Make EphemeralRunnerController MaxConcurrentReconciles configurable

controllers/actions.github.com/ephemeralrunner_controller.go

@@ -844,12 +844,14 @@ 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 +1,90 @@
+package actionsgithubcom
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+
+	"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 {
+	// RunnerMaxConcuncurrentReconciles is the maximum number of concurrent Reconciles which can be run
+	// by the EphemeralRunnerController.
+	RunnerMaxConcuncurrentReconciles 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{
+		RunnerMaxConcuncurrentReconciles: 1,
+	}
+}
+
+// LoadEnv loads the options from the environment variables.
+// This updates the option value only if the environment variable is set.
+// If the option is already set (via a command-line flag), the value from the environment variable takes precedence.
+func (o *Options) LoadEnv() error {
+	v, err := o.getEnvInt("RUNNER_MAX_CONCURRENT_RECONCILES")
+	if err != nil {
+		return err
+	}
+
+	if v != nil {
+		o.RunnerMaxConcuncurrentReconciles = *v
+	}
+
+	return nil
+}
+
+func (o *Options) getEnvInt(name string) (*int, error) {
+	s := os.Getenv(name)
+	if s == "" {
+		return nil, nil
+	}
+
+	v, err := strconv.Atoi(s)
+	if err != nil {
+		return nil, fmt.Errorf("failed to convert %s=%s to int: %w", name, s, err)
+	}
+
+	return &v, nil
+}
+
+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)
+}