Merge pull request #17 from Fedosin/small-cleanup

Remove unused fields

Author: Fedosin

README.md

@@ -14,7 +14,6 @@ This library extracts the battle-tested autoscaling algorithms from Knative Serv
 - **Configurable scale-up/down rates** to prevent flapping
 - **Scale-to-zero capabilities** with grace periods
 - **Support for multiple metrics**
-- **Burst capacity calculations** for traffic absorption
 
 ## Installation
 

algorithm/algorithm_test.go

@@ -42,16 +42,13 @@ func defaultConfig() api.AutoscalerConfig {
 		MaxScaleUpRate:        1000.0,
 		MaxScaleDownRate:      2.0,
 		TargetValue:           100.0,
-		TotalValue:            1000.0,
-		TargetBurstCapacity:   211.0,
 		PanicThreshold:        2.0, // 200%
 		PanicWindowPercentage: 10.0,
 		StableWindow:          60 * time.Second,
 		ScaleDownDelay:        0,
 		MinScale:              0,
 		MaxScale:              0,
 		ActivationScale:       1,
-		Reachable:             true,
 	}
 }
 
@@ -120,7 +117,6 @@ func TestSlidingWindowAutoscaler_Scale_BasicScaling(t *testing.T) {
 		config            api.AutoscalerConfig
 		snapshot          mockMetricSnapshot
 		expectedPodCount  int32
-		expectedEBC       int32 // excess burst capacity
 	}{
 		{
 			name:   "scale up based on stable value",
@@ -131,7 +127,6 @@ func TestSlidingWindowAutoscaler_Scale_BasicScaling(t *testing.T) {
 				readyPodCount: 2, // start with 2 pods instead of 1
 			},
 			expectedPodCount:  3, // ceil(250/100)
-			expectedEBC:       1539, // floor(2*1000 - 211 - 250)
 		},
 		{
 			name:   "scale down based on stable value",
@@ -142,7 +137,6 @@ func TestSlidingWindowAutoscaler_Scale_BasicScaling(t *testing.T) {
 				readyPodCount: 5,
 			},
 			expectedPodCount:  2, // limited by max scale down rate (5/2.0)
-			expectedEBC:       4739, // floor(5*1000 - 211 - 50)
 		},
 		{
 			name: "respect min scale",
@@ -217,11 +211,6 @@ func TestSlidingWindowAutoscaler_Scale_BasicScaling(t *testing.T) {
 			if recommendation.DesiredPodCount != tt.expectedPodCount {
 				t.Errorf("expected pod count %d, got %d", tt.expectedPodCount, recommendation.DesiredPodCount)
 			}
-			if tt.expectedEBC != 0 && (tt.name == "scale up based on stable value" || tt.name == "scale down based on stable value") {
-				if recommendation.ExcessBurstCapacity != tt.expectedEBC {
-					t.Errorf("expected excess burst capacity %d, got %d", tt.expectedEBC, recommendation.ExcessBurstCapacity)
-				}
-			}
 		})
 	}
 }
@@ -356,27 +345,6 @@ func TestSlidingWindowAutoscaler_Scale_ScaleToZero(t *testing.T) {
 	}
 }
 
-func TestSlidingWindowAutoscaler_Scale_NotReachable(t *testing.T) {
-	config := defaultConfig()
-	config.Reachable = false
-
-	autoscaler := NewSlidingWindowAutoscaler(config)
-	now := time.Now()
-
-	// When not reachable, maxScaleDown should be 0
-	snapshot := &mockMetricSnapshot{
-		stableValue:   10, // very low load
-		panicValue:    10,
-		readyPodCount: 5,
-		timestamp:     now,
-	}
-
-	recommendation := autoscaler.Scale(snapshot, now)
-	if recommendation.DesiredPodCount != 1 {
-		t.Errorf("expected pod count 1 (no scale down limit when not reachable), got %d", recommendation.DesiredPodCount)
-	}
-}
-
 func TestSlidingWindowAutoscaler_Scale_ActivationScaleWithZeroMetrics(t *testing.T) {
 	config := defaultConfig()
 	config.ActivationScale = 3
@@ -420,59 +388,6 @@ func TestSlidingWindowAutoscaler_Scale_ReadyPodCountZero(t *testing.T) {
 	}
 }
 
-func TestCalculateExcessBurstCapacity(t *testing.T) {
-	tests := []struct {
-		name                string
-		readyPods           int32
-		totalValue          float64
-		targetBurstCapacity float64
-		observedPanicValue  float64
-		expected            int32
-	}{
-		{
-			name:                "positive excess capacity",
-			readyPods:           5,
-			totalValue:          1000,
-			targetBurstCapacity: 211,
-			observedPanicValue:  500,
-			expected:            4289, // floor(5*1000 - 211 - 500)
-		},
-		{
-			name:                "negative excess capacity",
-			readyPods:           1,
-			totalValue:          1000,
-			targetBurstCapacity: 211,
-			observedPanicValue:  1000,
-			expected:            -211, // floor(1*1000 - 211 - 1000)
-		},
-		{
-			name:                "zero target burst capacity",
-			readyPods:           5,
-			totalValue:          1000,
-			targetBurstCapacity: 0,
-			observedPanicValue:  500,
-			expected:            0,
-		},
-		{
-			name:                "negative target burst capacity (unlimited)",
-			readyPods:           5,
-			totalValue:          1000,
-			targetBurstCapacity: -1,
-			observedPanicValue:  500,
-			expected:            -1,
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			result := calculateExcessBurstCapacity(tt.readyPods, tt.totalValue, tt.targetBurstCapacity, tt.observedPanicValue)
-			if result != tt.expected {
-				t.Errorf("expected %d, got %d", tt.expected, result)
-			}
-		})
-	}
-}
-
 // Tests for PanicModeCalculator
 func TestNewPanicModeCalculator(t *testing.T) {
 	config := defaultConfig()

algorithm/sliding_window.go

@@ -92,10 +92,7 @@ func (a *SlidingWindowAutoscaler) Scale(snapshot api.MetricSnapshot, now time.Ti
 
 	// Calculate scale limits based on current pod count
 	maxScaleUp := int32(math.Ceil(a.config.MaxScaleUpRate * float64(readyPodCount)))
-	maxScaleDown := int32(0)
-	if a.config.Reachable {
-		maxScaleDown = int32(math.Floor(float64(readyPodCount) / a.config.MaxScaleDownRate))
-	}
+	maxScaleDown := int32(math.Floor(float64(readyPodCount) / a.config.MaxScaleDownRate))
 
 	// raw pod counts calculated directly from metrics, prior to applying any rate limits.
 	var rawStablePodCount, rawPanicPodCount int32
@@ -162,7 +159,7 @@ func (a *SlidingWindowAutoscaler) Scale(snapshot api.MetricSnapshot, now time.Ti
 	}
 
 	// Apply scale-down delay if configured
-	if a.config.Reachable && a.maxTimeWindow != nil {
+	if a.maxTimeWindow != nil {
 		a.maxTimeWindow.Record(now, desiredPodCount)
 		desiredPodCount = a.maxTimeWindow.Current()
 	}
@@ -175,17 +172,8 @@ func (a *SlidingWindowAutoscaler) Scale(snapshot api.MetricSnapshot, now time.Ti
 		desiredPodCount = a.config.MaxScale
 	}
 
-	// Calculate excess burst capacity
-	excessBurstCapacity := calculateExcessBurstCapacity(
-		snapshot.ReadyPodCount(),
-		a.config.TotalValue,
-		a.config.TargetBurstCapacity,
-		observedPanicValue,
-	)
-
 	return api.ScaleRecommendation{
 		DesiredPodCount:     desiredPodCount,
-		ExcessBurstCapacity: excessBurstCapacity,
 		ScaleValid:          true,
 		InPanicMode:         inPanicMode,
 	}
@@ -212,19 +200,3 @@ func (a *SlidingWindowAutoscaler) GetConfig() api.AutoscalerConfig {
 	defer a.mu.RUnlock()
 	return a.config
 }
-
-// calculateExcessBurstCapacity computes the excess burst capacity.
-// A negative value means the deployment doesn't have enough capacity
-// to handle the target burst capacity.
-func calculateExcessBurstCapacity(readyPods int32, totalValue, targetBurstCapacity, observedPanicValue float64) int32 {
-	if targetBurstCapacity == 0 {
-		return 0
-	}
-	if targetBurstCapacity < 0 {
-		return -1 // Unlimited
-	}
-
-	totalCapacity := float64(readyPods) * totalValue
-	excessBurstCapacity := math.Floor(totalCapacity - targetBurstCapacity - observedPanicValue)
-	return int32(excessBurstCapacity)
-}

api/types.go

@@ -34,17 +34,9 @@ type AutoscalerConfig struct {
 	MaxScaleDownRate float64
 
 	// TargetValue is the desired value of the scaling metric per pod that we aim to maintain.
-	// This must be less than or equal to TotalValue. Default is 100.0.
+	// Default is 100.0.
 	TargetValue float64
 
-	// TotalValue is the total capacity of the scaling metric that a pod can handle.
-	// Default is 1000.0.
-	TotalValue float64
-
-	// TargetBurstCapacity is the desired burst capacity to maintain without queuing.
-	// If negative, it means unlimited burst capacity. Default is 211.0.
-	TargetBurstCapacity float64
-
 	// PanicThreshold is the threshold for entering panic mode, expressed as a
 	// percentage of desired pod count. If the observed load over the panic window
 	// exceeds this percentage of the current pod count capacity, panic mode is triggered.
@@ -78,11 +70,6 @@ type AutoscalerConfig struct {
 	// ScaleToZeroGracePeriod is the time to wait before scaling to zero
 	// after the service becomes idle. Default is 30s.
 	ScaleToZeroGracePeriod time.Duration
-
-	// Reachable indicates whether the service is reachable (has active traffic).
-	// This affects scale-down behavior. Default is true.
-	// Deprecated: Used in legacy scaling mode to support Knative Serving revisions.
-	Reachable bool
 }
 
 // Metrics represents collected metrics.
@@ -99,11 +86,6 @@ type ScaleRecommendation struct {
 	// DesiredPodCount is the recommended number of pods.
 	DesiredPodCount int32
 
-	// ExcessBurstCapacity is the difference between spare capacity and
-	// configured target burst capacity. Negative values indicate insufficient
-	// capacity for the desired burst level.
-	ExcessBurstCapacity int32
-
 	// ScaleValid indicates whether the recommendation is valid.
 	// False if insufficient data was available.
 	ScaleValid bool

config/config.go

@@ -34,7 +34,6 @@ const (
 	// Default values
 	defaultMaxScaleUpRate           = 1000.0
 	defaultMaxScaleDownRate         = 2.0
-	defaultTargetBurstCapacity      = 211.0
 	defaultPanicWindowPercentage    = 10.0
 	defaultPanicThresholdPercentage = 200.0
 	defaultStableWindow             = 60 * time.Second
@@ -95,12 +94,6 @@ func Load() (*api.AutoscalerConfig, error) {
 	targetValue, err := getEnvFloat("TARGET_VALUE", 0.0)
 	errs.add(err)
 
-	totalValue, err := getEnvFloat("TOTAL_VALUE", 0.0)
-	errs.add(err)
-
-	targetBurstCapacity, err := getEnvFloat("TARGET_BURST_CAPACITY", defaultTargetBurstCapacity)
-	errs.add(err)
-
 	panicThreshold, err := getEnvFloat("PANIC_THRESHOLD_PERCENTAGE", defaultPanicThresholdPercentage)
 	errs.add(err)
 
@@ -131,8 +124,6 @@ func Load() (*api.AutoscalerConfig, error) {
 		MaxScaleUpRate:         maxScaleUpRate,
 		MaxScaleDownRate:       maxScaleDownRate,
 		TargetValue:            targetValue,
-		TotalValue:             totalValue,
-		TargetBurstCapacity:    targetBurstCapacity,
 		PanicThreshold:         panicThreshold,
 		PanicWindowPercentage:  panicWindowPercentage,
 		StableWindow:           stableWindow,
@@ -167,12 +158,6 @@ func LoadFromMap(data map[string]string) (*api.AutoscalerConfig, error) {
 	targetValue, err := parseFloat(data["target-value"], 0.0)
 	errs.add(err)
 
-	totalValue, err := parseFloat(data["total-value"], 0.0)
-	errs.add(err)
-
-	targetBurstCapacity, err := parseFloat(data["target-burst-capacity"], defaultTargetBurstCapacity)
-	errs.add(err)
-
 	panicThreshold, err := parseFloat(data["panic-threshold-percentage"], defaultPanicThresholdPercentage)
 	errs.add(err)
 
@@ -203,8 +188,6 @@ func LoadFromMap(data map[string]string) (*api.AutoscalerConfig, error) {
 		MaxScaleUpRate:         maxScaleUpRate,
 		MaxScaleDownRate:       maxScaleDownRate,
 		TargetValue:            targetValue,
-		TotalValue:             totalValue,
-		TargetBurstCapacity:    targetBurstCapacity,
 		PanicThreshold:         panicThreshold,
 		PanicWindowPercentage:  panicWindowPercentage,
 		StableWindow:           stableWindow,
@@ -239,21 +222,10 @@ func validate(cfg *api.AutoscalerConfig) error {
 		errs.add(fmt.Errorf("scale-down-delay = %v, must be specified with at most second precision", cfg.ScaleDownDelay))
 	}
 
-	// Validate target burst capacity
-	if cfg.TargetBurstCapacity < 0 && cfg.TargetBurstCapacity != -1 {
-		errs.add(fmt.Errorf("target-burst-capacity must be either non-negative or -1 (for unlimited), was: %f", cfg.TargetBurstCapacity))
-	}
-
 	// Validate target values
-	if cfg.TargetValue > cfg.TotalValue {
-		errs.add(fmt.Errorf("target-value = %v, must be less than or equal to total-value = %v", cfg.TargetValue, cfg.TotalValue))
-	}
 	if cfg.TargetValue <= 0 {
 		errs.add(fmt.Errorf("target-value = %v, must be positive", cfg.TargetValue))
 	}
-	if cfg.TotalValue <= 0 {
-		errs.add(fmt.Errorf("total-value = %v, must be positive", cfg.TotalValue))
-	}
 
 	// Validate scale rates
 	if cfg.MaxScaleUpRate <= 1.0 {