feat: dynamic assignment of the scale down threshold flags

cluster-autoscaler/main.go

@@ -233,6 +233,16 @@ var (
 	forceDaemonSets                   = flag.Bool("force-ds", false, "Blocks scale-up of node groups too small for all suitable Daemon Sets pods.")
 )
 
+func isFlagPassed(name string) bool {
+	found := false
+	flag.Visit(func(f *flag.Flag) {
+		if f.Name == name {
+			found = true
+		}
+	})
+	return found
+}
+
 func createAutoscalingOptions() config.AutoscalingOptions {
 	minCoresTotal, maxCoresTotal, err := parseMinMaxFlag(*coresTotal)
 	if err != nil {
@@ -253,12 +263,22 @@ func createAutoscalingOptions() config.AutoscalingOptions {
 	if *maxDrainParallelismFlag > 1 && !*parallelDrain {
 		klog.Fatalf("Invalid configuration, could not use --max-drain-parallelism > 1 if --parallel-drain is false")
 	}
+	// cases we have 3, 1. Mebd was set, but msdp was not, 2 msdp was set, but mebd was not, 3. both were set
+	if isFlagPassed("max-empty-bulk-delete") && !isFlagPassed("max-scale-down-parallelism") {
+		// Set maxScaleDownParallelismFlag = maxEmptyBulkDeleteFlag to avoid inconsistent deletion thresholds for the legacy planner and the new actuator.
+		*maxScaleDownParallelismFlag = *maxEmptyBulkDeleteFlag
+	} else if !isFlagPassed("max-empty-bulk-delete") && isFlagPassed("max-scale-down-parallelism") {
+		// Set maxEmptyBulkDeleteFlag = maxScaleDownParallelismFlag to avoid inconsistent deletion thresholds for the legacy planner and the new actuator.
+		*maxEmptyBulkDeleteFlag = *maxScaleDownParallelismFlag
+	} else {
+		maxDeletionSize := int(math.Max(float64(*maxEmptyBulkDeleteFlag), float64(*maxScaleDownParallelismFlag)))
+		*maxEmptyBulkDeleteFlag = maxDeletionSize
+		*maxScaleDownParallelismFlag = maxDeletionSize
+
+	}
 
 	// In order to avoid inconsistent deletion thresholds for the legacy planner and the new actuator,
 	// we set the deletion threshold to the maximum of the two flags that are used to filter down deletion candidates.
-	maxDeletionSize := int(math.Max(float64(*maxEmptyBulkDeleteFlag), float64(*maxScaleDownParallelismFlag)))
-	*maxEmptyBulkDeleteFlag = maxDeletionSize
-	*maxScaleDownParallelismFlag = maxDeletionSize
 	return config.AutoscalingOptions{
 		NodeGroupDefaults: config.NodeGroupAutoscalingOptions{
 			ScaleDownUtilizationThreshold:    *scaleDownUtilizationThreshold,