*: Implement union discriminator pattern in Backend API (#10709)

Signed-off-by: timflannagan <[email protected]>

Author: timflannagan

api/applyconfiguration/api/v1alpha1/backendspec.go

@@ -22,40 +22,84 @@ type Backend struct {
 	Status BackendStatus `json:"status,omitempty"`
 }
 
-// +kubebuilder:object:root=true
-type BackendList struct {
-	metav1.TypeMeta `json:",inline"`
-	metav1.ListMeta `json:"metadata,omitempty"`
-	Items           []Backend `json:"items"`
-}
+// BackendType indicates the type of the backend.
+type BackendType string
 
-// +kubebuilder:validation:XValidation:message="There must one and only one backend type set",rule="(has(self.aws) && !has(self.static) && !has(self.ai)) || (!has(self.aws) && has(self.static) && !has(self.ai)) || (!has(self.aws) && !has(self.static) && has(self.ai))"
-// +kubebuilder:validation:MaxProperties=1
-// +kubebuilder:validation:MinProperties=1
+const (
+	// BackendTypeAI is the type for AI backends.
+	BackendTypeAI BackendType = "ai"
+	// BackendTypeAWS is the type for AWS backends.
+	BackendTypeAWS BackendType = "aws"
+	// BackendTypeStatic is the type for static backends.
+	BackendTypeStatic BackendType = "static"
+)
+
+// BackendSpec defines the desired state of Backend.
+// +union
+// +kubebuilder:validation:XValidation:message="ai backend must be nil if the type is not 'ai'",rule="!(has(self.ai) && self.type != 'ai')"
+// +kubebuilder:validation:XValidation:message="ai backend must be specified when type is 'ai'",rule="!(!has(self.ai) && self.type == 'ai')"
+// +kubebuilder:validation:XValidation:message="aws backend must be nil if the type is not 'aws'",rule="!(has(self.aws) && self.type != 'aws')"
+// +kubebuilder:validation:XValidation:message="aws backend must be specified when type is 'aws'",rule="!(!has(self.aws) && self.type == 'aws')"
+// +kubebuilder:validation:XValidation:message="static backend must be nil if the type is not 'static'",rule="!(has(self.static) && self.type != 'static')"
+// +kubebuilder:validation:XValidation:message="static backend must be specified when type is 'static'",rule="!(!has(self.static) && self.type == 'static')"
 type BackendSpec struct {
-	Aws    *AwsBackend    `json:"aws,omitempty"`
+	// Type indicates the type of the backend to be used.
+	// +unionDiscriminator
+	// +kubebuilder:validation:Enum=ai;aws;static
+	// +kubebuilder:validation:Required
+	Type BackendType `json:"type"`
+	// AI is the AI backend configuration.
+	// +optional
+	AI *AIBackend `json:"ai,omitempty"`
+	// Aws is the AWS backend configuration.
+	// +optional
+	Aws *AwsBackend `json:"aws,omitempty"`
+	// Static is the static backend configuration.
+	// +optional
 	Static *StaticBackend `json:"static,omitempty"`
-	AI     *AIBackend     `json:"ai,omitempty"`
 }
+
+// AwsBackend is the AWS backend configuration.
 type AwsBackend struct {
-	Region    string                      `json:"region,omitempty"`
+	// Region is the AWS region.
+	// +optional
+	Region string `json:"region,omitempty"`
+	// SecretRef is the secret reference for the AWS credentials.
+	// +optional
 	SecretRef corev1.LocalObjectReference `json:"secretRef,omitempty"`
 }
+
+// StaticBackend is the static backend configuration.
 type StaticBackend struct {
+	// Hosts is the list of hosts.
+	// +optional
+	// +kubebuilder:validation:MinItems=1
 	Hosts []Host `json:"hosts,omitempty"`
 }
 
+// Host is a host and port pair.
 type Host struct {
+	// Host is the host name.
 	// +kubebuilder:validation:MinLength=1
 	// +kubebuilder:validation:MaxLength=253
-	Host string          `json:"host"`
+	Host string `json:"host"`
+	// Port is the port number.
 	Port gwv1.PortNumber `json:"port"`
 }
 
+// BackendStatus defines the observed state of Backend.
 type BackendStatus struct {
+	// Conditions is the list of conditions for the backend.
 	// +optional
 	// +listType=map
 	// +listMapKey=type
 	// +kubebuilder:validation:MaxItems=8
 	Conditions []metav1.Condition `json:"conditions,omitempty"`
 }
+
+// +kubebuilder:object:root=true
+type BackendList struct {
+	metav1.TypeMeta `json:",inline"`
+	metav1.ListMeta `json:"metadata,omitempty"`
+	Items           []Backend `json:"items"`
+}

api/applyconfiguration/internal/internal.go

@@ -32,8 +32,6 @@ spec:
           metadata:
             type: object
           spec:
-            maxProperties: 1
-            minProperties: 1
             properties:
               ai:
                 maxProperties: 1
@@ -484,14 +482,31 @@ spec:
                       - host
                       - port
                       type: object
+                    minItems: 1
                     type: array
                 type: object
+              type:
+                enum:
+                - ai
+                - aws
+                - static
+                type: string
+            required:
+            - type
             type: object
             x-kubernetes-validations:
-            - message: There must one and only one backend type set
-              rule: (has(self.aws) && !has(self.static) && !has(self.ai)) || (!has(self.aws)
-                && has(self.static) && !has(self.ai)) || (!has(self.aws) && !has(self.static)
-                && has(self.ai))
+            - message: ai backend must be nil if the type is not 'ai'
+              rule: '!(has(self.ai) && self.type != ''ai'')'
+            - message: ai backend must be specified when type is 'ai'
+              rule: '!(!has(self.ai) && self.type == ''ai'')'
+            - message: aws backend must be nil if the type is not 'aws'
+              rule: '!(has(self.aws) && self.type != ''aws'')'
+            - message: aws backend must be specified when type is 'aws'
+              rule: '!(!has(self.aws) && self.type == ''aws'')'
+            - message: static backend must be nil if the type is not 'static'
+              rule: '!(has(self.static) && self.type != ''static'')'
+            - message: static backend must be specified when type is 'static'
+              rule: '!(!has(self.static) && self.type == ''static'')'
           status:
             properties:
               conditions:

api/v1alpha1/backend_types.go

@@ -35,7 +35,7 @@ const (
 	ParameterKind  = "Parameter"
 )
 const (
-	ExtensionName = "Upstream"
+	ExtensionName = "Backend"
 	FilterName    = "io.solo.aws_lambda"
 )
 
@@ -138,7 +138,7 @@ func NewPlugin(ctx context.Context, commoncol *common.CommonCollections) extensi
 		},
 		ContributesPolicies: map[schema.GroupKind]extensionsplug.PolicyPlugin{
 			ParameterGK: {
-				Name:                      "upstream",
+				Name:                      "backend",
 				NewGatewayTranslationPass: newPlug,
 				//			AttachmentPoints: []ir.AttachmentPoints{ir.HttpBackendRefAttachmentPoint},
 				PoliciesFetch: func(n, ns string) ir.PolicyIR {
@@ -187,16 +187,18 @@ func processUpstream(ctx context.Context, in ir.BackendObjectIR, out *envoy_conf
 	}
 
 	spec := up.Spec
-
 	switch {
-	case spec.Static != nil:
+	case spec.Type == v1alpha1.BackendTypeStatic:
 		processStatic(ctx, spec.Static, out)
-	case spec.Aws != nil:
+	case spec.Type == v1alpha1.BackendTypeAWS:
 		processAws(ctx, spec.Aws, ir, out)
 	}
 }
 
 func hostname(in *v1alpha1.Backend) string {
+	if in.Spec.Type != v1alpha1.BackendTypeStatic {
+		return ""
+	}
 	if in.Spec.Static != nil {
 		if len(in.Spec.Static.Hosts) > 0 {
 			return string(in.Spec.Static.Hosts[0].Host)
@@ -208,9 +210,9 @@ func hostname(in *v1alpha1.Backend) string {
 func processEndpoints(up *v1alpha1.Backend) *ir.EndpointsForBackend {
 	spec := up.Spec
 	switch {
-	case spec.Static != nil:
+	case spec.Type == v1alpha1.BackendTypeStatic:
 		return processEndpointsStatic(spec.Static)
-	case spec.Aws != nil:
+	case spec.Type == v1alpha1.BackendTypeAWS:
 		return processEndpointsAws(spec.Aws)
 	}
 	return nil
@@ -221,7 +223,7 @@ func newPlug(ctx context.Context, tctx ir.GwTranslationCtx) ir.ProxyTranslationP
 }
 
 func (p *backendPlugin) Name() string {
-	return "upstream"
+	return ExtensionName
 }
 
 // called 1 time for each listener

api/v1alpha1/zz_generated.deepcopy.go

@@ -81,6 +81,7 @@ metadata:
   name: log
   namespace: gwtest
 spec:
+  type: static
   static:
     hosts:
       - host: 1.2.3.4

install/helm/kgateway/crds/gateway.kgateway.dev_backends.yaml

@@ -35,6 +35,7 @@ metadata:
   name: static
   namespace: gwtest
 spec:
+  type: static
   static:
     hosts:
       - host: 1.2.3.4

internal/kgateway/extensions2/plugins/backend/plugin.go

@@ -38,10 +38,11 @@ kind: Backend
 metadata:
   name: aws-backend
 spec:
+  type: aws
   aws:
     region: us-east-1
     # TODO: add these back
     # roleArn: arn:aws:iam::123456789012:role/lambda-role
     # lambdaFunctions:
     #   - lambdaFunctionName: uppercase
-    #     logicalName: uppercase
+    #     logicalName: uppercase