CanSupportMe.Operator 1.0.0-nightly.21

CanSupportMe.Operator

CAUTION

This is still in development and is not yet ready for production use.
The biggest issue is a timeout on the connection to the Kubernetes API that is not yet resolving itself.
This is being investigated.

Overview

What is this?

This package will allow you to create a simple Kubernetes Operator in .NET.
It can pick up changes to CRDs, ConfigMaps or Secrets and say if it was added, modified or deleted. It can check if a CRD exists as well as retrieve, create, replace and delete configmaps and secrets. It can also update the status of any manifest that supports it.

What isn't this?

It is not a full blown Kubernetes Operator SDK. These exist and, if desired, this package can be used in conjunction with them. It has been developed to do what the project required and nothing more however this will likely fit the requirements of many similar projects too.

Getting Started

Prerequisites

• .NET 8 or later
• A Kubernetes cluster (either local or remote)
• Sufficient access to the cluster to read and watch secrets (for the demo)
• The ability to create a service account and cluster role binding with access to the resources you will be watching or creating
• A suitable pair of test secrets, created using the following bash script:

  kubectl apply -f - <<EOF
  apiVersion: v1
  kind: Secret
  metadata:
    name: test-secret-with-label
    namespace: default
    labels:
      app.kubernetes.io/managed-by: DemoOperator
  stringData:
    notImportant: SomeValue
  type: Opaque
  ---
  apiVersion: v1
  kind: Secret
  metadata:
    name: test-secret-without-label
    namespace: default
  stringData:
    notImportant: SomeValue
  type: Opaque
  EOF
  

Create a new .NET console application

Create a new .NET 8 console application and call it CanSupportMe.Operator.Demo.

Install the package

dotnet add package CanSupportMe.Operator

Create a simple operator

Where you are defining your services in Program.cs add the following:

services.AddOperator(options =>
{
	options.OperatorName = "DemoOperator";

	options.Group = "";
	options.Kind = "Secret";
	options.Version = "v1";
	options.Plural = "secrets";
	options.Scope = ResourceScope.Namespaced;

	# This limits the response to just secrets labelled with "app.kubernetes.io/managed-by=DemoOperator"
	options.LabelFilters.Add("app.kubernetes.io/managed-by", "DemoOperator");

	options.OnAdded = async (kind, name, @namespace, item, dataObjectManager) =>
	{
		Log.Information("A secret called {Name} in {Namespace} of type {Type} with {ItemCount} item(s) was added", name, @namespace, item.Type, item.Data?.Count);
	};

	# Note this is only required if pointing at a cluster/user that doesn't contain a token in KUBECONFIG
	options.FailoverToken = FAILOVER_TOKEN; 
});

Running the project will show it connecting to the cluster and watching for changes to secrets. It will then show test-secret-with-label as being added and not mention test-secret-without-label.

Retrieve service token

If a options.FailoverToken is required, one can be generated using the following bash script:

export SERVICEACCOUNT="cansupportme-operator"

kubectl apply -f - <<EOF
apiVersion: v1
kind: Secret
metadata:
  name: ${SERVICEACCOUNT}-token
  namespace: default
  annotations:
    kubernetes.io/service-account.name: $SERVICEACCOUNT
type: kubernetes.io/service-account-token
EOF

export TOKEN=$(kubectl -n default get secret ${SERVICEACCOUNT}-token -o jsonpath='{.data.token}' | base64 --decode)
echo $TOKEN

Listening for Custom Resource Definition (CRD) Changes

The more likely scenario for an operator is to listen out for CRD changes. The following example shows the simple file you need to create and how to configure the operator. Setting up a CRD is beyond the scope of this package's documentation.

Create a new file called MyCrd.cs in the root of the project and add the following:

using CanSupportMe.Operator.Interfaces;
using CanSupportMe.Operator.Models;
using System.Text.Json.Serialization;

namespace CanSupportMe.Operator.Demo;

public class MyCrd : KubernetesResource<MySpec, MyStatus>
{
}

public class MySpec : IKubernetesSpec
{
	[JsonPropertyName("secretName")]
	public required string SecretName { get; set; }
}

public class MyStatus : IKubernetesStatus
{
	[JsonPropertyName("status")]
	public required string Status { get; set; }
}

Then, in Program.cs add the following:

services.AddOperator<MySpec, MyStatus>(options =>
{
	options.OperatorName = "SeqApiKeyOperator";

	options.Group = "demokeys.cansupport.me";
	options.Kind = "DemoApiKey";
	options.Version = "v1alpha1";
	options.Plural = "demokeys";
	options.Scope = ResourceScope.Namespaced;

	options.OnAdded = async (kind, name, @namespace, item, dataObjectManager) =>
	{
		Log.Information("On {kind} Add: {Name} to {Namespace} to create secret called {SecretName}", kind, name, @namespace, item.Spec.SecretName);

		var existingSecret = await dataObjectManager.Get("Secret", item.Spec.SecretName, @namespace);
		if (existingSecret.IsSuccess)
		{
			Log.Debug("Secret {SecretName} already exists in {Namespace} and has a value of {ExistingValue}", 
				existingSecret.Value.Metadata.Name, 
				existingSecret.Value.Metadata.Namespace,
				existingSecret.Value.Data["seqApiKey"]);
		}
		else
		{
			Log.Debug("Secret {SecretName} does not exist in {Namespace}", item.Spec.SecretName, @namespace);

			await dataObjectManager.Create("Secret", item.Spec.SecretName, @namespace, new Dictionary<string, string>
			{
				{ "seqApiKey", $"Some random string at {DateTime.UtcNow}" }
			}, labels: new()
			{
				{ "cansupport.me/owned-by", name }
			});
		}
	};

	options.FailoverToken = FAILOVER_TOKEN;
});