docker run源码分析（一）之Docker client

妖狐艹你老母 2022-04-18 05:37 436阅读 0赞

## **1、什么是Docker？** ##

**Docker Linux 平台上的一款轻量级虚拟化容器的管理引擎。在全球范围内， Docker 还是一个开源项目，整个项目基于 Go 语言开发，代码托管于 GitHub 网站上，并遵从 Apache 2.0 协议。目前， Docker 可以帮助用户在容器内部快速自动化部署应用，并利用 Linux 内核特性命名空间( namespaces) 及控制组( cgroups) 等为容器提供隔离的运行环境。Docker 借助操作系统层的虚拟化实现资源的隔离，因此 Docker 容器在运行时与虚拟机 (VM) 的运行有很大的区别， Docker 容器与宿主机共享同一个操作系统，不会有额外的操作系统开销。**

## **2、Docker总体架构图** ##

**查看架构图详解，请参考：[https://www.infoq.cn/article/docker-source-code-analysis-part1][https_www.infoq.cn_article_docker-source-code-analysis-part1]**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2dvb3NlX2ZsZXNo_size_16_color_FFFFFF_t_70][]

## **3、背景：** ##

**了解Docker源码解析Dockerfile的流程，了解docker build以及docker run 在client、daemon和engine端的处理。**

### **4、 源码基于[Docker-ce17.09.][]** ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2dvb3NlX2ZsZXNo_size_16_color_FFFFFF_t_70 1][]

## **5、源码：** ##

**Docker Client 是Docker 架构中用户与 Docker Daemon 建立通信的客户端。从main（）函数开始，[位置点击][Link 1]。**

### **5.1、流程：（截图于博友，自己作图太麻烦，跟17.09有点差别，自己对比）** ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2dvb3NlX2ZsZXNo_size_16_color_FFFFFF_t_70 2][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2dvb3NlX2ZsZXNo_size_16_color_FFFFFF_t_70 3][]

### **5.2、源码分析：** ###

**docker client的入口函数main，在main中处理传入的参数，并把参数转化为cobra的command类型，最后通过cobra调用相应的方法。**

### **5.2.1、[func AddCommands（）][func AddCommands]函数** ###

// AddCommands adds all the commands from cli/command to the root command
    func AddCommands(cmd *cobra.Command, dockerCli *command.DockerCli) {
    	cmd.AddCommand(
    		// checkpoint
    		checkpoint.NewCheckpointCommand(dockerCli),
    
    		// config
    		config.NewConfigCommand(dockerCli),
    
    		// container
    		container.NewContainerCommand(dockerCli),
                   //添加子命令run及其选项
    		container.NewRunCommand(dockerCli),
    
    		// image
    		image.NewImageCommand(dockerCli),
    		image.NewBuildCommand(dockerCli),
    
    		// registry
    		registry.NewLoginCommand(dockerCli),
    		registry.NewLogoutCommand(dockerCli),
    		registry.NewSearchCommand(dockerCli),
    
    		// secret
    		secret.NewSecretCommand(dockerCli),
    
    		// service
    		service.NewServiceCommand(dockerCli),
    
    		// system
    		system.NewSystemCommand(dockerCli),
    		system.NewVersionCommand(dockerCli),
    
                   ……………………
    	)
    
    }

### **5.2.2、[func NewRunCommand（）][func_NewRunCommand]函数** ###

// NewRunCommand create a new `docker run` command
    func NewRunCommand(dockerCli *command.DockerCli) *cobra.Command {
    	var opts runOptions
    	var copts *containerOptions
    
    	cmd := &cobra.Command{
    		Use:   "run [OPTIONS] IMAGE [COMMAND] [ARG...]",
    		Short: "Run a command in a new container",
    		Args:  cli.RequiresMinArgs(1),
    		RunE: func(cmd *cobra.Command, args []string) error {
    			copts.Image = args[0]
    			if len(args) > 1 {
    				copts.Args = args[1:]
    			}
                            //run对应的客户端方法
    			return runRun(dockerCli, cmd.Flags(), &opts, copts)
    		},
    	}
    
    	flags := cmd.Flags()
    	flags.SetInterspersed(false)
    
    	// These are flags not stored in Config/HostConfig
    	flags.BoolVarP(&opts.detach, "detach", "d", false, "Run container in background and print container ID")
    	flags.BoolVar(&opts.sigProxy, "sig-proxy", true, "Proxy received signals to the process")
    	flags.StringVar(&opts.name, "name", "", "Assign a name to the container")
    	flags.StringVar(&opts.detachKeys, "detach-keys", "", "Override the key sequence for detaching a container")
    
    	// Add an explicit help that doesn't have a `-h` to prevent the conflict
    	// with hostname
    	flags.Bool("help", false, "Print usage")
    
    	command.AddTrustVerificationFlags(flags)
    	copts = addFlags(flags)
    	return cmd
    }

### **5.2.3、[func runRun][]（）函数** ###

func runRun(dockerCli *command.DockerCli, flags *pflag.FlagSet, ropts *runOptions, copts *containerOptions) error {
            //得到代理配置	// ConfigFile ~/.docker/config.json file info
            proxyConfig := dockerCli.ConfigFile().ParseProxyConfig(dockerCli.Client().DaemonHost(), copts.env.GetAll())
    	newEnv := []string{}
    	for k, v := range proxyConfig {
    		if v == nil {
    			newEnv = append(newEnv, k)
    		} else {
    			newEnv = append(newEnv, fmt.Sprintf("%s=%s", k, *v))
    		}
    	}
    	copts.env = *opts.NewListOptsRef(&newEnv, nil)
    	containerConfig, err := parse(flags, copts)
    	// just in case the parse does not exit
    	if err != nil {
    		reportError(dockerCli.Err(), "run", err.Error(), true)
    		return cli.StatusError{StatusCode: 125}
    	}
             //调用runContainer
    	return runContainer(dockerCli, ropts, copts, containerConfig)
    }

### **5.2.4、[func runContainer（）][func runContainer]函数** ###

func runContainer(dockerCli *command.DockerCli, opts *runOptions, copts *containerOptions, containerConfig *containerConfig) error {
    	config := containerConfig.Config
    	hostConfig := containerConfig.HostConfig
    	stdout, stderr := dockerCli.Out(), dockerCli.Err()
    	//实例化一个客户端，用于发送run命令请求
    	client := dockerCli.Client()
    
    	// TODO: pass this as an argument
    	cmdPath := "run"
    
    	warnOnOomKillDisable(*hostConfig, stderr)
    	warnOnLocalhostDNS(*hostConfig, stderr)
    
    	config.ArgsEscaped = false
    
    	if !opts.detach {
    		if err := dockerCli.In().CheckTty(config.AttachStdin, config.Tty); err != nil {
    			return err
    		}
    	} else {
    
             ……省略
    	ctx, cancelFun := context.WithCancel(context.Background())
    	//client向engine发送create容器请求
    	createResponse, err := createContainer(ctx, dockerCli, containerConfig, opts.name)
             ……省略
    	//start the container
    	client向engine发送start容器请求
    	if err := client.ContainerStart(ctx, createResponse.ID, types.ContainerStartOptions{}); err != nil {
    		
    }

### **5.2.5、[func createContainer（）][func createContainer]函数** ###

func createContainer(ctx context.Context, dockerCli command.Cli, containerConfig *containerConfig, name string) (*container.ContainerCreateCreatedBody, error) {
    	config := containerConfig.Config
    	hostConfig := containerConfig.HostConfig
    	networkingConfig := containerConfig.NetworkingConfig
    	stderr := dockerCli.Err()
    
    	var (
    		trustedRef reference.Canonical
    		namedRef   reference.Named
    	)
    
    	containerIDFile, err := newCIDFile(hostConfig.ContainerIDFile)
    	if err != nil {
    		return nil, err
    	}
    	defer containerIDFile.Close()
    
    	ref, err := reference.ParseAnyReference(config.Image)
    	if err != nil {
    		return nil, err
    	}
    	if named, ok := ref.(reference.Named); ok {
    		namedRef = reference.TagNameOnly(named)
    
    		if taggedRef, ok := namedRef.(reference.NamedTagged); ok && command.IsTrusted() {
    			var err error
    			trustedRef, err = image.TrustedReference(ctx, dockerCli, taggedRef, nil)
    			if err != nil {
    				return nil, err
    			}
    			config.Image = reference.FamiliarString(trustedRef)
    		}
    	}
    
    	//create the container
    	response, err := dockerCli.Client().ContainerCreate(ctx, config, hostConfig, networkingConfig, name)
    
    	//if image not found try to pull it
    	if err != nil {
    		if apiclient.IsErrImageNotFound(err) && namedRef != nil {
    			fmt.Fprintf(stderr, "Unable to find image '%s' locally\n", reference.FamiliarString(namedRef))
    
    			// we don't want to write to stdout anything apart from container.ID
    			if err := pullImage(ctx, dockerCli, config.Image, stderr); err != nil {
    				return nil, err
    			}
    			if taggedRef, ok := namedRef.(reference.NamedTagged); ok && trustedRef != nil {
    				if err := image.TagTrusted(ctx, dockerCli, trustedRef, taggedRef); err != nil {
    					return nil, err
    				}
    			}
    			// Retry
    			var retryErr error
    			response, retryErr = dockerCli.Client().ContainerCreate(ctx, config, hostConfig, networkingConfig, name)
    			if retryErr != nil {
    				return nil, retryErr
    			}
    		} else {
    			return nil, err
    		}
    	}
    
    	for _, warning := range response.Warnings {
    		fmt.Fprintf(stderr, "WARNING: %s\n", warning)
    	}
    	err = containerIDFile.Write(response.ID)
    	return &response, err
    }

### **5.2.6、[ContainerCreate()][ContainerCreate]** ###

// ContainerAPIClient defines API client methods for the containers
    type ContainerAPIClient interface {
    	//API create方法
            ContainerCreate(ctx context.Context, config *container.Config, hostConfig *container.HostConfig, networkingConfig *network.NetworkingConfig, containerName string) (container.ContainerCreateCreatedBody, error)
    	
            //API start方法
    	ContainerStart(ctx context.Context, container string, options types.ContainerStartOptions) error
    	
    }

//ContainerCreate基于给定配置创建新容器。 它可以与名称相关联，但不是强制性的。
    func (cli *Client) ContainerCreate(ctx context.Context, config *container.Config, hostConfig *container.HostConfig, networkingConfig *network.NetworkingConfig, containerName string) (container.ContainerCreateCreatedBody, error) {
    	var response container.ContainerCreateCreatedBody
    
    	if err := cli.NewVersionError("1.25", "stop timeout"); config != nil && config.StopTimeout != nil && err != nil {
    		return response, err
    	}
    
    	// When using API 1.24 and under, the client is responsible for removing the container
    	if hostConfig != nil && versions.LessThan(cli.ClientVersion(), "1.25") {
    		hostConfig.AutoRemove = false
    	}
    
    	query := url.Values{}
    	if containerName != "" {
    		query.Set("name", containerName)
    	}
    
    	body := configWrapper{
    		Config:           config,
    		HostConfig:       hostConfig,
    		NetworkingConfig: networkingConfig,
    	}
    	//发送post请求
    	serverResp, err := cli.post(ctx, "/containers/create", query, body, nil)
    	if err != nil {
    		if serverResp.statusCode == 404 && strings.Contains(err.Error(), "No such image") {
    			return response, imageNotFoundError{config.Image}
    		}
    		return response, err
    	}
    
    	err = json.NewDecoder(serverResp.body).Decode(&response)
    	ensureReaderClosed(serverResp)
    	return response, err
    }

### **5.3、总结** ###

**在第5.2.4节上，startContainer（）函数就不介绍了，跟createContainer类似，后面有需要，咱再分析。**

**下一篇章就分析docker run命令在daemon中的处理流程了。**

## **参考：** ##

**           [https://www.infoq.cn/article/docker-source-code-analysis-part1][https_www.infoq.cn_article_docker-source-code-analysis-part1]**

**[https://guanjunjian.github.io/2017/09/26/study-1-docker-1-client-excuting-flow-fo][https_guanjunjian.github.io_2017_09_26_study-1-docker-1-client-excuting-flow-fo]****[r-run/][https_guanjunjian.github.io_2017_09_26_study-1-docker-1-client-excuting-flow-fo]**

**[https://blog.csdn.net/warrior\_0319/article/details/79931987][https_blog.csdn.net_warrior_0319_article_details_79931987]**

**《docker源码分析》**

**百度网盘：链接: https://pan.baidu.com/s/1m5AqgfZKvPRu2BcmWz-WxA 提取码: wjrj **

[https_www.infoq.cn_article_docker-source-code-analysis-part1]: https://www.infoq.cn/article/docker-source-code-analysis-part1
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2dvb3NlX2ZsZXNo_size_16_color_FFFFFF_t_70]: /images/20220418/95bebc69eedf4040bad1f1cec9ab02df.png
[Docker-ce17.09.]: https://github.com/docker/docker-ce/tree/17.09
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2dvb3NlX2ZsZXNo_size_16_color_FFFFFF_t_70 1]: /images/20220418/b21f2df242774bfea872e1abfd0a317f.png
[Link 1]: https://github.com/docker/docker-ce/blob/17.09/components/cli/cmd/docker/docker.go#L160
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2dvb3NlX2ZsZXNo_size_16_color_FFFFFF_t_70 2]: /images/20220418/56152a3ebed5484eb796ccb10cfa28f5.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2dvb3NlX2ZsZXNo_size_16_color_FFFFFF_t_70 3]: /images/20220418/d8594d798b8d42a082d324774c7d35d1.png
[func AddCommands]: https://github.com/docker/cli/blob/HEAD/cli/command/commands/commands.go#L30:6
[func_NewRunCommand]: https://github.com/docker/cli/blob/HEAD/cli/command/container/run.go#L35:6
[func runRun]: https://github.com/docker/cli/blob/HEAD/cli/command/container/run.go#L100:6
[func runContainer]: https://github.com/docker/cli/blob/HEAD/cli/command/container/run.go#L121
[func createContainer]: https://github.com/docker/cli/blob/HEAD/cli/command/container/create.go#L162:6
[ContainerCreate]: https://github.com/docker/cli/blob/HEAD/vendor/github.com/docker/docker/client/interface.go#L50:2
[https_guanjunjian.github.io_2017_09_26_study-1-docker-1-client-excuting-flow-fo]: https://guanjunjian.github.io/2017/09/26/study-1-docker-1-client-excuting-flow-for-run/
[https_blog.csdn.net_warrior_0319_article_details_79931987]: https://blog.csdn.net/warrior_0319/article/details/79931987