k8s_csi_interface.md

目前，curve可以通过CSI插件的方式对接Kubernetes。本文给出的是CSI插件开发指导说明。curve csi插件源码请见curve-csi。

Curve Interface

curve提供命令行管理工具curve，用来创建、删除卷等管理操作。具体接口如下：

• 创建卷：curve create [-h] --filename FILENAME --length LENGTH --user USER
• 删除卷：curve delete [-h] --user USER --filename FILENAME
• 扩容卷：curve extend [-h] --user USER --filename FILENAME --length LENGTH
• 查询卷：curve stat [-h] --user USER --filename FILENAME
• rename卷：curve rename [-h] --user USER --filename FILENAME --newname NEWNAME
• 创建目录：curve mkdir [-h] --user USER --dirname DIRNAME
• 删除目录：curve rmdir [-h] --user USER --dirname DIRNAME
• 查询目录下所有文件：curve list [-h] --user USER --dirname DIRNAME

提供curve-nbd工具，在node节点上提供map，unmap，list功能:

Usage: curve-nbd [options] map <image>           (Map an image to nbd device)
            unmap <device|image>                            (Unmap nbd device)
            list-mapped                                              (List mapped nbd devices)
Map options:
--device <device path> Specify nbd device path (/dev/nbd{num})
--read-only Map read-only
--nbds_max <limit> Override for module param nbds_max
--max_part <limit> Override for module param max_part
--timeout <seconds> Set nbd request timeout
--try-netlink Use the nbd netlink interface

Implementing with Kubernetes CSI

CSI spec:

   CreateVolume +------------+ DeleteVolume
 +------------->|  CREATED   +--------------+
 |              +---+----^---+              |
 |       Controller |    | Controller       v
+++         Publish |    | Unpublish       +++
|X|          Volume |    | Volume          | |
+-+             +---v----+---+             +-+
                | NODE_READY |
                +---+----^---+
               Node |    | Node
              Stage |    | Unstage
             Volume |    | Volume
                +---v----+---+
                |  VOL_READY |
                +---+----^---+
               Node |    | Node
            Publish |    | Unpublish
             Volume |    | Volume
                +---v----+---+
                | PUBLISHED  |
                +------------+

CSI插件的对应：

• CreateVolume:
  • curve mkdir: DIRNAME在k8s storageClass定义
  • curve create: FILENAME为k8s persistentVolume name
  • curve stat: 等待卷ready
• Controller Publish Volume:
  • Nothing to do
• Node Stage Volume:
  • curve-nbd list-mapped: 查看是否已经被挂载
  • curve-nbd map: 挂载
• Node Publish Volume:
  • mount the stagePath to the publishPath
• Node Unpublish Volume:
  • umount publishPath
• Node Unstage Volume:
  • curve-nbd list-mapped: 查看是否已经被卸载
  • curve-nbd unmap: 卸载
• Controller Unpublish Volume:
  • Nothing to do
• DeleteVolume:
  • curve delete

其他可选支持：

• 扩容：

  • ControllerExpandVolume: curve extend
  • NodeExpandVolume: resize2fs/xfs_growfs

• 快照：暂未支持