kubeadm: use localhost for API server liveness probe

cmd/kubeadm/app/util/staticpod/BUILD

@@ -13,6 +13,7 @@ go_test(
     deps = [
         "//cmd/kubeadm/app/apis/kubeadm:go_default_library",
         "//cmd/kubeadm/app/constants:go_default_library",
+        "//cmd/kubeadm/app/features:go_default_library",
         "//vendor/k8s.io/api/core/v1:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/util/intstr:go_default_library",
@@ -26,6 +27,7 @@ go_library(
     deps = [
         "//cmd/kubeadm/app/apis/kubeadm:go_default_library",
         "//cmd/kubeadm/app/constants:go_default_library",
+        "//cmd/kubeadm/app/features:go_default_library",
         "//cmd/kubeadm/app/util:go_default_library",
         "//pkg/kubelet/types:go_default_library",
         "//vendor/k8s.io/api/core/v1:go_default_library",

cmd/kubeadm/app/util/staticpod/utils.go

@@ -29,6 +29,7 @@ import (
 	"k8s.io/apimachinery/pkg/api/resource"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/util/intstr"
+	"k8s.io/kubernetes/cmd/kubeadm/app/features"
 
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
@@ -184,7 +185,16 @@ func WriteStaticPodToDisk(componentName, manifestDir string, pod v1.Pod) error {
 func GetProbeAddress(cfg *kubeadmapi.MasterConfiguration, componentName string) string {
 	switch {
 	case componentName == kubeadmconstants.KubeAPIServer:
-		if cfg.API.AdvertiseAddress != "" {
+		// In the case of a self-hosted deployment, the initial host on which kubeadm --init is run,
+		// will generate a DaemonSet with a nodeSelector such that all nodes with the label
+		// node-role.kubernetes.io/master='' will have the API server deployed to it. Since the init
+		// is run only once on an initial host, the API advertise address will be invalid for any
+		// future hosts that do not have the same address. Furthermore, since liveness and readiness
+		// probes do not support the Downward API we cannot dynamically set the advertise address to
+		// the node's IP. The only option then is to use localhost.
+		if features.Enabled(cfg.FeatureGates, features.SelfHosting) {
+			return "127.0.0.1"
+		} else if cfg.API.AdvertiseAddress != "" {
 			return cfg.API.AdvertiseAddress
 		}
 	case componentName == kubeadmconstants.KubeControllerManager:

cmd/kubeadm/app/util/staticpod/utils_test.go

@@ -24,6 +24,7 @@ import (
 	"k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/util/intstr"
+	"k8s.io/kubernetes/cmd/kubeadm/app/features"
 
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
@@ -62,6 +63,22 @@ func TestComponentProbe(t *testing.T) {
 			expected:  "127.0.0.1",
 		},
 		{
+			name: "default apiserver advertise address with http",
+			cfg: &kubeadmapi.MasterConfiguration{
+				API: kubeadmapi.API{
+					AdvertiseAddress: "1.2.3.4",
+				},
+				FeatureGates: map[string]bool{
+					features.SelfHosting: true,
+				},
+			},
+			component: kubeadmconstants.KubeAPIServer,
+			port:      1,
+			path:      "foo",
+			scheme:    v1.URISchemeHTTP,
+			expected:  "127.0.0.1",
+		},
+		{
 			name: "default apiserver advertise address with https",
 			cfg: &kubeadmapi.MasterConfiguration{
 				API: kubeadmapi.API{