Docker源码学习之docker-version命令

docker源码学习之 docker version 子命令

说明： 使用的代码是 https://github.com/golang108/docker-cli.git (tag: v24.0.6)

1. 添加容器相关的几个子命令

其中就有我们这里说到 version 子命令。

容器相关的 子命令 在这里 被加入到 corba 中去

cli/command/commands/commands.go 文件

func AddCommands(cmd *cobra.Command, dockerCli command.Cli) {
	cmd.AddCommand(
		system.NewVersionCommand(dockerCli),
		......
		......
		......
	)
}

2. NewVersionCommand() 函数

func NewVersionCommand(dockerCli command.Cli) *cobra.Command {

}

基本上可以发现docker所有的子命令 都有个 NewXXXXCommand 的函数，cli/command/commands/commands.go 文件能一眼看到全部的。

1️⃣这个函数 主要作用 就是 初始化 cobra.Command{} 结构体 指针。然后返回这个指针。

2️⃣然后 设置 flags的解析。这里只有一个 -f、–format 选项。

通过打印 帮助可以看到 选项

$ ./build/docker version -h  
Flag shorthand -h has been deprecated, please use --help

Usage:  docker version [OPTIONS]

Show the Docker version information

Options:
  -f, --format string   Format output using a custom template:
                        'json':             Print in JSON format
                        'TEMPLATE':         Print output using the given Go template.
                        Refer to https://docs.docker.com/go/formatting/ for more information about formatting output with
                        templates

2.1 cmd := &cobra.Command{} 结构体的初始化

cmd := &cobra.Command{
	Use:   "version [OPTIONS]",
	Short: "Show the Docker version information",
	Args:  cli.NoArgs,
	RunE: func(cmd *cobra.Command, args []string) error {
		return runVersion(dockerCli, &opts)
	},
	Annotations: map[string]string{
		"category-top": "10",
	},
	ValidArgsFunction: completion.NoComplete,
}

1️⃣ 这里注册 runVersion(dockerCli, &opts) 函数

2️⃣Annotations中”category-top”: “10”的作用，这个和docker help显示 Common Commands 命令的排序有关系。

如下，为什么info命令排在最下面，是因为 info 这个值设置的是12，最大的。run命令排第一是因为设置的是最小的是1。

$ docker help 

Usage:  docker [OPTIONS] COMMAND

A self-sufficient runtime for containers

Common Commands:
  run         Create and run a new container from an image
  exec        Execute a command in a running container
  ps          List containers
  build       Build an image from a Dockerfile
  pull        Download an image from a registry
  push        Upload an image to a registry
  images      List images
  login       Log in to a registry
  logout      Log out from a registry
  search      Search Docker Hub for images
  version     Show the Docker version information
  info        Display system-wide information

在 cli/cobra.go 文件中可以看到：

func topCommands(cmd *cobra.Command) []*cobra.Command {
		省略。。。。
		return sortorder.NaturalLess(cmds[i].Annotations["category-top"], cmds[j].Annotations["category-top"])
		省略。。。。

2.2 添加 flags

cmd.Flags().StringVarP(&opts.format, "format", "f", "", flagsHelper.InspectFormatHelp)

这里只有一个 -f、–format 选项。

3. runVersion(dockerCli , opts) 函数

3.1 opts *versionOptions 参数介绍

type versionOptions struct {
	format string
}

opts 这个参数 是 `var opts versionOptions `,  在 func NewRunCommand() 函数开头
定义的一个， 是一个结构体类型。这里面就一个 format 属性字段，和flags -f/--format 绑定的。

4. newVersionTemplate(string) 函数

参数 就是上面刚刚讲的 versionOptions.format 。

如果参数是空字符串，也就是没有指定 -f、–format选项，这里会使用一个 默认的模板：defaultVersionTemplate。

如果指定了 -f、–format选项，这里会使用一个 formatter.JSONFormat 的模板。

1️⃣ 默认模板打印如下格式：

$ ./build/docker version 
Client:
 Version:           24.0.6-6-g13466649e5
 API version:       1.43
 Go version:        go1.19.1
 Git commit:        13466649e5
 Built:             Sun Sep 24 12:54:21 2023
 OS/Arch:           linux/amd64
 Context:           default

Server: Docker Engine - Community
 Engine:
  Version:          24.0.2
  API version:      1.43 (minimum version 1.12)
  Go version:       go1.20.4
  Git commit:       659604f
  Built:            Thu May 25 21:52:13 2023
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.6.21
  GitCommit:        3dce8eb055cbb6872793272b4f20ed16117344f8
 runc:
  Version:          1.1.7
  GitCommit:        v1.1.7-0-g860f061
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

2️⃣ json模式打印如下

{
	"Client": {
		"Version": "24.0.6-6-g13466649e5",
		"ApiVersion": "1.43",
		"DefaultAPIVersion": "1.43",
		"GitCommit": "13466649e5",
		"GoVersion": "go1.19.1",
		"Os": "linux",
		"Arch": "amd64",
		"BuildTime": "Sun Sep 24 12:54:21 2023",
		"Context": "default"
	},
	"Server": {
		"Platform": {
			"Name": "Docker Engine - Community"
		},
		"Components": [{
			"Name": "Engine",
			"Version": "24.0.2",
			"Details": {
				"ApiVersion": "1.43",
				"Arch": "amd64",
				"BuildTime": "Thu May 25 21:52:13 2023",
				"Experimental": "false",
				"GitCommit": "659604f",
				"GoVersion": "go1.20.4",
				"KernelVersion": "5.4.0-150-generic",
				"MinAPIVersion": "1.12",
				"Os": "linux"
			}
		}, {
			"Name": "containerd",
			"Version": "1.6.21",
			"Details": {
				"GitCommit": "3dce8eb055cbb6872793272b4f20ed16117344f8"
			}
		}, {
			"Name": "runc",
			"Version": "1.1.7",
			"Details": {
				"GitCommit": "v1.1.7-0-g860f061"
			}
		}, {
			"Name": "docker-init",
			"Version": "0.19.0",
			"Details": {
				"GitCommit": "de40ad0"
			}
		}],
		"Version": "24.0.2",
		"ApiVersion": "1.43",
		"MinAPIVersion": "1.12",
		"GitCommit": "659604f",
		"GoVersion": "go1.20.4",
		"Os": "linux",
		"Arch": "amd64",
		"KernelVersion": "5.4.0-150-generic",
		"BuildTime": "2023-05-25T21:52:13.000000000+00:00"
	}
}

3️⃣自定义模板字符串打印如下：

$ docker version --format '{{ .Client.Version }} {{ .Server.Version }}'
24.0.6-6-g13466649e5 24.0.2

模板引擎用的 go 自带的，text/template/template.go。

这个 双大括号的写法 和 vue 中很类似，web中目前流行有 Mustache、Hogan、doT.js、JsRender、Kendo UI Templates等。

5 newClientVersion(ctx, dockerCli)

获取 客户端的 版本信息

func newClientVersion(contextName string, dockerCli command.Cli) clientVersion {
	v := clientVersion{
		Version:   version.Version,
		GoVersion: runtime.Version(),
		GitCommit: version.GitCommit,
		BuildTime: reformatDate(version.BuildTime),
		Os:        runtime.GOOS,
		Arch:      arch(),
		Context:   contextName,
	}
	if version.PlatformName != "" {
		v.Platform = &platformInfo{Name: version.PlatformName}
	}
	if dockerCli != nil {
		v.APIVersion = dockerCli.CurrentVersion()
		v.DefaultAPIVersion = dockerCli.DefaultVersion()  // DefaultVersion of Current REST API, DefaultVersion = "1.43"
	}
	return v
}

其中有几个变量是在 cli/version/version.go 中定义的，然后编译的时候会加上

var (
	PlatformName = ""
	Version      = "unknown-version"
	GitCommit    = "unknown-commit"
	BuildTime    = "unknown-buildtime"
)

6 dockerCli.Client().ServerVersion(ctx)

获取 服务端的 版本信息

func (cli *Client) ServerVersion(ctx context.Context) (types.Version, error) {
	resp, err := cli.get(ctx, "/version", nil, nil)
	defer ensureReaderClosed(resp)
	if err != nil {
		return types.Version{}, err
	}

	var server types.Version
	err = json.NewDecoder(resp.body).Decode(&server)
	return server, err
}

类似的可以使用 curl 命令 发送http请求：

$ curl --unix-socket /var/run/docker.sock   http://localhost/version
{
	"Platform": {
		"Name": "Docker Engine - Community"
	},
	"Components": [{
		"Name": "Engine",
		"Version": "24.0.2",
		"Details": {
			"ApiVersion": "1.43",
			"Arch": "amd64",
			"BuildTime": "2023-05-25T21:52:13.000000000+00:00",
			"Experimental": "false",
			"GitCommit": "659604f",
			"GoVersion": "go1.20.4",
			"KernelVersion": "5.4.0-150-generic",
			"MinAPIVersion": "1.12",
			"Os": "linux"
		}
	}, {
		"Name": "containerd",
		"Version": "1.6.21",
		"Details": {
			"GitCommit": "3dce8eb055cbb6872793272b4f20ed16117344f8"
		}
	}, {
		"Name": "runc",
		"Version": "1.1.7",
		"Details": {
			"GitCommit": "v1.1.7-0-g860f061"
		}
	}, {
		"Name": "docker-init",
		"Version": "0.19.0",
		"Details": {
			"GitCommit": "de40ad0"
		}
	}],
	"Version": "24.0.2",
	"ApiVersion": "1.43",
	"MinAPIVersion": "1.12",
	"GitCommit": "659604f",
	"GoVersion": "go1.20.4",
	"Os": "linux",
	"Arch": "amd64",
	"KernelVersion": "5.4.0-150-generic",
	"BuildTime": "2023-05-25T21:52:13.000000000+00:00"
}