From f3e5c35c081355f34c7d53947ebfb55300fe8162 Mon Sep 17 00:00:00 2001
From: Maskym Vavilov <mvavilov@redhat.com>
Date: Mon, 8 Apr 2024 12:22:41 +0100
Subject: [PATCH] GH-35 randomize validation reconcilation

---
 internal/common/helper.go                   | 21 +++++++++++
 internal/common/helper_test.go              | 41 +++++++++++++++++++++
 internal/controller/dnsrecord_controller.go | 12 ++++--
 3 files changed, 71 insertions(+), 3 deletions(-)
 create mode 100644 internal/common/helper.go
 create mode 100644 internal/common/helper_test.go

diff --git a/internal/common/helper.go b/internal/common/helper.go
new file mode 100644
index 0000000..1214349
--- /dev/null
+++ b/internal/common/helper.go
@@ -0,0 +1,21 @@
+package common
+
+import (
+	"time"
+
+	"k8s.io/apimachinery/pkg/util/rand"
+)
+
+// RandomizeDuration randomizes duration for a given variance.
+// variance is expected to be of a format 0.1 for 10%, 0.5 for 50% and so on
+func RandomizeDuration(variance float64, duration time.Duration) time.Duration {
+	// we won't go smaller than a second - using milliseconds to have a relatively big number to randomize
+	millisecond := float64(duration.Milliseconds())
+
+	upperLimit := millisecond * (1.0 + variance)
+	lowerLimit := millisecond * (1.0 - variance)
+
+	return time.Millisecond * time.Duration(rand.Int63nRange(
+		int64(lowerLimit),
+		int64(upperLimit)))
+}
diff --git a/internal/common/helper_test.go b/internal/common/helper_test.go
new file mode 100644
index 0000000..f3bb466
--- /dev/null
+++ b/internal/common/helper_test.go
@@ -0,0 +1,41 @@
+package common
+
+import (
+	"testing"
+	"time"
+)
+
+func TestRandomizeDuration(t *testing.T) {
+	testIterations := 100
+
+	tests := []struct {
+		name     string
+		variance float64
+		duration time.Duration
+	}{
+		{
+			name:     "returns valid duration in range",
+			variance: 0.5,
+			duration: time.Second * 5,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			i := 0
+			for i < testIterations {
+				if got := RandomizeDuration(tt.variance, tt.duration); !isValidVariance(tt.duration, got, tt.variance) {
+					t.Errorf("RandomizeDuration() invalid randomization; got = %v", got.String())
+				}
+				i++
+			}
+		})
+	}
+}
+
+func isValidVariance(duration, randomizedDuration time.Duration, variance float64) bool {
+	upperLimit := float64(duration.Milliseconds()) + float64(duration.Milliseconds())*variance
+	lowerLimmit := float64(duration.Milliseconds()) - float64(duration.Milliseconds())*variance
+
+	return float64(randomizedDuration.Milliseconds()) > lowerLimmit &&
+		float64(randomizedDuration.Milliseconds()) < upperLimit
+}
diff --git a/internal/controller/dnsrecord_controller.go b/internal/controller/dnsrecord_controller.go
index 48b6098..f614821 100644
--- a/internal/controller/dnsrecord_controller.go
+++ b/internal/controller/dnsrecord_controller.go
@@ -37,17 +37,19 @@ import (
 	externaldnsprovider "sigs.k8s.io/external-dns/provider"
 
 	"github.com/kuadrant/dns-operator/api/v1alpha1"
+	"github.com/kuadrant/dns-operator/internal/common"
 	externaldnsplan "github.com/kuadrant/dns-operator/internal/external-dns/plan"
 	"github.com/kuadrant/dns-operator/internal/provider"
 )
 
 const (
-	DNSRecordFinalizer = "kuadrant.io/dns-record"
+	DNSRecordFinalizer        = "kuadrant.io/dns-record"
+	validationRequeueVariance = 0.5
 )
 
 var (
 	defaultRequeueTime    time.Duration
-	validationRequeueTime = time.Second * 5
+	validationRequeueTime = time.Millisecond * 5000
 	noRequeueDuration     = time.Duration(0)
 	validFor              time.Duration
 	reconcileStart                    = metav1.Time{}
@@ -69,6 +71,10 @@ func (r *DNSRecordReconciler) Reconcile(ctx context.Context, req ctrl.Request) (
 	logger := log.FromContext(ctx)
 
 	reconcileStart = metav1.Now()
+
+	// randomize validation reconcile delay
+	validationRequeueTime = common.RandomizeDuration(validationRequeueVariance, validationRequeueTime)
+
 	previous := &v1alpha1.DNSRecord{}
 	err := r.Client.Get(ctx, client.ObjectKey{Namespace: req.Namespace, Name: req.Name}, previous)
 	if err != nil {
@@ -138,7 +144,7 @@ func (r *DNSRecordReconciler) updateStatus(ctx context.Context, previous, curren
 		if apierrors.IsConflict(updateError) {
 			return ctrl.Result{Requeue: true}, nil
 		}
-		return ctrl.Result{}, updateError
+		return ctrl.Result{RequeueAfter: requeueAfter}, updateError
 	}
 	return ctrl.Result{RequeueAfter: requeueAfter}, nil
 }