Merge pull request #158 from pwittrock/docs-gen

Documentation for creating events

Author: Phillip Wittrock

docs/book/SUMMARY.md

@@ -23,6 +23,7 @@
   * [What is a Contoller](basics/what_is_a_controller.md)
   * [Simple Controller Example](basics/simple_controller.md)
   * [Controller Watch Functions](basics/controller_watches.md)
+  * [Creating Events](basics/creating_events.md)
 * Controller-Manager Fundamentals
   * [What is the Controller-Manager](basics/what_is_the_controller_manager.md)
   * [Simple Controller-Manager](basics/simple_controller_manager.md)

docs/book/basics/creating_events.md

@@ -0,0 +1,50 @@
+{% panel style="info", title="Under Development" %}
+This book is being actively developed.
+{% endpanel %}
+
+# 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.
+
+{% panel style="success", title="Getting Events" %}
+Recent Events for an object may be viewed by running `kubectl describe`
+{% endpanel %}
+
+{% method %}
+
+Events are published from a controller using an [EventRecorder](https://github.com/kubernetes/client-go/blob/master/tools/record/event.go#L56),
+which is automatically configured by `kubebuilder create resource`.  The event recorded is
+intended to be used from the `Reconcile` function.
+
+```go
+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.
+
+{% sample lang="go" %}
+```go
+import (
+  metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+  "k8s.io/api/core/v1"
+)
+
+func (bc *BeeController) Reconcile(k types.ReconcileKey) error {
+  b, err := bc.beeclient.
+  	Bees(k.Namespace).
+  	Get(k.Name, metav1.GetOptions{})
+  if err != nil {
+    return err
+  }
+  bc.beerecorder.Event(
+  	b, v1.EventTypeNormal, "ReconcileBee", b.Name)
+  return nil
+}
+```
+{% endmethod %}