Use patch instead of update to alleviate HRA conflict on webhook (#358)

We sometimes see that integration test fails due to runner replicas not meeting the expected number in a timely manner. After investigating a bit, this turned out to be due to that HRA updates on webhook-based autoscaler and HRA controller are conflicting. This changes the controllers to use Patch instead of Update to make conflicts less likely to happen.

I have also updated the hra controller to use Patch when updating RunnerDeployment, too.

Overall, these changes should make the webhook-based autoscaling more reliable due to less conflicts.

controllers/horizontal_runner_autoscaler_webhook.go

@@ -371,8 +371,6 @@ func (autoscaler *HorizontalRunnerAutoscalerGitHubWebhook) tryScaleUp(ctx contex
 		return nil
 	}
 
-	log := autoscaler.Log.WithValues("horizontalrunnerautoscaler", target.HorizontalRunnerAutoscaler.Name)
-
 	copy := target.HorizontalRunnerAutoscaler.DeepCopy()
 
 	amount := 1
@@ -388,10 +386,8 @@ func (autoscaler *HorizontalRunnerAutoscalerGitHubWebhook) tryScaleUp(ctx contex
 		Replicas:       amount,
 	})
 
-	if err := autoscaler.Client.Update(ctx, copy); err != nil {
-		log.Error(err, "Failed to update horizontalrunnerautoscaler resource")
-
-		return err
+	if err := autoscaler.Client.Patch(ctx, copy, client.MergeFrom(&target.HorizontalRunnerAutoscaler)); err != nil {
+		return fmt.Errorf("patching horizontalrunnerautoscaler to add capacity reservation: %w", err)
 	}
 
 	return nil

controllers/horizontalrunnerautoscaler_controller.go

@@ -18,6 +18,7 @@ package controllers
 
 import (
 	"context"
+	"fmt"
 	"time"
 
 	"github.com/summerwind/actions-runner-controller/github"
@@ -123,10 +124,8 @@ func (r *HorizontalRunnerAutoscalerReconciler) Reconcile(req ctrl.Request) (ctrl
 		copy := rd.DeepCopy()
 		copy.Spec.Replicas = &newDesiredReplicas
 
-		if err := r.Client.Update(ctx, copy); err != nil {
-			log.Error(err, "Failed to update runnerderployment resource")
-
-			return ctrl.Result{}, err
+		if err := r.Client.Patch(ctx, copy, client.MergeFrom(&rd)); err != nil {
+			return ctrl.Result{}, fmt.Errorf("patching runnerdeployment to have %d replicas: %w", newDesiredReplicas, err)
 		}
 	}
 
@@ -167,10 +166,8 @@ func (r *HorizontalRunnerAutoscalerReconciler) Reconcile(req ctrl.Request) (ctrl
 	}
 
 	if updated != nil {
-		if err := r.Status().Update(ctx, updated); err != nil {
-			log.Error(err, "Failed to update horizontalrunnerautoscaler status")
-
-			return ctrl.Result{}, err
+		if err := r.Status().Patch(ctx, updated, client.MergeFrom(&hra)); err != nil {
+			return ctrl.Result{}, fmt.Errorf("patching horizontalrunnerautoscaler status to add cache entry: %w", err)
 		}
 	}
 

controllers/integration_test.go

@@ -244,6 +244,7 @@ var _ = Context("INTEGRATION: Inside of a new namespace", func() {
 
 				ExpectRunnerSetsCountEventuallyEquals(ctx, ns.Name, 1)
 				ExpectRunnerSetsManagedReplicasCountEventuallyEquals(ctx, ns.Name, 3)
+				ExpectHRAStatusCacheEntryLengthEventuallyEquals(ctx, ns.Name, name, 1)
 			}
 
 			{
@@ -601,6 +602,21 @@ var _ = Context("INTEGRATION: Inside of a new namespace", func() {
 	})
 })
 
+func ExpectHRAStatusCacheEntryLengthEventuallyEquals(ctx context.Context, ns string, name string, value int, optionalDescriptions ...interface{}) {
+	EventuallyWithOffset(
+		1,
+		func() int {
+			var hra actionsv1alpha1.HorizontalRunnerAutoscaler
+
+			err := k8sClient.Get(ctx, types.NamespacedName{Namespace: ns, Name: name}, &hra)
+
+			ExpectWithOffset(1, err).NotTo(HaveOccurred(), "failed to get test HRA resource")
+
+			return len(hra.Status.CacheEntries)
+		},
+		time.Second*5, time.Millisecond*500).Should(Equal(value), optionalDescriptions...)
+}
+
 func ExpectHRADesiredReplicasEquals(ctx context.Context, ns, name string, desired int, optionalDescriptions ...interface{}) {
 	var rd actionsv1alpha1.HorizontalRunnerAutoscaler