【kubernetes/k8s源码分析】kube-controller-manager 源码分析之启动流程

野性酷女 2022-06-09 07:29 268阅读 0赞

# 前言 #

#      #

#     kubernetes 是谷歌 Borg 的一个开源版本，基于容器技术的集群管理系统，实现资源管理的自动化，以及多个数据中心资源使用率的最大化。分布式系统支撑平台，透明的服务注册和服务发现机制，内建智能负载均衡器，强大的故障发现和自我修复能力，服务滚动升级和在线扩容能力。 #

还提供了管理工具，包括开发，部署测试，运维监控

service 是分布式集群架构的核心：

*  一个唯一指定的名字
 *  一个虚拟IP（clusterIP serviceIP 或 VIP）和端口号
 *  提供远程服务能力
 *  映射到了提供这种服务能力的一组容器应用上

Service 和 Pod 之间的关联关系，kubernetes 给每个 pod 贴上一个标签。每个 pod 里运行一个 Pause 容器，业务容器共享 Pause 容器的网络栈和 volume 挂载卷

Master 节点运行集群管理相关的进程 kube-apiserver kube-controller-manager kube-scheduler

Node 节点管理的最小单位是 pod，负责 pod 的创建，启动，监控，重启，销毁，以及实现软件模式的负载均衡器

每个 Pod 都会被分配一个单独的 IP 地址，但这个 IP 地址会随着 Pod 的销毁而消失。问题来了：如果一组 Pod 组成一个集群来提供服务，那么如何来访问呢？

一个 service 可以看作一组提供相同服务的 Pod 的对外访问接口，service 作用哪些  Pod 是通过 label selector 来定义的

Controller Manager: 集群内部的管理控制中心，主要目的是实现集群的故障检测和恢复的自动化工作

# 1. 入口 main 函数 #

## ##

NewCMServer 主要是使用默认值初始化 CMServer结构体，主要执行体为 app.Run， 如下 1.1 所示

func main() {
           s := options.NewCMServer()
           s.AddFlags(pflag.CommandLine, app.KnownControllers(), app.ControllersDisabledByDefault.List())
    
           flag.InitFlags()
           logs.InitLogs()
           defer logs.FlushLogs()
    
           verflag.PrintAndExitIfRequested()
    
           if err := app.Run(s); err != nil {
                  fmt.Fprintf(os.Stderr, "%v\n", err)
                  os.Exit(1)
           }
    }

## ##

**1.1 Run 函数**

最主要的有两处函数，一个是 StartControllers，另一个是 leadereleaction.RunOrDie

// Run runs the CMServer.  This should never exit.
    func Run(s *options.CMServer) error {
           ......
           run := func(stop <-chan struct{}) {
                  ......
                  if err := StartControllers(ctx, saTokenControllerInitFunc, NewControllerInitializers()); err != nil {
                         glog.Fatalf("error starting controllers: %v", err)
                  }
    
                  ctx.InformerFactory.Start(ctx.Stop)
    
                  select {}
           }
           
           leaderelection.RunOrDie(leaderelection.LeaderElectionConfig{
                  Lock:          rl,
                  LeaseDuration: s.LeaderElection.LeaseDuration.Duration,
                  RenewDeadline: s.LeaderElection.RenewDeadline.Duration,
                  RetryPeriod:   s.LeaderElection.RetryPeriod.Duration,
                  Callbacks: leaderelection.LeaderCallbacks{
                         OnStartedLeading: run,
                         OnStoppedLeading: func() {
                                glog.Fatalf("leaderelection lost")
                         },
                  },
           })
           panic("unreachable")
    }

## ##

**1.1.1 NewControllerInitializers 函数**

初始化一大堆子控制函数

*  replicationcontroller: 从 apiserver 同步 ReplicationController对象，管理 pods
 *  nodecontroller: 从 cloudprovider 获取 node 的信息，然后监控 node 的更新信息
 *  servicecontroller: 同步cloud provider的服务信息，管理所有node上面的service
 *  resourcequota: 调用 syncResourceQuota，同步 node 资源的 quota 信息，ResourceQuota 根据 namespace 进行资源
 *  namespace: 定期从 api-server 同步 namespace 信息
 *  persistentvolume-binder: 定期同步磁盘卷挂载信息
 *  serviceaccount: namespace 不同账户的信息管理

// NewControllerInitializers is a public map of named controller groups (you can start more than one in an init func)
    // paired to their InitFunc.  This allows for structured downstream composition and subdivision.
    func NewControllerInitializers() map[string]InitFunc {
           controllers := map[string]InitFunc{}
           controllers["endpoint"] = startEndpointController
           controllers["replicationcontroller"] = startReplicationController
           controllers["podgc"] = startPodGCController
           controllers["resourcequota"] = startResourceQuotaController
           controllers["namespace"] = startNamespaceController
           controllers["serviceaccount"] = startServiceAccountController
           controllers["garbagecollector"] = startGarbageCollectorController
           controllers["daemonset"] = startDaemonSetController
           controllers["job"] = startJobController
           controllers["deployment"] = startDeploymentController
           controllers["replicaset"] = startReplicaSetController
           controllers["horizontalpodautoscaling"] = startHPAController
           controllers["disruption"] = startDisruptionController
           controllers["statefulset"] = startStatefulSetController
           controllers["cronjob"] = startCronJobController
           controllers["csrsigning"] = startCSRSigningController
           controllers["csrapproving"] = startCSRApprovingController
           controllers["ttl"] = startTTLController
           controllers["bootstrapsigner"] = startBootstrapSignerController
           controllers["tokencleaner"] = startTokenCleanerController
           controllers["service"] = startServiceController
           controllers["node"] = startNodeController
           controllers["route"] = startRouteController
           controllers["persistentvolume-binder"] = startPersistentVolumeBinderController
           controllers["attachdetach"] = startAttachDetachController
    
           return controllers
    }

**1.1.2 StartControllers 函数**

将 1.1.1 中初始化的各个控制器启动

func StartControllers(ctx ControllerContext, startSATokenController InitFunc, controllers map[string]InitFunc) error {
           // Always start the SA token controller first using a full-power client, since it needs to mint tokens for the rest
           // If this fails, just return here and fail since other controllers won't be able to get credentials.
           if _, err := startSATokenController(ctx); err != nil {
                  return err
           }
    
           for controllerName, initFn := range controllers {
                  if !ctx.IsControllerEnabled(controllerName) {
                         glog.Warningf("%q is disabled", controllerName)
                         continue
                  }
    
                  time.Sleep(wait.Jitter(ctx.Options.ControllerStartInterval.Duration, ControllerStartJitter))
    
                  glog.V(1).Infof("Starting %q", controllerName)
                  started, err := initFn(ctx)
                  if err != nil {
                         glog.Errorf("Error starting %q", controllerName)
                         return err
                  }
                  if !started {
                         glog.Warningf("Skipping %q", controllerName)
                         continue
                  }
                  glog.Infof("Started %q", controllerName)
           }
    
           return nil
    }

# 2. deployment分析 #

## ##

根据deployment函数为startDeploymentController

controllers["deployment"] = startDeploymentController

结构体DeploymentController

type DeploymentController struct {
       // rsControl is used for adopting/releasing replica sets.
       rsControl     controller.RSControlInterface
       client        clientset.Interface
       eventRecorder record.EventRecorder
    
       // To allow injection of syncDeployment for testing.
       syncHandler func(dKey string) error
       // used for unit testing
       enqueueDeployment func(deployment *extensions.Deployment)
    
       // dLister can list/get deployments from the shared informer's store
       dLister extensionslisters.DeploymentLister
       // rsLister can list/get replica sets from the shared informer's store
       rsLister extensionslisters.ReplicaSetLister
       // podLister can list/get pods from the shared informer's store
       podLister corelisters.PodLister
    
       // dListerSynced returns true if the Deployment store has been synced at least once.
       // Added as a member to the struct to allow injection for testing.
       dListerSynced cache.InformerSynced
       // rsListerSynced returns true if the ReplicaSet store has been synced at least once.
       // Added as a member to the struct to allow injection for testing.
       rsListerSynced cache.InformerSynced
       // podListerSynced returns true if the pod store has been synced at least once.
       // Added as a member to the struct to allow injection for testing.
       podListerSynced cache.InformerSynced
    
       // Deployments that need to be synced
       queue workqueue.RateLimitingInterface
    }

# 3. startDeploymentController函数 #

## ##

创建NewDeploymentController对象如下

func startDeploymentController(ctx ControllerContext) (bool, error) {
       if !ctx.AvailableResources[schema.GroupVersionResource{Group: "extensions", Version: "v1beta1", Resource: "deployments"}] {
          return false, nil
       }
       dc, err := deployment.NewDeploymentController(
          ctx.InformerFactory.Extensions().V1beta1().Deployments(),
          ctx.InformerFactory.Extensions().V1beta1().ReplicaSets(),
          ctx.InformerFactory.Core().V1().Pods(),
          ctx.ClientBuilder.ClientOrDie("deployment-controller"),
       )
       if err != nil {
          return true, fmt.Errorf("error creating Deployment controller: %v", err)
       }
       go dc.Run(int(ctx.Options.ConcurrentDeploymentSyncs), ctx.Stop)
       return true, nil
    }

# 3.1 NewDeploymentController函数 #

## ##

1.  创建`eventBroadcaster`并设置属性
2.  设置速率`RateLimiter` 
3.  创建`DeploymentController`对象
4.  设置`dInformer`,`rsInformer`和`podInformer`对应的事件回调函数
5.  设置`rsc.syncHandler`为`rsc.syncDeployment`函数

func NewDeploymentController(dInformer extensionsinformers.DeploymentInformer, rsInformer extensionsinformers.ReplicaSetInformer, podInformer coreinformers.PodInformer, client clientset.Interface) (*DeploymentController, error) {
       eventBroadcaster := record.NewBroadcaster()
       eventBroadcaster.StartLogging(glog.Infof)
       // TODO: remove the wrapper when every clients have moved to use the clientset.
       eventBroadcaster.StartRecordingToSink(&v1core.EventSinkImpl{Interface: v1core.New(client.CoreV1().RESTClient()).Events("")})
    
       if client != nil && client.CoreV1().RESTClient().GetRateLimiter() != nil {
          if err := metrics.RegisterMetricAndTrackRateLimiterUsage("deployment_controller", client.CoreV1().RESTClient().GetRateLimiter()); err != nil {
             return nil, err
          }
       }
       dc := &DeploymentController{
          client:        client,
          eventRecorder: eventBroadcaster.NewRecorder(scheme.Scheme, v1.EventSource{Component: "deployment-controller"}),
          queue:         workqueue.NewNamedRateLimitingQueue(workqueue.DefaultControllerRateLimiter(), "deployment"),
       }
       dc.rsControl = controller.RealRSControl{
          KubeClient: client,
          Recorder:   dc.eventRecorder,
       }
    
       dInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
          AddFunc:    dc.addDeployment,
          UpdateFunc: dc.updateDeployment,
          // This will enter the sync loop and no-op, because the deployment has been deleted from the store.
          DeleteFunc: dc.deleteDeployment,
       })
       rsInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
          AddFunc:    dc.addReplicaSet,
          UpdateFunc: dc.updateReplicaSet,
          DeleteFunc: dc.deleteReplicaSet,
       })
       podInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
          DeleteFunc: dc.deletePod,
       })
    
       dc.syncHandler = dc.syncDeployment
       dc.enqueueDeployment = dc.enqueue
    
       dc.dLister = dInformer.Lister()
       dc.rsLister = rsInformer.Lister()
       dc.podLister = podInformer.Lister()
       dc.dListerSynced = dInformer.Informer().HasSynced
       dc.rsListerSynced = rsInformer.Informer().HasSynced
       dc.podListerSynced = podInformer.Informer().HasSynced
       return dc, nil
    }

# 3.2 Run函数 #

## ##

1.  WaitForCacheSync等待Inform初始化完成
2.  启动worker协程

// Run begins watching and syncing.
    func (dc *DeploymentController) Run(workers int, stopCh <-chan struct{}) {
       defer utilruntime.HandleCrash()
       defer dc.queue.ShutDown()
    
       glog.Infof("Starting deployment controller")
       defer glog.Infof("Shutting down deployment controller")
    
       if !controller.WaitForCacheSync("deployment", stopCh, dc.dListerSynced, dc.rsListerSynced, dc.podListerSynced) {
          return
       }
    
       for i := 0; i < workers; i++ {
          go wait.Until(dc.worker, time.Second, stopCh)
       }
    
       <-stopCh
    }

# 3.3 worker函数 #

## ##

1.  从queue中取出key，调用syncHandler(syncDeployment)函数进行处理

func (dc *DeploymentController) worker() {
       for dc.processNextWorkItem() {
       }
    }
    
    func (dc *DeploymentController) processNextWorkItem() bool {
       key, quit := dc.queue.Get()
       if quit {
          return false
       }
       defer dc.queue.Done(key)
    
       err := dc.syncHandler(key.(string))
       dc.handleErr(err, key)
    
       return true
    }

# 3.4 syncDeployment函数 #

## ##

1.  SplitMetaNamespaceKey根据key以/分割获取到namespace，name
2.  获取deployment对象，k8s1.9类型为\*v1beat.Deployment
3.  getReplicaSetsForDeployment根据deployment获取所有replicaSet对象列表
4.  getPodMapForDeployment根据deployment以及rs获取pod对象列表
5.  checkPausedConditions检查是否暂停状态
6.  如果需要会滚，则进行会滚操作
7.  isScalingEvent判断副本是否需要调整
8.  判断执行更新操作rolloutRecreate还是rolloutRolling

func (dc *DeploymentController) syncDeployment(key string) error {
       namespace, name, err := cache.SplitMetaNamespaceKey(key)
       if err != nil {
          return err
       }
       deployment, err := dc.dLister.Deployments(namespace).Get(name)
    
       rsList, err := dc.getReplicaSetsForDeployment(d)
    
       podMap, err := dc.getPodMapForDeployment(d, rsList)
    
       if err = dc.checkPausedConditions(d); err != nil {
          return err
       }
    
       if d.Spec.Paused {
          return dc.sync(d, rsList, podMap)
       }
    
       if d.Spec.RollbackTo != nil {
          return dc.rollback(d, rsList, podMap)
       }
    
       scalingEvent, err := dc.isScalingEvent(d, rsList, podMap)
       if err != nil {
          return err
       }
       if scalingEvent {
          return dc.sync(d, rsList, podMap)
       }
    
       switch d.Spec.Strategy.Type {
       case extensions.RecreateDeploymentStrategyType:
          return dc.rolloutRecreate(d, rsList, podMap)
       case extensions.RollingUpdateDeploymentStrategyType:
          return dc.rolloutRolling(d, rsList, podMap)
       }
       return fmt.Errorf("unexpected deployment strategy type: %s", d.Spec.Strategy.Type)
    }

# 3.5 rolloutRecreate函数 #

## ##

1.  getAllReplicaSetAndSyncRevision获取旧rs，新rs,如果新rs不存在也不创建
2.  过滤旧rs实例不为0
3.  将旧rs实例更新为0
4.  scaleUpNewReplicaSetForRecreate设置新rs副本数为制定数

func (dc *DeploymentController) rolloutRecreate(d *extensions.Deployment, rsList []*extensions.ReplicaSet, podMap map[types.UID]*v1.PodList) error {
       // Don't create a new RS if not already existed, so that we avoid scaling up before scaling down.
       newRS, oldRSs, err := dc.getAllReplicaSetsAndSyncRevision(d, rsList, podMap, false)
    
       allRSs := append(oldRSs, newRS)
       activeOldRSs := controller.FilterActiveReplicaSets(oldRSs)
       scaledDown, err := dc.scaleDownOldReplicaSetsForRecreate(activeOldRSs, d)
     
       if scaledDown {
          return dc.syncRolloutStatus(allRSs, newRS, d)
       }
    
       // Do not process a deployment when it has old pods running.
       if oldPodsRunning(newRS, oldRSs, podMap) {
          return dc.syncRolloutStatus(allRSs, newRS, d)
       }
    
       // If we need to create a new RS, create it now.
       if newRS == nil {
          newRS, oldRSs, err = dc.getAllReplicaSetsAndSyncRevision(d, rsList, podMap, true)
          if err != nil {
             return err
          }
          allRSs = append(oldRSs, newRS)
       }
    
       // scale up new replica set.
       if _, err := dc.scaleUpNewReplicaSetForRecreate(newRS, d); err != nil {
          return err
       }
    
       if util.DeploymentComplete(d, &d.Status) {
          if err := dc.cleanupDeployment(oldRSs, d); err != nil {
             return err
          }
       }
    
       // Sync deployment status.
       return dc.syncRolloutStatus(allRSs, newRS, d)
    }