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DEVELOPMENT.md

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Development

You will see in the code ./operators defines how we filter and act on events

Here is a simple example that adds a label to the kubeops pod when it is installed in the cluster as a deployment (through the helm chart).

type ExamplePodOperator struct{}

func (ExamplePodOperator) WithElectedResource() interface{} {

	return &v1.Pod{}
}

func (ExamplePodOperator) WithEventType() []watch.EventType {

	return []watch.EventType {watch.Added, watch.Modified}
}

func (ExamplePodOperator) OnEvent(msg subscription.Message) {
	// This is a silly example that checks the kubeops pod
	// When we add, delete or modify the pod
	// Then we add an example label to it.
	pod := msg.Event.Object.(*v1.Pod)
	if pod.Labels["app.kubernetes.io/name"] == "kubeops" {

		log.Debugf("%v",pod)
		existingLabels := pod.Labels

		if _, ok := existingLabels["sneaky-label"]; !ok {
			//Let's add a label...
			existingLabels["sneaky-label"] = "is-an-example"
			pod.SetLabels(existingLabels)
			// Invoke a new pod client interface
			pi := msg.Client.CoreV1().Pods(pod.Namespace)
			if _, err := pi.Update(pod); err != nil {
				log.Error(err)
			}else {
				log.Debug("Added a new label...")
			}
		}
	}
}

This example struct adheres to the ISubscription interface.

Once you've created the operator add it into the main.go as a subscription.

  registry := &subscription.Registry{
    Subscriptions: []subscription.ISubscription{
      operators.ExamplePodOperator{},
      operators.ExampleDeploymentOperator{},

    },
  }

Anything you have registered in the watch channel you can filter for in the ISubscription

type ISubscription interface {
	OnEvent(msg Message)
	WithFilter() interface{}
    WithEventType() []watch.EventType
}
  • The WithFilter is important as it allows the runtime to selectively send messages to your handler OnEvent You'll also get the kubernetes client interface passed through to you to act on any incoming messages.
  • The WithEvent function is important as it allows selective event types to be filtered out of the incoming operator handler.
  registry := &subscription.Registry{
    Subscriptions: []subscription.ISubscription{
      operators.ExamplePodOperator{},

    },
  }

That's it - now you will get filtered watch events for your type (Providing they are in the lib/watcher GenerateWatchers channel setup.)

Adding watches for different Kubernetes resources

Out of the box you get some channels registered in lib/watcher/deployment

//main.go
  runtime.EventBuffer(context,client, registry,[]kubernetes.IObject{
    client.CoreV1().Pods(""),
    client.AppsV1().Deployments(""),
    client.CoreV1().ConfigMaps(""),
  })

These will automatically get picked up in the runtime.

Custom Resource Definitions with Kubebuilder

https://book.kubebuilder.io/quick-start.html#create-a-project