kubernetes ceph-csi分析目录导航

概述

kube-controller-manager组件中，有两个controller与存储相关，分别是PV controller与AD controller。

基于tag v1.17.4

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

AD Cotroller分析

AD Cotroller作用

AD Cotroller全称Attachment/Detachment 控制器，主要负责创建、删除VolumeAttachment对象，并调用volume plugin来做存储设备的Attach/Detach操作（将数据卷挂载到特定node节点上/从特定node节点上解除挂载），以及更新node.Status.VolumesAttached等。

不同的volume plugin的Attach/Detach操作逻辑有所不同，如通过ceph-csi（out-tree volume plugin）来使用ceph存储，则的Attach/Detach操作只是修改VolumeAttachment对象的状态，而不会真正的将数据卷挂载到节点/从节点上解除挂载。

kubelet启动参数--enable-controller-attach-detach

AD Cotroller与kubelet中的volume manager逻辑相似，都可以做Attach/Detach操作，但是kube-controller-manager与kubelet中，只会有一个组件做Attach/Detach操作，通过kubelet启动参数--enable-controller-attach-detach设置。设置为 true 表示启用kube-controller-manager的AD controller来做Attach/Detach操作，同时禁用 kubelet 执行 Attach/Detach 操作（默认值为 true）。

注意

当k8s通过ceph-csi来使用ceph存储，volume plugin为ceph-csi，AD controller的Attach/Detach操作，只是创建/删除VolumeAttachment对象，而不会真正的将数据卷挂载到节点/从节点上解除挂载；csi-attacer组件也不会做挂载/解除挂载操作，只是更新VolumeAttachment对象，真正的节点挂载/解除挂载操作由kubelet中的volume manager调用volume plugin（ceph-csi）来完成。

两个关键结构体

（1）desiredStateOfWorld: 记录着集群中期望要挂载到node的pod的volume信息，简称DSW。

（2）actualStateOfWorld: 记录着集群中实际已经挂载到node节点的volume信息，简称ASW。

node.Status.VolumesInUse作用

node对象中的node.Status.VolumesInUse记录的是已经attach到该node节点上，并已经mount了的volume信息。

该属性由kubelet的volume manager来更新。当一个volume加入dsw中，就会被更新到node.Status.VolumesInUse中，直到该volume在asw与dsw中均不存在或已经处于unmounted状态时，会从node.Status.VolumesInUse中移除。

AD controller做volume的dettach操作前，会先判断该属性，如果该属性值中含有该volume，则说明volume还在被使用，返回dettach失败的错误。

node.Status.VolumesAttached作用

node对象中的node.Status.VolumesAttached记录的是已经attach到该node节点上的volume信息。

该属性由kube-controller-manager中的AD controller根据asw的值来更新。

attachDetachController.Run源码分析

直接看到attachDetachController的Run()方法，来分析attachDetachController的主体处理逻辑。

主要调用了以下4个方法，下面会逐一分析：
（1）adc.populateActualStateOfWorld()
（2）adc.populateDesiredStateOfWorld()
（3）adc.reconciler.Run()
（4）adc.desiredStateOfWorldPopulator.Run()

// pkg/controller/volume/attachdetach/attach_detach_controller.go
func (adc *attachDetachController) Run(stopCh <-chan struct{}) {
	defer runtime.HandleCrash()
	defer adc.pvcQueue.ShutDown()

	klog.Infof("Starting attach detach controller")
	defer klog.Infof("Shutting down attach detach controller")

	synced := []kcache.InformerSynced{adc.podsSynced, adc.nodesSynced, adc.pvcsSynced, adc.pvsSynced}
	if adc.csiNodeSynced != nil {
		synced = append(synced, adc.csiNodeSynced)
	}
	if adc.csiDriversSynced != nil {
		synced = append(synced, adc.csiDriversSynced)
	}

	if !kcache.WaitForNamedCacheSync("attach detach", stopCh, synced...) {
		return
	}

	err := adc.populateActualStateOfWorld()
	if err != nil {
		klog.Errorf("Error populating the actual state of world: %v", err)
	}
	err = adc.populateDesiredStateOfWorld()
	if err != nil {
		klog.Errorf("Error populating the desired state of world: %v", err)
	}
	go adc.reconciler.Run(stopCh)
	go adc.desiredStateOfWorldPopulator.Run(stopCh)
	go wait.Until(adc.pvcWorker, time.Second, stopCh)
	metrics.Register(adc.pvcLister,
		adc.pvLister,
		adc.podLister,
		adc.actualStateOfWorld,
		adc.desiredStateOfWorld,
		&adc.volumePluginMgr,
		adc.csiMigratedPluginManager,
		adc.intreeToCSITranslator)

	<-stopCh
}

1 adc.populateActualStateOfWorld

作用：初始化actualStateOfWorld结构体。

主要逻辑：遍历node对象，获取node.Status.VolumesAttached与node.Status.VolumesInUse，再调用adc.actualStateOfWorld.MarkVolumeAsAttached与adc.processVolumesInUse更新actualStateOfWorld信息。

// pkg/controller/volume/attachdetach/attach_detach_controller.go
func (adc *attachDetachController) populateActualStateOfWorld() error {
	klog.V(5).Infof("Populating ActualStateOfworld")
	nodes, err := adc.nodeLister.List(labels.Everything())
	if err != nil {
		return err
	}

	for _, node := range nodes {
		nodeName := types.NodeName(node.Name)
		for _, attachedVolume := range node.Status.VolumesAttached {
			uniqueName := attachedVolume.Name
			// The nil VolumeSpec is safe only in the case the volume is not in use by any pod.
			// In such a case it should be detached in the first reconciliation cycle and the
			// volume spec is not needed to detach a volume. If the volume is used by a pod, it
			// its spec can be: this would happen during in the populateDesiredStateOfWorld which
			// scans the pods and updates their volumes in the ActualStateOfWorld too.
			err = adc.actualStateOfWorld.MarkVolumeAsAttached(uniqueName, nil /* VolumeSpec */, nodeName, attachedVolume.DevicePath)
			if err != nil {
				klog.Errorf("Failed to mark the volume as attached: %v", err)
				continue
			}
			adc.processVolumesInUse(nodeName, node.Status.VolumesInUse)
			adc.addNodeToDswp(node, types.NodeName(node.Name))
		}
	}
	return nil
}

2 adc.populateDesiredStateOfWorld

作用：初始化desiredStateOfWorld结构体。

主要逻辑：遍历pod列表，遍历pod的volume信息
（1）根据pod的volume信息来初始化desiredStateOfWorld；
（2）从actualStateOfWorld中查询，如果pod的volume已经attach到node了，则更新actualStateOfWorld，将该volume标记为已attach。

// pkg/controller/volume/attachdetach/attach_detach_controller.go
func (adc *attachDetachController) populateDesiredStateOfWorld() error {
	klog.V(5).Infof("Populating DesiredStateOfworld")

	pods, err := adc.podLister.List(labels.Everything())
	if err != nil {
		return err
	}
	for _, pod := range pods {
		podToAdd := pod
		adc.podAdd(podToAdd)
		for _, podVolume := range podToAdd.Spec.Volumes {
			nodeName := types.NodeName(podToAdd.Spec.NodeName)
			// The volume specs present in the ActualStateOfWorld are nil, let's replace those
			// with the correct ones found on pods. The present in the ASW with no corresponding
			// pod will be detached and the spec is irrelevant.
			volumeSpec, err := util.CreateVolumeSpec(podVolume, podToAdd.Namespace, nodeName, &adc.volumePluginMgr, adc.pvcLister, adc.pvLister, adc.csiMigratedPluginManager, adc.intreeToCSITranslator)
			if err != nil {
				klog.Errorf(
					"Error creating spec for volume %q, pod %q/%q: %v",
					podVolume.Name,
					podToAdd.Namespace,
					podToAdd.Name,
					err)
				continue
			}
			plugin, err := adc.volumePluginMgr.FindAttachablePluginBySpec(volumeSpec)
			if err != nil || plugin == nil {
				klog.V(10).Infof(
					"Skipping volume %q for pod %q/%q: it does not implement attacher interface. err=%v",
					podVolume.Name,
					podToAdd.Namespace,
					podToAdd.Name,
					err)
				continue
			}
			volumeName, err := volumeutil.GetUniqueVolumeNameFromSpec(plugin, volumeSpec)
			if err != nil {
				klog.Errorf(
					"Failed to find unique name for volume %q, pod %q/%q: %v",
					podVolume.Name,
					podToAdd.Namespace,
					podToAdd.Name,
					err)
				continue
			}
			if adc.actualStateOfWorld.IsVolumeAttachedToNode(volumeName, nodeName) {
				devicePath, err := adc.getNodeVolumeDevicePath(volumeName, nodeName)
				if err != nil {
					klog.Errorf("Failed to find device path: %v", err)
					continue
				}
				err = adc.actualStateOfWorld.MarkVolumeAsAttached(volumeName, volumeSpec, nodeName, devicePath)
				if err != nil {
					klog.Errorf("Failed to update volume spec for node %s: %v", nodeName, err)
				}
			}
		}
	}

	return nil
}

3 adc.reconciler.Run

主要是调用rc.reconcile做desiredStateOfWorld与actualStateOfWorld之间的调谐：对比desiredStateOfWorld与actualStateOfWorld，做attach与detach操作，更新actualStateOfWorld，并根据actualStateOfWorld更新node对象的.Status.VolumesAttached。

// pkg/controller/volume/attachdetach/reconciler/reconciler.go
func (rc *reconciler) Run(stopCh <-chan struct{}) {
	wait.Until(rc.reconciliationLoopFunc(), rc.loopPeriod, stopCh)
}

// reconciliationLoopFunc this can be disabled via cli option disableReconciliation.
// It periodically checks whether the attached volumes from actual state
// are still attached to the node and update the status if they are not.
func (rc *reconciler) reconciliationLoopFunc() func() {
	return func() {

		rc.reconcile()

		if rc.disableReconciliationSync {
			klog.V(5).Info("Skipping reconciling attached volumes still attached since it is disabled via the command line.")
		} else if rc.syncDuration < time.Second {
			klog.V(5).Info("Skipping reconciling attached volumes still attached since it is set to less than one second via the command line.")
		} else if time.Since(rc.timeOfLastSync) > rc.syncDuration {
			klog.V(5).Info("Starting reconciling attached volumes still attached")
			rc.sync()
		}
	}
}

3.1 rc.reconcile

主要逻辑：
（1）遍历actualStateOfWorld中已经attached的volume，判断desiredStateOfWorld中是否存在，如果不存在，则调用rc.attacherDetacher.DetachVolume执行该volume的Detach操作；
（2）遍历desiredStateOfWorld中期望被attached的volume，判断actualStateOfWorld中是否已经attached到node上，如果没有，则先调用rc.isMultiAttachForbidden判断该volume的AccessModes是否支持多节点挂载，如支持，则继续调用rc.attacherDetacher.AttachVolume执行该volume的attach操作；
（3）调用rc.nodeStatusUpdater.UpdateNodeStatuses()：根据从actualStateOfWorld获取已经attached到node的volume，更新node.Status.VolumesAttached的值。

// pkg/controller/volume/attachdetach/reconciler/reconciler.go
func (rc *reconciler) reconcile() {
	// Detaches are triggered before attaches so that volumes referenced by
	// pods that are rescheduled to a different node are detached first.

	// Ensure volumes that should be detached are detached.
	for _, attachedVolume := range rc.actualStateOfWorld.GetAttachedVolumes() {
		if !rc.desiredStateOfWorld.VolumeExists(
			attachedVolume.VolumeName, attachedVolume.NodeName) {
			// Don't even try to start an operation if there is already one running
			// This check must be done before we do any other checks, as otherwise the other checks
			// may pass while at the same time the volume leaves the pending state, resulting in
			// double detach attempts
			if rc.attacherDetacher.IsOperationPending(attachedVolume.VolumeName, "") {
				klog.V(10).Infof("Operation for volume %q is already running. Can't start detach for %q", attachedVolume.VolumeName, attachedVolume.NodeName)
				continue
			}

			// Set the detach request time
			elapsedTime, err := rc.actualStateOfWorld.SetDetachRequestTime(attachedVolume.VolumeName, attachedVolume.NodeName)
			if err != nil {
				klog.Errorf("Cannot trigger detach because it fails to set detach request time with error %v", err)
				continue
			}
			// Check whether timeout has reached the maximum waiting time
			timeout := elapsedTime > rc.maxWaitForUnmountDuration
			// Check whether volume is still mounted. Skip detach if it is still mounted unless timeout
			if attachedVolume.MountedByNode && !timeout {
				klog.V(5).Infof(attachedVolume.GenerateMsgDetailed("Cannot detach volume because it is still mounted", ""))
				continue
			}

			// Before triggering volume detach, mark volume as detached and update the node status
			// If it fails to update node status, skip detach volume
			err = rc.actualStateOfWorld.RemoveVolumeFromReportAsAttached(attachedVolume.VolumeName, attachedVolume.NodeName)
			if err != nil {
				klog.V(5).Infof("RemoveVolumeFromReportAsAttached failed while removing volume %q from node %q with: %v",
					attachedVolume.VolumeName,
					attachedVolume.NodeName,
					err)
			}

			// Update Node Status to indicate volume is no longer safe to mount.
			err = rc.nodeStatusUpdater.UpdateNodeStatuses()
			if err != nil {
				// Skip detaching this volume if unable to update node status
				klog.Errorf(attachedVolume.GenerateErrorDetailed("UpdateNodeStatuses failed while attempting to report volume as attached", err).Error())
				continue
			}

			// Trigger detach volume which requires verifying safe to detach step
			// If timeout is true, skip verifySafeToDetach check
			klog.V(5).Infof(attachedVolume.GenerateMsgDetailed("Starting attacherDetacher.DetachVolume", ""))
			verifySafeToDetach := !timeout
			err = rc.attacherDetacher.DetachVolume(attachedVolume.AttachedVolume, verifySafeToDetach, rc.actualStateOfWorld)
			if err == nil {
				if !timeout {
					klog.Infof(attachedVolume.GenerateMsgDetailed("attacherDetacher.DetachVolume started", ""))
				} else {
					metrics.RecordForcedDetachMetric()
					klog.Warningf(attachedVolume.GenerateMsgDetailed("attacherDetacher.DetachVolume started", fmt.Sprintf("This volume is not safe to detach, but maxWaitForUnmountDuration %v expired, force detaching", rc.maxWaitForUnmountDuration)))
				}
			}
			if err != nil && !exponentialbackoff.IsExponentialBackoff(err) {
				// Ignore exponentialbackoff.IsExponentialBackoff errors, they are expected.
				// Log all other errors.
				klog.Errorf(attachedVolume.GenerateErrorDetailed("attacherDetacher.DetachVolume failed to start", err).Error())
			}
		}
	}

	rc.attachDesiredVolumes()

	// Update Node Status
	err := rc.nodeStatusUpdater.UpdateNodeStatuses()
	if err != nil {
		klog.Warningf("UpdateNodeStatuses failed with: %v", err)
	}
}

rc.attachDesiredVolumes

主要逻辑：调用rc.attacherDetacher.AttachVolume触发attach逻辑。

// pkg/controller/volume/attachdetach/reconciler/reconciler.go
func (rc *reconciler) attachDesiredVolumes() {
	// Ensure volumes that should be attached are attached.
	for _, volumeToAttach := range rc.desiredStateOfWorld.GetVolumesToAttach() {
		if rc.actualStateOfWorld.IsVolumeAttachedToNode(volumeToAttach.VolumeName, volumeToAttach.NodeName) {
			// Volume/Node exists, touch it to reset detachRequestedTime
			if klog.V(5) {
				klog.Infof(volumeToAttach.GenerateMsgDetailed("Volume attached--touching", ""))
			}
			rc.actualStateOfWorld.ResetDetachRequestTime(volumeToAttach.VolumeName, volumeToAttach.NodeName)
			continue
		}
		// Don't even try to start an operation if there is already one running
		if rc.attacherDetacher.IsOperationPending(volumeToAttach.VolumeName, "") {
			if klog.V(10) {
				klog.Infof("Operation for volume %q is already running. Can't start attach for %q", volumeToAttach.VolumeName, volumeToAttach.NodeName)
			}
			continue
		}

		if rc.isMultiAttachForbidden(volumeToAttach.VolumeSpec) {
			nodes := rc.actualStateOfWorld.GetNodesForAttachedVolume(volumeToAttach.VolumeName)
			if len(nodes) > 0 {
				if !volumeToAttach.MultiAttachErrorReported {
					rc.reportMultiAttachError(volumeToAttach, nodes)
					rc.desiredStateOfWorld.SetMultiAttachError(volumeToAttach.VolumeName, volumeToAttach.NodeName)
				}
				continue
			}
		}

		// Volume/Node doesn't exist, spawn a goroutine to attach it
		if klog.V(5) {
			klog.Infof(volumeToAttach.GenerateMsgDetailed("Starting attacherDetacher.AttachVolume", ""))
		}
		err := rc.attacherDetacher.AttachVolume(volumeToAttach.VolumeToAttach, rc.actualStateOfWorld)
		if err == nil {
			klog.Infof(volumeToAttach.GenerateMsgDetailed("attacherDetacher.AttachVolume started", ""))
		}
		if err != nil && !exponentialbackoff.IsExponentialBackoff(err) {
			// Ignore exponentialbackoff.IsExponentialBackoff errors, they are expected.
			// Log all other errors.
			klog.Errorf(volumeToAttach.GenerateErrorDetailed("attacherDetacher.AttachVolume failed to start", err).Error())
		}
	}
}

rc.nodeStatusUpdater.UpdateNodeStatuses

主要逻辑：从actualStateOfWorld获取已经attach到node的volume，更新node对象的node.Status.VolumesAttached属性值。

// pkg/controller/volume/attachdetach/statusupdater/node_status_updater.go
func (nsu *nodeStatusUpdater) UpdateNodeStatuses() error {
	// TODO: investigate right behavior if nodeName is empty
	// kubernetes/kubernetes/issues/37777
	nodesToUpdate := nsu.actualStateOfWorld.GetVolumesToReportAttached()
	for nodeName, attachedVolumes := range nodesToUpdate {
		nodeObj, err := nsu.nodeLister.Get(string(nodeName))
		if errors.IsNotFound(err) {
			// If node does not exist, its status cannot be updated.
			// Do nothing so that there is no retry until node is created.
			klog.V(2).Infof(
				"Could not update node status. Failed to find node %q in NodeInformer cache. Error: '%v'",
				nodeName,
				err)
			continue
		} else if err != nil {
			// For all other errors, log error and reset flag statusUpdateNeeded
			// back to true to indicate this node status needs to be updated again.
			klog.V(2).Infof("Error retrieving nodes from node lister. Error: %v", err)
			nsu.actualStateOfWorld.SetNodeStatusUpdateNeeded(nodeName)
			continue
		}

		if err := nsu.updateNodeStatus(nodeName, nodeObj, attachedVolumes); err != nil {
			// If update node status fails, reset flag statusUpdateNeeded back to true
			// to indicate this node status needs to be updated again
			nsu.actualStateOfWorld.SetNodeStatusUpdateNeeded(nodeName)

			klog.V(2).Infof(
				"Could not update node status for %q; re-marking for update. %v",
				nodeName,
				err)

			// We currently always return immediately on error
			return err
		}
	}
	return nil
}

func (nsu *nodeStatusUpdater) updateNodeStatus(nodeName types.NodeName, nodeObj *v1.Node, attachedVolumes []v1.AttachedVolume) error {
	node := nodeObj.DeepCopy()
	node.Status.VolumesAttached = attachedVolumes
	_, patchBytes, err := nodeutil.PatchNodeStatus(nsu.kubeClient.CoreV1(), nodeName, nodeObj, node)
	if err != nil {
		return err
	}

	klog.V(4).Infof("Updating status %q for node %q succeeded. VolumesAttached: %v", patchBytes, nodeName, attachedVolumes)
	return nil
}

4 adc.desiredStateOfWorldPopulator.Run

作用：更新desiredStateOfWorld，跟踪desiredStateOfWorld初始化后的后续变化更新。

主要调用了两个方法：
（1）dswp.findAndRemoveDeletedPods：更新desiredStateOfWorld，从中删除已经不存在的pod；
（2）dswp.findAndAddActivePods：更新desiredStateOfWorld，将新增的pod volume加入desiredStateOfWorld。

// pkg/controller/volume/attachdetach/populator/desired_state_of_world_populator.go
func (dswp *desiredStateOfWorldPopulator) Run(stopCh <-chan struct{}) {
	wait.Until(dswp.populatorLoopFunc(), dswp.loopSleepDuration, stopCh)
}

func (dswp *desiredStateOfWorldPopulator) populatorLoopFunc() func() {
	return func() {
		dswp.findAndRemoveDeletedPods()

		// findAndAddActivePods is called periodically, independently of the main
		// populator loop.
		if time.Since(dswp.timeOfLastListPods) < dswp.listPodsRetryDuration {
			klog.V(5).Infof(
				"Skipping findAndAddActivePods(). Not permitted until %v (listPodsRetryDuration %v).",
				dswp.timeOfLastListPods.Add(dswp.listPodsRetryDuration),
				dswp.listPodsRetryDuration)

			return
		}
		dswp.findAndAddActivePods()
	}
}

4.1 dswp.findAndRemoveDeletedPods

主要逻辑：
（1）从desiredStateOfWorld中取出pod列表；
（2）查询该pod对象是否还存在于etcd；
（3）不存在则调用dswp.desiredStateOfWorld.DeletePod将该pod从desiredStateOfWorld中删除。

// pkg/controller/volume/attachdetach/populator/desired_state_of_world_populator.go
// Iterate through all pods in desired state of world, and remove if they no
// longer exist in the informer
func (dswp *desiredStateOfWorldPopulator) findAndRemoveDeletedPods() {
	for dswPodUID, dswPodToAdd := range dswp.desiredStateOfWorld.GetPodToAdd() {
		dswPodKey, err := kcache.MetaNamespaceKeyFunc(dswPodToAdd.Pod)
		if err != nil {
			klog.Errorf("MetaNamespaceKeyFunc failed for pod %q (UID %q) with: %v", dswPodKey, dswPodUID, err)
			continue
		}

		// Retrieve the pod object from pod informer with the namespace key
		namespace, name, err := kcache.SplitMetaNamespaceKey(dswPodKey)
		if err != nil {
			utilruntime.HandleError(fmt.Errorf("error splitting dswPodKey %q: %v", dswPodKey, err))
			continue
		}
		informerPod, err := dswp.podLister.Pods(namespace).Get(name)
		switch {
		case errors.IsNotFound(err):
			// if we can't find the pod, we need to delete it below
		case err != nil:
			klog.Errorf("podLister Get failed for pod %q (UID %q) with %v", dswPodKey, dswPodUID, err)
			continue
		default:
			volumeActionFlag := util.DetermineVolumeAction(
				informerPod,
				dswp.desiredStateOfWorld,
				true /* default volume action */)

			if volumeActionFlag {
				informerPodUID := volutil.GetUniquePodName(informerPod)
				// Check whether the unique identifier of the pod from dsw matches the one retrieved from pod informer
				if informerPodUID == dswPodUID {
					klog.V(10).Infof("Verified pod %q (UID %q) from dsw exists in pod informer.", dswPodKey, dswPodUID)
					continue
				}
			}
		}

		// the pod from dsw does not exist in pod informer, or it does not match the unique identifier retrieved
		// from the informer, delete it from dsw
		klog.V(1).Infof("Removing pod %q (UID %q) from dsw because it does not exist in pod informer.", dswPodKey, dswPodUID)
		dswp.desiredStateOfWorld.DeletePod(dswPodUID, dswPodToAdd.VolumeName, dswPodToAdd.NodeName)
	}
}

4.2 dswp.findAndAddActivePods()

主要逻辑：
（1）从etcd中获取全部pod信息；
（2）调用util.ProcessPodVolumes，将新增pod volume加入desiredStateOfWorld。

// pkg/controller/volume/attachdetach/populator/desired_state_of_world_populator.go
func (dswp *desiredStateOfWorldPopulator) findAndAddActivePods() {
	pods, err := dswp.podLister.List(labels.Everything())
	if err != nil {
		klog.Errorf("podLister List failed: %v", err)
		return
	}
	dswp.timeOfLastListPods = time.Now()

	for _, pod := range pods {
		if volutil.IsPodTerminated(pod, pod.Status) {
			// Do not add volumes for terminated pods
			continue
		}
		util.ProcessPodVolumes(pod, true,
			dswp.desiredStateOfWorld, dswp.volumePluginMgr, dswp.pvcLister, dswp.pvLister, dswp.csiMigratedPluginManager, dswp.intreeToCSITranslator)

	}

}

小结

attachDetachController.Run中4个主要方法作用：
（1）adc.populateActualStateOfWorld()：初始化actualStateOfWorld结构体。
（2）adc.populateDesiredStateOfWorld()：初始化desiredStateOfWorld结构体。
（3）adc.reconciler.Run()：做desiredStateOfWorld与actualStateOfWorld之间的调谐：对比desiredStateOfWorld与actualStateOfWorld，做attach与detach操作，更新actualStateOfWorld，并根据actualStateOfWorld更新node对象的.Status.VolumesAttached。
（4）adc.desiredStateOfWorldPopulator.Run()：更新desiredStateOfWorld，跟踪desiredStateOfWorld初始化后的后续变化更新。

NewAttachDetachController源码分析

接下来看到NewAttachDetachController方法，简单分析一下它的EventHandler。从代码中可以看到，主要是注册了pod对象与node对象的EventHandler。

// pkg/controller/volume/attachdetach/attach_detach_controller.go
// NewAttachDetachController returns a new instance of AttachDetachController.
func NewAttachDetachController(
...

podInformer.Informer().AddEventHandler(kcache.ResourceEventHandlerFuncs{
		AddFunc:    adc.podAdd,
		UpdateFunc: adc.podUpdate,
		DeleteFunc: adc.podDelete,
	})

...

nodeInformer.Informer().AddEventHandler(kcache.ResourceEventHandlerFuncs{
		AddFunc:    adc.nodeAdd,
		UpdateFunc: adc.nodeUpdate,
		DeleteFunc: adc.nodeDelete,
	})

...
}

1 adc.podAdd

与adc.podUpdate一致，看下面adc.podUpdate的分析。

2 adc.podUpdate

作用：主要是更新dsw，将新pod的volume加入dsw中。

主要看到util.ProcessPodVolumes方法。

// pkg/controller/volume/attachdetach/attach_detach_controller.go
func (adc *attachDetachController) podUpdate(oldObj, newObj interface{}) {
	pod, ok := newObj.(*v1.Pod)
	if pod == nil || !ok {
		return
	}
	if pod.Spec.NodeName == "" {
		// Ignore pods without NodeName, indicating they are not scheduled.
		return
	}

	volumeActionFlag := util.DetermineVolumeAction(
		pod,
		adc.desiredStateOfWorld,
		true /* default volume action */)

	util.ProcessPodVolumes(pod, volumeActionFlag, /* addVolumes */
		adc.desiredStateOfWorld, &adc.volumePluginMgr, adc.pvcLister, adc.pvLister, adc.csiMigratedPluginManager, adc.intreeToCSITranslator)
}

util.ProcessPodVolumes

主要是更新dsw，将新pod的volume加入dsw中。

// pkg/controller/volume/attachdetach/util/util.go
// ProcessPodVolumes processes the volumes in the given pod and adds them to the
// desired state of the world if addVolumes is true, otherwise it removes them.
func ProcessPodVolumes(pod *v1.Pod, addVolumes bool, desiredStateOfWorld cache.DesiredStateOfWorld, volumePluginMgr *volume.VolumePluginMgr, pvcLister corelisters.PersistentVolumeClaimLister, pvLister corelisters.PersistentVolumeLister, csiMigratedPluginManager csimigration.PluginManager, csiTranslator csimigration.InTreeToCSITranslator) {
	if pod == nil {
		return
	}

	if len(pod.Spec.Volumes) <= 0 {
		klog.V(10).Infof("Skipping processing of pod %q/%q: it has no volumes.",
			pod.Namespace,
			pod.Name)
		return
	}

	nodeName := types.NodeName(pod.Spec.NodeName)
	if nodeName == "" {
		klog.V(10).Infof(
			"Skipping processing of pod %q/%q: it is not scheduled to a node.",
			pod.Namespace,
			pod.Name)
		return
	} else if !desiredStateOfWorld.NodeExists(nodeName) {
		// If the node the pod is scheduled to does not exist in the desired
		// state of the world data structure, that indicates the node is not
		// yet managed by the controller. Therefore, ignore the pod.
		klog.V(4).Infof(
			"Skipping processing of pod %q/%q: it is scheduled to node %q which is not managed by the controller.",
			pod.Namespace,
			pod.Name,
			nodeName)
		return
	}

	// Process volume spec for each volume defined in pod
	for _, podVolume := range pod.Spec.Volumes {
		volumeSpec, err := CreateVolumeSpec(podVolume, pod.Namespace, nodeName, volumePluginMgr, pvcLister, pvLister, csiMigratedPluginManager, csiTranslator)
		if err != nil {
			klog.V(10).Infof(
				"Error processing volume %q for pod %q/%q: %v",
				podVolume.Name,
				pod.Namespace,
				pod.Name,
				err)
			continue
		}

		attachableVolumePlugin, err :=
			volumePluginMgr.FindAttachablePluginBySpec(volumeSpec)
		if err != nil || attachableVolumePlugin == nil {
			klog.V(10).Infof(
				"Skipping volume %q for pod %q/%q: it does not implement attacher interface. err=%v",
				podVolume.Name,
				pod.Namespace,
				pod.Name,
				err)
			continue
		}

		uniquePodName := util.GetUniquePodName(pod)
		if addVolumes {
			// Add volume to desired state of world
			_, err := desiredStateOfWorld.AddPod(
				uniquePodName, pod, volumeSpec, nodeName)
			if err != nil {
				klog.V(10).Infof(
					"Failed to add volume %q for pod %q/%q to desiredStateOfWorld. %v",
					podVolume.Name,
					pod.Namespace,
					pod.Name,
					err)
			}

		} else {
			// Remove volume from desired state of world
			uniqueVolumeName, err := util.GetUniqueVolumeNameFromSpec(
				attachableVolumePlugin, volumeSpec)
			if err != nil {
				klog.V(10).Infof(
					"Failed to delete volume %q for pod %q/%q from desiredStateOfWorld. GetUniqueVolumeNameFromSpec failed with %v",
					podVolume.Name,
					pod.Namespace,
					pod.Name,
					err)
				continue
			}
			desiredStateOfWorld.DeletePod(
				uniquePodName, uniqueVolumeName, nodeName)
		}
	}
	return
}

3 adc.podDelete

作用：将volume从dsw中删除。

// pkg/controller/volume/attachdetach/attach_detach_controller.go
func (adc *attachDetachController) podDelete(obj interface{}) {
	pod, ok := obj.(*v1.Pod)
	if pod == nil || !ok {
		return
	}

	util.ProcessPodVolumes(pod, false, /* addVolumes */
		adc.desiredStateOfWorld, &adc.volumePluginMgr, adc.pvcLister, adc.pvLister, adc.csiMigratedPluginManager, adc.intreeToCSITranslator)
}

4 adc.nodeAdd

主要是调用了adc.nodeUpdate方法进行处理，所以作用与adc.nodeUpdate基本相似，看adc.nodeUpdate的分析。

// pkg/controller/volume/attachdetach/attach_detach_controller.go
func (adc *attachDetachController) nodeAdd(obj interface{}) {
	node, ok := obj.(*v1.Node)
	// TODO: investigate if nodeName is empty then if we can return
	// kubernetes/kubernetes/issues/37777
	if node == nil || !ok {
		return
	}
	nodeName := types.NodeName(node.Name)
	adc.nodeUpdate(nil, obj)
	// kubernetes/kubernetes/issues/37586
	// This is to workaround the case when a node add causes to wipe out
	// the attached volumes field. This function ensures that we sync with
	// the actual status.
	adc.actualStateOfWorld.SetNodeStatusUpdateNeeded(nodeName)
}

5 adc.nodeUpdate

作用：往dsw中添加node，根据node.Status.VolumesInUse来更新asw。

// pkg/controller/volume/attachdetach/attach_detach_controller.go
func (adc *attachDetachController) nodeUpdate(oldObj, newObj interface{}) {
	node, ok := newObj.(*v1.Node)
	// TODO: investigate if nodeName is empty then if we can return
	if node == nil || !ok {
		return
	}

	nodeName := types.NodeName(node.Name)
	adc.addNodeToDswp(node, nodeName)
	adc.processVolumesInUse(nodeName, node.Status.VolumesInUse)
}

5.1 adc.addNodeToDswp

往dsw中添加node

func (adc *attachDetachController) addNodeToDswp(node *v1.Node, nodeName types.NodeName) {
	if _, exists := node.Annotations[volumeutil.ControllerManagedAttachAnnotation]; exists {
		keepTerminatedPodVolumes := false

		if t, ok := node.Annotations[volumeutil.KeepTerminatedPodVolumesAnnotation]; ok {
			keepTerminatedPodVolumes = (t == "true")
		}

		// Node specifies annotation indicating it should be managed by attach
		// detach controller. Add it to desired state of world.
		adc.desiredStateOfWorld.AddNode(nodeName, keepTerminatedPodVolumes)
	}
}

5.2 adc.processVolumesInUse

根据node.Status.VolumesInUse来更新asw

// processVolumesInUse processes the list of volumes marked as "in-use"
// according to the specified Node's Status.VolumesInUse and updates the
// corresponding volume in the actual state of the world to indicate that it is
// mounted.
func (adc *attachDetachController) processVolumesInUse(
	nodeName types.NodeName, volumesInUse []v1.UniqueVolumeName) {
	klog.V(4).Infof("processVolumesInUse for node %q", nodeName)
	for _, attachedVolume := range adc.actualStateOfWorld.GetAttachedVolumesForNode(nodeName) {
		mounted := false
		for _, volumeInUse := range volumesInUse {
			if attachedVolume.VolumeName == volumeInUse {
				mounted = true
				break
			}
		}
		err := adc.actualStateOfWorld.SetVolumeMountedByNode(attachedVolume.VolumeName, nodeName, mounted)
		if err != nil {
			klog.Warningf(
				"SetVolumeMountedByNode(%q, %q, %v) returned an error: %v",
				attachedVolume.VolumeName, nodeName, mounted, err)
		}
	}
}

6 adc.nodeDelete

作用：从dsw中删除node以及该node相关的挂载信息

func (adc *attachDetachController) nodeDelete(obj interface{}) {
	node, ok := obj.(*v1.Node)
	if node == nil || !ok {
		return
	}

	nodeName := types.NodeName(node.Name)
	if err := adc.desiredStateOfWorld.DeleteNode(nodeName); err != nil {
		// This might happen during drain, but we still want it to appear in our logs
		klog.Infof("error removing node %q from desired-state-of-world: %v", nodeName, err)
	}

	adc.processVolumesInUse(nodeName, node.Status.VolumesInUse)
}

小结

pod对象与node对象的EventHandler主要作用分别如下：
（1）adc.podAdd：更新dsw，将新pod的volume加入dsw中；
（2）adc.podUpdate：更新dsw，将新pod的volume加入dsw中；
（3）adc.podDelete：将volume从dsw中删除；
（4）adc.nodeAdd：往dsw中添加node，根据node.Status.VolumesInUse来更新asw；
（5）adc.nodeUpdate：往dsw中添加node，根据node.Status.VolumesInUse来更新asw；
（6）adc.nodeDelete：从dsw中删除node以及该node相关的挂载信息。

总结

AD Cotroller作用

AD Cotroller全称Attachment/Detachment 控制器，主要负责创建、删除VolumeAttachment对象，并调用volume plugin来做存储设备的Attach/Detach操作（将数据卷挂载到特定node节点上/从特定node节点上解除挂载），以及更新node.Status.VolumesAttached等。

不同的volume plugin的Attach/Detach操作逻辑有所不同，如通过ceph-csi（out-tree volume plugin）来使用ceph存储，则的Attach/Detach操作只是修改VolumeAttachment对象的状态，而不会真正的将数据卷挂载到节点/从节点上解除挂载。

两个关键结构体

（1）desiredStateOfWorld: 记录着集群中期望要挂载到node的pod的volume信息，简称DSW。

（2）actualStateOfWorld: 记录着集群中实际已经挂载到node节点的volume信息，简称ASW。

AD controller会做desiredStateOfWorld与actualStateOfWorld之间的调谐：对比desiredStateOfWorld与actualStateOfWorld，对volume做attach或detach操作。