Augmented kubelet healthz with syncLoop check.

Monit uses read-only port for health monitoring.

pkg/util/atomic_value.go

@@ -0,0 +1,42 @@
+/*
+Copyright 2015 The Kubernetes Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package util
+
+import (
+	"sync"
+)
+
+// TODO(ArtfulCoder)
+// sync/atomic/Value was added in golang 1.4
+// Once support is dropped for go 1.3, this type must be deprecated in favor of sync/atomic/Value.
+// The functions are named Load/Store to match sync/atomic/Value function names.
+type AtomicValue struct {
+	value      interface{}
+	valueMutex sync.RWMutex
+}
+
+func (at *AtomicValue) Store(val interface{}) {
+	at.valueMutex.Lock()
+	defer at.valueMutex.Unlock()
+	at.value = val
+}
+
+func (at *AtomicValue) Load() interface{} {
+	at.valueMutex.RLock()
+	defer at.valueMutex.RUnlock()
+	return at.value
+}