Only send cloud events when condition changes

docs/events.md

@@ -51,6 +51,11 @@ retrieving those events using the `kubectl describe` command. Tekton can also em
 When you [configure a sink](install.md#configuring-cloudevents-notifications), Tekton emits
 events as described in the table below.
 
+Tekton sends cloud events in a parallel routine to allow for retries without blocking the
+reconciler. A routine is started every time the `Succeeded` condition changes - either state,
+reason or message. Retries are sent using an exponential back-off strategy. 
+Because of retries, events are not guaranteed to be sent to the target sink in the order they happened.
+
 Resource      |Event    |Event Type
 :-------------|:-------:|:----------------------------------------------------------
 `TaskRun`     | `Started` | `dev.tekton.event.taskrun.started.v1`

pkg/reconciler/events/event.go

@@ -58,9 +58,12 @@ func Emit(ctx context.Context, beforeCondition *apis.Condition, afterCondition *
 	sendKubernetesEvents(recorder, beforeCondition, afterCondition, object)
 
 	if sendCloudEvents {
-		err := cloudevent.SendCloudEventWithRetries(ctx, object)
-		if err != nil {
-			logger.Warnf("Failed to emit cloud events %v", err.Error())
+		// Only send events if the new condition represents a change
+		if !equality.Semantic.DeepEqual(beforeCondition, afterCondition) {
+			err := cloudevent.SendCloudEventWithRetries(ctx, object)
+			if err != nil {
+				logger.Warnf("Failed to emit cloud events %v", err.Error())
+			}
 		}
 	}
 }