Merge pull request opencurve#42 from bai-charisu/master

add k8s csi doc

Author: opencurveadmin

README.md

@@ -12,6 +12,8 @@ CURVE是网易自主设计研发的高性能、高可用、高可靠分布式存
   - [Chunkserver](docs/cn/chunkserver_design.md)
   - [Snapshotcloneserver](docs/cn/snapshotcloneserver.md)
   - [CURVE质量体系介绍](docs/cn/quality.md)
+- CURVE上层应用
+  - [对接k8s文档](docs/cn/k8s_csi_interface.md)
 
 ## 快速开始
 

docs/cn/k8s_csi_interface.md

@@ -0,0 +1,88 @@
+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。内部使用的Curve CSI插件目前在联调测试中，后续会开源出来。
+
+## 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:
+
+```bash
+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