Using kubernetes karpenter.k8s.aws with apiregistration

Question

Pulumi · Accepted Answer

Karpenter is an open-source, flexible, high-performance Kubernetes cluster autoscaler built by AWS. It assists in the efficient provisioning and scaling of worker nodes in a Kubernetes cluster based on the scheduling needs of the workload. Karpenter can help optimize costs and ensure that the required compute resources are available to meet application demands.

The `kubernetes` package in Pulumi allows you to interact with Kubernetes resources, including custom resources like those provided by Karpenter. Karpenter typically requires certain permissions, such as creating and deleting EC2 instances, which are governed by AWS IAM roles and policies. However, deploying Karpenter requires interacting with the Kubernetes API to install and configure the necessary components.

The `apiregistration` API is a part of Kubernetes which allows you to register API services that extend the Kubernetes API. This is often used in conjunction with custom controllers and operators that add additional functionality to a Kubernetes cluster.

Below is a TypeScript program using Pulumi which sets up a simple framework into which Karpenter can fit. For deploying Karpenter into a Kubernetes cluster using Pulumi, you'd typically follow these steps:

1. Ensure you have a running EKS cluster with `eks` or `awsx` modules.
2. Deploy the necessary RBAC roles and bindings for Karpenter to interact with the Kubernetes API.
3. Install Karpenter Helm chart into the cluster, configuring it to use roles and permissions created.

For the sake of simplicity, the example below assumes you have a running EKS cluster and necessary AWS IAM roles and policies in place. This program will demonstrate how to create a Kubernetes namespace for Karpenter and apply necessary roles using Pulumi's `kubernetes` provider. Please note that you must configure your AWS and Kubernetes provider settings with Pulumi, which includes AWS access keys and Kubernetes kubeconfig.

Let's start by installing Karpenter's Helm chart into a dedicated namespace.

```typescript
import * as k8s from "@pulumi/kubernetes";

// This presumes that you have already configured your Pulumi program
// to connect to an existing Kubernetes cluster and AWS account.

// Create a namespace for Karpenter.
const karpenterNamespace = new k8s.core.v1.Namespace("karpenter", {
  metadata: { name: "karpenter" },
});

// Install the Karpenter Helm chart into the namespace we just created.
const karpenterChart = new k8s.helm.v3.Chart("karpenter", {
  chart: "karpenter",
  version: "0.x.x", // Specify the version of Karpenter you wish to install
  namespace: karpenterNamespace.metadata.name,
  fetchOpts: {
    repo: "https://charts.karpenter.sh",
  },
}, { dependsOn: [karpenterNamespace] });

// Export the namespace name where Karpenter is installed.
export const karpenterNamespaceName = karpenterNamespace.metadata.name;
```

In the above program:

- We initialize a new Kubernetes namespace resource called `karpenter` to isolate the components of Karpenter from other workloads.
  
- We then use the `helm.v3.Chart` resource to deploy the Karpenter Helm chart into our Kubernetes cluster. To do this, we specify the chart name (`karpenter`), the Helm chart version, and the repository URL where the Helm chart can be found.

- The `dependsOn` option ensures that the Helm chart is installed only after the namespace has been created.

For a comprehensive installation and to fully function, Karpenter will also require AWS resources like IAM Roles with certain policies attached to them, and the proper configuration of these roles within the Helm chart settings. However, managing IAM Roles and Policies is beyond the scope of this guide.

Remember to replace the `version` in the `karpenterChart` declaration with the specific version of Karpenter that you intend to install. You can find the version information and additional configuration options for Karpenter in the [official Helm chart repository](https://github.com/aws/karpenter/tree/main/charts/karpenter).

This type of Pulumi program provides an Infrastructure as Code (IaC) approach which is repeatable and version controllable, ensuring consistency across different environments and adherence to best practices.

To run this program:

1. Save the code to a file named `index.ts`.
2. Run `pulumi up` to preview and deploy the changes.

As you grow more familiar with Pulumi and want to expand this to include AWS-specific resources such as IAM roles and policies, you can integrate more AWS resources using the `@pulumi/aws` package.