Kubernetes Controllers for CRDs in C#

What is this?

This is a sample C# library for creating lightweight controllers for Kubernetes CRDs, using the Kubernetes C# client.

It is intended to show you how to get started writing your own controller for CRDs in C#, and it is not suited for production purposes.

Using this library

Considering a custom resource definition that can be found in KubeController.Sample/deploy/crd.yaml, building the C# object is done by creating an instance of the CustomResource generic class which mimics the structure of your CRD, and passing a handler function to be executed whenever an event is fired:

    var crd = new CustomResourceDefinition()
    {
        ApiVersion = "engineerd.dev/v1alpha1",
        PluralName = "examples",
        Kind = "Example",
        Namespace = "kubecontroller"
    };

    var controller = new Controller<ExampleCRD>(
        new Kubernetes(KubernetesClientConfiguration.BuildConfigFromConfigFile()),
        crd,
        (WatchEventType eventType, ExampleCRD example) =>
            Console.WriteLine("Event type: {0} for {1}", eventType, example.Metadata.Name));

    var cts = new CancellationTokenSource();
    await controller.StartAsync(cts.Token).ConfigureAwait(false);

Building from source

Prerequisites:

• a Kubernetes cluster
• .NET Core 2.2
• VS Code (optionally, for debugging)

To run the sample, you first need to deploy the CRD (the sample uses the kubecontroller namespace), then start the console application:

$ kubectl create -f KubeController.Sample/deploy/crd.yaml
$ dotnet run KubeController.Sample/

At this point, you can start operating on Example objects in your namespace, and the handler will get executed.