Refactor version cache into kubelet util

pkg/kubelet/util/cache/version_cache.go

@@ -0,0 +1,80 @@
+/*
+Copyright 2016 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 cache
+
+import (
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/golang/glog"
+
+	kubecontainer "k8s.io/kubernetes/pkg/kubelet/container"
+	"k8s.io/kubernetes/pkg/util/wait"
+)
+
+type VersionCache struct {
+	lock    sync.RWMutex
+	cache   map[string]versionInfo
+	updater func() (kubecontainer.Version, kubecontainer.Version, error)
+}
+
+// versionInfo caches api version and daemon version.
+type versionInfo struct {
+	apiVersion kubecontainer.Version
+	version    kubecontainer.Version
+}
+
+const maxVersionCacheEntries = 1000
+
+func NewVersionCache(f func() (kubecontainer.Version, kubecontainer.Version, error)) *VersionCache {
+	return &VersionCache{
+		cache:   map[string]versionInfo{},
+		updater: f,
+	}
+}
+
+// Update updates cached versionInfo by using a unique string (e.g. machineInfo) as the key.
+func (c *VersionCache) Update(key string) {
+	apiVersion, daemonVersion, err := c.updater()
+
+	if err != nil {
+		glog.Errorf("Fail to get version info from container runtime: %v", err)
+	} else {
+		c.lock.Lock()
+		defer c.lock.Unlock()
+		c.cache[key] = versionInfo{apiVersion, daemonVersion}
+	}
+}
+
+// Get gets cached versionInfo by using a unique string (e.g. machineInfo) as the key.
+// It returns apiVersion first and followed by daemon version.
+func (c *VersionCache) Get(key string) (kubecontainer.Version, kubecontainer.Version, error) {
+	c.lock.RLock()
+	defer c.lock.RUnlock()
+	value, ok := c.cache[key]
+	if !ok {
+		return nil, nil, fmt.Errorf("Failed to get version info from cache by key: ", key)
+	}
+	return value.apiVersion, value.version, nil
+}
+
+func (c *VersionCache) UpdateCachePeriodly(key string) {
+	go wait.Until(func() {
+		c.Update(key)
+	}, 1*time.Minute, wait.NeverStop)
+}