// All CDK applications start with a new cdk.App object.
const app = new cdk.App();

// Create a new EKS cluster at v1.23. Run all non-DaemonSet pods in the 
// `kube-system` (coredns, etc.) and `karpenter` namespaces in Fargate
// so that we don't have to maintain EC2 instances for them.
const clusterProvider = new blueprints.GenericClusterProvider({
  version: KubernetesVersion.V1_23,
  fargateProfiles: {
    main: {
      selectors: [
        { namespace: 'kube-system' },
        { namespace: 'karpenter' },
      ]
    }
  },
  clusterLogging: [
    ClusterLoggingTypes.API,
    ClusterLoggingTypes.AUDIT,
    ClusterLoggingTypes.AUTHENTICATOR,
    ClusterLoggingTypes.CONTROLLER_MANAGER,
    ClusterLoggingTypes.SCHEDULER
  ]
});

// EKS Blueprints uses a Builder pattern.
blueprints.EksBlueprint.builder()
  .clusterProvider(clusterProvider) // start with the Cluster Provider
  .addOns(
    // Use the EKS add-ons that manage coredns and the VPC CNI plugin
    new blueprints.addons.CoreDnsAddOn('v1.8.7-eksbuild.3'),
    new blueprints.addons.VpcCniAddOn('v1.12.0-eksbuild.1'),
    // Install Karpenter
    new blueprints.addons.KarpenterAddOn({
      provisionerSpecs: {
        // Karpenter examines scheduled pods for the following labels
        // in their `nodeSelector` or `nodeAffinity` rules and routes
        // the pods to the node with the best fit, provisioning a new
        // node if necessary to meet the requirements.
        //
        // Allow either amd64 or arm64 nodes to be provisioned 
        'kubernetes.io/arch': ['amd64', 'arm64'],
        // Allow either Spot or On-Demand nodes to be provisioned
        'karpenter.sh/capacity-type': ['spot', 'on-demand']
      },
      // Launch instances in the VPC private subnets
      subnetTags: {
        Name: 'gitlab-runner-eks-demo/gitlab-runner-eks-demo-vpc/PrivateSubnet*'
      },
      // Apply security groups that match the following tags to the launched instances
      securityGroupTags: {
        'kubernetes.io/cluster/gitlab-runner-eks-demo': 'owned'      
      }
    }),
    // Create a pair of a new GitLab runner deployments, one running on
    // arm64 (Graviton) instance, the other on an x86_64 instance.
    // We'll show the definition of the GitLabRunner class below.
    new GitLabRunner({
      arch: CpuArch.ARM_64,
      // If you're using an on-premise GitLab installation, you'll want
      // to change the URL below.
      gitlabUrl: 'https://gitlab.com',
      // Kubernetes Secret containing the runner registration token
      // (discussed later)
      secretName: 'gitlab-runner-secret'
    }),
    new GitLabRunner({
      arch: CpuArch.X86_64,
      gitlabUrl: 'https://gitlab.com',
      secretName: 'gitlab-runner-secret'
    }),
  )
  .build(app, 
         // Stack name
         'gitlab-runner-eks-demo');
The GitLabRunner class is a HelmAddOn subclass that takes a few parameters from the top-level application:
// The location and name of the GitLab Runner Helm chart
const CHART_REPO = 'https://charts.gitlab.io';
const HELM_CHART = 'gitlab-runner';

// The default namespace for the runner
const DEFAULT_NAMESPACE = 'gitlab';

// The default Helm chart version
const DEFAULT_VERSION = '0.40.1';

export enum CpuArch {
    ARM_64 = 'arm64',
    X86_64 = 'amd64'
}

// Configuration parameters
interface GitLabRunnerProps {
    // The CPU architecture of the node on which the runner pod will reside
    arch: CpuArch
    // The GitLab API URL 
    gitlabUrl: string
    // Kubernetes Secret containing the runner registration token (discussed later)
    secretName: string
    // Optional tags for the runner. These will be added to the default list 
    // corresponding to the runner's CPU architecture.
    tags?: string[]
    // Optional Kubernetes namespace in which the runner will be installed
    namespace?: string
    // Optional Helm chart version
    chartVersion?: string
}

export class GitLabRunner extends HelmAddOn {
    private arch: CpuArch;
    private gitlabUrl: string;
    private secretName: string;
    private tags: string[] = [];

    constructor(props: GitLabRunnerProps) {
        // Invoke the superclass (HelmAddOn) constructor
        super({
            name: `gitlab-runner-${props.arch}`,
            chart: HELM_CHART,
            repository: CHART_REPO,
            namespace: props.namespace || DEFAULT_NAMESPACE,
            version: props.chartVersion || DEFAULT_VERSION,
            release: `gitlab-runner-${props.arch}`,
        });

        this.arch = props.arch;
        this.gitlabUrl = props.gitlabUrl;
        this.secretName = props.secretName;

        // Set default runner tags
        switch (this.arch) {
            case CpuArch.X86_64:
                this.tags.push('amd64', 'x86', 'x86-64', 'x86_64');
                break;
            case CpuArch.ARM_64:
                this.tags.push('arm64');
                break;
        }
        this.tags.push(...props.tags || []); // Add any custom tags
    };

    // `deploy` method required by the abstract class definition. Our implementation
    // simply installs a Helm chart to the cluster with the proper values.
    deploy(clusterInfo: ClusterInfo): void | Promise<Construct> {
        const chart = this.addHelmChart(clusterInfo, this.getValues(), true);
        return Promise.resolve(chart);
    }

    // Returns the values for the GitLab Runner Helm chart
    private getValues(): Values {
        return {
            gitlabUrl: this.gitlabUrl,
            runners: {
                config: this.runnerConfig(), // runner config.toml file, from below
                name: `demo-runner-${this.arch}`, // name as seen in GitLab UI
                tags: uniq(this.tags).join(','),
                secret: this.secretName, // see below
            },
            // Labels to constrain the nodes where this runner can be placed
            nodeSelector: {
                'kubernetes.io/arch': this.arch,
                'karpenter.sh/capacity-type': 'on-demand'
            },
            // Default pod label
            podLabels: {
                'gitlab-role': 'manager'
            },
            // Create all the necessary RBAC resources including the ServiceAccount
            rbac: {
                create: true
            },
            // Required resources (memory/CPU) for the runner pod. The runner
            // is fairly lightweight as it's a self-contained Golang app.
            resources: {
                requests: {
                    memory: '128Mi',
                    cpu: '256m'
                }
            }
        };
    }

    // This string contains the runner's `config.toml` file including the
    // Kubernetes executor's configuration. Note the nodeSelector constraints 
    // (including the use of Spot capacity and the CPU architecture).
    private runnerConfig(): string {
        return `
  [[runners]]
    [runners.kubernetes]
      namespace = "{{.Release.Namespace}}"
      image = "ubuntu:16.04"
    [runners.kubernetes.node_selector]
      "kubernetes.io/arch" = "${this.arch}"
      "kubernetes.io/os" = "linux"
      "karpenter.sh/capacity-type" = "spot"
    [runners.kubernetes.pod_labels]
      gitlab-role = "runner"
      `.trim();
    }
}

# These two values must match the parameters supplied to the GitLabRunner constructor
NAMESPACE=gitlab
SECRET_NAME=gitlab-runner-secret
# The value of the registration token.
TOKEN=GRxxxxxxxxxxxxxxxxxxxxxx

kubectl -n $NAMESPACE create secret generic $SECRET_NAME \
        --from-literal="runner-registration-token=$TOKEN" \
        --from-literal="runner-token="

variables:
  # These are used by the runner to configure the Kubernetes executor, and define
  # the values of spec.containers[].resources.limits.{memory,cpu} for the Pod(s).
  KUBERNETES_MEMORY_REQUEST: 1Gi
  KUBERNETES_CPU_REQUEST: 1

# List of stages for jobs, and their order of execution  
stages:    
  - build
  - test
  - create-multiarch-manifest
Here’s what our build stage job looks like. Note the matrix of variables which are set in BUILD_ARCH as the two jobs are run in parallel:
build-job:
  stage: build
  parallel:
    matrix:              # This job is run twice, once on amd64 (x86), once on arm64
    - BUILD_ARCH: amd64
    - BUILD_ARCH: arm64
  tags: [$BUILD_ARCH]    # Associate the job with the appropriate runner
  image:
    name: gcr.io/kaniko-project/executor:debug
    entrypoint: [""]
  script:
    - mkdir -p /kaniko/.docker
    # Configure authentication data for Kaniko so it can push to the
    # GitLab container registry
    - echo "{\"auths\":{\"${CI_REGISTRY}\":{\"auth\":\"$(printf "%s:%s" "${CI_REGISTRY_USER}" "${CI_REGISTRY_PASSWORD}" | base64 | tr -d '\n')\"}}}" > /kaniko/.docker/config.json
    # Build the image and push to the registry. In this stage, we append the build
    # architecture as a tag suffix.
    - >-
      /kaniko/executor
      --context "${CI_PROJECT_DIR}"
      --dockerfile "${CI_PROJECT_DIR}/Dockerfile"
      --destination "${CI_REGISTRY_IMAGE}:${CI_COMMIT_SHORT_SHA}-${BUILD_ARCH}"

build-job:
  stage: build
  parallel:
    matrix:              # This job is run twice, once on amd64 (x86), once on arm64
    - BUILD_ARCH: amd64
    - BUILD_ARCH: arm64
  tags: [$BUILD_ARCH]    # Associate the job with the appropriate runner
  image:
    # Use the image we just built
    name: "${CI_REGISTRY_IMAGE}:${CI_COMMIT_SHORT_SHA}-${BUILD_ARCH}"
  script:
    - make test-container

create-manifest-job:
  stage: create-multiarch-manifest
  tags: [arm64] 
  image: public.ecr.aws/docker/library/fedora:36
  script:
    - yum -y install podman
    - echo "${CI_REGISTRY_PASSWORD}" | podman login -u "${CI_REGISTRY_USER}" --password-stdin "${CI_REGISTRY}"
    - COMPOSITE_IMAGE=${CI_REGISTRY_IMAGE}:${CI_COMMIT_SHORT_SHA}
    - podman manifest create ${COMPOSITE_IMAGE}
    - >-
      for arch in arm64 amd64; do
        podman manifest add ${COMPOSITE_IMAGE} docker://${COMPOSITE_IMAGE}-${arch};
      done
    - podman manifest inspect ${COMPOSITE_IMAGE}
    # The composite image manifest omits the architecture from the tag suffix.
    - podman manifest push ${COMPOSITE_IMAGE} docker://${COMPOSITE_IMAGE}