Kubernetes CSI插件注册（二）—— Kubelet CSI插件注册机制源码分析

1、概述

Kubernetes的CSI Plugin注册机制的实现分为两个部分，第一部分是 sidecar "node-driver-registrar"，第二部分是Kubelet的pluginManager，第一部分详细内容请参见《Kubernetes CSI插件注册（一）—— node-driver-registrar源码分析》，本文主要讲后者，即Kubelet的pluginManager模块的源码。

工程源码：https://github.com/kubernetes/kubernetes/tree/release-1.24

注意：本文基于Kubernetes 1.24.10版本编写。

2、Kubelet CSI插件注册原理

Kubelet的pluginManager模块会监听特定的目录 /var/lib/kubelet/plugins_registry（其中 /var/lib/kubelet 是Kubelet工作路径，可以变更）, sidecar "node-driver-registrar"实现了特定的接口（GRPC服务，RegistrationServer）向Kubelet提供插件注册信息并创建一个socket放到该目录下（每个csi 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，socket文件命名规则为：csi插件名-reg.sock），Kubelet的pluginManager模块会通过该socket获取CSI Plugin的信息（主要是csi plugin name和csi plugin socket的路径），并将其写入k8s node节点的annotations，从而实现CSI Plugin的注册操作。

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

结合sidecar "node-driver-registrar"和Kubelet的pluginManager可得出Kubernetes CSI插件注册的完整步骤，步骤如下：

第 1 步

Node Driver Registrar 连接 csi plugin 组件暴露的 grpc 服务 socket 地址，调用 GetPluginInfo 接口，获取 csi plugin 的 driver 名称。

第 2 步

在/var/lib/kubelet/plugins_registry目录下启动一个 socket（socket文件名规则，csi插件名-reg.sock），对外暴露 GetInfo 和 NotifyRegistrationStatus 两个方法向Kubelet提供插件注册信息。Kubelet 通过 Watcher 可以发现该 socket。

第 3 步

Kubelet 通过 Watcher 监控/var/lib/kubelet/plugins_registry/目录，发现上述 socket 后，通过该 socket 调用 Node-Driver-Registrar 的 GetInfo 方法，获取 csi plugin 类型、csi plugin 的 driver 名称、csi plugin 暴露的 grpc 服务 socket 地址以及 csi plugin 支持的版本。

第 4 步

Kubelet 通过 csi plugin 组件暴露的 grpc 服务 socket 地址对其 NodeGetInfo 方法进行调用，获取 csi plugin 的 nodeID、存储卷最大挂载数、拓扑信息。

第 5 步

Kubelet 根据上一步获得的信息，去更新 node 节点的 Annotations信息，同时创建（或更新）一个 CSINode 对象。

第 6 步

Kubelet 通过 socket 调用 Node-Driver-Registrar 容器的 NotifyRegistrationStatus 方法，通知注册 csi plugin 成功。

通过以上 6 步就实现了Kubernetes CSI Plugin注册机制。

3、Kubelet pluginManger源码分析

Kubelet的pluginManager模块借助sidecar "node-driver-registrar"提供的GRPC服务（即RegistrationServer）完成Kubernetes CSI插件注册，在《Kubernetes CSI插件注册（一）—— node-driver-registrar源码分析》这篇博文中分析了node-driver-registrar工程源码，在此篇博文中重点分析下Kubelet的pluginManager模块的源码，分析将分为pluginManager的初始化分析以及pluginManager的运行（处理逻辑）两部分。

3.1 pluginManager的初始化源码分析

NewMainKubelet():

Kubelet进程启动时，会调用NewMainKubelet()方法初始化Kubelet，紧接着NewMainKubelet()方法会调用pluginmanager.NewPluginManager来初始化pluginManager，所以把NewMainKubelet()作为分析入口，Kubelet程序从main方法启动到调用NewMainKubelet()方法的调用栈如下：

  kubelet的main()方法 (cmd/kubelet/kubelet.go 40行) --> code := run(command) (cmd/kubelet/kubelet.go 47行) --> 
  return Run(....)（cmd/kubelet/app/server.go 267行）-->  err := run(....);（cmd/kubelet/app/server.go 406行）--> 
  RunKubelet(....)（cmd/kubelet/app/server.go 760行）--> createAndInitKubelet(....) （cmd/kubelet/app/server.go 1131行）--> 
  kubelet.NewMainKubelet(....)（cmd/kubelet/app/server.go 1236行）

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

        // pkg/kubelet/kubelet:740
	klet.pluginManager = pluginmanager.NewPluginManager(
		//  这里sockDir的值就是 /var/lib/kubelet/plugins_registry
		klet.getPluginsRegistrationDir(), /* sockDir */
		kubeDeps.Recorder,
	)

接着看下pluginManager结构体对象初始化及pluginManager的结构体的结构。

PluginManager结构体的初始化（pkg/kubelet/pluginmanager/plugin_manager.go）:

调用创建pluginManager结构体对象时会将sockDir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会在该目录下创建暴露服务的socket文件），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。

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
}

PluginManager结构体（pkg/kubelet/pluginmanager/plugin_manager.go）:

注意看，pluginManager结构体中定义了desiredStateOfWorldPopulator、actualStateOfWorld、desiredStateOfWorld 和 reconciler 字段。

type PluginManager interface {
	// Starts the plugin manager and all the asynchronous loops that it controls
	Run(sourcesReady config.SourcesReady, stopCh <-chan struct{})

	// AddHandler adds the given plugin handler for a specific plugin type, which
	// will be added to the actual state of world cache so that it can be passed to
	// the desired state of world cache in order to be used during plugin
	// registration/deregistration
	AddHandler(pluginType string, pluginHandler cache.PluginHandler)
}

const (
	// loopSleepDuration is the amount of time the reconciler loop waits
	// between successive executions
	loopSleepDuration = 1 * time.Second
)

// 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
}

var _ PluginManager = &pluginManager{}

如果没怎么看过其他的k8s代码，可能对k8s的actualStateOfWorld（后文简称asw）和desiredStateOfWorld（后文简称dsw）不熟悉。
在遵循声明式管理的k8s中，dsw一般对应了k8s资源的spec，即期望状态。asw一般对应了k8s资源的status，即实际状态。k8s最常见的一个处理框架，即是监测到外界变化后，先将其写入dsw，然后在reconciler中对dsw和asw进行比较，做相应的处理后，再把dsw中的变化写入asw，让两者同步。
在pluginManger中，也有着相似的处理:
asw中存放的是已经在k8s中已成功注册的plugin信息，dsw中存放的是期望注册的plugin信息，后续会讲到Kubelet是如何监测到plugin的变化并将其存储到dsw，最终同步到asw。

actualStateOfWorld（pkg/kubelet/pluginmanager/cache/actual_state_of_world.go）：

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。

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 reconciler 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
}

var _ ActualStateOfWorld = &actualStateOfWorld{}

// PluginInfo holds information of a plugin
type PluginInfo struct {
	SocketPath string
	Timestamp  time.Time
	Handler    PluginHandler
	Name       string
}

desiredStateOfWorld（pkg/kubelet/pluginmanager/cache/desired_state_of_world.go）：

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信息。

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
}

var _ DesiredStateOfWorld = &desiredStateOfWorld{}

reconciler（pkg/kubelet/pluginmanager/reconciler/reconciler.go）:

reconciler对比desiredStateOfWorld与actualStateOfWorld做调谐，做plugin的注册操作/取消注册操作。

type Reconciler interface {
	// Run starts running the reconciliation loop which executes periodically,
	// checks if plugins are correctly registered or unregistered.
	// If not, it will trigger register/unregister operations to rectify.
	Run(stopCh <-chan struct{})

	// AddHandler adds the given plugin handler for a specific plugin type,
	// which will be added to the actual state of world cache.
	AddHandler(pluginType string, pluginHandler cache.PluginHandler)
}

// NewReconciler returns a new instance of Reconciler.
//
// loopSleepDuration - the amount of time the reconciler loop sleeps between
//
//	successive executions
//	syncDuration - the amount of time the syncStates sleeps between
//	successive executions
//
// operationExecutor - used to trigger register/unregister operations safely
//
//	(prevents more than one operation from being triggered on the same
//	socket path)
//
// desiredStateOfWorld - cache containing the desired state of the world
// actualStateOfWorld - cache containing the actual state of the world
func NewReconciler(
	operationExecutor operationexecutor.OperationExecutor,
	loopSleepDuration time.Duration,
	desiredStateOfWorld cache.DesiredStateOfWorld,
	actualStateOfWorld cache.ActualStateOfWorld) Reconciler {
	return &reconciler{
		operationExecutor:   operationExecutor,
		loopSleepDuration:   loopSleepDuration,
		desiredStateOfWorld: desiredStateOfWorld,
		actualStateOfWorld:  actualStateOfWorld,
		handlers:            make(map[string]cache.PluginHandler),
	}
}

type reconciler struct {
	operationExecutor   operationexecutor.OperationExecutor
	loopSleepDuration   time.Duration
	desiredStateOfWorld cache.DesiredStateOfWorld
	actualStateOfWorld  cache.ActualStateOfWorld
	handlers            map[string]cache.PluginHandler
	sync.RWMutex
}

var _ Reconciler = &reconciler{}

Watcher（pkg/kubelet/pluginmanager/pluginwatcher/plugin_watcher.go）:

监听plugins_registry目录下socket文件的新增/删除，进而更新dsw中存放的plugin信息。

// Watcher is the plugin watcher
type Watcher struct {
	path                string
	fs                  utilfs.Filesystem
	fsWatcher           *fsnotify.Watcher
	desiredStateOfWorld cache.DesiredStateOfWorld
}

// NewWatcher provides a new watcher for socket registration
func NewWatcher(sockDir string, desiredStateOfWorld cache.DesiredStateOfWorld) *Watcher {
	return &Watcher{
		path:                sockDir,
		fs:                  &utilfs.DefaultFs{},
		desiredStateOfWorld: desiredStateOfWorld,
	}
}

3.2 pluginManager的运行（处理逻辑）源码分析 

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main()方法 (cmd/kubelet/kubelet.go 40行) --> code := run(command) (cmd/kubelet/kubelet.go 47行) --> 
  return Run(....)（cmd/kubelet/app/server.go 267行）-->  err := run(....);（cmd/kubelet/app/server.go 406行）--> 
  RunKubelet(....)（cmd/kubelet/app/server.go 760行）--> startKubelet(....) （cmd/kubelet/app/server.go 1181行）--> 
  go k.Run(....)（cmd/kubelet/app/server.go 1190行）--> 	go wait.Until(kl.updateRuntimeUp, ...) (pkg/kubelet/kubelet.go 1438行) --> 
  kl.oneTimeInitializer.Do(kl.initializeRuntimeDependentModules) (pkg/kubelet/kubelet.go 2370行,oneTimeInitializer是sync.Once函数)-->
  go kl.pluginManager.Run(kl.sourcesReady, wait.NeverStop) (pkg/kubelet/kubelet.go 1396行) 

注意，在执行kl.pluginManager.Run()方法前，pluginManager对象添加了CSI插件注册回调方法和设备插件回调方法。

	// Adding Registration Callback function for CSI Driver
	kl.pluginManager.AddHandler(pluginwatcherapi.CSIPlugin, plugincache.PluginHandler(csi.PluginHandler))
	// Adding Registration Callback function for Device Manager
	kl.pluginManager.AddHandler(pluginwatcherapi.DevicePlugin, kl.containerManager.GetPluginRegistrationHandler())
	// Start the plugin manager
	klog.V(4).InfoS("Starting plugin manager")
	go kl.pluginManager.Run(kl.sourcesReady, wait.NeverStop)

插件handler结构体必须实现插件验证方法、插件注册方法以及插件删除方法。

type PluginHandler interface {
	// Validate returns an error if the information provided by
	// the potential plugin is erroneous (unsupported version, ...)
	ValidatePlugin(pluginName string, endpoint string, versions []string) error
	// RegisterPlugin is called so that the plugin can be register by any
	// plugin consumer
	// Error encountered here can still be Notified to the plugin.
	RegisterPlugin(pluginName, endpoint string, versions []string) error
	// DeRegister is called once the pluginwatcher observes that the socket has
	// been deleted.
	DeRegisterPlugin(pluginName string)
}

kl.pluginManager.Run（pkg/kubelet/pluginmanager/plugin_manager.go  109行）:

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/var/lib/kubelet/plugins_registry/目录下socket文件的变化事件（遍历/var/lib/kubelet/plugins_registry/目录包括其子目录下的所有socket文件），将Node Driver Registrar的socket信息写入desiredStateOfWorld中/从desiredStateOfWorld中删除；
（2）pm.reconciler.Run()： 对dsw和asw进行了同步，完成了plugin的注册/取消注册的操作。

func (pm *pluginManager) Run(sourcesReady config.SourcesReady, stopCh <-chan struct{}) {
	// 捕获崩溃并记录错误，默认不传参的话，在程序发送崩溃时，在控制台打印一下崩溃日志后再崩溃，方便技术人员排查程序错误
	defer runtime.HandleCrash()

	/*
	   对 plugins_registry 目录启动了一个watcher，监听create和delete的操作
	   监听到 create 事件，会将socket路径写入 dsw
	   监听到 delete 事件，会将socket路径从 dsw 移除
	*/
	pm.desiredStateOfWorldPopulator.Start(stopCh)
	klog.V(2).InfoS("The desired_state_of_world populator (plugin watcher) starts")

	klog.InfoS("Starting Kubelet Plugin Manager")
	/*
	   调用了常见的 wait.Until，以cron的形式去调rc.reconcile()，对比dsw和asw，并进行同步
	*/
	go pm.reconciler.Run(stopCh)

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

pm.desiredStateOfWorldPopulator.Start(stopCh) （pkg/kubelet/pluginmanager/pluginwatcher/plugin_watcher.go）:

对 plugins_registry 目录启动了一个watcher，然后遍历plugins_registry目录（遍历目录中的现有子级），如果是dir便添加到watcher中监控，如果是socket文件便调用w.handleCreateEvent，将该socket加入到desiredStateOfWorld中，主要用于当节点kubelet服务重启时，注册节点已存在的kubelet插件。

之后运行一个goroutine，持续监听plugins_registry注册目录的变化事件：
（1）当变化事件为新增事件时，即plugins_registry目录下多了文件，则调用w.handleCreateEvent，如果多的文件是socket文件类型，将该socket加入到desiredStateOfWorld中；
（2）当变化事件为删除事件时，即plugins_registry目录下删除了文件，则调用w.handleDeleteEvent，，如果删除的文件是socket文件类型，将该socket从desiredStateOfWorld中删除。　

// Start watches for the creation and deletion of plugin sockets at the path
func (w *Watcher) Start(stopCh <-chan struct{}) error {
	klog.V(2).InfoS("Plugin Watcher Start", "path", w.path)

	// 如果plugins_registry目录（/var/lib/kubelet/plugins_registry/）目录不存在的话便创建plugins_registry目录
	// 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

	/*
	 在开始插件处理goroutine之前，遍历plugins_registry目录（遍历目录中的现有子级），如果是dir便添加到fsWtacher对象中监控，如果是socket文件便
	 新增fsnotify事件，并调用w.handleCreateEvent，将该socket加入到dsw中，如果是其他普通文件便忽略掉。其主要作用是当节点kubelet服务重启时，将
	 当前节点plugins_registry目录下已经存在的各种csi类型的Node Driver Registrar组件暴露的socket文件（当然也可能是设备插件暴露的socket文件）
	 注册到dsw，以使得kubelet的pluginManager组件完成各种csi组件的注册。
	 */
	// Traverse plugin dir and add filesystem watchers before starting the plugin processing goroutine.
	if err := w.traversePluginDir(w.path); err != nil {
		klog.ErrorS(err, "Failed to traverse plugin socket path", "path", w.path)
	}

	// 启动协程，for循环监听plugins_registry目录（遍历目录中的现有子级）下产生的fsnotify.create和fsnotify.delete的事件，并调用w.handleCreateEvent方法
	go func(fsWatcher *fsnotify.Watcher) {
		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.ErrorS(err, "Error when handling create event", "event", event)
					}
				} else if event.Op&fsnotify.Remove == fsnotify.Remove {
					w.handleDeleteEvent(event)
				}
				continue
			case err := <-fsWatcher.Errors:
				if err != nil {
					klog.ErrorS(err, "FsWatcher received error")
				}
				continue
			case <-stopCh:
				w.fsWatcher.Close()
				return
			}
		}
	}(fsWatcher)

	return nil
}

// Walks through the plugin directory discover any existing plugin sockets.
// Ignore all errors except root dir not being walkable
func (w *Watcher) traversePluginDir(dir string) error {
	// watch the new dir
	err := w.fsWatcher.Add(dir)
	if err != nil {
		return fmt.Errorf("failed to watch %s, err: %v", w.path, err)
	}
	// traverse existing children in the dir
	return w.fs.Walk(dir, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			if path == dir {
				return fmt.Errorf("error accessing path: %s error: %v", path, err)
			}

			klog.ErrorS(err, "Error accessing path", "path", path)
			return nil
		}

		// do not call fsWatcher.Add twice on the root dir to avoid potential problems.
		if path == dir {
			return nil
		}

		switch mode := info.Mode(); {
		case mode.IsDir():
			if err := w.fsWatcher.Add(path); err != nil {
				return fmt.Errorf("failed to watch %s, err: %v", path, err)
			}
		case mode&os.ModeSocket != 0:
			event := fsnotify.Event{
				Name: path,
				Op:   fsnotify.Create,
			}
			//TODO: Handle errors by taking corrective measures
			if err := w.handleCreateEvent(event); err != nil {
				klog.ErrorS(err, "Error when handling create", "event", event)
			}
		default:
			klog.V(5).InfoS("Ignoring file", "path", path, "mode", mode)
		}

		return nil
	})
}

w.handleCreateEvent()（pkg/kubelet/pluginmanager/pluginwatcher/plugin_watcher.go）:

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。

func (w *Watcher) handleCreateEvent(event fsnotify.Event) error {
	klog.V(6).InfoS("Handling create event", "event", event)

	fi, err := os.Stat(event.Name)
	// TODO: This is a workaround for Windows 20H2 issue for os.Stat(). Please see
	// microsoft/Windows-Containers#97 for details.
	// Once the issue is resvolved, the following os.Lstat() is not needed.
	if err != nil && runtime.GOOS == "windows" {
		fi, err = os.Lstat(event.Name)
	}
	if err != nil {
		return fmt.Errorf("stat file %s failed: %v", event.Name, err)
	}

	if strings.HasPrefix(fi.Name(), ".") {
		klog.V(5).InfoS("Ignoring file (starts with '.')", "path", 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).InfoS("Ignoring non socket file", "path", fi.Name())
			return nil
		}

		return w.handlePluginRegistration(event.Name)
	}

	// 如果新增的是dir，再将dir及dir中所有文件添加到fsWtacher对象中监控
	return w.traversePluginDir(event.Name)
}

func (w *Watcher) handlePluginRegistration(socketPath string) error {
	if runtime.GOOS == "windows" {
		socketPath = util.NormalizePath(socketPath)
	}
	// 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).InfoS("Adding socket path or updating timestamp to desired state cache", "path", 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
}

func (dsw *desiredStateOfWorld) AddOrUpdatePlugin(socketPath string) error {
	dsw.Lock()
	defer dsw.Unlock()

	if socketPath == "" {
		return fmt.Errorf("socket path is empty")
	}
	if _, ok := dsw.socketFileToInfo[socketPath]; ok {
		klog.V(2).InfoS("Plugin exists in actual state cache, timestamp will be updated", "path", socketPath)
	}

	// Update the PluginInfo object.
	// Note that we only update the timestamp in the desired state of world, not the actual state of world
	// because in the reconciler, we need to check if the plugin in the actual state of world is the same
	// version as the plugin in the desired state of world
	dsw.socketFileToInfo[socketPath] = PluginInfo{
		SocketPath: socketPath,
		Timestamp:  time.Now(),
	}
	return nil
}

w.handleDeleteEvent(event)（pkg/kubelet/pluginmanager/pluginwatcher/plugin_watcher.go）:

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

func (w *Watcher) handleDeleteEvent(event fsnotify.Event) {
	klog.V(6).InfoS("Handling delete event", "event", event)

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

func (dsw *desiredStateOfWorld) RemovePlugin(socketPath string) {
	dsw.Lock()
	defer dsw.Unlock()

	delete(dsw.socketFileToInfo, socketPath)
}

pm.reconciler.Run(stopCh)（pkg/kubelet/pluginmanager/reconciler/reconciler.go）:

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。

// 定时调度器，每隔1秒调用1次rc.reconcile()方法，时间间隔不包括执行rc.reconcile()方法逻辑时间
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
		// 如果desiredStateOfWorld中没有该socket信息，则说明该plugin需要取消注册
		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() {
				// 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，然后再重新完成一次注册操作流程）
				if dswPlugin.SocketPath == registeredPlugin.SocketPath && dswPlugin.Timestamp != registeredPlugin.Timestamp {
					klog.V(5).InfoS("An updated version of plugin has been found, unregistering the plugin first before reregistering", "plugin", registeredPlugin)
					unregisterPlugin = true
					break
				}
			}
		}

		// 取消插件
		if unregisterPlugin {
			klog.V(5).InfoS("Starting operationExecutor.UnregisterPlugin", "plugin", registeredPlugin)
			err := rc.operationExecutor.UnregisterPlugin(registeredPlugin, 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.ErrorS(err, "OperationExecutor.UnregisterPlugin failed", "plugin", registeredPlugin)
			}
			if err == nil {
				klog.V(1).InfoS("OperationExecutor.UnregisterPlugin started", "plugin", registeredPlugin)
			}
		}
	}

	// Ensure plugins that should be registered are registered
	for _, pluginToRegister := range rc.desiredStateOfWorld.GetPluginsToRegister() {
		// 忽略已注册的插件，即desiredStateOfWorld中该socket的Timestamp值与actualStateOfWorld中的相等
		if !rc.actualStateOfWorld.PluginExistsWithCorrectTimestamp(pluginToRegister) {
			klog.V(5).InfoS("Starting operationExecutor.RegisterPlugin", "plugin", pluginToRegister)
			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.ErrorS(err, "OperationExecutor.RegisterPlugin failed", "plugin", pluginToRegister)
			}
			if err == nil {
				klog.V(1).InfoS("OperationExecutor.RegisterPlugin started", "plugin", pluginToRegister)
			}
		}
	}
}

rc.operationExecutor.RegisterPlugin(....)  （pkg/kubelet/pluginmanager/operationexecutor/operation_executor.go）:

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.pendingOperations.Run() --> oe.operationGenerator.GenerateRegisterPluginFunc()
--> handler.RegisterPlugin() --> nim.InstallCSIDriver() --> nim.updateNode() && nim.updateCSINode()　　

下面来对plugin注册操作的部分关键方法进行分析。

GenerateRegisterPluginFunc(....)  (pkg/kubelet/pluginmanager/operationexecutor/operation_generator.go)

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（获取 csi插件类型、csi插件名、csi插件监听的grpc服务socket地址以及此csi插件支持的版本）；
（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；注意：自Kubernetes v1.17起，不再支持CSI v0.x 版本；
（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。

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)

func (grm *goRoutineMap) Run(
	operationName string,
	operationFunc func() error) error {
	grm.lock.Lock()
	defer grm.lock.Unlock()

	existingOp, exists := grm.operations[operationName]
	if exists {
		// Operation with name exists
		if existingOp.operationPending {
			return NewAlreadyExistsError(operationName)
		}

		if err := existingOp.expBackoff.SafeToRetry(operationName); err != nil {
			return err
		}
	}

	grm.operations[operationName] = operation{
		operationPending: true,
		expBackoff:       existingOp.expBackoff,
	}
	go func() (err error) {
		// 捕获崩溃并记录错误，默认不传参的话，在程序发送崩溃时，在控制台打印一下崩溃日志后再崩溃，方便技术人员排查程序错误。
		defer k8sRuntime.HandleCrash()
		/*
		  调用插件注册/删除方法不报错或者grm.exponentialBackOffOnError=false的话，将从grm.operations中移除此协程；
		  调用插件注册/删除方法报错并且grm.exponentialBackOffOnError=true，则将产生指数级补偿，到达补偿时间后才能调用插件注册/删除方法
		 */
		// Handle completion of and error, if any, from operationFunc()
		defer grm.operationComplete(operationName, &err)
		// Handle panic, if any, from operationFunc()
		defer k8sRuntime.RecoverFromPanic(&err)
		return operationFunc()
	}()

	return nil
}

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()

		// kubelet 作为Grpc客户端调用Grpc服务端（node-driver-registrar组件 RegistrationServer服务）的GetInfo方法，获取 csi插件类型、csi插件名、csi插件监听的grpc服务socket地址以及此csi插件支持的版本
		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)
		}

		// 判断此插件的类型是否在reconciler的Handlers中注册了，kubelet默认只注册了CSIPlugin和DevicePlugin两个类型
		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)
		}

		// 如果csi插件监听的grpc服务socket地址为空的话便设置其值为node-driver-registrar监听的socket地址
		if infoResp.Endpoint == "" {
			infoResp.Endpoint = socketPath
		}
		// 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；注意：自Kubernetes v1.17起，不再支持CSI v0.x 版本。
		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")
		}

		// 向actualStateOfWorld中增加该Node Driver Registrar组件的socket信息；
		// 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,   // node-driver-registrar监听的socket地址
			Timestamp:  timestamp,
			Handler:    handler,
			Name:       infoResp.Name,
		})
		if err != nil {
			klog.ErrorS(err, "RegisterPlugin error -- failed to add plugin", "path", socketPath)
		}
		/*
		插件注册
		1）插件版本验证；
		2）csiDrivers使用全局变量存放注册csi插件信息（后续kubelet调用csi plugin进行存储的挂载/解除挂载操作，将通过plugin名称从此变量中拿到socket地址并进行通信）；
		3）kubelet 作为Grpc客户端调用Grpc服务端（csi Plugin的NodeServer服务）的NodeGetInfo方法，返回参数：node在k8s集群id、存储卷最大挂载数、拓扑信息；
		4）更新node对象注解和标签（accessibleTopology值不为nil的话）；创建或更新CSINode对象，维护上此插件的drivers信息。
		 */
		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
}

// 告知Node Driver Registrar组件插件是否注册成功
func (og *operationGenerator) notifyPlugin(client registerapi.RegistrationClient, registered bool, errStr string) error {
	ctx, cancel := context.WithTimeout(context.Background(), notifyTimeoutDuration)
	defer cancel()

	status := &registerapi.RegistrationStatus{
		PluginRegistered: registered,
		Error:            errStr,
	}

	if _, err := client.NotifyRegistrationStatus(ctx, status); err != nil {
		return fmt.Errorf("%s: %w", errStr, err)
	}

	if errStr != "" {
		return errors.New(errStr)
	}

	return nil
}

// 用于创建访问Node Driver Registrar组件（RegistrationServer服务）的grpc客户端
// Dial establishes the gRPC communication with the picked up plugin socket. https://godoc.org/google.golang.org/grpc#Dial
func dial(unixSocketPath string, timeout time.Duration) (registerapi.RegistrationClient, *grpc.ClientConn, error) {
	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()

	c, err := grpc.DialContext(ctx, unixSocketPath, grpc.WithInsecure(), grpc.WithBlock(),
		grpc.WithContextDialer(func(ctx context.Context, addr string) (net.Conn, error) {
			return (&net.Dialer{}).DialContext(ctx, "unix", addr)
		}),
	)

	if err != nil {
		return nil, nil, fmt.Errorf("failed to dial socket %s, err: %v", unixSocketPath, err)
	}

	return registerapi.NewRegistrationClient(c), c, nil
}

handler.RegisterPlugin() （go/src/kubernetes_projects/kubernetes-1.24.10/pkg/volume/csi/csi_plugin.go）：

 handler.RegisterPlugin()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）kubelet 作为Grpc客户端调用Grpc服务端（csi Plugin的NodeServer服务）的NodeGetInfo方法，返回参数：node在k8s集群id、存储卷最大挂载数、拓扑信息
（3）调用nim.InstallCSIDriver，做进一步的plugin注册操作（插件注册，更新node对象注解和标签（accessibleTopology值不为nil的话）；创建或更新CSINode对象）。

// 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))

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

	// csiDrivers使用全局变量存放已注册csi插件信息，包括csi插件监听的grpc服务socket地址以及csi插件支持的最高版本
	// 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()

	// kubelet 作为Grpc客户端调用Grpc服务端（csi Plugin的NodeServer服务）的NodeGetInfo方法，返回参数：node在k8s集群id、存储卷最大挂载数、拓扑信息
	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
	}

	// 插件注册，更新node对象注解和标签（accessibleTopology值不为nil的话）；创建或更新CSINode对象。
	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() （pkg/volume/csi/nodeinfomanager/nodeinfomanager.go）

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。

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),
		updateTopologyLabels(topology),
	}

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

	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
}

// 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
	}
}

// updateTopologyLabels returns a function that updates labels of a Node object with the given
// topology information.
func updateTopologyLabels(topology map[string]string) nodeUpdateFunc {
	return func(node *v1.Node) (*v1.Node, bool, error) {
		if len(topology) == 0 {
			return node, false, nil
		}

		for k, v := range topology {
			if curVal, exists := node.Labels[k]; exists && curVal != v {
				return nil, false, fmt.Errorf("detected topology value collision: driver reported %q:%q but existing label is %q:%q", k, v, k, curVal)
			}
		}

		if node.Labels == nil {
			node.Labels = make(map[string]string)
		}
		for k, v := range topology {
			node.Labels[k] = v
		}
		return node, true, nil
	}
}

rc.operationExecutor.UnregisterPlugin(....)  （pkg/kubelet/pluginmanager/operationexecutor/operation_executor.go）:

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.uninstallDriverFromCSINode() --> nim.updateNode(
removeMaxAttachLimit(driverName),removeNodeIDFromNode(driverName))

下面来对plugin取消注册操作的部分关键方法进行分析。

GenerateUnregisterPluginFunc(....)  (pkg/kubelet/pluginmanager/operationexecutor/operation_generator.go)

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）从actualStateOfWorld中删除该Node Driver Registrar组件的socket信息；
（2）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。

func (oe *operationExecutor) UnregisterPlugin(
	pluginInfo cache.PluginInfo,
	actualStateOfWorld ActualStateOfWorldUpdater) error {
	generatedOperation :=
		oe.operationGenerator.GenerateUnregisterPluginFunc(pluginInfo, actualStateOfWorld)

	return oe.pendingOperations.Run(
		pluginInfo.SocketPath, generatedOperation)
}

func (grm *goRoutineMap) Run(
	operationName string,
	operationFunc func() error) error {
	grm.lock.Lock()
	defer grm.lock.Unlock()

	existingOp, exists := grm.operations[operationName]
        ......
        ......

	return nil
}

func (og *operationGenerator) GenerateUnregisterPluginFunc(
	pluginInfo cache.PluginInfo,
	actualStateOfWorldUpdater ActualStateOfWorldUpdater) func() error {

	unregisterPluginFunc := func() error {
		if pluginInfo.Handler == nil {
			return fmt.Errorf("UnregisterPlugin error -- failed to get plugin handler for %s", pluginInfo.SocketPath)
		}

		// actualStateOfWorld中删除该Node Driver Registrar组件的socket信息；
		// 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(pluginInfo.SocketPath)
        /*
		插件删除
		1）csiDrivers全局变量中删除已注册csi插件信息；
		2）更新或者删除csinode对象，删除此插件的drivers信息；更新node对象注解和status（maxAttachLimit或allocatable值不为nil的话）
         */
		pluginInfo.Handler.DeRegisterPlugin(pluginInfo.Name)

		klog.V(4).InfoS("DeRegisterPlugin called", "pluginName", pluginInfo.Name, "pluginHandler", pluginInfo.Handler)
		return nil
	}
	return unregisterPluginFunc
}

handler.DeRegisterPlugin() （go/src/kubernetes_projects/kubernetes-1.24.10/pkg/volume/csi/csi_plugin.go）：

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。

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()（pkg/volume/csi/nodeinfomanager/nodeinfomanager.go）:

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: '{"nfs.csi.k8s.io":"node2","rook-ceph.cephfs.csi.ceph.com":"node2","rook-ceph.rbd.csi.ceph.com":"node2"}'

CSINode对象示例：

[root@node2 ~]# kubectl get csinodes.storage.k8s.io node2  -o yaml
apiVersion: storage.k8s.io/v1
kind: CSINode
metadata:
  annotations:
    storage.alpha.kubernetes.io/migrated-plugins: kubernetes.io/cinder
  creationTimestamp: "2022-03-27T04:38:23Z"
  name: node2
  ownerReferences:
  - apiVersion: v1
    kind: Node
    name: node2
    uid: 1ec4f78b-9144-4255-8b65-464eccdb032b
  resourceVersion: "104431682"
  uid: 8542cd13-8f12-4549-8d05-94723fd83b8f
spec:
  drivers:
  - name: nfs.csi.k8s.io
    nodeID: node2
    topologyKeys: null
  - name: rook-ceph.cephfs.csi.ceph.com
    nodeID: node2
    topologyKeys: null
  - name: rook-ceph.rbd.csi.ceph.com
    nodeID: node2
    topologyKeys: null

nim.UninstallCSIDriver()源码：

func (nim *nodeInfoManager) UninstallCSIDriver(driverName string) error {
	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) 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 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
	}
}

// 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
	}
}

4、总结

本节主要讲解了Kubelet注册CSI Plugin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。

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CSI Plugin暴露的socket与CSI Plugin进行通信，做存储卷挂载/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）；
（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。

参考：https://juejin.cn/post/7126222522755842055

参考：https://www.cnblogs.com/lianngkyle/p/14906274.html

参考：https://www.jianshu.com/p/1d21a1e529d7