Kubernetes Node Controller源码分析之Taint Controller

pkg/controller/node/nodecontroller.go:195

func NewNodeController(..) (*NodeController, error) {
	...
    podInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
		AddFunc: func(obj interface{}) {
			...
			if nc.taintManager != nil {
				nc.taintManager.PodUpdated(nil, pod)
			}
		},
		...
	}
	...
	} else {
		nodeEventHandlerFuncs = cache.ResourceEventHandlerFuncs{
			AddFunc: func(originalObj interface{}) {
				...
				if nc.taintManager != nil {
					nc.taintManager.NodeUpdated(nil, node)
				}
			},
			...
		}
	}
	...
	if nc.runTaintManager {
		nc.taintManager = NewNoExecuteTaintManager(kubeClient)
	}

    ...

	return nc, nil
}

pkg/controller/node/taint_controller.go:152

func NewNoExecuteTaintManager(c clientset.Interface) *NoExecuteTaintManager {
	...

	tm := &NoExecuteTaintManager{
		client:            c,
		recorder:          recorder,
		
		// taintedNodes记录每个Node对应的Taint信息。
		taintedNodes:      make(map[string][]v1.Taint),
		
		// nodeUpdateQueue中取出的updateItem会发送到nodeUpdateChannel，Tait Manager从该Channel中取出对应的node update info。
		nodeUpdateChannel: make(chan *nodeUpdateItem, nodeUpdateChannelSize),
		
		// podUpdateQueue中取出的updateItem会发送到podUpdateChannel，Tait Manager从该Channel中取出对应的pod update info。
		podUpdateChannel:  make(chan *podUpdateItem, podUpdateChannelSize),
        
        // Node Controller监听到的node update info会发送到nodeUpdateQueue。
		nodeUpdateQueue: workqueue.New(),
		
		// Node Controller监听到的pod update info会发送到podUpdateQueue。
		podUpdateQueue:  workqueue.New(),
	}
	
	// CreateWorkerQueue creates a new TimedWorkerQueue for workers that will execute deletePodHandler.
	tm.taintEvictionQueue = CreateWorkerQueue(deletePodHandler(c, tm.emitPodDeletionEvent))

	return tm
}

func deletePodHandler(c clientset.Interface, emitEventFunc func(types.NamespacedName)) func(args *WorkArgs) error {
	return func(args *WorkArgs) error {
		ns := args.NamespacedName.Namespace
		name := args.NamespacedName.Name
		glog.V(0).Infof("NoExecuteTaintManager is deleting Pod: %v", args.NamespacedName.String())
		if emitEventFunc != nil {
			emitEventFunc(args.NamespacedName)
		}
		var err error
		
		// 按照失败重试5次，每次间隔10s的重试机制，调用apiserver的api删除对应的Pod。
		for i := 0; i < retries; i++ {
			err = c.Core().Pods(ns).Delete(name, &metav1.DeleteOptions{})
			if err == nil {
				break
			}
			time.Sleep(10 * time.Millisecond)
		}
		return err
	}
}

pkg/controller/node/nodecontroller.go:550

func (nc *NodeController) Run() {
	go func() {
		...

		if nc.runTaintManager {
			go nc.taintManager.Run(wait.NeverStop)
		}

		...
	}()
}

pkg/controller/node/taint_controller.go:179

// Run starts NoExecuteTaintManager which will run in loop until `stopCh` is closed.
func (tc *NoExecuteTaintManager) Run(stopCh <-chan struct{}) {
	glog.V(0).Infof("Starting NoExecuteTaintManager")
	
	// Functions that are responsible for taking work items out of the workqueues and putting them into channels.
	// 从tc.nodeUpdateQueue中获取updateItem，并发送到tc.nodeUpdateChannel。
	go func(stopCh <-chan struct{}) {
		for {
			item, shutdown := tc.nodeUpdateQueue.Get()
			if shutdown {
				break
			}
			nodeUpdate := item.(*nodeUpdateItem)
			select {
			case <-stopCh:
				break
			case tc.nodeUpdateChannel <- nodeUpdate:
			}
		}
	}(stopCh)

    // 从tc.podUpdateQueue中获取updateItem，并发送到tc.podUpdateChannel。
	go func(stopCh <-chan struct{}) {
		for {
			item, shutdown := tc.podUpdateQueue.Get()
			if shutdown {
				break
			}
			podUpdate := item.(*podUpdateItem)
			select {
			case <-stopCh:
				break
			case tc.podUpdateChannel <- podUpdate:
			}
		}
	}(stopCh)

	// When processing events we want to prioritize Node updates over Pod updates,
	// as NodeUpdates that interest NoExecuteTaintManager should be handled as soon as possible -
	// we don't want user (or system) to wait until PodUpdate queue is drained before it can
	// start evicting Pods from tainted Nodes.
	for {
		select {
		case <-stopCh:
			break
			
		// 从tc.nodeUpdateChannel获取nodeUpdate数据，然后invoke tc.handleNodeUpdate进行处理。
		case nodeUpdate := <-tc.nodeUpdateChannel:
			tc.handleNodeUpdate(nodeUpdate)
			
		// 从tc.podUpdateChannel获取podUpdate数据，在invoke tc.handlePodUpdate进行处理之前，先确保tc.nodeUpdateQueue中的数据已经被处理完。
		case podUpdate := <-tc.podUpdateChannel:
		
		// If we found a Pod update we need to empty Node queue first.
		priority:
			for {
				select {
				case nodeUpdate := <-tc.nodeUpdateChannel:
					tc.handleNodeUpdate(nodeUpdate)
				default:
					break priority
				}
			}
			
			// After Node queue is emptied we process podUpdate.
			tc.handlePodUpdate(podUpdate)
		}
	}
}

// pkg/controller/node/taint_controller.go:365

func (tc *NoExecuteTaintManager) handleNodeUpdate(nodeUpdate *nodeUpdateItem) {
	// Delete
	// 如果nodeUpdate.newNode == nil，则表明该Node被删除了，那么将该Node的Taints信息从tc.taintedNodes缓存中删除。
	if nodeUpdate.newNode == nil {
		node := nodeUpdate.oldNode
		glog.V(4).Infof("Noticed node deletion: %#v", node.Name)
		tc.taintedNodesLock.Lock()
		defer tc.taintedNodesLock.Unlock()
		delete(tc.taintedNodes, node.Name)
		return
	}
	
	// Create or Update
	// 如果是Node Create或者Node Update Event，则更新tc.taintedNodes缓存中记录的该Node的Taints信息。
	glog.V(4).Infof("Noticed node update: %#v", nodeUpdate)
	node := nodeUpdate.newNode
	taints := nodeUpdate.newTaints
	func() {
		tc.taintedNodesLock.Lock()
		defer tc.taintedNodesLock.Unlock()
		glog.V(4).Infof("Updating known taints on node %v: %v", node.Name, taints)
		if len(taints) == 0 {
			delete(tc.taintedNodes, node.Name)
		} else {
			tc.taintedNodes[node.Name] = taints
		}
	}()
	
	// 然后，获取该Node上所有pods list。
	pods, err := getPodsAssignedToNode(tc.client, node.Name)
	if err != nil {
		glog.Errorf(err.Error())
		return
	}
	if len(pods) == 0 {
		return
	}
	
	
	// Short circuit, to make this controller a bit faster.
	// 如果该Node上的Taints被删除了，则取消所有该node上的pod evictions。
	if len(taints) == 0 {
		glog.V(4).Infof("All taints were removed from the Node %v. Cancelling all evictions...", node.Name)
		for i := range pods {
			tc.cancelWorkWithEvent(types.NamespacedName{Namespace: pods[i].Namespace, Name: pods[i].Name})
		}
		return
	}

    // 否则，调用tc.processPodOnNode根据Node Taints info和Pod Tolerations info处理该Node上的Pod Eviction。
	now := time.Now()
	for i := range pods {
		pod := &pods[i]
		podNamespacedName := types.NamespacedName{Namespace: pod.Namespace, Name: pod.Name}
		tc.processPodOnNode(podNamespacedName, node.Name, pod.Spec.Tolerations, taints, now)
	}
}

// pkg/controller/node/taint_controller.go:334

func (tc *NoExecuteTaintManager) handlePodUpdate(podUpdate *podUpdateItem) {
	// Delete
	// 如果podUpdate.newPod == nil，则表明该Pod被删除了，那么取消该Pod Evictions。
	if podUpdate.newPod == nil {
		pod := podUpdate.oldPod
		podNamespacedName := types.NamespacedName{Namespace: pod.Namespace, Name: pod.Name}
		glog.V(4).Infof("Noticed pod deletion: %#v", podNamespacedName)
		tc.cancelWorkWithEvent(podNamespacedName)
		return
	}
	
	// Create or Update
	// 如果是Pod Create或者Pod Update Event，则取出该pod的node上的Taints info。
	pod := podUpdate.newPod
	podNamespacedName := types.NamespacedName{Namespace: pod.Namespace, Name: pod.Name}
	glog.V(4).Infof("Noticed pod update: %#v", podNamespacedName)
	nodeName := pod.Spec.NodeName
	if nodeName == "" {
		return
	}
	taints, ok := func() ([]v1.Taint, bool) {
		tc.taintedNodesLock.Lock()
		defer tc.taintedNodesLock.Unlock()
		taints, ok := tc.taintedNodes[nodeName]
		return taints, ok
	}()
	// It's possible that Node was deleted, or Taints were removed before, which triggered
	// eviction cancelling if it was needed.
	if !ok {
		return
	}
	
	// 然后，调用tc.processPodOnNode根据Node Taints info和Pod Tolerations info处理该Node上的Pod Eviction。
	tc.processPodOnNode(podNamespacedName, nodeName, podUpdate.newTolerations, taints, time.Now())
}

pkg/controller/node/taint_controller.go:295

func (tc *NoExecuteTaintManager) processPodOnNode(
	podNamespacedName types.NamespacedName,
	nodeName string,
	tolerations []v1.Toleration,
	taints []v1.Taint,
	now time.Time,
) {

    // 如果该node的taints info为空，则取消Taint Eviction Pods。
	if len(taints) == 0 {
		tc.cancelWorkWithEvent(podNamespacedName)
	}
	
	// 对比node的taints info和pod tolerations info，判断出node的taints是否都能被pod所能容忍。
	allTolerated, usedTolerations := v1.GetMatchingTolerations(taints, tolerations)
	
	// 如果不是全部都能容忍，那么调用立刻调用AddWork来创建worker，启动tc.taintEvictionQueue注册的deletePodHandler来删除该pod。
	if !allTolerated {
		glog.V(2).Infof("Not all taints are tolerated after update for Pod %v on %v", podNamespacedName.String(), nodeName)
		// We're canceling scheduled work (if any), as we're going to delete the Pod right away.
		tc.cancelWorkWithEvent(podNamespacedName)
		tc.taintEvictionQueue.AddWork(NewWorkArgs(podNamespacedName.Name, podNamespacedName.Namespace), time.Now(), time.Now())
		return
	}
	
	// 否则，取pod的所有tolerations的TolerationSeconds的最小值作为minTolerationTime。如果某个Toleration没有设置TolerationSeconds，则表示0，如果设置的值为负数，则用0替代。
	minTolerationTime := getMinTolerationTime(usedTolerations)
	// getMinTolerationTime returns negative value to denote infinite toleration.
	if minTolerationTime < 0 {
		glog.V(4).Infof("New tolerations for %v tolerate forever. Scheduled deletion won't be cancelled if already scheduled.", podNamespacedName.String())
		return
	}

	startTime := now
	triggerTime := startTime.Add(minTolerationTime)
	
	// 从tc.taintEvictionQueue中获取Worker-scheduledEviction
	scheduledEviction := tc.taintEvictionQueue.GetWorkerUnsafe(podNamespacedName.String())
	
	// 如果获取到不为空的scheduledEviction，则判断worker创建时间加上minTolerationTime是否达到触发时间要求，如果没达到，则不进行Taint Pod Eviction，流程结束。
	if scheduledEviction != nil {
		startTime = scheduledEviction.CreatedAt
		if startTime.Add(minTolerationTime).Before(triggerTime) {
			return
		} else {
			tc.cancelWorkWithEvent(podNamespacedName)
		}
	}
	
	// 如果达到触发时间要求，则取消worker，并立刻调用AddWork来创建worker，启动tc.taintEvictionQueue注册的deletePodHandler来删除该pod。
	tc.taintEvictionQueue.AddWork(NewWorkArgs(podNamespacedName.Name, podNamespacedName.Namespace), startTime, triggerTime)
}