Make EphemeralRunnerController MaxConcurrentReconciles configurable (#3832)

Co-authored-by: Bassem Dghaidi <568794+Link-@users.noreply.github.com>

controllers/actions.github.com/ephemeralrunner_controller.go

@@ -823,12 +823,14 @@ func (r *EphemeralRunnerReconciler) deleteRunnerFromService(ctx context.Context,
 }
 
 // SetupWithManager sets up the controller with the Manager.
-func (r *EphemeralRunnerReconciler) SetupWithManager(mgr ctrl.Manager) error {
-	return ctrl.NewControllerManagedBy(mgr).
-		For(&v1alpha1.EphemeralRunner{}).
-		Owns(&corev1.Pod{}).
-		WithEventFilter(predicate.ResourceVersionChangedPredicate{}).
-		Complete(r)
+func (r *EphemeralRunnerReconciler) SetupWithManager(mgr ctrl.Manager, opts ...Option) error {
+	return builderWithOptions(
+		ctrl.NewControllerManagedBy(mgr).
+			For(&v1alpha1.EphemeralRunner{}).
+			Owns(&corev1.Pod{}).
+			WithEventFilter(predicate.ResourceVersionChangedPredicate{}),
+		opts,
+	).Complete(r)
 }
 
 func runnerContainerStatus(pod *corev1.Pod) *corev1.ContainerStatus {

controllers/actions.github.com/options.go

@@ -0,0 +1,56 @@
+package actionsgithubcom
+
+import (
+	"sigs.k8s.io/controller-runtime/pkg/builder"
+	"sigs.k8s.io/controller-runtime/pkg/controller"
+)
+
+// Options is the optional configuration for the controllers, which can be
+// set via command-line flags or environment variables.
+type Options struct {
+	// RunnerMaxConcurrentReconciles is the maximum number of concurrent Reconciles which can be run
+	// by the EphemeralRunnerController.
+	RunnerMaxConcurrentReconciles int
+}
+
+// OptionsWithDefault returns the default options.
+// This is here to maintain the options and their default values in one place,
+// rather than having to correlate those in multiple places.
+func OptionsWithDefault() Options {
+	return Options{
+		RunnerMaxConcurrentReconciles: 2,
+	}
+}
+
+type Option func(*controller.Options)
+
+// WithMaxConcurrentReconciles sets the maximum number of concurrent Reconciles which can be run.
+//
+// This is useful to improve the throughput of the controller, but it may also increase the load on the API server and
+// the external service (e.g. GitHub API). The default value is 1, as defined by the controller-runtime.
+//
+// See https://github.com/actions/actions-runner-controller/issues/3021 for more information
+// on real-world use cases and the potential impact of this option.
+func WithMaxConcurrentReconciles(n int) Option {
+	return func(b *controller.Options) {
+		b.MaxConcurrentReconciles = n
+	}
+}
+
+// builderWithOptions applies the given options to the provided builder, if any.
+// This is a helper function to avoid the need to import the controller-runtime package in every reconciler source file
+// and the command package that creates the controller.
+// This is also useful for reducing code duplication around setting controller options in
+// multiple reconcilers.
+func builderWithOptions(b *builder.Builder, opts []Option) *builder.Builder {
+	if len(opts) == 0 {
+		return b
+	}
+
+	var controllerOpts controller.Options
+	for _, opt := range opts {
+		opt(&controllerOpts)
+	}
+
+	return b.WithOptions(controllerOpts)
+}