[源码分析] kubelet源码分析(二)之 NewMainKubelet

Posted by 胡伟煌 on 2018-10-03

kubelet源码分析(二)之 NewMainKubelet

以下代码分析基于 kubernetes v1.12.0 版本。

本文主要分析 https://github.com/kubernetes/kubernetes/tree/v1.12.0/pkg/kubelet 部分的代码。

1. NewMainKubelet

NewMainKubelet主要用来初始化和构造一个kubelet结构体,kubelet结构体定义参考:https://github.com/kubernetes/kubernetes/blob/v1.12.0/pkg/kubelet/kubelet.go#L888

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// NewMainKubelet instantiates a new Kubelet object along with all the required internal modules.
// No initialization of Kubelet and its modules should happen here.
func NewMainKubelet(kubeCfg *kubeletconfiginternal.KubeletConfiguration,
kubeDeps *Dependencies,
crOptions *config.ContainerRuntimeOptions,
containerRuntime string,
runtimeCgroups string,
hostnameOverride string,
nodeIP string,
providerID string,
cloudProvider string,
certDirectory string,
rootDirectory string,
registerNode bool,
registerWithTaints []api.Taint,
allowedUnsafeSysctls []string,
remoteRuntimeEndpoint string,
remoteImageEndpoint string,
experimentalMounterPath string,
experimentalKernelMemcgNotification bool,
experimentalCheckNodeCapabilitiesBeforeMount bool,
experimentalNodeAllocatableIgnoreEvictionThreshold bool,
minimumGCAge metav1.Duration,
maxPerPodContainerCount int32,
maxContainerCount int32,
masterServiceNamespace string,
registerSchedulable bool,
nonMasqueradeCIDR string,
keepTerminatedPodVolumes bool,
nodeLabels map[string]string,
seccompProfileRoot string,
bootstrapCheckpointPath string,
nodeStatusMaxImages int32) (*Kubelet, error) {
...
}

1.1. PodConfig

通过makePodSourceConfig生成Pod config。

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if kubeDeps.PodConfig == nil {
var err error
kubeDeps.PodConfig, err = makePodSourceConfig(kubeCfg, kubeDeps, nodeName, bootstrapCheckpointPath)
if err != nil {
return nil, err
}
}

1.1.1. makePodSourceConfig

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// makePodSourceConfig creates a config.PodConfig from the given
// KubeletConfiguration or returns an error.
func makePodSourceConfig(kubeCfg *kubeletconfiginternal.KubeletConfiguration, kubeDeps *Dependencies, nodeName types.NodeName, bootstrapCheckpointPath string) (*config.PodConfig, error) {
...
// source of all configuration
cfg := config.NewPodConfig(config.PodConfigNotificationIncremental, kubeDeps.Recorder)

// define file config source
if kubeCfg.StaticPodPath != "" {
glog.Infof("Adding pod path: %v", kubeCfg.StaticPodPath)
config.NewSourceFile(kubeCfg.StaticPodPath, nodeName, kubeCfg.FileCheckFrequency.Duration, cfg.Channel(kubetypes.FileSource))
}

// define url config source
if kubeCfg.StaticPodURL != "" {
glog.Infof("Adding pod url %q with HTTP header %v", kubeCfg.StaticPodURL, manifestURLHeader)
config.NewSourceURL(kubeCfg.StaticPodURL, manifestURLHeader, nodeName, kubeCfg.HTTPCheckFrequency.Duration, cfg.Channel(kubetypes.HTTPSource))
}

// Restore from the checkpoint path
// NOTE: This MUST happen before creating the apiserver source
// below, or the checkpoint would override the source of truth.
...
if kubeDeps.KubeClient != nil {
glog.Infof("Watching apiserver")
if updatechannel == nil {
updatechannel = cfg.Channel(kubetypes.ApiserverSource)
}
config.NewSourceApiserver(kubeDeps.KubeClient, nodeName, updatechannel)
}
return cfg, nil
}

1.1.2. NewPodConfig

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// NewPodConfig creates an object that can merge many configuration sources into a stream
// of normalized updates to a pod configuration.
func NewPodConfig(mode PodConfigNotificationMode, recorder record.EventRecorder) *PodConfig {
updates := make(chan kubetypes.PodUpdate, 50)
storage := newPodStorage(updates, mode, recorder)
podConfig := &PodConfig{
pods: storage,
mux: config.NewMux(storage),
updates: updates,
sources: sets.String{},
}
return podConfig
}

1.1.3. NewSourceApiserver

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// NewSourceApiserver creates a config source that watches and pulls from the apiserver.
func NewSourceApiserver(c clientset.Interface, nodeName types.NodeName, updates chan<- interface{}) {
lw := cache.NewListWatchFromClient(c.CoreV1().RESTClient(), "pods", metav1.NamespaceAll, fields.OneTermEqualSelector(api.PodHostField, string(nodeName)))
newSourceApiserverFromLW(lw, updates)
}

1.2. Lister

serviceListernodeLister分别通过List-Watch机制监听servicenode的列表变化。

1.2.1. serviceLister

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serviceIndexer := cache.NewIndexer(cache.MetaNamespaceKeyFunc, cache.Indexers{cache.NamespaceIndex: cache.MetaNamespaceIndexFunc})
if kubeDeps.KubeClient != nil {
serviceLW := cache.NewListWatchFromClient(kubeDeps.KubeClient.CoreV1().RESTClient(), "services", metav1.NamespaceAll, fields.Everything())
r := cache.NewReflector(serviceLW, &v1.Service{}, serviceIndexer, 0)
go r.Run(wait.NeverStop)
}
serviceLister := corelisters.NewServiceLister(serviceIndexer)

1.2.2. nodeLister

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nodeIndexer := cache.NewIndexer(cache.MetaNamespaceKeyFunc, cache.Indexers{})
if kubeDeps.KubeClient != nil {
fieldSelector := fields.Set{api.ObjectNameField: string(nodeName)}.AsSelector()
nodeLW := cache.NewListWatchFromClient(kubeDeps.KubeClient.CoreV1().RESTClient(), "nodes", metav1.NamespaceAll, fieldSelector)
r := cache.NewReflector(nodeLW, &v1.Node{}, nodeIndexer, 0)
go r.Run(wait.NeverStop)
}
nodeInfo := &predicates.CachedNodeInfo{NodeLister: corelisters.NewNodeLister(nodeIndexer)}

1.3. 各种Manager

1.3.1. containerRefManager

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containerRefManager := kubecontainer.NewRefManager()

1.3.2. oomWatcher

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oomWatcher := NewOOMWatcher(kubeDeps.CAdvisorInterface, kubeDeps.Recorder)

1.3.3. dnsConfigurer

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clusterDNS := make([]net.IP, 0, len(kubeCfg.ClusterDNS))
for _, ipEntry := range kubeCfg.ClusterDNS {
ip := net.ParseIP(ipEntry)
if ip == nil {
glog.Warningf("Invalid clusterDNS ip '%q'", ipEntry)
} else {
clusterDNS = append(clusterDNS, ip)
}
}
...

dns.NewConfigurer(kubeDeps.Recorder, nodeRef, parsedNodeIP, clusterDNS, kubeCfg.ClusterDomain, kubeCfg.ResolverConfig),

1.3.4. secretManager & configMapManager

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var secretManager secret.Manager
var configMapManager configmap.Manager
switch kubeCfg.ConfigMapAndSecretChangeDetectionStrategy {
case kubeletconfiginternal.WatchChangeDetectionStrategy:
secretManager = secret.NewWatchingSecretManager(kubeDeps.KubeClient)
configMapManager = configmap.NewWatchingConfigMapManager(kubeDeps.KubeClient)
case kubeletconfiginternal.TTLCacheChangeDetectionStrategy:
secretManager = secret.NewCachingSecretManager(
kubeDeps.KubeClient, manager.GetObjectTTLFromNodeFunc(klet.GetNode))
configMapManager = configmap.NewCachingConfigMapManager(
kubeDeps.KubeClient, manager.GetObjectTTLFromNodeFunc(klet.GetNode))
case kubeletconfiginternal.GetChangeDetectionStrategy:
secretManager = secret.NewSimpleSecretManager(kubeDeps.KubeClient)
configMapManager = configmap.NewSimpleConfigMapManager(kubeDeps.KubeClient)
default:
return nil, fmt.Errorf("unknown configmap and secret manager mode: %v", kubeCfg.ConfigMapAndSecretChangeDetectionStrategy)
}

klet.secretManager = secretManager
klet.configMapManager = configMapManager

1.3.5. livenessManager

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klet.livenessManager = proberesults.NewManager()

1.3.6. podManager

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// podManager is also responsible for keeping secretManager and configMapManager contents up-to-date.
klet.podManager = kubepod.NewBasicPodManager(kubepod.NewBasicMirrorClient(klet.kubeClient), secretManager, configMapManager, checkpointManager)

1.3.7. resourceAnalyzer

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klet.resourceAnalyzer = serverstats.NewResourceAnalyzer(klet, kubeCfg.VolumeStatsAggPeriod.Duration)

1.3.8. containerGC

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// setup containerGC
containerGC, err := kubecontainer.NewContainerGC(klet.containerRuntime, containerGCPolicy, klet.sourcesReady)
if err != nil {
return nil, err
}
klet.containerGC = containerGC
klet.containerDeletor = newPodContainerDeletor(klet.containerRuntime, integer.IntMax(containerGCPolicy.MaxPerPodContainer, minDeadContainerInPod))

1.3.9. imageManager

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// setup imageManager
imageManager, err := images.NewImageGCManager(klet.containerRuntime, klet.StatsProvider, kubeDeps.Recorder, nodeRef, imageGCPolicy, crOptions.PodSandboxImage)
if err != nil {
return nil, fmt.Errorf("failed to initialize image manager: %v", err)
}
klet.imageManager = imageManager

1.3.10. statusManager

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klet.statusManager = status.NewManager(klet.kubeClient, klet.podManager, klet)

1.3.11. probeManager

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klet.probeManager = prober.NewManager(
klet.statusManager,
klet.livenessManager,
klet.runner,
containerRefManager,
kubeDeps.Recorder)

1.3.12. tokenManager

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tokenManager := token.NewManager(kubeDeps.KubeClient)

1.3.13. volumePluginMgr

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klet.volumePluginMgr, err =
NewInitializedVolumePluginMgr(klet, secretManager, configMapManager, tokenManager, kubeDeps.VolumePlugins, kubeDeps.DynamicPluginProber)
if err != nil {
return nil, err
}
if klet.enablePluginsWatcher {
klet.pluginWatcher = pluginwatcher.NewWatcher(klet.getPluginsDir())
}

1.3.14. volumeManager

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// setup volumeManager
klet.volumeManager = volumemanager.NewVolumeManager(
kubeCfg.EnableControllerAttachDetach,
nodeName,
klet.podManager,
klet.statusManager,
klet.kubeClient,
klet.volumePluginMgr,
klet.containerRuntime,
kubeDeps.Mounter,
klet.getPodsDir(),
kubeDeps.Recorder,
experimentalCheckNodeCapabilitiesBeforeMount,
keepTerminatedPodVolumes)

1.3.15. evictionManager

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// setup eviction manager
evictionManager, evictionAdmitHandler := eviction.NewManager(klet.resourceAnalyzer, evictionConfig, killPodNow(klet.podWorkers, kubeDeps.Recorder), klet.imageManager, klet.containerGC, kubeDeps.Recorder, nodeRef, klet.clock)

klet.evictionManager = evictionManager
klet.admitHandlers.AddPodAdmitHandler(evictionAdmitHandler)

1.4. containerRuntime

目前pod所使用的runtime只有dockerremote两种,rkt已经废弃。

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if containerRuntime == "rkt" {
glog.Fatalln("rktnetes has been deprecated in favor of rktlet. Please see https://github.com/kubernetes-incubator/rktlet for more information.")
}

runtimedocker的时候,会执行docker相关操作。

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switch containerRuntime {
case kubetypes.DockerContainerRuntime:
// Create and start the CRI shim running as a grpc server.
...
// The unix socket for kubelet <-> dockershim communication.
...
// Create dockerLegacyService when the logging driver is not supported.
...
case kubetypes.RemoteContainerRuntime:
// No-op.
break
default:
return nil, fmt.Errorf("unsupported CRI runtime: %q", containerRuntime)
}

1.4.1. NewDockerService

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// Create and start the CRI shim running as a grpc server.
streamingConfig := getStreamingConfig(kubeCfg, kubeDeps, crOptions)
ds, err := dockershim.NewDockerService(kubeDeps.DockerClientConfig, crOptions.PodSandboxImage, streamingConfig,
&pluginSettings, runtimeCgroups, kubeCfg.CgroupDriver, crOptions.DockershimRootDirectory, !crOptions.RedirectContainerStreaming)
if err != nil {
return nil, err
}
if crOptions.RedirectContainerStreaming {
klet.criHandler = ds
}

1.4.2. NewDockerServer

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// The unix socket for kubelet <-> dockershim communication.
glog.V(5).Infof("RemoteRuntimeEndpoint: %q, RemoteImageEndpoint: %q",
remoteRuntimeEndpoint,
remoteImageEndpoint)
glog.V(2).Infof("Starting the GRPC server for the docker CRI shim.")
server := dockerremote.NewDockerServer(remoteRuntimeEndpoint, ds)
if err := server.Start(); err != nil {
return nil, err
}

1.4.3. DockerServer.Start

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// Start starts the dockershim grpc server.
func (s *DockerServer) Start() error {
// Start the internal service.
if err := s.service.Start(); err != nil {
glog.Errorf("Unable to start docker service")
return err
}

glog.V(2).Infof("Start dockershim grpc server")
l, err := util.CreateListener(s.endpoint)
if err != nil {
return fmt.Errorf("failed to listen on %q: %v", s.endpoint, err)
}
// Create the grpc server and register runtime and image services.
s.server = grpc.NewServer(
grpc.MaxRecvMsgSize(maxMsgSize),
grpc.MaxSendMsgSize(maxMsgSize),
)
runtimeapi.RegisterRuntimeServiceServer(s.server, s.service)
runtimeapi.RegisterImageServiceServer(s.server, s.service)
go func() {
if err := s.server.Serve(l); err != nil {
glog.Fatalf("Failed to serve connections: %v", err)
}
}()
return nil
}

1.5. podWorker

构造podWorkersworkQueue

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klet.workQueue = queue.NewBasicWorkQueue(klet.clock)
klet.podWorkers = newPodWorkers(klet.syncPod, kubeDeps.Recorder, klet.workQueue, klet.resyncInterval, backOffPeriod, klet.podCache)

1.5.1. PodWorkers接口

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// PodWorkers is an abstract interface for testability.
type PodWorkers interface {
UpdatePod(options *UpdatePodOptions)
ForgetNonExistingPodWorkers(desiredPods map[types.UID]empty)
ForgetWorker(uid types.UID)
}

podWorker主要用来对pod相应事件进行处理和同步,包含以下三个方法:UpdatePodForgetNonExistingPodWorkersForgetWorker

2. 总结

  1. NewMainKubelet主要用来构造kubelet结构体,其中kubelet除了包含必要的配置和client(例如:kubeClient、csiClient等)外,最主要的包含各种manager来管理不同的任务。

  2. 核心的manager有以下几种:

    • oomWatcher:监控pod内存是否发生OOM。
    • podManager:管理pod的生命周期,包括对pod的增删改查操作等。
    • containerGC:对死亡容器进行垃圾回收。
    • imageManager:对容器镜像进行垃圾回收。
    • statusManager:与apiserver同步pod状态,同时也作状态缓存。
    • volumeManager:对pod的volume进行attached/detached/mounted/unmounted操作。
    • evictionManager:保证节点稳定,必要时对pod进行驱逐(例如资源不足的情况下)。
  3. NewMainKubelet还包含了serviceListernodeLister来监听servicenode的列表变化。

  4. kubelet使用到的containerRuntime目前主要是docker,其中rkt已废弃。NewMainKubelet启动了dockershim grpc server来执行docker相关操作。

  5. 构建了podWorker来对pod相关的更新逻辑进行处理。

参考文章:



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