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Creating Events

It is often useful to publish Event objects from the controller Reconcile function.

Events allow users to see what is going on with a particular object, and allow automated processes to see and respond to them.

Getting Events

Recent Events for an object can be viewed by running kubectl describe

Events are published from a Controller using an EventRecorder, which can be created for a Controller by calling GetRecorder(name string) on a Manager.

Name should be identifiable and descriptive as it will appear in the From column of kubectl describe command.

// Annotation for generating RBAC role for writing Events
// +kubebuilder:rbac:groups="",resources=events,verbs=create;patch

// ReconcileContainerSet reconciles a ContainerSet object
type ReconcileContainerSet struct {
  client.Client
  scheme *runtime.Scheme
  recorder record.EventRecorder
}

// newReconciler returns a new reconcile.Reconciler
func newReconciler(mgr manager.Manager) reconcile.Reconciler {
  return &ReconcileContainerSet{
    Client:   mgr.GetClient(),
    scheme:   mgr.GetScheme(),
    recorder: mgr.GetRecorder("containerset-controller"),
  }
}

Writing Events

Anatomy of an Event:

Event(object runtime.Object, eventtype, reason, message string)
  • object is the object this event is about.
  • eventtype is the type of this event, and is either Normal or Warning.
  • reason is the reason this event is generated. It should be short and unique with UpperCamelCase format. The value could appear in switch statements by automation.
  • message is intended to be consumed by humans.

Building on the example introduced in Controller Example, we can add Events to our reconcile logic using recorder as our EventRecorder

  //Reconcile logic up here...

  // Create the resource
  found := &appsv1.Deployment{}
  err = r.Get(context.TODO(), types.NamespacedName{Name: deploy.Name, Namespace: deploy.Namespace}, found)
  if err != nil && errors.IsNotFound(err) {
    log.Printf("Creating Deployment %s/%s\n", deploy.Namespace, deploy.Name)
    err = r.Create(context.TODO(), deploy)
    if err != nil {
      return reconcile.Result{}, err
    }

    // Write an event to the ContainerSet instance with the namespace and name of the 
    // created deployment
    r.recorder.Event(instance, "Normal", "Created", fmt.Sprintf("Created deployment %s/%s", deploy.Namespace, deploy.Name))

  } else if err != nil {
    return reconcile.Result{}, err
  }

  // Preform update
  if !reflect.DeepEqual(deploy.Spec, found.Spec) {
    found.Spec = deploy.Spec
    log.Printf("Updating Deployment %s/%s\n", deploy.Namespace, deploy.Name)
    err = r.Update(context.TODO(), found)
    if err != nil {
      return reconcile.Result{}, err
    }

    // Write an event to the ContainerSet instance with the namespace and name of the 
    // updated deployment
    r.recorder.Event(instance, "Normal", "Updated", fmt.Sprintf("Updated deployment %s/%s", deploy.Namespace, deploy.Name))

  }
  return reconcile.Result{}, nil
}