main.tf

provider "aws" {
  region = local.region
}

provider "aws" {
  region = "us-east-1"
  alias  = "virginia"
}

provider "kubernetes" {
  host                   = module.eks.cluster_endpoint
  cluster_ca_certificate = base64decode(module.eks.cluster_certificate_authority_data)

  exec {
    api_version = "client.authentication.k8s.io/v1beta1"
    command     = "aws"
    # This requires the awscli to be installed locally where Terraform is executed
    args = ["eks", "get-token", "--cluster-name", module.eks.cluster_name]
  }
}

provider "helm" {
  kubernetes {
    host                   = module.eks.cluster_endpoint
    cluster_ca_certificate = base64decode(module.eks.cluster_certificate_authority_data)

    exec {
      api_version = "client.authentication.k8s.io/v1beta1"
      command     = "aws"
      # This requires the awscli to be installed locally where Terraform is executed
      args = ["eks", "get-token", "--cluster-name", module.eks.cluster_name]
    }
  }
}

provider "kubectl" {
  apply_retry_count      = 5
  host                   = module.eks.cluster_endpoint
  cluster_ca_certificate = base64decode(module.eks.cluster_certificate_authority_data)
  load_config_file       = false

  exec {
    api_version = "client.authentication.k8s.io/v1beta1"
    command     = "aws"
    # This requires the awscli to be installed locally where Terraform is executed
    args = ["eks", "get-token", "--cluster-name", module.eks.cluster_name]
  }
}

data "aws_availability_zones" "available" {}
data "aws_ecrpublic_authorization_token" "token" {
  provider = aws.virginia
}

locals {
  name            = "ex-${replace(basename(path.cwd), "_", "-")}"
  cluster_version = "1.27"
  region          = "eu-west-1"

  vpc_cidr = "10.0.0.0/16"
  azs      = slice(data.aws_availability_zones.available.names, 0, 3)

  tags = {
    Example    = local.name
    GithubRepo = "terraform-aws-eks"
    GithubOrg  = "terraform-aws-modules"
  }
}

################################################################################
# EKS Module
################################################################################

module "eks" {
  source = "../.."

  cluster_name                   = local.name
  cluster_version                = local.cluster_version
  cluster_endpoint_public_access = true

  cluster_addons = {
    kube-proxy = {}
    vpc-cni    = {}
    coredns = {
      configuration_values = jsonencode({
        computeType = "Fargate"
        # Ensure that we fully utilize the minimum amount of resources that are supplied by
        # Fargate https://docs.aws.amazon.com/eks/latest/userguide/fargate-pod-configuration.html
        # Fargate adds 256 MB to each pod's memory reservation for the required Kubernetes
        # components (kubelet, kube-proxy, and containerd). Fargate rounds up to the following
        # compute configuration that most closely matches the sum of vCPU and memory requests in
        # order to ensure pods always have the resources that they need to run.
        resources = {
          limits = {
            cpu = "0.25"
            # We are targeting the smallest Task size of 512Mb, so we subtract 256Mb from the
            # request/limit to ensure we can fit within that task
            memory = "256M"
          }
          requests = {
            cpu = "0.25"
            # We are targeting the smallest Task size of 512Mb, so we subtract 256Mb from the
            # request/limit to ensure we can fit within that task
            memory = "256M"
          }
        }
      })
    }
  }

  vpc_id                   = module.vpc.vpc_id
  subnet_ids               = module.vpc.private_subnets
  control_plane_subnet_ids = module.vpc.intra_subnets

  # Fargate profiles use the cluster primary security group so these are not utilized
  create_cluster_security_group = false
  create_node_security_group    = false

  manage_aws_auth_configmap = true
  aws_auth_roles = [
    # We need to add in the Karpenter node IAM role for nodes launched by Karpenter
    {
      rolearn  = module.karpenter.role_arn
      username = "system:node:{{EC2PrivateDNSName}}"
      groups = [
        "system:bootstrappers",
        "system:nodes",
      ]
    },
  ]

  fargate_profiles = {
    karpenter = {
      selectors = [
        { namespace = "karpenter" }
      ]
    }
    kube-system = {
      selectors = [
        { namespace = "kube-system" }
      ]
    }
  }

  tags = merge(local.tags, {
    # NOTE - if creating multiple security groups with this module, only tag the
    # security group that Karpenter should utilize with the following tag
    # (i.e. - at most, only one security group should have this tag in your account)
    "karpenter.sh/discovery" = local.name
  })
}

################################################################################
# Karpenter
################################################################################

module "karpenter" {
  source = "../../modules/karpenter"

  cluster_name           = module.eks.cluster_name
  irsa_oidc_provider_arn = module.eks.oidc_provider_arn

  policies = {
    AmazonSSMManagedInstanceCore = "arn:aws:iam::aws:policy/AmazonSSMManagedInstanceCore"
  }

  tags = local.tags
}

resource "helm_release" "karpenter" {
  namespace        = "karpenter"
  create_namespace = true

  name                = "karpenter"
  repository          = "oci://public.ecr.aws/karpenter"
  repository_username = data.aws_ecrpublic_authorization_token.token.user_name
  repository_password = data.aws_ecrpublic_authorization_token.token.password
  chart               = "karpenter"
  version             = "v0.21.1"

  set {
    name  = "settings.aws.clusterName"
    value = module.eks.cluster_name
  }

  set {
    name  = "settings.aws.clusterEndpoint"
    value = module.eks.cluster_endpoint
  }

  set {
    name  = "serviceAccount.annotations.eks\\.amazonaws\\.com/role-arn"
    value = module.karpenter.irsa_arn
  }

  set {
    name  = "settings.aws.defaultInstanceProfile"
    value = module.karpenter.instance_profile_name
  }

  set {
    name  = "settings.aws.interruptionQueueName"
    value = module.karpenter.queue_name
  }
}

resource "kubectl_manifest" "karpenter_provisioner" {
  yaml_body = <<-YAML
    apiVersion: karpenter.sh/v1alpha5
    kind: Provisioner
    metadata:
      name: default
    spec:
      requirements:
        - key: karpenter.sh/capacity-type
          operator: In
          values: ["spot"]
      limits:
        resources:
          cpu: 1000
      providerRef:
        name: default
      ttlSecondsAfterEmpty: 30
  YAML

  depends_on = [
    helm_release.karpenter
  ]
}

resource "kubectl_manifest" "karpenter_node_template" {
  yaml_body = <<-YAML
    apiVersion: karpenter.k8s.aws/v1alpha1
    kind: AWSNodeTemplate
    metadata:
      name: default
    spec:
      subnetSelector:
        karpenter.sh/discovery: ${module.eks.cluster_name}
      securityGroupSelector:
        karpenter.sh/discovery: ${module.eks.cluster_name}
      tags:
        karpenter.sh/discovery: ${module.eks.cluster_name}
  YAML

  depends_on = [
    helm_release.karpenter
  ]
}

# Example deployment using the [pause image](https://www.ianlewis.org/en/almighty-pause-container)
# and starts with zero replicas
resource "kubectl_manifest" "karpenter_example_deployment" {
  yaml_body = <<-YAML
    apiVersion: apps/v1
    kind: Deployment
    metadata:
      name: inflate
    spec:
      replicas: 0
      selector:
        matchLabels:
          app: inflate
      template:
        metadata:
          labels:
            app: inflate
        spec:
          terminationGracePeriodSeconds: 0
          containers:
            - name: inflate
              image: public.ecr.aws/eks-distro/kubernetes/pause:3.7
              resources:
                requests:
                  cpu: 1
  YAML

  depends_on = [
    helm_release.karpenter
  ]
}

################################################################################
# Supporting Resources
################################################################################

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "~> 4.0"

  name = local.name
  cidr = local.vpc_cidr

  azs             = local.azs
  private_subnets = [for k, v in local.azs : cidrsubnet(local.vpc_cidr, 4, k)]
  public_subnets  = [for k, v in local.azs : cidrsubnet(local.vpc_cidr, 8, k + 48)]
  intra_subnets   = [for k, v in local.azs : cidrsubnet(local.vpc_cidr, 8, k + 52)]

  enable_nat_gateway = true
  single_nat_gateway = true

  public_subnet_tags = {
    "kubernetes.io/role/elb" = 1
  }

  private_subnet_tags = {
    "kubernetes.io/role/internal-elb" = 1
    # Tags subnets for Karpenter auto-discovery
    "karpenter.sh/discovery" = local.name
  }

  tags = local.tags
}