fix: abort scaledowns stable RS for canary with traffic routing

- Don't set desiredNewReplica to 0 if rollout is aborted

Signed-off-by: Hui Kang <hui.kang@salesforce.com>

test/e2e/istio_test.go

@@ -197,3 +197,30 @@ func (s *IstioSuite) TestIstioSubsetSplitSingleRoute() {
 		}).
 		ExpectRevisionPodCount("1", 1) // don't scale down old replicaset since it will be within scaleDownDelay
 }
+
+func (s *IstioSuite) TestIstioAbortUpdate() {
+	s.Given().
+		RolloutObjects("@istio/istio-host-split.yaml").
+		When().
+		ApplyManifests().
+		WaitForRolloutStatus("Healthy").
+		Then().
+		When().
+		AbortRollout().
+		WaitForRolloutStatus("Degraded").
+		Then().
+		ExpectRevisionPodCount("1", 1).
+		When().
+		UpdateSpec().
+		WaitForRolloutStatus("Paused").
+		Then().
+		When().
+		PromoteRollout().
+		WaitForRolloutStatus("Healthy").
+		Then().
+		When().
+		AbortRollout().
+		WaitForRolloutStatus("Degraded").
+		Then().
+		ExpectRevisionPodCount("2", 1)
+}

utils/replicaset/canary.go

@@ -107,7 +107,7 @@ func CalculateReplicaCountsForCanary(rollout *v1alpha1.Rollout, newRS *appsv1.Re
 	desiredStableRSReplicaCount := int32(math.Ceil(float64(rolloutSpecReplica) * (1 - (float64(weight) / 100))))
 	desiredNewRSReplicaCount := int32(math.Ceil(float64(rolloutSpecReplica) * (float64(weight) / 100)))
 
-	if rollout.Spec.Strategy.Canary.TrafficRouting != nil {
+	if rollout.Spec.Strategy.Canary.TrafficRouting != nil && !rollout.Status.Abort {
 		return desiredNewRSReplicaCount, rolloutSpecReplica
 	}