Load balancing UDP traffic to multiple pods via IngressRouteUDP

Question

Pulumi · Accepted Answer

To load balance UDP traffic to multiple pods in Kubernetes using Pulumi, we'll create a Kubernetes `Service` of type `LoadBalancer` that targets UDP traffic, and we'll also utilize `IngressRouteUDP` to define our load balancing rules. Kubernetes Services allow you to expose an application running on a set of Pods as a network service. Since standard Kubernetes `Ingress` only supports HTTP/HTTPS, for UDP we need a custom resource like `IngressRouteUDP` which is provided by ingress controllers like Traefik.

In this example, we will assume you have Traefik installed in your cluster, which allows you to use the `IngressRouteUDP` custom resource. If Traefik is not installed, you would first need to install it and ensure it supports the `IngressRouteUDP` resource. We will:

1. Create a `Service` that selects our pods using a `selector`. This service will also define the UDP port through which traffic will flow.
2. Create the `IngressRouteUDP` resource provided by the Traefik Kubernetes Ingress Controller to manage and load balance the UDP traffic to the service we created.

Let's start with the TypeScript program:

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

// Define the labels to associate with the Pods that the Service will select.
const appLabels = { app: "udp-server" };

// Create the Service that exposes the UDP server Pods.
const udpService = new k8s.core.v1.Service("udp-service", {
    metadata: {
        labels: appLabels,
        name: "udp-service", // The name of the service.
    },
    spec: {
        // Using `LoadBalancer` type to expose the Service outside of the cluster.
        type: "LoadBalancer",
        ports: [{ port: 12345, protocol: "UDP" }], // Replace with your desired port.
        selector: appLabels, // Selects the Pods that are running our UDP application.
    },
});

// Assuming Traefik is installed and configured to watch `IngressRouteUDP` resources:
// Create a Traefik IngressRouteUDP to handle the UDP traffic.
const ingressRouteUdp = new k8s.apiextensions.CustomResource("ingressrouteudp", {
    apiVersion: "traefik.containo.us/v1alpha1",
    kind: "IngressRouteUDP",
    metadata: { name: "udp-route" }, // The name of the IngressRouteUDP resource.
    spec: {
        entryPoints: ["udp"], // The entry point defined in Traefik for UDP traffic. (Make sure it's configured in Traefik)
        routes: [{
            services: [{
                name: udpService.metadata.name,
                port: 12345, // The target port on the Pods managed by the Service.
            }],
        }],
    },
});

// Export the external IP address of the Service. This is where you'll send UDP traffic.
export const externalIP = udpService.status.loadBalancer.ingress[0].ip;
```

In this program:

- We import the necessary Pulumi Kubernetes package.
- We define labels that we will use to tag our application Pods so that the Service can select them.
- We create a Service of type `LoadBalancer`. This is so we can accept traffic from outside the cluster. The Service selects Pods based on the `appLabels` definition.
- We then define a `CustomResource` of a kind `IngressRouteUDP`, which Traefik uses to route UDP traffic. This resource points to our Service and specifies the entry point for UDP traffic in Traefik.
- Finally, we export an `externalIP`, which will be assigned by the LoadBalancer service. This is the IP you would use on your UDP client to send traffic to your Kubernetes Pods.

Make sure you have configured Pulumi with the appropriate access to your Kubernetes cluster and that Traefik has been installed. When you deploy this Pulumi program, it will create the Service and IngressRouteUDP that together will direct UDP traffic to your application Pods.