ceph-csi源码分析（5）-rbd driver-nodeserver分析（上）
当ceph-csi组件启动时指定的driver type为rbd时，会启动rbd driver相关的服务。然后再根据controllerserver、nodeserver的参数配置，决定启动ControllerServer与IdentityServer，或NodeServer与IdentityServer。
基于tag v3.0.0
https://github.com/ceph/ceph-csi/releases/tag/v3.0.0
rbd driver分析将分为4个部分，分别是服务入口分析、controllerserver分析、nodeserver分析与IdentityServer分析。
这节进行nodeserver分析，nodeserver主要包括了NodeGetCapabilities（获取driver能力）、NodeGetVolumeStats（存储探测及metrics获取）、NodeStageVolume（map rbd与mount stagingPath）、NodePublishVolume（mount targetPath）、NodeUnpublishVolume（umount targetPath）、NodeUnstageVolume（umount stagingPath与unmap rbd）、NodeExpandVolume（node端存储扩容）操作，将一一进行分析。这节进行NodeGetCapabilities（获取driver能力）、NodeGetVolumeStats（存储探测及metrics获取）、NodeExpandVolume（node端存储扩容）的分析。
nodeserver分析
（1）NodeGetCapabilities
简介
NodeGetCapabilities主要用于获取该ceph-csi driver的能力。
该方法由由kubelet调用，在kubelet调用NodeExpandVolume、NodeStageVolume、NodeUnstageVolume等方法前，会先调用NodeGetCapabilities来获取该ceph-csi driver的能力，看是否支持对这些方法的调用。
kubelet中调用的有关代码位于pkg/volume/csi/csi_client.go。
NodeGetCapabilities
NodeGetCapabilities方法中注册了csi driver的能力。
如下代码表示该csi组件支持的能力有：
（1）挂载存储到节点，把存储从节点上解除挂载；
（2）获取节点上的存储状态；
（3）存储扩容。
// ceph-csi/internal/rbd/nodeserver.go
// NodeGetCapabilities returns the supported capabilities of the node server.
func (ns *NodeServer) NodeGetCapabilities(ctx context.Context, req *csi.NodeGetCapabilitiesRequest) (*csi.NodeGetCapabilitiesResponse, error) {
return &csi.NodeGetCapabilitiesResponse{
Capabilities: []*csi.NodeServiceCapability{
{
Type: &csi.NodeServiceCapability_Rpc{
Rpc: &csi.NodeServiceCapability_RPC{
Type: csi.NodeServiceCapability_RPC_STAGE_UNSTAGE_VOLUME,
},
},
},
{
Type: &csi.NodeServiceCapability_Rpc{
Rpc: &csi.NodeServiceCapability_RPC{
Type: csi.NodeServiceCapability_RPC_GET_VOLUME_STATS,
},
},
},
{
Type: &csi.NodeServiceCapability_Rpc{
Rpc: &csi.NodeServiceCapability_RPC{
Type: csi.NodeServiceCapability_RPC_EXPAND_VOLUME,
},
},
},
},
}, nil
}
（2）NodeGetVolumeStats
简介
NodeGetVolumeStats用于探测挂载存储的状态，并返回该存储的相关metrics给kubelet。
由kubelet定时循环调用，获取volume相关指标。kubelet定时调用的代码位于pkg/kubelet/server/stats/volume_stat_calculator.go-StartOnce()。
NodeGetVolumeStats
主要逻辑：
（1）获取存储挂载路径；
（2）检测存储挂载路径是否为挂载点（对比指定路径与其父目录的stat结果中的device的值，如果device值不一致，则是挂载点）；
（3）通过stat获取存储挂载路径的Metrics并返回。
// internal/csi-common/nodeserver-default.go
// NodeGetVolumeStats returns volume stats.
func (ns *DefaultNodeServer) NodeGetVolumeStats(ctx context.Context, req *csi.NodeGetVolumeStatsRequest) (*csi.NodeGetVolumeStatsResponse, error) {
// 获取存储挂载路径
var err error
targetPath := req.GetVolumePath()
if targetPath == "" {
err = fmt.Errorf("targetpath %v is empty", targetPath)
return nil, status.Error(codes.InvalidArgument, err.Error())
}
/*
volID := req.GetVolumeId()
TODO: Map the volumeID to the targetpath.
CephFS:
we need secret to connect to the ceph cluster to get the volumeID from volume
Name, however `secret` field/option is not available in NodeGetVolumeStats spec,
Below issue covers this request and once its available, we can do the validation
as per the spec.
https://github.com/container-storage-interface/spec/issues/371
RBD:
Below issue covers this request for RBD and once its available, we can do the validation
as per the spec.
https://github.com/ceph/ceph-csi/issues/511
*/
// 检测存储挂载路径是否为mountpoint
isMnt, err := util.IsMountPoint(targetPath)
if err != nil {
if os.IsNotExist(err) {
return nil, status.Errorf(codes.InvalidArgument, "targetpath %s doesnot exist", targetPath)
}
return nil, err
}
if !isMnt {
return nil, status.Errorf(codes.InvalidArgument, "targetpath %s is not mounted", targetPath)
}
// 通过stat获取存储挂载路径的Metrics
cephMetricsProvider := volume.NewMetricsStatFS(targetPath)
volMetrics, volMetErr := cephMetricsProvider.GetMetrics()
if volMetErr != nil {
return nil, status.Error(codes.Internal, volMetErr.Error())
}
available, ok := (*(volMetrics.Available)).AsInt64()
if !ok {
klog.Errorf(util.Log(ctx, "failed to fetch available bytes"))
}
capacity, ok := (*(volMetrics.Capacity)).AsInt64()
if !ok {
klog.Errorf(util.Log(ctx, "failed to fetch capacity bytes"))
return nil, status.Error(codes.Unknown, "failed to fetch capacity bytes")
}
used, ok := (*(volMetrics.Used)).AsInt64()
if !ok {
klog.Errorf(util.Log(ctx, "failed to fetch used bytes"))
}
inodes, ok := (*(volMetrics.Inodes)).AsInt64()
if !ok {
klog.Errorf(util.Log(ctx, "failed to fetch available inodes"))
return nil, status.Error(codes.Unknown, "failed to fetch available inodes")
}
inodesFree, ok := (*(volMetrics.InodesFree)).AsInt64()
if !ok {
klog.Errorf(util.Log(ctx, "failed to fetch free inodes"))
}
inodesUsed, ok := (*(volMetrics.InodesUsed)).AsInt64()
if !ok {
klog.Errorf(util.Log(ctx, "failed to fetch used inodes"))
}
return &csi.NodeGetVolumeStatsResponse{
Usage: []*csi.VolumeUsage{
{
Available: available,
Total: capacity,
Used: used,
Unit: csi.VolumeUsage_BYTES,
},
{
Available: inodesFree,
Total: inodes,
Used: inodesUsed,
Unit: csi.VolumeUsage_INODES,
},
},
}, nil
}
IsMountPoint
通过调用IsLikelyNotMountPoint来判断该路径是否为挂载点。
// internal/util/util.go
// IsMountPoint checks if the given path is mountpoint or not.
func IsMountPoint(p string) (bool, error) {
dummyMount := mount.New("")
notMnt, err := dummyMount.IsLikelyNotMountPoint(p)
if err != nil {
return false, status.Error(codes.Internal, err.Error())
}
return !notMnt, nil
}
dummyMount.IsLikelyNotMountPoint()主要逻辑：
（1）对指定路径执行stat操作；
（2）对指定路径的父目录执行stat操作；
（3）通过对比指定路径与其父目录的stat结果中的device的值，判断出该路径是否为挂载点（如果device值不一致，则是挂载点）。
// vendor/k8s.io/utils/mount/mount_linux.go
// IsLikelyNotMountPoint determines if a directory is not a mountpoint.
// It is fast but not necessarily ALWAYS correct. If the path is in fact
// a bind mount from one part of a mount to another it will not be detected.
// It also can not distinguish between mountpoints and symbolic links.
// mkdir /tmp/a /tmp/b; mount --bind /tmp/a /tmp/b; IsLikelyNotMountPoint("/tmp/b")
// will return true. When in fact /tmp/b is a mount point. If this situation
// is of interest to you, don't use this function...
func (mounter *Mounter) IsLikelyNotMountPoint(file string) (bool, error) {
stat, err := os.Stat(file)
if err != nil {
return true, err
}
rootStat, err := os.Stat(filepath.Dir(strings.TrimSuffix(file, "/")))
if err != nil {
return true, err
}
// If the directory has a different device as parent, then it is a mountpoint.
if stat.Sys().(*syscall.Stat_t).Dev != rootStat.Sys().(*syscall.Stat_t).Dev {
return false, nil
}
return true, nil
}
（3）NodeExpandVolume
简介
负责node端的存储扩容操作。主要是在node上做相应操作，将存储的扩容信息同步到node上。
NodeExpandVolume resizes rbd volumes.
实际上，存储扩容分为两大步骤，第一步是csi的ControllerExpandVolume，主要负责将底层存储扩容；第二步是csi的NodeExpandVolume，当volumemode是filesystem时，主要负责将底层rbd image的扩容信息同步到rbd/nbd device，对xfs/ext文件系统进行扩展；当volumemode是block，则不用进行node端扩容操作。
NodeExpandVolume
主体流程：
（1）校验请求参数；
（2）判断指定路径是否为挂载点；
（3）获取devicePath；
（4）调用resizefs.NewResizeFs初始化resizer；
（5）调用resizer.Resize做进一步操作。
func (ns *NodeServer) NodeExpandVolume(ctx context.Context, req *csi.NodeExpandVolumeRequest) (*csi.NodeExpandVolumeResponse, error) {
volumeID := req.GetVolumeId()
if volumeID == "" {
return nil, status.Error(codes.InvalidArgument, "volume ID must be provided")
}
volumePath := req.GetVolumePath()
if volumePath == "" {
return nil, status.Error(codes.InvalidArgument, "volume path must be provided")
}
if acquired := ns.VolumeLocks.TryAcquire(volumeID); !acquired {
klog.Errorf(util.Log(ctx, util.VolumeOperationAlreadyExistsFmt), volumeID)
return nil, status.Errorf(codes.Aborted, util.VolumeOperationAlreadyExistsFmt, volumeID)
}
defer ns.VolumeLocks.Release(volumeID)
// volumePath is targetPath for block PVC and stagingPath for filesystem.
// check the path is mountpoint or not, if it is
// mountpoint treat this as block PVC or else it is filesystem PVC
// TODO remove this once ceph-csi supports CSI v1.2.0 spec
notMnt, err := mount.IsNotMountPoint(ns.mounter, volumePath)
if err != nil {
if os.IsNotExist(err) {
return nil, status.Error(codes.NotFound, err.Error())
}
return nil, status.Error(codes.Internal, err.Error())
}
if !notMnt {
return &csi.NodeExpandVolumeResponse{}, nil
}
devicePath, err := getDevicePath(ctx, volumePath)
if err != nil {
return nil, status.Error(codes.Internal, err.Error())
}
diskMounter := &mount.SafeFormatAndMount{Interface: ns.mounter, Exec: utilexec.New()}
// TODO check size and return success or error
volumePath += "/" + volumeID
resizer := resizefs.NewResizeFs(diskMounter)
ok, err := resizer.Resize(devicePath, volumePath)
if !ok {
return nil, fmt.Errorf("rbd: resize failed on path %s, error: %v", req.GetVolumePath(), err)
}
return &csi.NodeExpandVolumeResponse{}, nil
}
resizer.Resize
根据相应的文件系统格式，调用相应的resize方法。
func (resizefs *ResizeFs) Resize(devicePath string, deviceMountPath string) (bool, error) {
format, err := resizefs.mounter.GetDiskFormat(devicePath)
if err != nil {
formatErr := fmt.Errorf("ResizeFS.Resize - error checking format for device %s: %v", devicePath, err)
return false, formatErr
}
// If disk has no format, there is no need to resize the disk because mkfs.*
// by default will use whole disk anyways.
if format == "" {
return false, nil
}
klog.V(3).Infof("ResizeFS.Resize - Expanding mounted volume %s", devicePath)
switch format {
case "ext3", "ext4":
return resizefs.extResize(devicePath)
case "xfs":
return resizefs.xfsResize(deviceMountPath)
}
return false, fmt.Errorf("ResizeFS.Resize - resize of format %s is not supported for device %s mounted at %s", format, devicePath, deviceMountPath)
}
xfsResize
xfs文件系统使用xfs_growfs命令。
func (resizefs *ResizeFs) xfsResize(deviceMountPath string) (bool, error) {
args := []string{"-d", deviceMountPath}
output, err := resizefs.mounter.Exec.Command("xfs_growfs", args...).CombinedOutput()
if err == nil {
klog.V(2).Infof("Device %s resized successfully", deviceMountPath)
return true, nil
}
resizeError := fmt.Errorf("resize of device %s failed: %v. xfs_growfs output: %s", deviceMountPath, err, string(output))
return false, resizeError
}
extResize
ext文件系统使用resize2fs命令。
func (resizefs *ResizeFs) extResize(devicePath string) (bool, error) {
output, err := resizefs.mounter.Exec.Command("resize2fs", devicePath).CombinedOutput()
if err == nil {
klog.V(2).Infof("Device %s resized successfully", devicePath)
return true, nil
}
resizeError := fmt.Errorf("resize of device %s failed: %v. resize2fs output: %s", devicePath, err, string(output))
return false, resizeError
}
rbd driver-nodeserver分析（上）-小结
这节分析了NodeGetCapabilities、NodeGetVolumeStats、NodeExpandVolume方法，作用分别如下：