这一篇文章我们先从NewMainKubelet开始。
一、NewMainKubelet
cmd/kubelet/kubelet.go
// 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(......) (*Kubelet, error) {
...
hostname, err := nodeutil.GetHostname(hostnameOverride)
if err != nil {
return nil, err
}
// Query the cloud provider for our node name, default to hostname
nodeName := types.NodeName(hostname)
if kubeDeps.Cloud != nil {
var err error
instances, ok := kubeDeps.Cloud.Instances()
if !ok {
return nil, fmt.Errorf("failed to get instances from cloud provider")
}
nodeName, err = instances.CurrentNodeName(context.TODO(), hostname)
if err != nil {
return nil, fmt.Errorf("error fetching current instance name from cloud provider: %v", err)
}
klog.V(2).Infof("cloud provider determined current node name to be %s", nodeName)
}
if kubeDeps.PodConfig == nil {
var err error
kubeDeps.PodConfig, err = makePodSourceConfig(kubeCfg, kubeDeps, nodeName, bootstrapCheckpointPath)
if err != nil {
return nil, err
}
}
containerGCPolicy := kubecontainer.ContainerGCPolicy{
MinAge: minimumGCAge.Duration,
MaxPerPodContainer: int(maxPerPodContainerCount),
MaxContainers: int(maxContainerCount),
}
daemonEndpoints := &v1.NodeDaemonEndpoints{
KubeletEndpoint: v1.DaemonEndpoint{Port: kubeCfg.Port},
}
imageGCPolicy := images.ImageGCPolicy{
MinAge: kubeCfg.ImageMinimumGCAge.Duration,
HighThresholdPercent: int(kubeCfg.ImageGCHighThresholdPercent),
LowThresholdPercent: int(kubeCfg.ImageGCLowThresholdPercent),
}
enforceNodeAllocatable := kubeCfg.EnforceNodeAllocatable
if experimentalNodeAllocatableIgnoreEvictionThreshold {
// Do not provide kubeCfg.EnforceNodeAllocatable to eviction threshold parsing if we are not enforcing Evictions
enforceNodeAllocatable = []string{}
}
thresholds, err := eviction.ParseThresholdConfig(enforceNodeAllocatable, kubeCfg.EvictionHard, kubeCfg.EvictionSoft, kubeCfg.EvictionSoftGracePeriod, kubeCfg.EvictionMinimumReclaim)
if err != nil {
return nil, err
}
evictionConfig := eviction.Config{
PressureTransitionPeriod: kubeCfg.EvictionPressureTransitionPeriod.Duration,
MaxPodGracePeriodSeconds: int64(kubeCfg.EvictionMaxPodGracePeriod),
Thresholds: thresholds,
KernelMemcgNotification: experimentalKernelMemcgNotification,
PodCgroupRoot: kubeDeps.ContainerManager.GetPodCgroupRoot(),
}
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)
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)}
// TODO: get the real node object of ourself,
// and use the real node name and UID.
// TODO: what is namespace for node?
nodeRef := &v1.ObjectReference{
Kind: "Node",
Name: string(nodeName),
UID: types.UID(nodeName),
Namespace: "",
}
containerRefManager := kubecontainer.NewRefManager()
oomWatcher := NewOOMWatcher(kubeDeps.CAdvisorInterface, kubeDeps.Recorder)
clusterDNS := make([]net.IP, 0, len(kubeCfg.ClusterDNS))
for _, ipEntry := range kubeCfg.ClusterDNS {
ip := net.ParseIP(ipEntry)
if ip == nil {
klog.Warningf("Invalid clusterDNS ip '%q'", ipEntry)
} else {
clusterDNS = append(clusterDNS, ip)
}
}
httpClient := &http.Client{}
parsedNodeIP := net.ParseIP(nodeIP)
protocol := utilipt.ProtocolIpv4
if parsedNodeIP != nil && parsedNodeIP.To4() == nil {
klog.V(0).Infof("IPv6 node IP (%s), assume IPv6 operation", nodeIP)
protocol = utilipt.ProtocolIpv6
}
klet := &Kubelet{
hostname: hostname,
hostnameOverridden: len(hostnameOverride) > 0,
nodeName: nodeName,
kubeClient: kubeDeps.KubeClient,
csiClient: kubeDeps.CSIClient,
heartbeatClient: kubeDeps.HeartbeatClient,
onRepeatedHeartbeatFailure: kubeDeps.OnHeartbeatFailure,
rootDirectory: rootDirectory,
resyncInterval: kubeCfg.SyncFrequency.Duration,
sourcesReady: config.NewSourcesReady(kubeDeps.PodConfig.SeenAllSources),
registerNode: registerNode,
registerWithTaints: registerWithTaints,
registerSchedulable: registerSchedulable,
dnsConfigurer: dns.NewConfigurer(kubeDeps.Recorder, nodeRef, parsedNodeIP, clusterDNS, kubeCfg.ClusterDomain, kubeCfg.ResolverConfig),
serviceLister: serviceLister,
nodeInfo: nodeInfo,
masterServiceNamespace: masterServiceNamespace,
streamingConnectionIdleTimeout: kubeCfg.StreamingConnectionIdleTimeout.Duration,
recorder: kubeDeps.Recorder,
cadvisor: kubeDeps.CAdvisorInterface,
cloud: kubeDeps.Cloud,
externalCloudProvider: cloudprovider.IsExternal(cloudProvider),
providerID: providerID,
nodeRef: nodeRef,
nodeLabels: nodeLabels,
nodeStatusUpdateFrequency: kubeCfg.NodeStatusUpdateFrequency.Duration,
nodeStatusReportFrequency: kubeCfg.NodeStatusReportFrequency.Duration,
os: kubeDeps.OSInterface,
oomWatcher: oomWatcher,
cgroupsPerQOS: kubeCfg.CgroupsPerQOS,
cgroupRoot: kubeCfg.CgroupRoot,
mounter: kubeDeps.Mounter,
maxPods: int(kubeCfg.MaxPods),
podsPerCore: int(kubeCfg.PodsPerCore),
syncLoopMonitor: atomic.Value{},
daemonEndpoints: daemonEndpoints,
containerManager: kubeDeps.ContainerManager,
containerRuntimeName: containerRuntime,
redirectContainerStreaming: crOptions.RedirectContainerStreaming,
nodeIP: parsedNodeIP,
nodeIPValidator: validateNodeIP,
clock: clock.RealClock{},
enableControllerAttachDetach: kubeCfg.EnableControllerAttachDetach,
iptClient: utilipt.New(utilexec.New(), utildbus.New(), protocol),
makeIPTablesUtilChains: kubeCfg.MakeIPTablesUtilChains,
iptablesMasqueradeBit: int(kubeCfg.IPTablesMasqueradeBit),
iptablesDropBit: int(kubeCfg.IPTablesDropBit),
experimentalHostUserNamespaceDefaulting: utilfeature.DefaultFeatureGate.Enabled(features.ExperimentalHostUserNamespaceDefaultingGate),
keepTerminatedPodVolumes: keepTerminatedPodVolumes,
nodeStatusMaxImages: nodeStatusMaxImages,
enablePluginsWatcher: utilfeature.DefaultFeatureGate.Enabled(features.KubeletPluginsWatcher),
}
if klet.cloud != nil {
klet.cloudResourceSyncManager = cloudresource.NewSyncManager(klet.cloud, nodeName, klet.nodeStatusUpdateFrequency)
}
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
if klet.experimentalHostUserNamespaceDefaulting {
klog.Infof("Experimental host user namespace defaulting is enabled.")
}
machineInfo, err := klet.cadvisor.MachineInfo()
if err != nil {
return nil, err
}
klet.machineInfo = machineInfo
imageBackOff := flowcontrol.NewBackOff(backOffPeriod, MaxContainerBackOff)
klet.livenessManager = proberesults.NewManager()
klet.podCache = kubecontainer.NewCache()
var checkpointManager checkpointmanager.CheckpointManager
if bootstrapCheckpointPath != "" {
checkpointManager, err = checkpointmanager.NewCheckpointManager(bootstrapCheckpointPath)
if err != nil {
return nil, fmt.Errorf("failed to initialize checkpoint manager: %+v", err)
}
}
// podManager is also responsible for keeping secretManager and configMapManager contents up-to-date.
klet.podManager = kubepod.NewBasicPodManager(kubepod.NewBasicMirrorClient(klet.kubeClient), secretManager, configMapManager, checkpointManager)
klet.statusManager = status.NewManager(klet.kubeClient, klet.podManager, klet)
if remoteRuntimeEndpoint != "" {
// remoteImageEndpoint is same as remoteRuntimeEndpoint if not explicitly specified
if remoteImageEndpoint == "" {
remoteImageEndpoint = remoteRuntimeEndpoint
}
}
// TODO: These need to become arguments to a standalone docker shim.
pluginSettings := dockershim.NetworkPluginSettings{
HairpinMode: kubeletconfiginternal.HairpinMode(kubeCfg.HairpinMode),
NonMasqueradeCIDR: nonMasqueradeCIDR,
PluginName: crOptions.NetworkPluginName,
PluginConfDir: crOptions.CNIConfDir,
PluginBinDirString: crOptions.CNIBinDir,
MTU: int(crOptions.NetworkPluginMTU),
}
klet.resourceAnalyzer = serverstats.NewResourceAnalyzer(klet, kubeCfg.VolumeStatsAggPeriod.Duration)
if containerRuntime == "rkt" {
klog.Fatalln("rktnetes has been deprecated in favor of rktlet. Please see https://github.com/kubernetes-incubator/rktlet for more information.")
}
// if left at nil, that means it is unneeded
var legacyLogProvider kuberuntime.LegacyLogProvider
switch containerRuntime {
case kubetypes.DockerContainerRuntime:
// 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
}
// The unix socket for kubelet <-> dockershim communication.
klog.V(5).Infof("RemoteRuntimeEndpoint: %q, RemoteImageEndpoint: %q",
remoteRuntimeEndpoint,
remoteImageEndpoint)
klog.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
}
// Create dockerLegacyService when the logging driver is not supported.
supported, err := ds.IsCRISupportedLogDriver()
if err != nil {
return nil, err
}
if !supported {
klet.dockerLegacyService = ds
legacyLogProvider = ds
}
case kubetypes.RemoteContainerRuntime:
// No-op.
break
default:
return nil, fmt.Errorf("unsupported CRI runtime: %q", containerRuntime)
}
runtimeService, imageService, err := getRuntimeAndImageServices(remoteRuntimeEndpoint, remoteImageEndpoint, kubeCfg.RuntimeRequestTimeout)
if err != nil {
return nil, err
}
klet.runtimeService = runtimeService
if utilfeature.DefaultFeatureGate.Enabled(features.RuntimeClass) && kubeDeps.DynamicKubeClient != nil {
klet.runtimeClassManager = runtimeclass.NewManager(kubeDeps.DynamicKubeClient)
}
runtime, err := kuberuntime.NewKubeGenericRuntimeManager(
kubecontainer.FilterEventRecorder(kubeDeps.Recorder),
klet.livenessManager,
seccompProfileRoot,
containerRefManager,
machineInfo,
klet,
kubeDeps.OSInterface,
klet,
httpClient,
imageBackOff,
kubeCfg.SerializeImagePulls,
float32(kubeCfg.RegistryPullQPS),
int(kubeCfg.RegistryBurst),
kubeCfg.CPUCFSQuota,
kubeCfg.CPUCFSQuotaPeriod,
runtimeService,
imageService,
kubeDeps.ContainerManager.InternalContainerLifecycle(),
legacyLogProvider,
klet.runtimeClassManager,
)
if err != nil {
return nil, err
}
klet.containerRuntime = runtime
klet.streamingRuntime = runtime
klet.runner = runtime
runtimeCache, err := kubecontainer.NewRuntimeCache(klet.containerRuntime)
if err != nil {
return nil, err
}
klet.runtimeCache = runtimeCache
if cadvisor.UsingLegacyCadvisorStats(containerRuntime, remoteRuntimeEndpoint) {
klet.StatsProvider = stats.NewCadvisorStatsProvider(
klet.cadvisor,
klet.resourceAnalyzer,
klet.podManager,
klet.runtimeCache,
klet.containerRuntime,
klet.statusManager)
} else {
klet.StatsProvider = stats.NewCRIStatsProvider(
klet.cadvisor,
klet.resourceAnalyzer,
klet.podManager,
klet.runtimeCache,
runtimeService,
imageService,
stats.NewLogMetricsService())
}
klet.pleg = pleg.NewGenericPLEG(klet.containerRuntime, plegChannelCapacity, plegRelistPeriod, klet.podCache, clock.RealClock{})
klet.runtimeState = newRuntimeState(maxWaitForContainerRuntime)
klet.runtimeState.addHealthCheck("PLEG", klet.pleg.Healthy)
if _, err := klet.updatePodCIDR(kubeCfg.PodCIDR); err != nil {
klog.Errorf("Pod CIDR update failed %v", err)
}
// 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))
// 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
if containerRuntime == kubetypes.RemoteContainerRuntime && utilfeature.DefaultFeatureGate.Enabled(features.CRIContainerLogRotation) {
// setup containerLogManager for CRI container runtime
containerLogManager, err := logs.NewContainerLogManager(
klet.runtimeService,
kubeCfg.ContainerLogMaxSize,
int(kubeCfg.ContainerLogMaxFiles),
)
if err != nil {
return nil, fmt.Errorf("failed to initialize container log manager: %v", err)
}
klet.containerLogManager = containerLogManager
} else {
klet.containerLogManager = logs.NewStubContainerLogManager()
}
if kubeCfg.ServerTLSBootstrap && kubeDeps.TLSOptions != nil && utilfeature.DefaultFeatureGate.Enabled(features.RotateKubeletServerCertificate) {
klet.serverCertificateManager, err = kubeletcertificate.NewKubeletServerCertificateManager(klet.kubeClient, kubeCfg, klet.nodeName, klet.getLastObservedNodeAddresses, certDirectory)
if err != nil {
return nil, fmt.Errorf("failed to initialize certificate manager: %v", err)
}
kubeDeps.TLSOptions.Config.GetCertificate = func(*tls.ClientHelloInfo) (*tls.Certificate, error) {
cert := klet.serverCertificateManager.Current()
if cert == nil {
return nil, fmt.Errorf("no serving certificate available for the kubelet")
}
return cert, nil
}
}
klet.probeManager = prober.NewManager(
klet.statusManager,
klet.livenessManager,
klet.runner,
containerRefManager,
kubeDeps.Recorder)
tokenManager := token.NewManager(kubeDeps.KubeClient)
if !utilfeature.DefaultFeatureGate.Enabled(features.MountPropagation) {
return nil, fmt.Errorf("mount propagation feature gate has been deprecated and will be removed in 1.14")
}
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.getPluginsRegistrationDir(), /* sockDir */
klet.getPluginsDir(), /* deprecatedSockDir */
)
}
// If the experimentalMounterPathFlag is set, we do not want to
// check node capabilities since the mount path is not the default
if len(experimentalMounterPath) != 0 {
experimentalCheckNodeCapabilitiesBeforeMount = false
// Replace the nameserver in containerized-mounter's rootfs/etc/resolve.conf with kubelet.ClusterDNS
// so that service name could be resolved
klet.dnsConfigurer.SetupDNSinContainerizedMounter(experimentalMounterPath)
}
// 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)
klet.reasonCache = NewReasonCache()
klet.workQueue = queue.NewBasicWorkQueue(klet.clock)
klet.podWorkers = newPodWorkers(klet.syncPod, kubeDeps.Recorder, klet.workQueue, klet.resyncInterval, backOffPeriod, klet.podCache)
klet.backOff = flowcontrol.NewBackOff(backOffPeriod, MaxContainerBackOff)
klet.podKillingCh = make(chan *kubecontainer.PodPair, podKillingChannelCapacity)
// 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)
if utilfeature.DefaultFeatureGate.Enabled(features.Sysctls) {
// add sysctl admission
runtimeSupport, err := sysctl.NewRuntimeAdmitHandler(klet.containerRuntime)
if err != nil {
return nil, err
}
// Safe, whitelisted sysctls can always be used as unsafe sysctls in the spec.
// Hence, we concatenate those two lists.
safeAndUnsafeSysctls := append(sysctlwhitelist.SafeSysctlWhitelist(), allowedUnsafeSysctls...)
sysctlsWhitelist, err := sysctl.NewWhitelist(safeAndUnsafeSysctls)
if err != nil {
return nil, err
}
klet.admitHandlers.AddPodAdmitHandler(runtimeSupport)
klet.admitHandlers.AddPodAdmitHandler(sysctlsWhitelist)
}
// enable active deadline handler
activeDeadlineHandler, err := newActiveDeadlineHandler(klet.statusManager, kubeDeps.Recorder, klet.clock)
if err != nil {
return nil, err
}
klet.AddPodSyncLoopHandler(activeDeadlineHandler)
klet.AddPodSyncHandler(activeDeadlineHandler)
criticalPodAdmissionHandler := preemption.NewCriticalPodAdmissionHandler(klet.GetActivePods, killPodNow(klet.podWorkers, kubeDeps.Recorder), kubeDeps.Recorder)
klet.admitHandlers.AddPodAdmitHandler(lifecycle.NewPredicateAdmitHandler(klet.getNodeAnyWay, criticalPodAdmissionHandler, klet.containerManager.UpdatePluginResources))
// apply functional Option's
for _, opt := range kubeDeps.Options {
opt(klet)
}
klet.appArmorValidator = apparmor.NewValidator(containerRuntime)
klet.softAdmitHandlers.AddPodAdmitHandler(lifecycle.NewAppArmorAdmitHandler(klet.appArmorValidator))
klet.softAdmitHandlers.AddPodAdmitHandler(lifecycle.NewNoNewPrivsAdmitHandler(klet.containerRuntime))
if utilfeature.DefaultFeatureGate.Enabled(features.NodeLease) {
klet.nodeLeaseController = nodelease.NewController(klet.clock, klet.heartbeatClient, string(klet.nodeName), kubeCfg.NodeLeaseDurationSeconds, klet.onRepeatedHeartbeatFailure)
}
klet.softAdmitHandlers.AddPodAdmitHandler(lifecycle.NewProcMountAdmitHandler(klet.containerRuntime))
// Finally, put the most recent version of the config on the Kubelet, so
// people can see how it was configured.
klet.kubeletConfiguration = *kubeCfg
// Generating the status funcs should be the last thing we do,
// since this relies on the rest of the Kubelet having been constructed.
klet.setNodeStatusFuncs = klet.defaultNodeStatusFuncs()
return klet, nil
}
方法非常长，但是很重要。主要做了以下几件事：
（1）为kubelet加载各种配置，比如pod信息源、垃圾回收相关配置、监听的端口等。其中的podConfig引申一下，它是pod的三种信息来源的聚合（文件、URL和API Server）。进入makePodSourceConfig方法即可发现这一点。kubelet可以通过这三条途径获取pod的信息。
（2）根据前面的一系列配置，创建一个kubelet实例。可以看到kubelet实例的元素有数十个之多；
（3）创建manager等配置项，完善kubelet实例。manager用于管理pod运行时所需要加载的资源。如servicemanager和configmapmanager就是管理Pod运行时所需的secret和configmap的。注意这里有对于secret和configmap的不同的更新策略的选择；
（4）判断容器运行时。可见，rkt已经废弃，可用的就是docker和其他。如果是docker，则创建一个docker shim server并运行。这一块很重要，后面详细分析；
（5）继续包装这个kubelet实例，为实例添加垃圾回收、imagemanager、volumemanager等等各种组件。其中有的组件值得仔细研究，我们后面进行分析；
（6）将NodeStatusFunc加入kubelet实例。这一步通过调用defaultNodeStatusFuncs方法实现。
进入这一方法：
pkg/kubelet/kubelet_node_status.go
// defaultNodeStatusFuncs is a factory that generates the default set of // setNodeStatus funcs func (kl *Kubelet) defaultNodeStatusFuncs() []func(*v1.Node) error { // if cloud is not nil, we expect the cloud resource sync manager to exist var nodeAddressesFunc func() ([]v1.NodeAddress, error) if kl.cloud != nil { nodeAddressesFunc = kl.cloudResourceSyncManager.NodeAddresses } var validateHostFunc func() error if kl.appArmorValidator != nil { validateHostFunc = kl.appArmorValidator.ValidateHost } var setters []func(n *v1.Node) error setters = append(setters, nodestatus.NodeAddress(kl.nodeIP, kl.nodeIPValidator, kl.hostname, kl.hostnameOverridden, kl.externalCloudProvider, kl.cloud, nodeAddressesFunc), nodestatus.MachineInfo(string(kl.nodeName), kl.maxPods, kl.podsPerCore, kl.GetCachedMachineInfo, kl.containerManager.GetCapacity, kl.containerManager.GetDevicePluginResourceCapacity, kl.containerManager.GetNodeAllocatableReservation, kl.recordEvent), nodestatus.VersionInfo(kl.cadvisor.VersionInfo, kl.containerRuntime.Type, kl.containerRuntime.Version), nodestatus.DaemonEndpoints(kl.daemonEndpoints), nodestatus.Images(kl.nodeStatusMaxImages, kl.imageManager.GetImageList), nodestatus.GoRuntime(), ) if utilfeature.DefaultFeatureGate.Enabled(features.AttachVolumeLimit) { setters = append(setters, nodestatus.VolumeLimits(kl.volumePluginMgr.ListVolumePluginWithLimits)) } setters = append(setters, nodestatus.MemoryPressureCondition(kl.clock.Now, kl.evictionManager.IsUnderMemoryPressure, kl.recordNodeStatusEvent), nodestatus.DiskPressureCondition(kl.clock.Now, kl.evictionManager.IsUnderDiskPressure, kl.recordNodeStatusEvent), nodestatus.PIDPressureCondition(kl.clock.Now, kl.evictionManager.IsUnderPIDPressure, kl.recordNodeStatusEvent), nodestatus.ReadyCondition(kl.clock.Now, kl.runtimeState.runtimeErrors, kl.runtimeState.networkErrors, validateHostFunc, kl.containerManager.Status, kl.recordNodeStatusEvent), nodestatus.VolumesInUse(kl.volumeManager.ReconcilerStatesHasBeenSynced, kl.volumeManager.GetVolumesInUse), // TODO(mtaufen): I decided not to move this setter for now, since all it does is send an event // and record state back to the Kubelet runtime object. In the future, I'd like to isolate // these side-effects by decoupling the decisions to send events and partial status recording // from the Node setters. kl.recordNodeSchedulableEvent, ) return setters }
可以看到方法将维护宿主节点运行状态相关的函数都加入进一个setters数组，并返回。这些函数，包括地址、内存、磁盘、存储卷等，维护了宿主机的信息和状态。
下面我们首先看一下docker shim server相关的内容。
二、DockerServer
前面提到，在NewMainKubelet方法中会判断容器运行时，对于docker的容器运行时进行一系列操作。
具体说来，先创建一个DockerService对象（通过NewDockerService方法）。这个对象中包含了一个CRI shim运行时需要包含的方法集合。根据这个对象创建一个DockerServer（通过NewDockerServer方法）结构体实例，然后执行server.Start方法运行这个实例。
看一下DockerServer结构体：
pkg/kubelet/dockershim/remote/docker_server.go
// DockerServer is the grpc server of dockershim.
type DockerServer struct {
// endpoint is the endpoint to serve on.
endpoint string
// service is the docker service which implements runtime and image services.
service dockershim.CRIService
// server is the grpc server.
server *grpc.Server
}
可以看出，结构体包含了这个grpc服务运行的端点、包含的CRIService、以及服务自身。
CRIService是一个接口，进入接口可以看到：
pkg/kubelet/dockershim/docker_service.go
// CRIService includes all methods necessary for a CRI server. type CRIService interface { runtimeapi.RuntimeServiceServer runtimeapi.ImageServiceServer Start() error }
对于一个CRI，需要包含RuntimeServiceServer和ImageServiceServer两大类方法，分别用于操作容器和镜像。
进入RuntimeServiceServer接口，可以看到接口定义了容器的启动、停止、删除、状态、进入等一系列容器级别的操作，以及对pod sandbox的pod级别的操作。
而进入ImageServiceServer接口，则可以看到镜像的列举、状态、拉取、删除、信息五条操作。
也就是说，只要我们能够将这两个接口中定义的全部方法都实现，我们也可以定义自己的CRI。这就是kubelet与CRI的解耦。用图片来表示，就是这样：
kubelet通过grpc协议调用grpc server中定义的一系列方法，实现与CRI的交互，对容器和镜像进行具体操作。
事实上，由于docker是k8s默认的CRI，如上所说，启动docker shim的过程都写在了k8s的源码中了。同样的，docker CRI的RuntimeServiceServer和ImageServiceServer两大类方法也都在k8s源码中定义好了，具体位置在pkg/kubelet/dockershim包中，这里就不一一列举了。