docker插件开发示例

官方示例文档

官方以开发一个sshfs的volume plugin为例。

$ git clone https://github.com/vieux/docker-volume-sshfs
$ cd docker-volume-sshfs
$ go get github.com/docker/go-plugins-helpers/volume
$ go build -o docker-volume-sshfs main.go  
$ docker build -t rootfsimage .
$ id=$(docker create rootfsimage true) # id was cd851ce43a403 when the image was created
$ sudo mkdir -p myplugin/rootfs
$ sudo docker export "$id" | sudo tar -x -C myplugin/rootfs
$ docker rm -vf "$id"
$ docker rmi rootfsimage

我们可以看到sshfs的Dockerfile是这样的：

FROM alpine

RUN apk update && apk add sshfs

RUN mkdir -p /run/docker/plugins /mnt/state /mnt/volumes

COPY docker-volume-sshfs docker-volume-sshfs

CMD ["docker-volume-sshfs"]

实际上是讲编译好的可执行文件复制到alpine linux容器中运行。

编译rootfsimage镜像的过程。

docker build -t rootfsimage .
Sending build context to Docker daemon 11.71 MB
Step 1/5 : FROM alpine
 ---> 4a415e366388
Step 2/5 : RUN apk update && apk add sshfs
 ---> Running in 1551ecc1c847
fetch http://dl-cdn.alpinelinux.org/alpine/v3.5/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.5/community/x86_64/APKINDEX.tar.gz
v3.5.2-2-ge626ce8c3c [http://dl-cdn.alpinelinux.org/alpine/v3.5/main]
v3.5.1-71-gc7bb9a04f0 [http://dl-cdn.alpinelinux.org/alpine/v3.5/community]
OK: 7959 distinct packages available
(1/10) Installing openssh-client (7.4_p1-r0)
(2/10) Installing fuse (2.9.7-r0)
(3/10) Installing libffi (3.2.1-r2)
(4/10) Installing libintl (0.19.8.1-r0)
(5/10) Installing libuuid (2.28.2-r1)
(6/10) Installing libblkid (2.28.2-r1)
(7/10) Installing libmount (2.28.2-r1)
(8/10) Installing pcre (8.39-r0)
(9/10) Installing glib (2.50.2-r0)
(10/10) Installing sshfs (2.8-r0)
Executing busybox-1.25.1-r0.trigger
Executing glib-2.50.2-r0.trigger
OK: 11 MiB in 21 packages
 ---> 1a73c501f431
Removing intermediate container 1551ecc1c847
Step 3/5 : RUN mkdir -p /run/docker/plugins /mnt/state /mnt/volumes
 ---> Running in 032af3b2595a
 ---> 30c7e8463e96
Removing intermediate container 032af3b2595a
Step 4/5 : COPY docker-volume-sshfs docker-volume-sshfs
 ---> a924c6fcc1e4
Removing intermediate container ffc5e3c97707
Step 5/5 : CMD docker-volume-sshfs
 ---> Running in 0dc938fe4f4e
 ---> 0fd2e3d94860
Removing intermediate container 0dc938fe4f4e
Successfully built 0fd2e3d94860

编写config.json文档

{
    "description": "sshFS plugin for Docker",
    "documentation": "https://docs.docker.com/engine/extend/plugins/",
    "entrypoint": ["/go/bin/docker-volume-sshfs"],
    "network": {
           "type": "host"
           },
    "interface" : {
           "types": ["docker.volumedriver/1.0"],
           "socket": "sshfs.sock"
    },
    "linux": {
        "capabilities": ["CAP_SYS_ADMIN"]
    }
}

该插件使用host网络类型，使用/run/docker/plugins/sshfs.sock接口与docker engine通信。

创建plugin

使用docker plugin create <plugin_name> /path/to/plugin/data/命令创建插件。

具体到sshfs插件，在myplugin目录下使用如下命令创建插件：

docker plugin create jimmysong/sshfs:latest .

现在就可以看到刚创建的插件了

docker plugin ls
ID                  NAME                 DESCRIPTION               ENABLED
8aa1f6098fca        vieux/sshfs:latest   sshFS plugin for Docker   true

push plugin

先登录你的docker hub账户，然后使用docker plugin push jimmysong/sshfs:latest即可以推送docker plugin到docker hub中。

目前推送到harbor镜像仓库有问题，报错信息：

c08c951b53b7: Preparing 
denied: requested access to the resource is denied

已给harbor提issue-1532