws_iam_role" "custom_fargate_iam_role" {
+  count = local.create_eks && ! var.create_fargate_pod_execution_role ? 1 : 0
+  name  = var.fargate_pod_execution_role_name
+}

modules/fargate/fargate.tf

@@ -0,0 +1,29 @@
+resource "aws_iam_role" "eks_fargate_pod" {
+  count              = local.create_eks && var.create_fargate_pod_execution_role ? 1 : 0
+  name_prefix        = format("%s-fargate", var.cluster_name)
+  assume_role_policy = data.aws_iam_policy_document.eks_fargate_pod_assume_role[0].json
+  tags               = var.tags
+  path               = var.iam_path
+}
+
+resource "aws_iam_role_policy_attachment" "eks_fargate_pod" {
+  count      = local.create_eks && var.create_fargate_pod_execution_role ? 1 : 0
+  policy_arn = "${var.iam_policy_arn_prefix}/AmazonEKSFargatePodExecutionRolePolicy"
+  role       = aws_iam_role.eks_fargate_pod[0].name
+}
+
+resource "aws_eks_fargate_profile" "this" {
+  for_each               = local.create_eks ? local.fargate_profiles_expanded : {}
+  cluster_name           = var.cluster_name
+  fargate_profile_name   = lookup(each.value, "name", format("%s-fargate-%s", var.cluster_name, replace(each.key, "_", "-")))
+  pod_execution_role_arn = local.pod_execution_role_arn
+  subnet_ids             = var.subnets
+  tags                   = each.value.tags
+
+  selector {
+    namespace = each.value.namespace
+    labels    = lookup(each.value, "labels", null)
+  }
+
+  depends_on = [var.eks_depends_on]
+}

modules/fargate/locals.tf

@@ -0,0 +1,10 @@
+locals {
+  create_eks              = var.create_eks && length(var.fargate_profiles) > 0
+  pod_execution_role_arn  = var.create_fargate_pod_execution_role ? element(concat(aws_iam_role.eks_fargate_pod.*.arn, list("")), 0) : element(concat(data.aws_iam_role.custom_fargate_iam_role.*.arn, list("")), 0)
+  pod_execution_role_name = var.create_fargate_pod_execution_role ? element(concat(aws_iam_role.eks_fargate_pod.*.name, list("")), 0) : element(concat(data.aws_iam_role.custom_fargate_iam_role.*.name, list("")), 0)
+
+  fargate_profiles_expanded = { for k, v in var.fargate_profiles : k => merge(
+    { tags = var.tags },
+    v,
+  ) if var.create_eks }
+}