Add cache for api version

Expose runtime interface

pkg/kubelet/container/runtime.go

@@ -55,8 +55,10 @@ type Runtime interface {
 
 	// Version returns the version information of the container runtime.
 	Version() (Version, error)
-	// APIVersion returns the API version information of the container
+
-	// runtime. This may be different from the runtime engine's version.
+	// APIVersion returns the cached API version information of the container
+	// runtime. Implementation is expected to update this cache periodically.
+	// This may be different from the runtime engine's version.
 	// TODO(random-liu): We should fold this into Version()
 	APIVersion() (Version, error)
 	// Status returns error if the runtime is unhealthy; nil otherwise.

pkg/kubelet/dockertools/manager.go

@@ -55,6 +55,7 @@ import (
 	"k8s.io/kubernetes/pkg/util/procfs"
 	utilruntime "k8s.io/kubernetes/pkg/util/runtime"
 	utilstrings "k8s.io/kubernetes/pkg/util/strings"
+	"k8s.io/kubernetes/pkg/util/wait"
 )
 
 const (
@@ -158,6 +159,9 @@ type DockerManager struct {
 	// A false value means the kubelet just backs off from setting it,
 	// it might already be true.
 	configureHairpinMode bool
+
+	// The api version cache of docker daemon.
+	versionCache *VersionCache
 }
 
 // A subset of the pod.Manager interface extracted for testing purposes.
@@ -235,6 +239,7 @@ func NewDockerManager(
 		cpuCFSQuota:            cpuCFSQuota,
 		enableCustomMetrics:    enableCustomMetrics,
 		configureHairpinMode:   hairpinMode,
+		versionCache:           NewVersionCache(),
 	}
 	dm.runner = lifecycle.NewHandlerRunner(httpClient, dm, dm)
 	if serializeImagePulls {
@@ -249,6 +254,21 @@ func NewDockerManager(
 		optf(dm)
 	}
 
+	apiVersion, err := dm.APIVersion()
+	if err != nil {
+		glog.Errorf("Failed to get api version from docker %v", err)
+	}
+
+	daemonVersion, err := dm.Version()
+	if err != nil {
+		glog.Errorf("Failed to get daemon version from docker %v", err)
+	}
+
+	// Update version cache periodically
+	go wait.Until(func() {
+		dm.versionCache.Update(dm.machineInfo.MachineID, apiVersion, daemonVersion)
+	}, 5*time.Second, wait.NeverStop)
+
 	return dm
 }
 
@@ -1437,17 +1457,7 @@ func (dm *DockerManager) applyOOMScoreAdj(container *api.Container, containerInf
 		}
 		return err
 	}
-	// Set OOM score of the container based on the priority of the container.
+	oomScoreAdj := dm.calculateOomScoreAdj(container)
-	// Processes in lower-priority pods should be killed first if the system runs out of memory.
-	// The main pod infrastructure container is considered high priority, since if it is killed the
-	// whole pod will die.
-	// TODO: Cache this value.
-	var oomScoreAdj int
-	if containerInfo.Name == PodInfraContainerName {
-		oomScoreAdj = qos.PodInfraOOMAdj
-	} else {
-		oomScoreAdj = qos.GetContainerOOMScoreAdjust(container, int64(dm.machineInfo.MemoryCapacity))
-	}
 	if err = dm.oomAdjuster.ApplyOOMScoreAdjContainer(cgroupName, oomScoreAdj, 5); err != nil {
 		if err == os.ErrNotExist {
 			// Container exited. We cannot do anything about it. Ignore this error.
@@ -1482,17 +1492,7 @@ func (dm *DockerManager) runContainerInPod(pod *api.Pod, container *api.Containe
 		utsMode = namespaceModeHost
 	}
 
-	// Set OOM score of the container based on the priority of the container.
+	oomScoreAdj := dm.calculateOomScoreAdj(container)
-	// Processes in lower-priority pods should be killed first if the system runs out of memory.
-	// The main pod infrastructure container is considered high priority, since if it is killed the
-	// whole pod will die.
-	var oomScoreAdj int
-	if container.Name == PodInfraContainerName {
-		oomScoreAdj = qos.PodInfraOOMAdj
-	} else {
-		oomScoreAdj = qos.GetContainerOOMScoreAdjust(container, int64(dm.machineInfo.MemoryCapacity))
-
-	}
 
 	id, err := dm.runContainer(pod, container, opts, ref, netMode, ipcMode, utsMode, pidMode, restartCount, oomScoreAdj)
 	if err != nil {
@@ -1566,20 +1566,52 @@ func (dm *DockerManager) applyOOMScoreAdjIfNeeded(container *api.Container, cont
 	return nil
 }
 
-// Check current docker API version against expected version.
+func (dm *DockerManager) calculateOomScoreAdj(container *api.Container) int {
+	// Set OOM score of the container based on the priority of the container.
+	// Processes in lower-priority pods should be killed first if the system runs out of memory.
+	// The main pod infrastructure container is considered high priority, since if it is killed the
+	// whole pod will die.
+	var oomScoreAdj int
+	if container.Name == PodInfraContainerName {
+		oomScoreAdj = qos.PodInfraOOMAdj
+	} else {
+		oomScoreAdj = qos.GetContainerOOMScoreAdjust(container, int64(dm.machineInfo.MemoryCapacity))
+
+	}
+
+	return oomScoreAdj
+}
+
+// getCachedApiVersion gets cached api version of docker runtime.
+func (dm *DockerManager) getCachedApiVersion() (kubecontainer.Version, error) {
+	apiVersion, _, err := dm.versionCache.Get(dm.machineInfo.MachineID)
+	if err != nil {
+		glog.Errorf("Failed to get cached docker api version %v ", err)
+	}
+	// If we got nil apiVersion, try to get api version directly.
+	if apiVersion == nil {
+		apiVersion, err = dm.APIVersion()
+		if err != nil {
+			glog.Errorf("Failed to get docker api version directly %v ", err)
+		}
+		dm.versionCache.Update(dm.machineInfo.MachineID, apiVersion, nil)
+	}
+	return apiVersion, err
+}
+
+// checkDockerAPIVersion checks current docker API version against expected version.
 // Return:
 // 1 : newer than expected version
 // -1: older than expected version
 // 0 : same version
 func (dm *DockerManager) checkDockerAPIVersion(expectedVersion string) int {
-	apiVersion, err := dm.APIVersion()
+	apiVersion, err := dm.getCachedApiVersion()
 	if err != nil {
-		glog.Errorf("failed to get current docker version - %v", err)
+		glog.Errorf("Failed to get cached docker api version %v ", err)
 	}
-
 	result, err := apiVersion.Compare(expectedVersion)
 	if err != nil {
-		glog.Errorf("failed to compare current docker version %v with OOMScoreAdj supported Docker version %q - %v",
+		glog.Errorf("Failed to compare current docker api version %v with OOMScoreAdj supported Docker version %q - %v",
 			apiVersion, expectedVersion, err)
 	}
 	return result

pkg/kubelet/dockertools/version_cache.go

@@ -0,0 +1,62 @@
+/*
+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 dockertools
+
+import (
+	"fmt"
+	"sync"
+
+	"github.com/golang/groupcache/lru"
+	kubecontainer "k8s.io/kubernetes/pkg/kubelet/container"
+)
+
+type VersionCache struct {
+	lock  sync.RWMutex
+	cache *lru.Cache
+}
+
+// versionInfo caches api version and daemon version.
+type versionInfo struct {
+	apiVersion kubecontainer.Version
+	version    kubecontainer.Version
+}
+
+const maxVersionCacheEntries = 1000
+
+func NewVersionCache() *VersionCache {
+	return &VersionCache{cache: lru.New(maxVersionCacheEntries)}
+}
+
+// Update updates cached versionInfo by using a unique string (e.g. machineInfo) as the key.
+func (c *VersionCache) Update(key string, apiVersion kubecontainer.Version, version kubecontainer.Version) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	c.cache.Add(key, versionInfo{apiVersion, version})
+}
+
+// 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.Get(key)
+	if !ok {
+		return nil, nil, fmt.Errorf("Failed to get version info from cache by key: ", key)
+	}
+	versions := value.(versionInfo)
+	return versions.apiVersion, versions.version, nil
+}