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西安网站建设开发制作,全网最全搜索引擎app,wordpress 收藏插件,网站设计的规范更多ceph-csi其他源码分析，请查看下面这篇博文：kubernetes ceph-csi分析目录导航 external-provisioner源码分析（2）-main方法与Leader选举分析本文将分为两大部分，第一部分对main方法进行分析，第二部分对…

更多ceph-csi其他源码分析，请查看下面这篇博文：kubernetes ceph-csi分析目录导航

external-provisioner源码分析（2）-main方法与Leader选举分析

本文将分为两大部分，第一部分对main方法进行分析，第二部分对该组件的Leader选举进行分析。

基于tag v1.6.0

https://github.com/kubernetes-csi/external-provisioner/releases/tag/v1.6.0

关联链接

external-provisioner组件的源码分析分为三部分：
（1）主体处理逻辑分析；
（2）main方法与Leader选举分析；
（3）组件启动参数分析。

1.main方法分析

主要对main方法的主要逻辑进行分析，以及分析下组件的EventHandler，看该组件list/watch哪些对象，对象事件来了怎么处理，以及claimQueue与volumeQueue的对象来源。

main方法主要逻辑分析

main方法主要逻辑：
（1）解析启动参数；
（2）根据配置建立clientset；
（3）与csi driver建立连接，建立grpc client；
（4）进行grpc探测（探测csi driver服务是否准备好），直至探测成功；
（5）与csi driver进行通信，获取driver名称与能力；
（6）根据clientset建立informers；
（7）构建provisionController对象；
（8）定义run方法（包括了provisionController.Run）；
（9）根据--enable-leader-election组件启动参数配置决定是否开启Leader 选举，当不开启时，直接运行run方法，开启时调用le.Run()。

func main() {var config *rest.Configvar err errorflag.Var(utilflag.NewMapStringBool(&featureGates), "feature-gates", "A set of key=value pairs that describe feature gates for alpha/experimental features. "+"Options are:\n"+strings.Join(utilfeature.DefaultFeatureGate.KnownFeatures(), "\n"))klog.InitFlags(nil)flag.CommandLine.AddGoFlagSet(goflag.CommandLine)flag.Set("logtostderr", "true")flag.Parse()if err := utilfeature.DefaultMutableFeatureGate.SetFromMap(featureGates); err != nil {klog.Fatal(err)}if *showVersion {fmt.Println(os.Args[0], version)os.Exit(0)}klog.Infof("Version: %s", version)// get the KUBECONFIG from env if specified (useful for local/debug cluster)kubeconfigEnv := os.Getenv("KUBECONFIG")if kubeconfigEnv != "" {klog.Infof("Found KUBECONFIG environment variable set, using that..")kubeconfig = &kubeconfigEnv}if *master != "" || *kubeconfig != "" {klog.Infof("Either master or kubeconfig specified. building kube config from that..")config, err = clientcmd.BuildConfigFromFlags(*master, *kubeconfig)} else {klog.Infof("Building kube configs for running in cluster...")config, err = rest.InClusterConfig()}if err != nil {klog.Fatalf("Failed to create config: %v", err)}clientset, err := kubernetes.NewForConfig(config)if err != nil {klog.Fatalf("Failed to create client: %v", err)}// snapclientset.NewForConfig creates a new Clientset for VolumesnapshotV1beta1ClientsnapClient, err := snapclientset.NewForConfig(config)if err != nil {klog.Fatalf("Failed to create snapshot client: %v", err)}// The controller needs to know what the server version is because out-of-tree// provisioners aren't officially supported until 1.5serverVersion, err := clientset.Discovery().ServerVersion()if err != nil {klog.Fatalf("Error getting server version: %v", err)}metricsManager := metrics.NewCSIMetricsManager("" /* driverName */)grpcClient, err := ctrl.Connect(*csiEndpoint, metricsManager)if err != nil {klog.Error(err.Error())os.Exit(1)}   // 循环探测，直至CSI driver即cephcsi-rbd服务准备好err = ctrl.Probe(grpcClient, *operationTimeout)if err != nil {klog.Error(err.Error())os.Exit(1)}// 从ceph-csi组件中获取driver nameprovisionerName, err := ctrl.GetDriverName(grpcClient, *operationTimeout)if err != nil {klog.Fatalf("Error getting CSI driver name: %s", err)}klog.V(2).Infof("Detected CSI driver %s", provisionerName)metricsManager.SetDriverName(provisionerName)metricsManager.StartMetricsEndpoint(*metricsAddress, *metricsPath)// 从ceph-csi组件中获取driver能力pluginCapabilities, controllerCapabilities, err := ctrl.GetDriverCapabilities(grpcClient, *operationTimeout)if err != nil {klog.Fatalf("Error getting CSI driver capabilities: %s", err)}// Generate a unique ID for this provisionertimeStamp := time.Now().UnixNano() / int64(time.Millisecond)identity := strconv.FormatInt(timeStamp, 10) + "-" + strconv.Itoa(rand.Intn(10000)) + "-" + provisionerName// 开始构建infomerfactory := informers.NewSharedInformerFactory(clientset, ctrl.ResyncPeriodOfCsiNodeInformer)// -------------------------------// Listers// Create informer to prevent hit the API server for all resource requestscLister := factory.Storage().V1().StorageClasses().Lister()claimLister := factory.Core().V1().PersistentVolumeClaims().Lister()var csiNodeLister storagelistersv1beta1.CSINodeListervar nodeLister v1.NodeListerif ctrl.SupportsTopology(pluginCapabilities) {csiNodeLister = factory.Storage().V1beta1().CSINodes().Lister()nodeLister = factory.Core().V1().Nodes().Lister()}// -------------------------------// PersistentVolumeClaims informerrateLimiter := workqueue.NewItemExponentialFailureRateLimiter(*retryIntervalStart, *retryIntervalMax)claimQueue := workqueue.NewNamedRateLimitingQueue(rateLimiter, "claims")claimInformer := factory.Core().V1().PersistentVolumeClaims().Informer()// Setup optionsprovisionerOptions := []func(*controller.ProvisionController) error{controller.LeaderElection(false), // Always disable leader election in provisioner lib. Leader election should be done here in the CSI provisioner level instead.controller.FailedProvisionThreshold(0),controller.FailedDeleteThreshold(0),controller.RateLimiter(rateLimiter),controller.Threadiness(int(*workerThreads)),controller.CreateProvisionedPVLimiter(workqueue.DefaultControllerRateLimiter()),controller.ClaimsInformer(claimInformer),}translator := csitrans.New()supportsMigrationFromInTreePluginName := ""if translator.IsMigratedCSIDriverByName(provisionerName) {supportsMigrationFromInTreePluginName, err = translator.GetInTreeNameFromCSIName(provisionerName)if err != nil {klog.Fatalf("Failed to get InTree plugin name for migrated CSI plugin %s: %v", provisionerName, err)}klog.V(2).Infof("Supports migration from in-tree plugin: %s", supportsMigrationFromInTreePluginName)provisionerOptions = append(provisionerOptions, controller.AdditionalProvisionerNames([]string{supportsMigrationFromInTreePluginName}))}// Create the provisioner: it implements the Provisioner interface expected by// the controllercsiProvisioner := ctrl.NewCSIProvisioner(clientset,*operationTimeout,identity,*volumeNamePrefix,*volumeNameUUIDLength,grpcClient,snapClient,provisionerName,pluginCapabilities,controllerCapabilities,supportsMigrationFromInTreePluginName,*strictTopology,translator,scLister,csiNodeLister,nodeLister,claimLister,*extraCreateMetadata,)provisionController = controller.NewProvisionController(clientset,provisionerName,csiProvisioner,serverVersion.GitVersion,provisionerOptions...,)csiClaimController := ctrl.NewCloningProtectionController(clientset,claimLister,claimInformer,claimQueue,)// 主循环函数run := func(context.Context) {stopCh := context.Background().Done()factory.Start(stopCh)cacheSyncResult := factory.WaitForCacheSync(stopCh)for _, v := range cacheSyncResult {if !v {klog.Fatalf("Failed to sync Informers!")}}// 跑两个controller，后面主要分析provisionControllergo csiClaimController.Run(int(*finalizerThreads), stopCh)provisionController.Run(wait.NeverStop)}// Leader 选举相关if !*enableLeaderElection {run(context.TODO())} else {// this lock name pattern is also copied from sigs.k8s.io/sig-storage-lib-external-provisioner/v5/controller// to preserve backwards compatibilitylockName := strings.Replace(provisionerName, "/", "-", -1)// 使用endpoints或leases资源对象来选leadervar le leaderElectionif *leaderElectionType == "endpoints" {klog.Warning("The 'endpoints' leader election type is deprecated and will be removed in a future release. Use '--leader-election-type=leases' instead.")le = leaderelection.NewLeaderElectionWithEndpoints(clientset, lockName, run)} else if *leaderElectionType == "leases" {le = leaderelection.NewLeaderElection(clientset, lockName, run)} else {klog.Error("--leader-election-type must be either 'endpoints' or 'leases'")os.Exit(1)}if *leaderElectionNamespace != "" {le.WithNamespace(*leaderElectionNamespace)}// 处理Leader 选举逻辑的方法if err := le.Run(); err != nil {klog.Fatalf("failed to initialize leader election: %v", err)}}}

controller.NewProvisionController

主要看到EventHandler，定义了该组件list/watch的对象，对象事件来了怎么处理，以及claimQueue与volumeQueue的对象来源。

claimHandler

可以看到，claimQueue的来源是pvc对象的新增、更新事件（对claimQueue的处理已在external-provisioner源码分析（1）-主体处理逻辑分析中讲过，忘了的话可以回头看下）。

    ...// PersistentVolumeClaimsclaimHandler := cache.ResourceEventHandlerFuncs{AddFunc:    func(obj interface{}) { controller.enqueueClaim(obj) },UpdateFunc: func(oldObj, newObj interface{}) { controller.enqueueClaim(newObj) },DeleteFunc: func(obj interface{}) {// NOOP. The claim is either in claimsInProgress and in the queue, so it will be processed as usual// or it's not in claimsInProgress and then we don't care},}if controller.claimInformer != nil {controller.claimInformer.AddEventHandlerWithResyncPeriod(claimHandler, controller.resyncPeriod)} else {controller.claimInformer = informer.Core().V1().PersistentVolumeClaims().Informer()controller.claimInformer.AddEventHandler(claimHandler)}...

// enqueueClaim takes an obj and converts it into UID that is then put onto claim work queue.
func (ctrl *ProvisionController) enqueueClaim(obj interface{}) {uid, err := getObjectUID(obj)if err != nil {utilruntime.HandleError(err)return}if ctrl.claimQueue.NumRequeues(uid) == 0 {ctrl.claimQueue.Add(uid)}
}

volumeHandler

可以看到，volumeQueue的来源是pv对象的新增、更新事件（对volumeQueue的处理已在external-provisioner源码分析（1）-主体处理逻辑分析中讲过，忘了的话可以回头看下）。

    ...// PersistentVolumesvolumeHandler := cache.ResourceEventHandlerFuncs{AddFunc:    func(obj interface{}) { controller.enqueueVolume(obj) },UpdateFunc: func(oldObj, newObj interface{}) { controller.enqueueVolume(newObj) },DeleteFunc: func(obj interface{}) { controller.forgetVolume(obj) },}if controller.volumeInformer != nil {controller.volumeInformer.AddEventHandlerWithResyncPeriod(volumeHandler, controller.resyncPeriod)} else {controller.volumeInformer = informer.Core().V1().PersistentVolumes().Informer()controller.volumeInformer.AddEventHandler(volumeHandler)}...

// enqueueVolume takes an obj and converts it into a namespace/name string which
// is then put onto the given work queue.
func (ctrl *ProvisionController) enqueueVolume(obj interface{}) {var key stringvar err errorif key, err = cache.DeletionHandlingMetaNamespaceKeyFunc(obj); err != nil {utilruntime.HandleError(err)return}// Re-Adding is harmless but try to add it to the queue only if it is not// already there, because if it is already there we *must* be retrying itif ctrl.volumeQueue.NumRequeues(key) == 0 {ctrl.volumeQueue.Add(key)}
}

// forgetVolume Forgets an obj from the given work queue, telling the queue to
// stop tracking its retries because e.g. the obj was deleted
func (ctrl *ProvisionController) forgetVolume(obj interface{}) {var key stringvar err errorif key, err = cache.DeletionHandlingMetaNamespaceKeyFunc(obj); err != nil {utilruntime.HandleError(err)return}ctrl.volumeQueue.Forget(key)ctrl.volumeQueue.Done(key)
}

2.Leader 选举分析

在 Golang 中，k8s client-go 这个package 针对 Leader 相关功能进行了封装，支持3种锁资源，endpoint，configmap，lease，方便使用。

Leader 选举基本原理

Leader 选举基本原理其实就是利用通过Kubernetes中 configmap ， endpoints 或者 lease 资源实现一个分布式锁，抢(acqure)到锁的节点成为leader，并且定期更新（renew）。其他进程也在不断的尝试进行抢占，抢占不到则继续等待下次循环。当leader节点挂掉之后，租约到期，其他节点就成为新的leader。

抢到锁其实就是成功把该进程的相关信息（如进程唯一标识）写入configmap、endpoints 或者 lease 资源对象中；而定期更新其实就是定期更新该资源的锁更新时间，以延续租期。

多个进程同时获取锁（更新锁资源）时，由apiserver来保证锁资源update的原子操作，通过对比resourceVersion版本号（resourceVersion的取值最终来源于etcd的modifiedindex），保证只有一个进程能修改成功，也即只有一个进程能成功获取到锁。

锁示例如下：

apiVersion: coordination.k8s.io/v1
kind: Lease
metadata:creationTimestamp: "2020-08-21T11:56:46Z"name: rbd-csi-ceph-comnamespace: defaultresourceVersion: "69642798"selfLink: /apis/coordination.k8s.io/v1/namespaces/default/leases/rbd-csi-ceph-comuid: c9a7ea00-c000-4c5c-b90f-d0e7c85240ca
spec:acquireTime: "2020-08-21T11:56:46.907075Z"holderIdentity: node-1leaseDurationSeconds: 15leaseTransitions: 0renewTime: "2020-09-07T02:38:24.587170Z"

其中holderIdentity记录了获取到锁的进程信息，renewTime记录了锁更新时间。

external-provisioner的Leader 选举

从main方法代码中可以看出，在external-provisioner组件中，仅支持endpoint与lease两种锁资源，且endpoints锁会在后续被弃用，所以建议使用lease锁。

external-provisioner组件的高可用选主逻辑与k8s中的kube-controller-manager、kube-scheduler等组件的高可用选主逻辑类似。

概要过程：
（1）组件启动时，定期循环的去获取lease锁，获取成功则成为leader且返回，否则一直阻塞；
（2）获取lease锁成功，则竞选leader成功，然后运行external-provisioner组件的主体处理逻辑；
（3）竞选leader成功后，继续定期循环续约，以保证leader的长久性。

下面进行代码的分析。

le.Run()

当--enable-leader-election组件启动参数为true时，运行该方法，主要逻辑为：
（1）定义leaderConfig结构体；
（2）调用leaderelection.RunOrDie做进一步的选主逻辑处理。

func (l *leaderElection) Run() error {if l.identity == "" {id, err := defaultLeaderElectionIdentity()if err != nil {return fmt.Errorf("error getting the default leader identity: %v", err)}l.identity = id}if l.namespace == "" {l.namespace = inClusterNamespace()}broadcaster := record.NewBroadcaster()broadcaster.StartRecordingToSink(&corev1.EventSinkImpl{Interface: l.clientset.CoreV1().Events(l.namespace)})eventRecorder := broadcaster.NewRecorder(scheme.Scheme, v1.EventSource{Component: fmt.Sprintf("%s/%s", l.lockName, string(l.identity))})rlConfig := resourcelock.ResourceLockConfig{Identity:      sanitizeName(l.identity),EventRecorder: eventRecorder,}lock, err := resourcelock.New(l.resourceLock, l.namespace, sanitizeName(l.lockName), l.clientset.CoreV1(), l.clientset.CoordinationV1(), rlConfig)if err != nil {return err}leaderConfig := leaderelection.LeaderElectionConfig{Lock:          lock,LeaseDuration: l.leaseDuration,RenewDeadline: l.renewDeadline,RetryPeriod:   l.retryPeriod,Callbacks: leaderelection.LeaderCallbacks{OnStartedLeading: func(ctx context.Context) {klog.V(2).Info("became leader, starting")l.runFunc(ctx)},OnStoppedLeading: func() {klog.Fatal("stopped leading")},OnNewLeader: func(identity string) {klog.V(3).Infof("new leader detected, current leader: %s", identity)},},}leaderelection.RunOrDie(context.TODO(), leaderConfig)return nil // should never reach here
}

leaderelection.RunOrDie()

主要逻辑：
（1）调用le.acquire()方法来尝试竞选为leader（acquire方法会定期循环的去获取lease锁，获取成功则成为leader且返回，否则一直阻塞）；
（2）竞选leader成功，运行run方法；
（3）调用le.renew()续约方法，定期循环续约。

// RunOrDie starts a client with the provided config or panics if the config
// fails to validate.
func RunOrDie(ctx context.Context, lec LeaderElectionConfig) {le, err := NewLeaderElector(lec)if err != nil {panic(err)}if lec.WatchDog != nil {lec.WatchDog.SetLeaderElection(le)}le.Run(ctx)
}// Run starts the leader election loop
func (le *LeaderElector) Run(ctx context.Context) {defer func() {runtime.HandleCrash()le.config.Callbacks.OnStoppedLeading()}()if !le.acquire(ctx) {return // ctx signalled done}ctx, cancel := context.WithCancel(ctx)defer cancel()go le.config.Callbacks.OnStartedLeading(ctx)le.renew(ctx)
}// acquire会不断循环的去获取lease锁，获取成功则成为leader且返回
// acquire loops calling tryAcquireOrRenew and returns true immediately when tryAcquireOrRenew succeeds.
// Returns false if ctx signals done.
func (le *LeaderElector) acquire(ctx context.Context) bool {ctx, cancel := context.WithCancel(ctx)defer cancel()succeeded := falsedesc := le.config.Lock.Describe()klog.Infof("attempting to acquire leader lease  %v...", desc)wait.JitterUntil(func() {succeeded = le.tryAcquireOrRenew()le.maybeReportTransition()if !succeeded {klog.V(4).Infof("failed to acquire lease %v", desc)return}le.config.Lock.RecordEvent("became leader")le.metrics.leaderOn(le.config.Name)klog.Infof("successfully acquired lease %v", desc)cancel()}, le.config.RetryPeriod, JitterFactor, true, ctx.Done())return succeeded
}// 续约方法，不断循环续约
// renew loops calling tryAcquireOrRenew and returns immediately when tryAcquireOrRenew fails or ctx signals done.
func (le *LeaderElector) renew(ctx context.Context) {ctx, cancel := context.WithCancel(ctx)defer cancel()wait.Until(func() {timeoutCtx, timeoutCancel := context.WithTimeout(ctx, le.config.RenewDeadline)defer timeoutCancel()err := wait.PollImmediateUntil(le.config.RetryPeriod, func() (bool, error) {done := make(chan bool, 1)go func() {defer close(done)done <- le.tryAcquireOrRenew()}()select {case <-timeoutCtx.Done():return false, fmt.Errorf("failed to tryAcquireOrRenew %s", timeoutCtx.Err())case result := <-done:return result, nil}}, timeoutCtx.Done())le.maybeReportTransition()desc := le.config.Lock.Describe()if err == nil {klog.V(5).Infof("successfully renewed lease %v", desc)return}le.config.Lock.RecordEvent("stopped leading")le.metrics.leaderOff(le.config.Name)klog.Infof("failed to renew lease %v: %v", desc, err)cancel()}, le.config.RetryPeriod, ctx.Done())// if we hold the lease, give it upif le.config.ReleaseOnCancel {le.release()}
}

总结

external-provisioner组件主要list/watch pvc对象的新增、更新事件，以及pv对象的新增、更新、删除事件，然后放入claimQueue与volumeQueue，接着provisionController负责处理claimQueue（，根据需要调用ceph-csi组件的CreateVolume方法来创建存储，并创建pv对象，provisionController处理volumeQueue，根据pv的状态以及回收策略决定是否调用ceph-csi组件的DeleteVolume方法来删除存储，并删除pv对象。