diff --git a/api/openapi-spec/swagger.json b/api/openapi-spec/swagger.json
index b6613e045d8..8069e5e7980 100644
--- a/api/openapi-spec/swagger.json
+++ b/api/openapi-spec/swagger.json
@@ -3126,7 +3126,7 @@
           "description": "resource refers to a resource metric (such as those specified in requests and limits) known to Kubernetes describing each pod in the current scale target (e.g. CPU or memory). Such metrics are built in to Kubernetes, and have special scaling options on top of those available to normal per-pod metrics using the \"pods\" source."
         },
         "type": {
-          "description": "type is the type of metric source.  It should be one of \"Object\", \"Pods\" or \"Resource\", each mapping to a matching field in the object.",
+          "description": "type is the type of metric source.  It should be one of \"Object\", \"Pods\", \"Resource\" or \"External\", each mapping to a matching field in the object.",
           "type": "string"
         }
       },
@@ -3648,7 +3648,7 @@
           "description": "resource refers to a resource metric (such as those specified in requests and limits) known to Kubernetes describing each pod in the current scale target (e.g. CPU or memory). Such metrics are built in to Kubernetes, and have special scaling options on top of those available to normal per-pod metrics using the \"pods\" source."
         },
         "type": {
-          "description": "type is the type of metric source.  It should be one of \"Object\", \"Pods\" or \"Resource\", each mapping to a matching field in the object.",
+          "description": "type is the type of metric source.  It should be one of \"Object\", \"Pods\", \"Resource\" or \"External\", each mapping to a matching field in the object.",
           "type": "string"
         }
       },
diff --git a/staging/src/k8s.io/api/autoscaling/v2beta1/generated.proto b/staging/src/k8s.io/api/autoscaling/v2beta1/generated.proto
index 9c67aa4230e..23d3214d8c1 100644
--- a/staging/src/k8s.io/api/autoscaling/v2beta1/generated.proto
+++ b/staging/src/k8s.io/api/autoscaling/v2beta1/generated.proto
@@ -201,7 +201,7 @@ message HorizontalPodAutoscalerStatus {
 // (only `type` and one other matching field should be set at once).
 message MetricSpec {
   // type is the type of metric source.  It should be one of "Object",
-  // "Pods" or "Resource", each mapping to a matching field in the object.
+  // "Pods", "Resource" or "External", each mapping to a matching field in the object.
   optional string type = 1;
 
   // object refers to a metric describing a single kubernetes object
diff --git a/staging/src/k8s.io/api/autoscaling/v2beta1/types.go b/staging/src/k8s.io/api/autoscaling/v2beta1/types.go
index d76e879678a..f5fe9f2acfe 100644
--- a/staging/src/k8s.io/api/autoscaling/v2beta1/types.go
+++ b/staging/src/k8s.io/api/autoscaling/v2beta1/types.go
@@ -88,7 +88,7 @@ const (
 // (only `type` and one other matching field should be set at once).
 type MetricSpec struct {
 	// type is the type of metric source.  It should be one of "Object",
-	// "Pods" or "Resource", each mapping to a matching field in the object.
+	// "Pods", "Resource" or "External", each mapping to a matching field in the object.
 	Type MetricSourceType `json:"type" protobuf:"bytes,1,name=type"`
 
 	// object refers to a metric describing a single kubernetes object
diff --git a/staging/src/k8s.io/api/autoscaling/v2beta1/types_swagger_doc_generated.go b/staging/src/k8s.io/api/autoscaling/v2beta1/types_swagger_doc_generated.go
index a0d5f533758..d945a9f08ae 100644
--- a/staging/src/k8s.io/api/autoscaling/v2beta1/types_swagger_doc_generated.go
+++ b/staging/src/k8s.io/api/autoscaling/v2beta1/types_swagger_doc_generated.go
@@ -124,7 +124,7 @@ func (HorizontalPodAutoscalerStatus) SwaggerDoc() map[string]string {
 
 var map_MetricSpec = map[string]string{
 	"":         "MetricSpec specifies how to scale based on a single metric (only `type` and one other matching field should be set at once).",
-	"type":     "type is the type of metric source.  It should be one of \"Object\", \"Pods\" or \"Resource\", each mapping to a matching field in the object.",
+	"type":     "type is the type of metric source.  It should be one of \"Object\", \"Pods\", \"Resource\" or \"External\", each mapping to a matching field in the object.",
 	"object":   "object refers to a metric describing a single kubernetes object (for example, hits-per-second on an Ingress object).",
 	"pods":     "pods refers to a metric describing each pod in the current scale target (for example, transactions-processed-per-second).  The values will be averaged together before being compared to the target value.",
 	"resource": "resource refers to a resource metric (such as those specified in requests and limits) known to Kubernetes describing each pod in the current scale target (e.g. CPU or memory). Such metrics are built in to Kubernetes, and have special scaling options on top of those available to normal per-pod metrics using the \"pods\" source.",
diff --git a/staging/src/k8s.io/api/autoscaling/v2beta2/generated.proto b/staging/src/k8s.io/api/autoscaling/v2beta2/generated.proto
index f711ba1a036..de2a9c23c22 100644
--- a/staging/src/k8s.io/api/autoscaling/v2beta2/generated.proto
+++ b/staging/src/k8s.io/api/autoscaling/v2beta2/generated.proto
@@ -257,7 +257,7 @@ message MetricIdentifier {
 // (only `type` and one other matching field should be set at once).
 message MetricSpec {
   // type is the type of metric source.  It should be one of "Object",
-  // "Pods" or "Resource", each mapping to a matching field in the object.
+  // "Pods", "Resource" or "External", each mapping to a matching field in the object.
   optional string type = 1;
 
   // object refers to a metric describing a single kubernetes object
diff --git a/staging/src/k8s.io/api/autoscaling/v2beta2/types.go b/staging/src/k8s.io/api/autoscaling/v2beta2/types.go
index ae7fa173ded..da2733d2f36 100644
--- a/staging/src/k8s.io/api/autoscaling/v2beta2/types.go
+++ b/staging/src/k8s.io/api/autoscaling/v2beta2/types.go
@@ -97,7 +97,7 @@ type CrossVersionObjectReference struct {
 // (only `type` and one other matching field should be set at once).
 type MetricSpec struct {
 	// type is the type of metric source.  It should be one of "Object",
-	// "Pods" or "Resource", each mapping to a matching field in the object.
+	// "Pods", "Resource" or "External", each mapping to a matching field in the object.
 	Type MetricSourceType `json:"type" protobuf:"bytes,1,name=type"`
 
 	// object refers to a metric describing a single kubernetes object
diff --git a/staging/src/k8s.io/api/autoscaling/v2beta2/types_swagger_doc_generated.go b/staging/src/k8s.io/api/autoscaling/v2beta2/types_swagger_doc_generated.go
index 3f38880f952..1c1b229f873 100644
--- a/staging/src/k8s.io/api/autoscaling/v2beta2/types_swagger_doc_generated.go
+++ b/staging/src/k8s.io/api/autoscaling/v2beta2/types_swagger_doc_generated.go
@@ -163,7 +163,7 @@ func (MetricIdentifier) SwaggerDoc() map[string]string {
 
 var map_MetricSpec = map[string]string{
 	"":         "MetricSpec specifies how to scale based on a single metric (only `type` and one other matching field should be set at once).",
-	"type":     "type is the type of metric source.  It should be one of \"Object\", \"Pods\" or \"Resource\", each mapping to a matching field in the object.",
+	"type":     "type is the type of metric source.  It should be one of \"Object\", \"Pods\", \"Resource\" or \"External\", each mapping to a matching field in the object.",
 	"object":   "object refers to a metric describing a single kubernetes object (for example, hits-per-second on an Ingress object).",
 	"pods":     "pods refers to a metric describing each pod in the current scale target (for example, transactions-processed-per-second).  The values will be averaged together before being compared to the target value.",
 	"resource": "resource refers to a resource metric (such as those specified in requests and limits) known to Kubernetes describing each pod in the current scale target (e.g. CPU or memory). Such metrics are built in to Kubernetes, and have special scaling options on top of those available to normal per-pod metrics using the \"pods\" source.",