kubelet分析-csi driver注册源码分析

kubelet注册csi driver分析

kubelet注册csi driver的相关功能代码与kubelet的pluginManager有关，所以接下来对pluginManager进行分析。分析将分为pluginManager的初始化分析以及pluginManager的运行（处理逻辑）分析。

基于tag v1.17.4

https://github.com/kubernetes/kubernetes/releases/tag/v1.17.4

kubelet注册csi driver的原理

kubelet的pluginManager会监听某个特定目录，而负责向kubelet注册csi driver的组件Node Driver Registrar会创建暴露服务的socket在该目录下（每个plugin会对应一个Node Driver Registrar组件，也就是说，一个Node Driver Registrar只负责一个plugin的注册工作），pluginManager通过Node Driver Registrar组件暴露的socket获取plugin信息（包括plugin的socket地址、plugin名称等），从而最终做到根据该目录下socket文件的新增/删除来做相应的plugin注册/取消注册操作。

该图是Node Driver Registrar向kubelet注册csi driver的步骤流程图，这里大概看一下，具体请看这篇博客：Node Driver Registrar源码分析，结合本篇博客一起理解kubelet注册csi driver的整个过程。

plugin注册完成后，后续kubelet将通过plugin暴露的socket与plugin进行通信，做存储挂载/解除挂载等操作。

Node Driver Registrar

Node Driver Registrar在前面的文章中介绍过，它是一个sidecar容器，通过Kubelet的插件注册机制将CSI plugin（csi driver，两个名词意义一样）注册到Kubelet，让kubelet做volume的mount/umount操作时知道怎么调用相应的csi plugin。

kubelet pluginManager源码分析

1 pluginManager的初始化

调用NewMainKubelet()初始化kubelet的时候，会调用pluginmanager.NewPluginManager来初始化pluginManager，所以把NewMainKubelet()作为分析入口。

NewMainKubelet()

NewMainKubelet()中调用了pluginmanager.NewPluginManager来初始化pluginManager。

这里留意klet.getPluginsRegistrationDir()，调用该方法实际会返回plugins_registry，而该sockDir会传参进入pluginManager的desiredStateOfWorldPopulator结构体当中，相当于pluginManager会监听plugins_registry目录（负责向kubelet注册csi driver的组件Node Driver Registrar会创建暴露服务的socket在该目录下），pluginManager通过Node Driver Registrar组件暴露的socket获取plugin信息（包括plugin的socket地址、plugin名称等），从而最终做到根据该目录下socket文件的新增/删除来做相应的plugin注册/取消注册操作。

// pkg/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(kubeCfg *kubeletconfiginternal.KubeletConfiguration,
	...
	nodeStatusMaxImages int32) (*Kubelet, error) {
	...
    klet.pluginManager = pluginmanager.NewPluginManager(
		klet.getPluginsRegistrationDir(), /* sockDir */
		kubeDeps.Recorder,
	)
	...
}

// pkg/kubelet/pluginmanager/plugin_manager.go
// NewPluginManager returns a new concrete instance implementing the
// PluginManager interface.
func NewPluginManager(
	sockDir string,
	recorder record.EventRecorder) PluginManager {
	asw := cache.NewActualStateOfWorld()
	dsw := cache.NewDesiredStateOfWorld()
	reconciler := reconciler.NewReconciler(
		operationexecutor.NewOperationExecutor(
			operationexecutor.NewOperationGenerator(
				recorder,
			),
		),
		loopSleepDuration,
		dsw,
		asw,
	)

	pm := &pluginManager{
		desiredStateOfWorldPopulator: pluginwatcher.NewWatcher(
			sockDir,
			dsw,
		),
		reconciler:          reconciler,
		desiredStateOfWorld: dsw,
		actualStateOfWorld:  asw,
	}
	return pm
}

klet.getPluginsRegistrationDir()

调用klet.getPluginsRegistrationDir()会返回plugins_registry。

// pkg/kubelet/kubelet_getters.go
// getPluginsRegistrationDir returns the full path to the directory under which
// plugins socket should be placed to be registered.
// More information is available about plugin registration in the pluginwatcher
// module
func (kl *Kubelet) getPluginsRegistrationDir() string {
	return filepath.Join(kl.getRootDir(), config.DefaultKubeletPluginsRegistrationDirName)
}

// pkg/kubelet/config/defaults.go
const (
    ...
    DefaultKubeletPluginsRegistrationDirName = "plugins_registry"
    ...
)

2 pluginManager struct

再来看到pluginManager结构体，pluginManager结构体与volumeManager结构体类似，都有actualStateOfWorld与desiredStateOfWorld两个属性。

kubelet pluginManager监听的socket注册目录每增加/删除一个socket文件，都会写入desiredStateOfWorld中/从desiredStateOfWorld中删除。

// pkg/kubelet/pluginmanager/plugin_manager.go
// pluginManager implements the PluginManager interface
type pluginManager struct {
	// desiredStateOfWorldPopulator (the plugin watcher) runs an asynchronous
	// periodic loop to populate the desiredStateOfWorld.
	desiredStateOfWorldPopulator *pluginwatcher.Watcher

	// reconciler runs an asynchronous periodic loop to reconcile the
	// desiredStateOfWorld with the actualStateOfWorld by triggering register
	// and unregister operations using the operationExecutor.
	reconciler reconciler.Reconciler

	// actualStateOfWorld is a data structure containing the actual state of
	// the world according to the manager: i.e. which plugins are registered.
	// The data structure is populated upon successful completion of register
	// and unregister actions triggered by the reconciler.
	actualStateOfWorld cache.ActualStateOfWorld

	// desiredStateOfWorld is a data structure containing the desired state of
	// the world according to the plugin manager: i.e. what plugins are registered.
	// The data structure is populated by the desired state of the world
	// populator (plugin watcher).
	desiredStateOfWorld cache.DesiredStateOfWorld
}

actualStateOfWorld

actualStateOfWorld结构体中存放的是已经完成了plugin注册操作的Node Driver Registrar组件暴露的socket相关信息。

// ActualStateOfWorld defines a set of thread-safe operations for the kubelet
// plugin manager's actual state of the world cache.
// This cache contains a map of socket file path to plugin information of
// all plugins attached to this node.
type ActualStateOfWorld interface {

	// GetRegisteredPlugins generates and returns a list of plugins
	// that are successfully registered plugins in the current actual state of world.
	GetRegisteredPlugins() []PluginInfo

	// AddPlugin add the given plugin in the cache.
	// An error will be returned if socketPath of the PluginInfo object is empty.
	// Note that this is different from desired world cache's AddOrUpdatePlugin
	// because for the actual state of world cache, there won't be a scenario where
	// we need to update an existing plugin if the timestamps don't match. This is
	// because the plugin should have been unregistered in the reconciller and therefore
	// removed from the actual state of world cache first before adding it back into
	// the actual state of world cache again with the new timestamp
	AddPlugin(pluginInfo PluginInfo) error

	// RemovePlugin deletes the plugin with the given socket path from the actual
	// state of world.
	// If a plugin does not exist with the given socket path, this is a no-op.
	RemovePlugin(socketPath string)

	// PluginExists checks if the given plugin exists in the current actual
	// state of world cache with the correct timestamp
	PluginExistsWithCorrectTimestamp(pluginInfo PluginInfo) bool
}

// NewActualStateOfWorld returns a new instance of ActualStateOfWorld
func NewActualStateOfWorld() ActualStateOfWorld {
	return &actualStateOfWorld{
		socketFileToInfo: make(map[string]PluginInfo),
	}
}

type actualStateOfWorld struct {

	// socketFileToInfo is a map containing the set of successfully registered plugins
	// The keys are plugin socket file paths. The values are PluginInfo objects
	socketFileToInfo map[string]PluginInfo
	sync.RWMutex
}

desiredStateOfWorld

desiredStateOfWorld结构体中存放的是在pluginManager监听目录下存在的，希望完成plugin注册操作的Node Driver Registrar组件暴露的socket相关信息。

// DesiredStateOfWorld defines a set of thread-safe operations for the kubelet
// plugin manager's desired state of the world cache.
// This cache contains a map of socket file path to plugin information of
// all plugins attached to this node.
type DesiredStateOfWorld interface {
	// AddOrUpdatePlugin add the given plugin in the cache if it doesn't already exist.
	// If it does exist in the cache, then the timestamp of the PluginInfo object in the cache will be updated.
	// An error will be returned if socketPath is empty.
	AddOrUpdatePlugin(socketPath string) error

	// RemovePlugin deletes the plugin with the given socket path from the desired
	// state of world.
	// If a plugin does not exist with the given socket path, this is a no-op.
	RemovePlugin(socketPath string)

	// GetPluginsToRegister generates and returns a list of plugins
	// in the current desired state of world.
	GetPluginsToRegister() []PluginInfo

	// PluginExists checks if the given socket path exists in the current desired
	// state of world cache
	PluginExists(socketPath string) bool
}

// NewDesiredStateOfWorld returns a new instance of DesiredStateOfWorld.
func NewDesiredStateOfWorld() DesiredStateOfWorld {
	return &desiredStateOfWorld{
		socketFileToInfo: make(map[string]PluginInfo),
	}
}

type desiredStateOfWorld struct {

	// socketFileToInfo is a map containing the set of successfully registered plugins
	// The keys are plugin socket file paths. The values are PluginInfo objects
	socketFileToInfo map[string]PluginInfo
	sync.RWMutex
}

3 pluginManager的运行

上面介绍了pluginManager的初始化，接下来介绍pluginManager的运行也即Run方法进行分析，分析一下pluginManager的处理逻辑。

因为调用逻辑比较复杂，这里直接跳过了调用过程的分析，直接进入kl.pluginManager.Run()的分析，下面只给出该方法的一个调用链：
kubelet的Run()方法（pkg/kubelet/kubelet.go） --> kl.updateRuntimeUp()（pkg/kubelet/kubelet.go） --> kl.initializeRuntimeDependentModules()（pkg/kubelet/kubelet.go） --> kl.pluginManager.Run()

kl.pluginManager.Run

下面直接看到kl.pluginManager.Run的代码。
该方法主要逻辑有两个：
（1）pm.desiredStateOfWorldPopulator.Start()：持续监听plugin的socket注册目录的变化事件，将Node Driver Registrar的socket信息写入desiredStateOfWorld中/从desiredStateOfWorld中删除；
（2）pm.reconciler.Run()。

// pkg/kubelet/pluginmanager/plugin_manager.go
func (pm *pluginManager) Run(sourcesReady config.SourcesReady, stopCh <-chan struct{}) {
	defer runtime.HandleCrash()

	pm.desiredStateOfWorldPopulator.Start(stopCh)
	klog.V(2).Infof("The desired_state_of_world populator (plugin watcher) starts")

	klog.Infof("Starting Kubelet Plugin Manager")
	go pm.reconciler.Run(stopCh)

	metrics.Register(pm.actualStateOfWorld, pm.desiredStateOfWorld)
	<-stopCh
	klog.Infof("Shutting down Kubelet Plugin Manager")
}

3.1 pm.desiredStateOfWorldPopulator.Start()

跑一个goroutine，持续监听plugin的socket注册目录的变化事件：
（1）当变化事件为新增事件时，即socket目录下多了文件，则调用w.handleCreateEvent，将该socket加入到desiredStateOfWorld中；
（2）当变化事件为删除事件时，即socket目录下删除了文件，则调用w.handleDeleteEvent，将该socket从desiredStateOfWorld中删除。

// pkg/kubelet/pluginmanager/pluginwatcher/plugin_watcher.go
// Start watches for the creation and deletion of plugin sockets at the path
func (w *Watcher) Start(stopCh <-chan struct{}) error {
	klog.V(2).Infof("Plugin Watcher Start at %s", w.path)

	w.stopped = make(chan struct{})

	// Creating the directory to be watched if it doesn't exist yet,
	// and walks through the directory to discover the existing plugins.
	if err := w.init(); err != nil {
		return err
	}

	fsWatcher, err := fsnotify.NewWatcher()
	if err != nil {
		return fmt.Errorf("failed to start plugin fsWatcher, err: %v", err)
	}
	w.fsWatcher = fsWatcher

	// Traverse plugin dir and add filesystem watchers before starting the plugin processing goroutine.
	if err := w.traversePluginDir(w.path); err != nil {
		klog.Errorf("failed to traverse plugin socket path %q, err: %v", w.path, err)
	}

	go func(fsWatcher *fsnotify.Watcher) {
		defer close(w.stopped)
		for {
			select {
			case event := <-fsWatcher.Events:
				//TODO: Handle errors by taking corrective measures
				if event.Op&fsnotify.Create == fsnotify.Create {
					err := w.handleCreateEvent(event)
					if err != nil {
						klog.Errorf("error %v when handling create event: %s", err, event)
					}
				} else if event.Op&fsnotify.Remove == fsnotify.Remove {
					w.handleDeleteEvent(event)
				}
				continue
			case err := <-fsWatcher.Errors:
				if err != nil {
					klog.Errorf("fsWatcher received error: %v", err)
				}
				continue
			case <-stopCh:
				// In case of plugin watcher being stopped by plugin manager, stop
				// probing the creation/deletion of plugin sockets.
				// Also give all pending go routines a chance to complete
				select {
				case <-w.stopped:
				case <-time.After(11 * time.Second):
					klog.Errorf("timeout on stopping watcher")
				}
				w.fsWatcher.Close()
				return
			}
		}
	}(fsWatcher)

	return nil
}

w.handleCreateEvent()

w.handleCreateEvent()主要逻辑：
（1）判断新增事件是否为文件，且是否是socket文件；
（2）是socket文件，则调用w.handlePluginRegistration做处理，主要是将该socket加入到desiredStateOfWorld中。

// pkg/kubelet/pluginmanager/pluginwatcher/plugin_watcher.go
func (w *Watcher) handleCreateEvent(event fsnotify.Event) error {
	klog.V(6).Infof("Handling create event: %v", event)

	fi, err := os.Stat(event.Name)
	if err != nil {
		return fmt.Errorf("stat file %s failed: %v", event.Name, err)
	}

	if strings.HasPrefix(fi.Name(), ".") {
		klog.V(5).Infof("Ignoring file (starts with '.'): %s", fi.Name())
		return nil
	}

	if !fi.IsDir() {
		isSocket, err := util.IsUnixDomainSocket(util.NormalizePath(event.Name))
		if err != nil {
			return fmt.Errorf("failed to determine if file: %s is a unix domain socket: %v", event.Name, err)
		}
		if !isSocket {
			klog.V(5).Infof("Ignoring non socket file %s", fi.Name())
			return nil
		}

		return w.handlePluginRegistration(event.Name)
	}

	return w.traversePluginDir(event.Name)
}

func (w *Watcher) handlePluginRegistration(socketPath string) error {
	if runtime.GOOS == "windows" {
		socketPath = util.NormalizePath(socketPath)
	}
	//TODO: Implement rate limiting to mitigate any DOS kind of attacks.
	// Update desired state of world list of plugins
	// If the socket path does exist in the desired world cache, there's still
	// a possibility that it has been deleted and recreated again before it is
	// removed from the desired world cache, so we still need to call AddOrUpdatePlugin
	// in this case to update the timestamp
	klog.V(2).Infof("Adding socket path or updating timestamp %s to desired state cache", socketPath)
	err := w.desiredStateOfWorld.AddOrUpdatePlugin(socketPath)
	if err != nil {
		return fmt.Errorf("error adding socket path %s or updating timestamp to desired state cache: %v", socketPath, err)
	}
	return nil
}

w.handleDeleteEvent()

w.handleDeleteEvent()主要逻辑：
（1）将socket从desiredStateOfWorld中删除。

// pkg/kubelet/pluginmanager/pluginwatcher/plugin_watcher.go
func (w *Watcher) handleDeleteEvent(event fsnotify.Event) {
	klog.V(6).Infof("Handling delete event: %v", event)

	socketPath := event.Name
	klog.V(2).Infof("Removing socket path %s from desired state cache", socketPath)
	w.desiredStateOfWorld.RemovePlugin(socketPath)
}

3.2 pm.reconciler.Run()

pm.reconciler.Run()主要逻辑为对比desiredStateOfWorld与actualStateOfWorld做调谐，做plugin的注册操作/取消注册操作。具体逻辑如下：
（1）对比actualStateOfWorld，如果desiredStateOfWorld中没有该socket信息，或者desiredStateOfWorld中该socket的Timestamp值与actualStateOfWorld中的不相等（即plugin更新了），则说明该plugin需要取消注册（更新的plugin需先取消注册，然后再次注册），调用rc.operationExecutor.UnregisterPlugin做plugin取消注册操作；
（2）对比desiredStateOfWorld，如果actualStateOfWorld中没有该socket信息，则调用rc.operationExecutor.RegisterPlugin做plugin注册操作。

// pkg/kubelet/pluginmanager/reconciler/reconciler.go
func (rc *reconciler) Run(stopCh <-chan struct{}) {
	wait.Until(func() {
		rc.reconcile()
	},
		rc.loopSleepDuration,
		stopCh)
}


func (rc *reconciler) reconcile() {
	// Unregisterations are triggered before registrations

	// Ensure plugins that should be unregistered are unregistered.
	for _, registeredPlugin := range rc.actualStateOfWorld.GetRegisteredPlugins() {
		unregisterPlugin := false
		if !rc.desiredStateOfWorld.PluginExists(registeredPlugin.SocketPath) {
			unregisterPlugin = true
		} else {
			// We also need to unregister the plugins that exist in both actual state of world
			// and desired state of world cache, but the timestamps don't match.
			// Iterate through desired state of world plugins and see if there's any plugin
			// with the same socket path but different timestamp.
			for _, dswPlugin := range rc.desiredStateOfWorld.GetPluginsToRegister() {
				if dswPlugin.SocketPath == registeredPlugin.SocketPath && dswPlugin.Timestamp != registeredPlugin.Timestamp {
					klog.V(5).Infof(registeredPlugin.GenerateMsgDetailed("An updated version of plugin has been found, unregistering the plugin first before reregistering", ""))
					unregisterPlugin = true
					break
				}
			}
		}

		if unregisterPlugin {
			klog.V(5).Infof(registeredPlugin.GenerateMsgDetailed("Starting operationExecutor.UnregisterPlugin", ""))
			err := rc.operationExecutor.UnregisterPlugin(registeredPlugin.SocketPath, rc.getHandlers(), rc.actualStateOfWorld)
			if err != nil &&
				!goroutinemap.IsAlreadyExists(err) &&
				!exponentialbackoff.IsExponentialBackoff(err) {
				// Ignore goroutinemap.IsAlreadyExists and exponentialbackoff.IsExponentialBackoff errors, they are expected.
				// Log all other errors.
				klog.Errorf(registeredPlugin.GenerateErrorDetailed("operationExecutor.UnregisterPlugin failed", err).Error())
			}
			if err == nil {
				klog.V(1).Infof(registeredPlugin.GenerateMsgDetailed("operationExecutor.UnregisterPlugin started", ""))
			}
		}
	}

	// Ensure plugins that should be registered are registered
	for _, pluginToRegister := range rc.desiredStateOfWorld.GetPluginsToRegister() {
		if !rc.actualStateOfWorld.PluginExistsWithCorrectTimestamp(pluginToRegister) {
			klog.V(5).Infof(pluginToRegister.GenerateMsgDetailed("Starting operationExecutor.RegisterPlugin", ""))
			err := rc.operationExecutor.RegisterPlugin(pluginToRegister.SocketPath, pluginToRegister.Timestamp, rc.getHandlers(), rc.actualStateOfWorld)
			if err != nil &&
				!goroutinemap.IsAlreadyExists(err) &&
				!exponentialbackoff.IsExponentialBackoff(err) {
				// Ignore goroutinemap.IsAlreadyExists and exponentialbackoff.IsExponentialBackoff errors, they are expected.
				klog.Errorf(pluginToRegister.GenerateErrorDetailed("operationExecutor.RegisterPlugin failed", err).Error())
			}
			if err == nil {
				klog.V(1).Infof(pluginToRegister.GenerateMsgDetailed("operationExecutor.RegisterPlugin started", ""))
			}
		}
	}
}

3.2.1 rc.operationExecutor.UnregisterPlugin()

rc.operationExecutor.UnregisterPlugin()主要逻辑：做plugin取消注册操作。

那plugin取消注册操作具体做了什么呢？继续往下分析。

plugin取消注册操作方法调用链

kl.pluginManager.Run --> pm.desiredStateOfWorldPopulator.Start() --> pm.reconciler.Run() --> rc.reconcile() --> rc.operationExecutor.UnregisterPlugin() --> oe.operationGenerator.GenerateUnregisterPluginFunc() --> handler.DeRegisterPlugin() --> nim.UninstallCSIDriver() --> nim.updateNode()

下面来对plugin取消注册操作的部分关键方法进行分析。

GenerateUnregisterPluginFunc

下面来分析下GenerateUnregisterPluginFunc的逻辑，主要是定义并实现一个plugin取消注册的方法，然后返回。plugin取消注册方法主要逻辑如下：
（1）检测Node Driver Registrar组件socket的连通性；
（2）通过Node Driver Registrar组件socket获取plugin信息；
（3）从actualStateOfWorld中删除该Node Driver Registrar组件的socket信息；
（4）调用handler.DeRegisterPlugin做进一步的plugin取消注册操作。

所以接下来会对handler.DeRegisterPlugin方法进行分析。

// pkg/kubelet/pluginmanager/operationexecutor/operation_executor.go
func (oe *operationExecutor) UnregisterPlugin(
	socketPath string,
	pluginHandlers map[string]cache.PluginHandler,
	actualStateOfWorld ActualStateOfWorldUpdater) error {
	generatedOperation :=
		oe.operationGenerator.GenerateUnregisterPluginFunc(socketPath, pluginHandlers, actualStateOfWorld)

	return oe.pendingOperations.Run(
		socketPath, generatedOperation)
}

// pkg/kubelet/pluginmanager/operationexecutor/operation_generator.go
func (og *operationGenerator) GenerateUnregisterPluginFunc(
	socketPath string,
	pluginHandlers map[string]cache.PluginHandler,
	actualStateOfWorldUpdater ActualStateOfWorldUpdater) func() error {

	unregisterPluginFunc := func() error {
		client, conn, err := dial(socketPath, dialTimeoutDuration)
		if err != nil {
			return fmt.Errorf("UnregisterPlugin error -- dial failed at socket %s, err: %v", socketPath, err)
		}
		defer conn.Close()

		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
		defer cancel()

		infoResp, err := client.GetInfo(ctx, &registerapi.InfoRequest{})
		if err != nil {
			return fmt.Errorf("UnregisterPlugin error -- failed to get plugin info using RPC GetInfo at socket %s, err: %v", socketPath, err)
		}

		handler, ok := pluginHandlers[infoResp.Type]
		if !ok {
			return fmt.Errorf("UnregisterPlugin error -- no handler registered for plugin type: %s at socket %s", infoResp.Type, socketPath)
		}

		// We remove the plugin to the actual state of world cache before calling a plugin consumer's Unregister handle
		// so that if we receive a register event during Register Plugin, we can process it as a Register call.
		actualStateOfWorldUpdater.RemovePlugin(socketPath)

		handler.DeRegisterPlugin(infoResp.Name)
		return nil
	}
	return unregisterPluginFunc
}

handler.DeRegisterPlugin()

handler.DeRegisterPlugin()方法里逻辑比较简单，主要是调用了unregisterDriver()方法。

unregisterDriver()方法主要逻辑：
（1）从csiDrivers变量中删除该plugin信息（后续kubelet调用csi plugin进行存储的挂载/解除挂载操作，将通过plugin名称从csiDrivers变量中拿到socket地址并进行通信，所以取消注册plugin时，需要从csiDrivers变量中把该plugin信息去除）；
（2）调用nim.UninstallCSIDriver()做进一步处理。

// pkg/volume/csi/csi_plugin.go
// DeRegisterPlugin is called when a plugin removed its socket, signaling
// it is no longer available
func (h *RegistrationHandler) DeRegisterPlugin(pluginName string) {
	klog.Info(log("registrationHandler.DeRegisterPlugin request for plugin %s", pluginName))
	if err := unregisterDriver(pluginName); err != nil {
		klog.Error(log("registrationHandler.DeRegisterPlugin failed: %v", err))
	}
}

func unregisterDriver(driverName string) error {
	csiDrivers.Delete(driverName)

	if err := nim.UninstallCSIDriver(driverName); err != nil {
		return errors.New(log("Error uninstalling CSI driver: %v", err))
	}

	return nil
}

nim.UninstallCSIDriver()

接下来看到nim.UninstallCSIDriver()方法的分析。

nim.UninstallCSIDriver()中主要看到nim.uninstallDriverFromCSINode()、removeMaxAttachLimit()与removeNodeIDFromNode()3个方法，主要逻辑都在其中：
（1）nim.uninstallDriverFromCSINode()：更新CSINode对象，从中去除取消注册的plugin的相关信息。
（2）removeMaxAttachLimit()：更新node对象，从node.Status.Capacity及node.Status.Allocatable中去除取消注册的plugin的相关信息。
（3）removeNodeIDFromNode()：更新node对象，从node对象的annotation中key为csi.volume.kubernetes.io/nodeid的值中去除取消注册的plugin信息。

node对象的annotation示例：

csi.volume.kubernetes.io/nodeid: '{"cephfs.csi.ceph.com":"192.168.1.10","rbd.csi.ceph.com":"192.168.1.10"}'

CSIDriver对象示例：

apiVersion: storage.k8s.io/v1
kind: CSINode
metadata:
  name: 192.168.1.10
spec:
  drivers:
  - name: cephfs.csi.ceph.com
    nodeID: 192.168.1.10
    topologyKeys: null
  - name: rbd.csi.ceph.com
    nodeID: 192.168.1.10
    topologyKeys: null

nim.UninstallCSIDriver()源码：

// pkg/volume/csi/nodeinfomanager/nodeinfomanager.go
// UninstallCSIDriver removes the node ID annotation from the Node object and CSIDrivers field from the
// CSINode object. If the CSINOdeInfo object contains no CSIDrivers, it will be deleted.
// If multiple calls to UninstallCSIDriver() are made in parallel, some calls might receive Node or
// CSINode update conflicts, which causes the function to retry the corresponding update.
func (nim *nodeInfoManager) UninstallCSIDriver(driverName string) error {
	if utilfeature.DefaultFeatureGate.Enabled(features.CSINodeInfo) {
		err := nim.uninstallDriverFromCSINode(driverName)
		if err != nil {
			return fmt.Errorf("error uninstalling CSI driver from CSINode object %v", err)
		}
	}

	err := nim.updateNode(
		removeMaxAttachLimit(driverName),
		removeNodeIDFromNode(driverName),
	)
	if err != nil {
		return fmt.Errorf("error removing CSI driver node info from Node object %v", err)
	}
	return nil
}

func (nim *nodeInfoManager) updateNode(updateFuncs ...nodeUpdateFunc) error {
	var updateErrs []error
	err := wait.ExponentialBackoff(updateBackoff, func() (bool, error) {
		if err := nim.tryUpdateNode(updateFuncs...); err != nil {
			updateErrs = append(updateErrs, err)
			return false, nil
		}
		return true, nil
	})
	if err != nil {
		return fmt.Errorf("error updating node: %v; caused by: %v", err, utilerrors.NewAggregate(updateErrs))
	}
	return nil
}

（1）nim.uninstallDriverFromCSINode()：更新CSINode对象，从中去除取消注册的plugin的相关信息。

// pkg/volume/csi/nodeinfomanager/nodeinfomanager.go
func (nim *nodeInfoManager) uninstallDriverFromCSINode(
	csiDriverName string) error {

	csiKubeClient := nim.volumeHost.GetKubeClient()
	if csiKubeClient == nil {
		return fmt.Errorf("error getting CSI client")
	}

	var updateErrs []error
	err := wait.ExponentialBackoff(updateBackoff, func() (bool, error) {
		if err := nim.tryUninstallDriverFromCSINode(csiKubeClient, csiDriverName); err != nil {
			updateErrs = append(updateErrs, err)
			return false, nil
		}
		return true, nil
	})
	if err != nil {
		return fmt.Errorf("error updating CSINode: %v; caused by: %v", err, utilerrors.NewAggregate(updateErrs))
	}
	return nil
}

func (nim *nodeInfoManager) tryUninstallDriverFromCSINode(
	csiKubeClient clientset.Interface,
	csiDriverName string) error {

	nodeInfoClient := csiKubeClient.StorageV1().CSINodes()
	nodeInfo, err := nodeInfoClient.Get(string(nim.nodeName), metav1.GetOptions{})
	if err != nil && errors.IsNotFound(err) {
		return nil
	} else if err != nil {
		return err
	}

	hasModified := false
	// Uninstall CSINodeDriver with name csiDriverName
	drivers := nodeInfo.Spec.Drivers[:0]
	for _, driver := range nodeInfo.Spec.Drivers {
		if driver.Name != csiDriverName {
			drivers = append(drivers, driver)
		} else {
			// Found a driver with name csiDriverName
			// Set hasModified to true because it will be removed
			hasModified = true
		}
	}

	if !hasModified {
		// No changes, don't update
		return nil
	}
	nodeInfo.Spec.Drivers = drivers

	_, err = nodeInfoClient.Update(nodeInfo)

	return err // do not wrap error

}

（2）removeMaxAttachLimit()：更新node对象，从node.Status.Capacity及node.Status.Allocatable中去除取消注册的plugin的相关信息。

// pkg/volume/csi/nodeinfomanager/nodeinfomanager.go
func removeMaxAttachLimit(driverName string) nodeUpdateFunc {
	return func(node *v1.Node) (*v1.Node, bool, error) {
		limitKey := v1.ResourceName(util.GetCSIAttachLimitKey(driverName))

		capacityExists := false
		if node.Status.Capacity != nil {
			_, capacityExists = node.Status.Capacity[limitKey]
		}

		allocatableExists := false
		if node.Status.Allocatable != nil {
			_, allocatableExists = node.Status.Allocatable[limitKey]
		}

		if !capacityExists && !allocatableExists {
			return node, false, nil
		}

		delete(node.Status.Capacity, limitKey)
		if len(node.Status.Capacity) == 0 {
			node.Status.Capacity = nil
		}

		delete(node.Status.Allocatable, limitKey)
		if len(node.Status.Allocatable) == 0 {
			node.Status.Allocatable = nil
		}

		return node, true, nil
	}
}

（3）removeNodeIDFromNode()：更新node对象，从node对象的annotation中key为csi.volume.kubernetes.io/nodeid的值中去除取消注册的plugin信息。

// pkg/volume/csi/nodeinfomanager/nodeinfomanager.go
// removeNodeIDFromNode returns a function that removes node ID information matching the given
// driver name from a Node object.
func removeNodeIDFromNode(csiDriverName string) nodeUpdateFunc {
	return func(node *v1.Node) (*v1.Node, bool, error) {
		var previousAnnotationValue string
		if node.ObjectMeta.Annotations != nil {
			previousAnnotationValue =
				node.ObjectMeta.Annotations[annotationKeyNodeID]
		}

		if previousAnnotationValue == "" {
			return node, false, nil
		}

		// Parse previousAnnotationValue as JSON
		existingDriverMap := map[string]string{}
		if err := json.Unmarshal([]byte(previousAnnotationValue), &existingDriverMap); err != nil {
			return nil, false, fmt.Errorf(
				"failed to parse node's %q annotation value (%q) err=%v",
				annotationKeyNodeID,
				previousAnnotationValue,
				err)
		}

		if _, ok := existingDriverMap[csiDriverName]; !ok {
			// Value is already missing in node annotation, nothing more to do
			return node, false, nil
		}

		// Delete annotation value
		delete(existingDriverMap, csiDriverName)
		if len(existingDriverMap) == 0 {
			delete(node.ObjectMeta.Annotations, annotationKeyNodeID)
		} else {
			jsonObj, err := json.Marshal(existingDriverMap)
			if err != nil {
				return nil, false, fmt.Errorf(
					"failed while trying to remove key %q from node %q annotation. Existing data: %v",
					csiDriverName,
					annotationKeyNodeID,
					previousAnnotationValue)
			}

			node.ObjectMeta.Annotations[annotationKeyNodeID] = string(jsonObj)
		}

		return node, true, nil
	}
}

3.2.2 rc.operationExecutor.RegisterPlugin()

rc.operationExecutor.RegisterPlugin()主要逻辑：做plugin注册操作。

那plugin注册操作具体做了什么呢？继续往下分析。

plugin注册操作方法调用链

kl.pluginManager.Run --> pm.desiredStateOfWorldPopulator.Start() --> pm.reconciler.Run() --> rc.reconcile() --> rc.operationExecutor.RegisterPlugin() --> oe.operationGenerator.GenerateRegisterPluginFunc() --> handler.RegisterPlugin() --> nim.InstallCSIDriver() --> nim.updateNode()

下面来对plugin注册操作的部分关键方法进行分析。

GenerateRegisterPluginFunc

下面来分析下GenerateRegisterPluginFunc的逻辑，主要是定义并实现一个plugin注册的方法，然后返回。plugin注册方法主要逻辑如下：
（1）检测Node Driver Registrar组件socket的连通性；
（2）通过Node Driver Registrar组件socket获取plugin信息（包括plugin的socket地址、plugin名称等）；
（3）调用handler.ValidatePlugin()，检查已注册的plugin中是否有比该需要注册的plugin同名的的更高的版本，如有，则返回注册失败，并通知plugin注册失败；
（4）向actualStateOfWorld中增加该Node Driver Registrar组件的socket信息；
（5）调用handler.RegisterPlugin()做进一步的plugin注册操作;
（6）调用og.notifyPlugin，通知plugin，已经向kubelet注册成功/注册失败。

所以接下来会对handler.RegisterPlugin()方法进行分析。

// pkg/kubelet/pluginmanager/operationexecutor/operation_executor.go
func (oe *operationExecutor) RegisterPlugin(
	socketPath string,
	timestamp time.Time,
	pluginHandlers map[string]cache.PluginHandler,
	actualStateOfWorld ActualStateOfWorldUpdater) error {
	generatedOperation :=
		oe.operationGenerator.GenerateRegisterPluginFunc(socketPath, timestamp, pluginHandlers, actualStateOfWorld)

	return oe.pendingOperations.Run(
		socketPath, generatedOperation)
}

// pkg/kubelet/pluginmanager/operationexecutor/operation_generator.go
func (og *operationGenerator) GenerateRegisterPluginFunc(
	socketPath string,
	timestamp time.Time,
	pluginHandlers map[string]cache.PluginHandler,
	actualStateOfWorldUpdater ActualStateOfWorldUpdater) func() error {

	registerPluginFunc := func() error {
		client, conn, err := dial(socketPath, dialTimeoutDuration)
		if err != nil {
			return fmt.Errorf("RegisterPlugin error -- dial failed at socket %s, err: %v", socketPath, err)
		}
		defer conn.Close()

		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
		defer cancel()

		infoResp, err := client.GetInfo(ctx, &registerapi.InfoRequest{})
		if err != nil {
			return fmt.Errorf("RegisterPlugin error -- failed to get plugin info using RPC GetInfo at socket %s, err: %v", socketPath, err)
		}

		handler, ok := pluginHandlers[infoResp.Type]
		if !ok {
			if err := og.notifyPlugin(client, false, fmt.Sprintf("RegisterPlugin error -- no handler registered for plugin type: %s at socket %s", infoResp.Type, socketPath)); err != nil {
				return fmt.Errorf("RegisterPlugin error -- failed to send error at socket %s, err: %v", socketPath, err)
			}
			return fmt.Errorf("RegisterPlugin error -- no handler registered for plugin type: %s at socket %s", infoResp.Type, socketPath)
		}

		if infoResp.Endpoint == "" {
			infoResp.Endpoint = socketPath
		}
		if err := handler.ValidatePlugin(infoResp.Name, infoResp.Endpoint, infoResp.SupportedVersions); err != nil {
			if err = og.notifyPlugin(client, false, fmt.Sprintf("RegisterPlugin error -- plugin validation failed with err: %v", err)); err != nil {
				return fmt.Errorf("RegisterPlugin error -- failed to send error at socket %s, err: %v", socketPath, err)
			}
			return fmt.Errorf("RegisterPlugin error -- pluginHandler.ValidatePluginFunc failed")
		}
		// We add the plugin to the actual state of world cache before calling a plugin consumer's Register handle
		// so that if we receive a delete event during Register Plugin, we can process it as a DeRegister call.
		err = actualStateOfWorldUpdater.AddPlugin(cache.PluginInfo{
			SocketPath: socketPath,
			Timestamp:  timestamp,
		})
		if err != nil {
			klog.Errorf("RegisterPlugin error -- failed to add plugin at socket %s, err: %v", socketPath, err)
		}
		if err := handler.RegisterPlugin(infoResp.Name, infoResp.Endpoint, infoResp.SupportedVersions); err != nil {
			return og.notifyPlugin(client, false, fmt.Sprintf("RegisterPlugin error -- plugin registration failed with err: %v", err))
		}

		// Notify is called after register to guarantee that even if notify throws an error Register will always be called after validate
		if err := og.notifyPlugin(client, true, ""); err != nil {
			return fmt.Errorf("RegisterPlugin error -- failed to send registration status at socket %s, err: %v", socketPath, err)
		}
		return nil
	}
	return registerPluginFunc
}

handler.RegisterPlugin()

handler.DeRegisterPlugin()方法主要逻辑：
（1）存储该plugin信息（主要是plugin名称与plugin的socket地址）到csiDrivers变量中（后续kubelet调用csi plugin进行存储的挂载/解除挂载操作，将通过plugin名称从此变量中拿到socket地址并进行通信）；
（2）检测Node Driver Registrar组件socket的连通性；
（3）通过plugin的socket获取plugin信息（包括plugin的NodeId、最大挂载数量限制、拓扑信息等）；
（4）调用nim.InstallCSIDriver，做进一步的plugin注册操作。

// pkg/volume/csi/csi_plugin.go

// TODO (verult) consider using a struct instead of global variables
// csiDrivers map keep track of all registered CSI drivers on the node and their
// corresponding sockets
var csiDrivers = &DriversStore{}

// RegisterPlugin is called when a plugin can be registered
func (h *RegistrationHandler) RegisterPlugin(pluginName string, endpoint string, versions []string) error {
	klog.Infof(log("Register new plugin with name: %s at endpoint: %s", pluginName, endpoint))

	highestSupportedVersion, err := h.validateVersions("RegisterPlugin", pluginName, endpoint, versions)
	if err != nil {
		return err
	}

	// Storing endpoint of newly registered CSI driver into the map, where CSI driver name will be the key
	// all other CSI components will be able to get the actual socket of CSI drivers by its name.
	csiDrivers.Set(pluginName, Driver{
		endpoint:                endpoint,
		highestSupportedVersion: highestSupportedVersion,
	})

	// Get node info from the driver.
	csi, err := newCsiDriverClient(csiDriverName(pluginName))
	if err != nil {
		return err
	}

	ctx, cancel := context.WithTimeout(context.Background(), csiTimeout)
	defer cancel()

	driverNodeID, maxVolumePerNode, accessibleTopology, err := csi.NodeGetInfo(ctx)
	if err != nil {
		if unregErr := unregisterDriver(pluginName); unregErr != nil {
			klog.Error(log("registrationHandler.RegisterPlugin failed to unregister plugin due to previous error: %v", unregErr))
		}
		return err
	}

	err = nim.InstallCSIDriver(pluginName, driverNodeID, maxVolumePerNode, accessibleTopology)
	if err != nil {
		if unregErr := unregisterDriver(pluginName); unregErr != nil {
			klog.Error(log("registrationHandler.RegisterPlugin failed to unregister plugin due to previous error: %v", unregErr))
		}
		return err
	}

	return nil
}

nim.InstallCSIDriver()

nim.InstallCSIDriver()中主要看到updateNodeIDInNode()与nim.updateCSINode()两个方法，主要逻辑都在其中：
（1）updateNodeIDInNode()：更新node对象，向node对象的annotation中key为csi.volume.kubernetes.io/nodeid的值中去增加注册的plugin信息。
（2）nim.updateCSINode()：创建或更新CSINode对象。

// pkg/volume/csi/nodeinfomanager/nodeinfomanager.go
// InstallCSIDriver updates the node ID annotation in the Node object and CSIDrivers field in the
// CSINode object. If the CSINode object doesn't yet exist, it will be created.
// If multiple calls to InstallCSIDriver() are made in parallel, some calls might receive Node or
// CSINode update conflicts, which causes the function to retry the corresponding update.
func (nim *nodeInfoManager) InstallCSIDriver(driverName string, driverNodeID string, maxAttachLimit int64, topology map[string]string) error {
	if driverNodeID == "" {
		return fmt.Errorf("error adding CSI driver node info: driverNodeID must not be empty")
	}

	nodeUpdateFuncs := []nodeUpdateFunc{
		updateNodeIDInNode(driverName, driverNodeID),
	}

	if utilfeature.DefaultFeatureGate.Enabled(features.CSINodeInfo) {
		nodeUpdateFuncs = append(nodeUpdateFuncs, updateTopologyLabels(topology))
	}

	err := nim.updateNode(nodeUpdateFuncs...)
	if err != nil {
		return fmt.Errorf("error updating Node object with CSI driver node info: %v", err)
	}

	if utilfeature.DefaultFeatureGate.Enabled(features.CSINodeInfo) {
		err = nim.updateCSINode(driverName, driverNodeID, maxAttachLimit, topology)
		if err != nil {
			return fmt.Errorf("error updating CSINode object with CSI driver node info: %v", err)
		}
	}
	return nil
}

// pkg/volume/csi/nodeinfomanager/nodeinfomanager.go
// updateNodeIDInNode returns a function that updates a Node object with the given
// Node ID information.
func updateNodeIDInNode(
	csiDriverName string,
	csiDriverNodeID string) nodeUpdateFunc {
	return func(node *v1.Node) (*v1.Node, bool, error) {
		existingDriverMap, err := buildNodeIDMapFromAnnotation(node)
		if err != nil {
			return nil, false, err
		}

		if val, ok := existingDriverMap[csiDriverName]; ok {
			if val == csiDriverNodeID {
				// Value already exists in node annotation, nothing more to do
				return node, false, nil
			}
		}

		// Add/update annotation value
		existingDriverMap[csiDriverName] = csiDriverNodeID
		jsonObj, err := json.Marshal(existingDriverMap)
		if err != nil {
			return nil, false, fmt.Errorf(
				"error while marshalling node ID map updated with driverName=%q, nodeID=%q: %v",
				csiDriverName,
				csiDriverNodeID,
				err)
		}

		if node.ObjectMeta.Annotations == nil {
			node.ObjectMeta.Annotations = make(map[string]string)
		}
		node.ObjectMeta.Annotations[annotationKeyNodeID] = string(jsonObj)

		return node, true, nil
	}
}

// pkg/volume/csi/nodeinfomanager/nodeinfomanager.go
func (nim *nodeInfoManager) updateCSINode(
	driverName string,
	driverNodeID string,
	maxAttachLimit int64,
	topology map[string]string) error {

	csiKubeClient := nim.volumeHost.GetKubeClient()
	if csiKubeClient == nil {
		return fmt.Errorf("error getting CSI client")
	}

	var updateErrs []error
	err := wait.ExponentialBackoff(updateBackoff, func() (bool, error) {
		if err := nim.tryUpdateCSINode(csiKubeClient, driverName, driverNodeID, maxAttachLimit, topology); err != nil {
			updateErrs = append(updateErrs, err)
			return false, nil
		}
		return true, nil
	})
	if err != nil {
		return fmt.Errorf("error updating CSINode: %v; caused by: %v", err, utilerrors.NewAggregate(updateErrs))
	}
	return nil
}

总结

本节主要讲解了kubelet注册csi driver的原理，以及其代码的分析，也顺带提了一下Node Driver Registrar组件，下面来做个总结。

Node Driver Registrar

Node Driver Registrar在后面的文章中会介绍，Node Driver Registrar源码分析，它是一个sidecar容器，通过Kubelet的插件注册机制将CSI plugin（csi driver，两个名词意义一样）注册到Kubelet，让kubelet做volume的mount/umount操作时知道怎么调用相应的csi plugin。

kubelet注册csi driver的原理

kubelet的pluginManager会监听某个特定目录，而负责向kubelet注册csi driver的组件Node Driver Registrar会创建暴露服务的socket在该目录下（每个plugin会对应一个Node Driver Registrar组件，也就是说，一个Node Driver Registrar只负责一个plugin的注册工作），pluginManager通过Node Driver Registrar组件暴露的socket获取plugin信息（包括plugin的socket地址、plugin名称等），从而最终做到根据该目录下socket文件的新增/删除来做相应的plugin注册/取消注册操作。

plugin注册完成后，后续kubelet将通过plugin暴露的socket与plugin进行通信，做存储挂载/解除挂载等操作。

下面再来总结一下在kubelet的pluginManager中，plugin的注册/取消注册操作分别做了什么动作。

plugin注册操作

（1）存储该plugin信息（主要是plugin名称与plugin的socket地址）到csiDrivers变量中（后续kubelet调用csi plugin进行存储的挂载/解除挂载操作，将通过plugin名称从此变量中拿到socket地址并进行通信；csiDriver变量代码位置-pkg/volume/csi/csi_plugin.go）；
（2）更新node对象，向node对象的annotation中key为csi.volume.kubernetes.io/nodeid的值中去增加注册的plugin信息。
（3）创建或更新CSINode对象。

plugin取消注册操作

（1）从csiDrivers变量中删除该plugin信息（后续kubelet调用csi plugin进行存储的挂载/解除挂载操作，将通过plugin名称从csiDrivers变量（csiDriver变量代码位置-pkg/volume/csi/csi_plugin.go）中拿到socket地址并进行通信，所以取消注册plugin时，需要从csiDrivers变量中把该plugin信息去除）；
（2）更新CSINode对象，从中去除取消注册的plugin的相关信息。
（3）更新node对象，从node.Status.Capacity及node.Status.Allocatable中去除取消注册的plugin的相关信息。
（4）更新node对象，从node对象的annotation中key为csi.volume.kubernetes.io/nodeid的值中去除取消注册的plugin信息。