feat: add HorizontalPodAutoscaler support for EnvoyProxy API

api/v1alpha1/envoyproxy_helpers.go

@@ -9,6 +9,11 @@ import (
 	"fmt"
 	"sort"
 	"strings"
+
+	autoscalingv2 "k8s.io/api/autoscaling/v2"
+	v1 "k8s.io/api/core/v1"
+
+	"github.com/envoyproxy/gateway/internal/utils/ptr"
 )
 
 // DefaultEnvoyProxyProvider returns a new EnvoyProxyProvider with default settings.
@@ -37,6 +42,21 @@ func DefaultEnvoyProxyKubeProvider() *EnvoyProxyKubernetesProvider {
 	}
 }
 
+func DefaultEnvoyProxyHpaMetrics() []autoscalingv2.MetricSpec {
+	return []autoscalingv2.MetricSpec{
+		{
+			Resource: &autoscalingv2.ResourceMetricSource{
+				Name: v1.ResourceCPU,
+				Target: autoscalingv2.MetricTarget{
+					Type:               autoscalingv2.UtilizationMetricType,
+					AverageUtilization: ptr.To[int32](80),
+				},
+			},
+			Type: autoscalingv2.ResourceMetricSourceType,
+		},
+	}
+}
+
 // GetEnvoyProxyKubeProvider returns the EnvoyProxyKubernetesProvider of EnvoyProxyProvider or
 // a default EnvoyProxyKubernetesProvider if unspecified. If EnvoyProxyProvider is not of
 // type "Kubernetes", a nil EnvoyProxyKubernetesProvider is returned.
@@ -64,6 +84,10 @@ func (r *EnvoyProxyProvider) GetEnvoyProxyKubeProvider() *EnvoyProxyKubernetesPr
 		r.Kubernetes.EnvoyService.Type = GetKubernetesServiceType(ServiceTypeLoadBalancer)
 	}
 
+	if r.Kubernetes.EnvoyHpa != nil {
+		r.Kubernetes.EnvoyHpa.setDefault()
+	}
+
 	return r.Kubernetes
 }
 

api/v1alpha1/envoyproxy_types.go

@@ -127,6 +127,15 @@ type EnvoyProxyKubernetesProvider struct {
 	// +kubebuilder:validation:XValidation:message="loadBalancerIP can only be set for LoadBalancer type",rule="!has(self.loadBalancerIP) || self.type == 'LoadBalancer'"
 	// +kubebuilder:validation:XValidation:message="loadBalancerIP must be a valid IPv4 address",rule="!has(self.loadBalancerIP) || self.loadBalancerIP.matches(r\"^(((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)(\\.|$)){4})\")"
 	EnvoyService *KubernetesServiceSpec `json:"envoyService,omitempty"`
+
+	// EnvoyHpa defines the Horizontal Pod Autoscaler settings for Envoy Proxy Deployment.
+	// Once the HPA is being set, Replicas field from EnvoyDeployment will be ignored.
+	//
+	// +optional
+	// +kubebuilder:validation:XValidation:message="minReplicas must be greater than 0",rule="!has(self.minReplicas) || self.minReplicas > 0"
+	// +kubebuilder:validation:XValidation:message="maxReplicas must be greater than 0",rule="!has(self.maxReplicas) || self.maxReplicas > 0"
+	// +kubebuilder:validation:XValidation:message="maxReplicas cannot be less than or equal to minReplicas",rule="!has(self.minReplicas) || self.maxReplicas > self.minReplicas"
+	EnvoyHpa *KubernetesHorizontalPodAutoscalerSpec `json:"envoyHpa,omitempty"`
 }
 
 // ProxyLogging defines logging parameters for managed proxies.

api/v1alpha1/kubernetes_helpers.go

@@ -106,3 +106,9 @@ func (deployment *KubernetesDeploymentSpec) defaultKubernetesDeploymentSpec(imag
 		deployment.Container.Image = DefaultKubernetesContainerImage(image)
 	}
 }
+
+func (hpa *KubernetesHorizontalPodAutoscalerSpec) setDefault() {
+	if len(hpa.Metrics) == 0 {
+		hpa.Metrics = DefaultEnvoyProxyHpaMetrics()
+	}
+}

api/v1alpha1/shared_types.go

@@ -7,6 +7,7 @@ package v1alpha1
 
 import (
 	appv1 "k8s.io/api/apps/v1"
+	autoscalingv2 "k8s.io/api/autoscaling/v2"
 	corev1 "k8s.io/api/core/v1"
 )
 
@@ -275,3 +276,34 @@ const (
 	// https://github.com/google/re2/wiki/Syntax.
 	StringMatchRegularExpression StringMatchType = "RegularExpression"
 )
+
+// KubernetesHorizontalPodAutoscalerSpec defines Kubernetes Horizontal Pod Autoscaler settings of Envoy Proxy Deployment
+// See k8s.io.autoscaling.v2.HorizontalPodAutoScalerSpec
+type KubernetesHorizontalPodAutoscalerSpec struct {
+	// minReplicas is the lower limit for the number of replicas to which the autoscaler
+	// can scale down. It defaults to 1 replica.
+	//
+	// +optional
+	MinReplicas *int32 `json:"minReplicas,omitempty"`
+
+	// maxReplicas is the upper limit for the number of replicas to which the autoscaler can scale up.
+	// It cannot be less that minReplicas.
+	//
+	MaxReplicas *int32 `json:"maxReplicas"`
+
+	// metrics contains the specifications for which to use to calculate the
+	// desired replica count (the maximum replica count across all metrics will
+	// be used).
+	// If left empty, it defaults to being based on CPU utilization with average on 80% usage.
+	//
+	// +optional
+	Metrics []autoscalingv2.MetricSpec `json:"metrics,omitempty"`
+
+	// behavior configures the scaling behavior of the target
+	// in both Up and Down directions (scaleUp and scaleDown fields respectively).
+	// If not set, the default HPAScalingRules for scale up and scale down are used.
+	// See k8s.io.autoscaling.v2.HorizontalPodAutoScalerBehavior.
+	//
+	// +optional
+	Behavior *autoscalingv2.HorizontalPodAutoscalerBehavior `json:"behavior,omitempty"`
+}