Fixing bugs related to Endpoint Slices

This should fix a bug that could break masters when the EndpointSlice
feature gate was enabled. This was all tied to how the apiserver creates
and manages it's own services and endpoints (or in this case endpoint
slices). Consumers of endpoint slices also need to know about the
corresponding service. Previously we were trying to set an owner
reference here for this purpose, but that came with potential downsides
and increased complexity. This commit changes behavior of the apiserver
endpointslice integration to set the service name label instead of owner
references, and simplifies consumer logic to reference that (both are
set by the EndpointSlice controller).

Additionally, this should fix a bug with the EndpointSlice GenerateName
value that had previously been set with a "." as a suffix.

pkg/controller/endpointslice/utils.go

@@ -32,6 +32,7 @@ import (
 	"k8s.io/klog"
 	podutil "k8s.io/kubernetes/pkg/api/v1/pod"
 	api "k8s.io/kubernetes/pkg/apis/core"
+	"k8s.io/kubernetes/pkg/apis/discovery/validation"
 	"k8s.io/kubernetes/pkg/util/hash"
 )
 
@@ -158,8 +159,8 @@ func newEndpointSlice(service *corev1.Service, endpointMeta *endpointMeta) *disc
 	ownerRef := metav1.NewControllerRef(service, gvk)
 	return &discovery.EndpointSlice{
 		ObjectMeta: metav1.ObjectMeta{
-			Labels:          map[string]string{serviceNameLabel: service.Name},
-			GenerateName:    fmt.Sprintf("%s.", service.Name),
+			Labels:          map[string]string{discovery.LabelServiceName: service.Name},
+			GenerateName:    getEndpointSlicePrefix(service.Name),
 			OwnerReferences: []metav1.OwnerReference{*ownerRef},
 			Namespace:       service.Namespace,
 		},
@@ -169,6 +170,16 @@ func newEndpointSlice(service *corev1.Service, endpointMeta *endpointMeta) *disc
 	}
 }
 
+// getEndpointSlicePrefix returns a suitable prefix for an EndpointSlice name.
+func getEndpointSlicePrefix(serviceName string) string {
+	// use the dash (if the name isn't too long) to make the pod name a bit prettier
+	prefix := fmt.Sprintf("%s-", serviceName)
+	if len(validation.ValidateEndpointSliceName(prefix, true)) != 0 {
+		prefix = serviceName
+	}
+	return prefix
+}
+
 // boolPtrChanged returns true if a set of bool pointers have different values.
 func boolPtrChanged(ptr1, ptr2 *bool) bool {
 	if (ptr1 == nil) != (ptr2 == nil) {