feat: external calculation via gRPC servers

CHANGELOG.md

@@ -53,7 +53,7 @@ To learn more about active deprecations, we recommend checking [GitHub Discussio
 ### Improvements
 
 - **General:**: Add ScaledObject/ScaledJob names to output of `kubectl get triggerauthentication/clustertriggerauthentication` ([#796](https://github.com/kedacore/keda/issues/796))
-
+- **General**: Add ComplexScalingLogic structure to SO for advanced scaling options ([#3567](https://github.com/kedacore/keda/issues/3567)) and ([#2440](https://github.com/kedacore/keda/issues/2440))
 ### Fixes
 
 - **General**: Metrics server exposes Prometheus metrics ([#4776](https://github.com/kedacore/keda/issues/4776))

Makefile

@@ -160,14 +160,16 @@ proto-gen: protoc-gen ## Generate Liiklus, ExternalScaler and MetricsService pro
 	PATH="$(LOCALBIN):$(PATH)" protoc -I vendor --proto_path=pkg/metricsservice/api metrics.proto --go_out=pkg/metricsservice/api --go-grpc_out=pkg/metricsservice/api
 
 .PHONY: mockgen-gen
-mockgen-gen: mockgen pkg/mock/mock_scaling/mock_interface.go pkg/mock/mock_scaling/mock_executor/mock_interface.go pkg/mock/mock_scaler/mock_scaler.go pkg/mock/mock_scale/mock_interfaces.go pkg/mock/mock_client/mock_interfaces.go pkg/scalers/liiklus/mocks/mock_liiklus.go pkg/mock/mock_secretlister/mock_interfaces.go
+mockgen-gen: mockgen pkg/mock/mock_scaling/mock_interface.go pkg/mock/mock_scaling/mock_executor/mock_interface.go pkg/mock/mock_scaler/mock_scaler.go pkg/mock/mock_scale/mock_interfaces.go pkg/mock/mock_client/mock_interfaces.go pkg/scalers/liiklus/mocks/mock_liiklus.go pkg/mock/mock_secretlister/mock_interfaces.go pkg/mock/mock_externalscaling/mock_externalscaling.go
 
 pkg/mock/mock_scaling/mock_interface.go: pkg/scaling/scale_handler.go
 	$(MOCKGEN) -destination=$@ -package=mock_scaling -source=$^
 pkg/mock/mock_scaling/mock_executor/mock_interface.go: pkg/scaling/executor/scale_executor.go
 	$(MOCKGEN) -destination=$@ -package=mock_executor -source=$^
 pkg/mock/mock_scaler/mock_scaler.go: pkg/scalers/scaler.go
 	$(MOCKGEN) -destination=$@ -package=mock_scalers -source=$^
+pkg/mock/mock_externalscaling/mock_externalscaling.go: pkg/externalscaling/api/externalCalculation_grpc.pb.go
+	$(MOCKGEN) -destination=$@ -package=mock_externalscaling -source=$^
 pkg/mock/mock_secretlister/mock_interfaces.go: vendor/k8s.io/client-go/listers/core/v1/secret.go
 	mkdir -p pkg/mock/mock_secretlister
 	$(MOCKGEN) k8s.io/client-go/listers/core/v1 SecretLister,SecretNamespaceLister > $@

apis/keda/v1alpha1/condition_types.go

@@ -32,6 +32,8 @@ const (
 	ConditionActive ConditionType = "Active"
 	// ConditionFallback specifies that the resource has a fallback active.
 	ConditionFallback ConditionType = "Fallback"
+	// ConditionExternalFallback specifies that the resource has external fallback active.
+	ConditionExternalFallback ConditionType = "ExternalFallback"
 	// ConditionPaused specifies that the resource is paused.
 	ConditionPaused ConditionType = "Paused"
 )
@@ -88,6 +90,8 @@ func (c *Conditions) AreInitialized() bool {
 	foundActive := false
 	foundFallback := false
 	foundPaused := false
+	foundExternalFallback := false
+
 	if *c != nil {
 		for _, condition := range *c {
 			if condition.Type == ConditionReady {
@@ -113,14 +117,19 @@ func (c *Conditions) AreInitialized() bool {
 				break
 			}
 		}
+		for _, condition := range *c {
+			if condition.Type == ConditionExternalFallback {
+				foundExternalFallback = true
+			}
+		}
 	}
 
-	return foundReady && foundActive && foundFallback && foundPaused
+	return foundReady && foundActive && foundFallback && foundPaused && foundExternalFallback
 }
 
 // GetInitializedConditions returns Conditions initialized to the default -> Status: Unknown
 func GetInitializedConditions() *Conditions {
-	return &Conditions{{Type: ConditionReady, Status: metav1.ConditionUnknown}, {Type: ConditionActive, Status: metav1.ConditionUnknown}, {Type: ConditionFallback, Status: metav1.ConditionUnknown}, {Type: ConditionPaused, Status: metav1.ConditionUnknown}}
+	return &Conditions{{Type: ConditionReady, Status: metav1.ConditionUnknown}, {Type: ConditionActive, Status: metav1.ConditionUnknown}, {Type: ConditionFallback, Status: metav1.ConditionUnknown}, {Type: ConditionPaused, Status: metav1.ConditionUnknown}, {Type: ConditionExternalFallback, Status: metav1.ConditionUnknown}}
 }
 
 // IsTrue is true if the condition is True
@@ -171,6 +180,14 @@ func (c *Conditions) SetFallbackCondition(status metav1.ConditionStatus, reason
 	c.setCondition(ConditionFallback, status, reason, message)
 }
 
+// SetExternalFallbackCondition modifies ExternalFallback Condition according to input parameters (for ExternalCalculators)
+func (c *Conditions) SetExternalFallbackCondition(status metav1.ConditionStatus, reason string, message string) {
+	if *c == nil {
+		c = GetInitializedConditions()
+	}
+	c.setCondition(ConditionExternalFallback, status, reason, message)
+}
+
 // SetPausedCondition modifies Paused Condition according to input parameters
 func (c *Conditions) SetPausedCondition(status metav1.ConditionStatus, reason string, message string) {
 	if *c == nil {
@@ -211,6 +228,13 @@ func (c *Conditions) GetPausedCondition() Condition {
 	return c.getCondition(ConditionPaused)
 }
 
+func (c *Conditions) GetExternalFallbackCondition() Condition {
+	if *c == nil {
+		c = GetInitializedConditions()
+	}
+	return c.getCondition(ConditionExternalFallback)
+}
+
 func (c Conditions) getCondition(conditionType ConditionType) Condition {
 	for i := range c {
 		if c[i].Type == conditionType {

apis/keda/v1alpha1/scaledobject_types.go

@@ -102,6 +102,31 @@ type AdvancedConfig struct {
 	HorizontalPodAutoscalerConfig *HorizontalPodAutoscalerConfig `json:"horizontalPodAutoscalerConfig,omitempty"`
 	// +optional
 	RestoreToOriginalReplicaCount bool `json:"restoreToOriginalReplicaCount,omitempty"`
+	// +optional
+	ComplexScalingLogic ComplexScalingLogic `json:"complexScalingLogic,omitempty"`
+}
+
+// ComplexScalingLogic describes advanced scaling logic options like formula
+// and gRPC server for external calculations
+type ComplexScalingLogic struct {
+	// +optional
+	ExternalCalculations []ExternalCalculation `json:"externalCalculators,omitempty"`
+	// +optional
+	Formula string `json:"formula,omitempty"`
+	// +optional
+	Target string `json:"target,omitempty"`
+}
+
+// ExternalCalculation structure describes name and URL of a gRPC server
+// that KEDA can connect to with collected metrics and modify them. Each server
+// has a timeout and tls certification. If certDir is left empty, it will
+// connect with insecure.NewCredentials()
+type ExternalCalculation struct {
+	Name    string `json:"name"`
+	URL     string `json:"url"`
+	Timeout string `json:"timeout"`
+	// +optional
+	CertificateDirectory string `json:"certDir"`
 }
 
 // HorizontalPodAutoscalerConfig specifies horizontal scale config
@@ -141,6 +166,10 @@ type ScaledObjectStatus struct {
 	// +optional
 	ResourceMetricNames []string `json:"resourceMetricNames,omitempty"`
 	// +optional
+	CompositeScalerName string `json:"compositeScalerName,omitempty"`
+	// +optional
+	ExternalCalculationHealth map[string]HealthStatus `json:"externalCalculationHealth,omitempty"`
+	// +optional
 	Conditions Conditions `json:"conditions,omitempty"`
 	// +optional
 	Health map[string]HealthStatus `json:"health,omitempty"`

apis/keda/v1alpha1/scaledobject_webhook.go

@@ -19,7 +19,11 @@ package v1alpha1
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
+	"reflect"
+	"strconv"
+	"time"
 
 	appsv1 "k8s.io/api/apps/v1"
 	autoscalingv2 "k8s.io/api/autoscaling/v2"
@@ -213,6 +217,16 @@ func verifyScaledObjects(incomingSo *ScaledObject, action string) error {
 		}
 	}
 
+	// verify ComplexScalingLogic structure if defined in ScaledObject
+	if incomingSo.Spec.Advanced != nil && !reflect.DeepEqual(incomingSo.Spec.Advanced.ComplexScalingLogic, ComplexScalingLogic{}) {
+		_, _, err = ValidateComplexScalingLogic(incomingSo, []autoscalingv2.MetricSpec{})
+		if err != nil {
+			scaledobjectlog.Error(err, "error validating ComplexScalingLogic")
+			prommetrics.RecordScaledObjectValidatingErrors(incomingSo.Namespace, action, "complex-scaling-logic")
+
+			return err
+		}
+	}
 	return nil
 }
 
@@ -297,3 +311,109 @@ func verifyCPUMemoryScalers(incomingSo *ScaledObject, action string) error {
 	}
 	return nil
 }
+
+// ValidateComplexScalingLogic validates all combinations of given arguments
+// and their values
+func ValidateComplexScalingLogic(so *ScaledObject, specs []autoscalingv2.MetricSpec) (float64, autoscalingv2.MetricTargetType, error) {
+	csl := so.Spec.Advanced.ComplexScalingLogic
+
+	// if Formula AND ExternalCalculations is empty, return an error
+	if csl.Formula == "" && len(csl.ExternalCalculations) < 1 {
+		return -1, autoscalingv2.MetricTargetType(""), fmt.Errorf("error atleast one ComplexScalingLogic function needs to be specified (formula or externalCalculation)")
+	}
+
+	var num float64
+	var metricType autoscalingv2.MetricTargetType
+
+	// validate formula if not empty
+	if err := validateCSLformula(so); err != nil {
+		err := errors.Join(fmt.Errorf("error validating formula in ComplexScalingLogic"), err)
+		return -1, autoscalingv2.MetricTargetType(""), err
+	}
+	// validate externalCalculators if not empty
+	if err := validateCSLexternalCalculations(csl); err != nil {
+		err := errors.Join(fmt.Errorf("error validating externalCalculator in ComplexScalingLogic"), err)
+		return -1, autoscalingv2.MetricTargetType(""), err
+	}
+	// validate target if not empty
+	num, metricType, err := validateCSLtarget(csl, specs)
+	if err != nil {
+		err := errors.Join(fmt.Errorf("error validating target in ComplexScalingLogic"), err)
+		return -1, autoscalingv2.MetricTargetType(""), err
+	}
+	return num, metricType, nil
+}
+
+func validateCSLformula(so *ScaledObject) error {
+	csl := so.Spec.Advanced.ComplexScalingLogic
+
+	// if formula is empty, nothing to validate
+	if csl.Formula == "" {
+		return nil
+	}
+	// formula needs target because it's always transformed to Composite scaler
+	if csl.Target == "" {
+		return fmt.Errorf("formula is given but target is empty")
+	}
+
+	// possible TODO: this could be more soffisticated - only check for names that
+	// are used in the formula itself. This would require parsing the formula.
+	for _, trig := range so.Spec.Triggers {
+		if trig.Name == "" {
+			return fmt.Errorf("trigger of type '%s' has empty name but csl.Formula is defined", trig.Type)
+		}
+	}
+	if len(csl.ExternalCalculations) > 0 {
+		if csl.ExternalCalculations[len(csl.ExternalCalculations)-1].Name == "" {
+			return fmt.Errorf("last externalCalculator has empty name but csl.Formula is defined")
+		}
+	}
+	return nil
+}
+
+func validateCSLexternalCalculations(cls ComplexScalingLogic) error {
+	// timeout check
+	for _, ec := range cls.ExternalCalculations {
+		_, err := strconv.ParseInt(ec.Timeout, 10, 64)
+		if err != nil {
+			// expect timeout in time format like 1m10s
+			_, err = time.ParseDuration(ec.Timeout)
+			if err != nil {
+				return fmt.Errorf("%s: error while converting type of timeout for external calculator", err)
+			}
+		}
+		if ec.URL == "" {
+			return fmt.Errorf("URL is empty for externalCalculator '%s'", ec.Name)
+		}
+	}
+
+	return nil
+}
+
+func validateCSLtarget(csl ComplexScalingLogic, specs []autoscalingv2.MetricSpec) (float64, autoscalingv2.MetricTargetType, error) {
+	if csl.Target == "" {
+		return -1, "", nil
+	}
+	// convert string to float
+	num, err := strconv.ParseFloat(csl.Target, 64)
+	if err != nil || num <= 0.0 {
+		return -1, "", fmt.Errorf("error converting target for complex logic (string->float) to valid target: %w", err)
+	}
+
+	var metricType autoscalingv2.MetricTargetType
+	// if target is given, composite scaler for metric collection will be
+	// passed to HPA config -> all types need to be the same
+	// make sure all scalers have the same metricTargetType
+	for _, metric := range specs {
+		if metric.External == nil {
+			continue
+		}
+		if metricType == "" {
+			metricType = metric.External.Target.Type
+		} else if metric.External.Target.Type != metricType {
+			err := fmt.Errorf("error metric target type not the same for composite scaler: %s & %s", metricType, metric.External.Target.Type)
+			return -1, "", err
+		}
+	}
+	return num, metricType, nil
+}