make namespace-lifecycle controller more responsive

pkg/controller/namespace/namespace_controller.go

@@ -20,6 +20,8 @@ import (
 	"fmt"
 	"time"
 
+	"golang.org/x/time/rate"
+
 	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -71,7 +73,7 @@ func NewNamespaceController(
 
 	// create the controller so we can inject the enqueue function
 	namespaceController := &NamespaceController{
-		queue:                      workqueue.NewNamedRateLimitingQueue(workqueue.DefaultControllerRateLimiter(), "namespace"),
+		queue:                      workqueue.NewNamedRateLimitingQueue(nsControllerRateLimiter(), "namespace"),
 		namespacedResourcesDeleter: deletion.NewNamespacedResourcesDeleter(kubeClient.CoreV1().Namespaces(), metadataClient, kubeClient.CoreV1(), discoverResourcesFn, finalizerToken),
 	}
 
@@ -99,6 +101,18 @@ func NewNamespaceController(
 	return namespaceController
 }
 
+// nsControllerRateLimiter is tuned for a faster than normal recycle time with default backoff speed and default overall
+// requeing speed.  We do this so that namespace cleanup is reliably faster and we know that the number of namespaces being
+// deleted is smaller than total number of other namespace scoped resources in a cluster.
+func nsControllerRateLimiter() workqueue.RateLimiter {
+	return workqueue.NewMaxOfRateLimiter(
+		// this ensures that we retry namespace deletion at least every minute, never longer.
+		workqueue.NewItemExponentialFailureRateLimiter(5*time.Millisecond, 60*time.Second),
+		// 10 qps, 100 bucket size.  This is only for retry speed and its only the overall factor (not per item)
+		&workqueue.BucketRateLimiter{Limiter: rate.NewLimiter(rate.Limit(10), 100)},
+	)
+}
+
 // enqueueNamespace adds an object to the controller work queue
 // obj could be an *v1.Namespace, or a DeletionFinalStateUnknown item.
 func (nm *NamespaceController) enqueueNamespace(obj interface{}) {