kubelet VolumeManager

概述

VolumeManager主要负责在kubelet中进行volume状态的管理。其整体思路同样遵循k8s声明式的设计思想，通过循环同步volume的预期状态与实际状态来触发pod与volume的attach/detach，mount/unmount等行为。

VolumeManager 接口

// VolumeManager runs a set of asynchronous loops that figure out which volumes
// need to be attached/mounted/unmounted/detached based on the pods scheduled on
// this node and makes it so.
type VolumeManager interface {
   
	// Starts the volume manager and all the asynchronous loops that it controls
	Run(sourcesReady config.SourcesReady, stopCh <-chan struct{
   })

	// WaitForAttachAndMount processes the volumes referenced in the specified
	// pod and blocks until they are all attached and mounted (reflected in
	// actual state of the world).
	// An error is returned if all volumes are not attached and mounted within
	// the duration defined in podAttachAndMountTimeout.
	WaitForAttachAndMount(pod *v1.Pod) error

	// GetMountedVolumesForPod returns a VolumeMap containing the volumes
	// referenced by the specified pod that are successfully attached and
	// mounted. The key in the map is the OuterVolumeSpecName (i.e.
	// pod.Spec.Volumes[x].Name). It returns an empty VolumeMap if pod has no
	// volumes.
	GetMountedVolumesForPod(podName types.UniquePodName) container.VolumeMap

	// GetExtraSupplementalGroupsForPod returns a list of the extra
	// supplemental groups for the Pod. These extra supplemental groups come
	// from annotations on persistent volumes that the pod depends on.
	GetExtraSupplementalGroupsForPod(pod *v1.Pod) []int64

	// GetVolumesInUse returns a list of all volumes that implement the volume.Attacher
	// interface and are currently in use according to the actual and desired
	// state of the world caches. A volume is considered "in use" as soon as it
	// is added to the desired state of world, indicating it *should* be
	// attached to this node and remains "in use" until it is removed from both
	// the desired state of the world and the actual state of the world, or it
	// has been unmounted (as indicated in actual state of world).
	GetVolumesInUse() []v1.UniqueVolumeName

	// ReconcilerStatesHasBeenSynced returns true only after the actual states in reconciler
	// has been synced at least once after kubelet starts so that it is safe to update mounted
	// volume list retrieved from actual state.
	ReconcilerStatesHasBeenSynced() bool

	// VolumeIsAttached returns true if the given volume is attached to this
	// node.
	VolumeIsAttached(volumeName v1.UniqueVolumeName) bool

	// Marks the specified volume as having successfully been reported as "in
	// use" in the nodes's volume status.
	MarkVolumesAsReportedInUse(volumesReportedAsInUse