使用插件扩展kubectl

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func main() {
    //创建kubectl命令的默认参数
	command := cmd.NewDefaultKubectlCommand() 
	//执行command
	if err := cli.RunNoErrOutput(command); err != nil {
		// Pretty-print the error and exit with an error.
		util.CheckErr(err)
	}

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// NewDefaultKubectlCommand creates the `kubectl` command with default arguments
func NewDefaultKubectlCommand() *cobra.Command {
	return NewDefaultKubectlCommandWithArgs(KubectlOptions{
		PluginHandler: NewDefaultPluginHandler(plugin.ValidPluginFilenamePrefixes),
		Arguments:     os.Args,
		ConfigFlags:   defaultConfigFlags,
		IOStreams:     genericclioptions.IOStreams{In: os.Stdin, Out: os.Stdout, ErrOut: os.Stderr},
	})
}

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// NewDefaultKubectlCommandWithArgs creates the `kubectl` command with arguments
func NewDefaultKubectlCommandWithArgs(o KubectlOptions) *cobra.Command {
    //创建一个kubectl命令
	cmd := NewKubectlCommand(o)

	if o.PluginHandler == nil {
		return cmd
	}

    //o.Arguments为标准输入，例如 kubetl apply -f test.yaml
	if len(o.Arguments) > 1 { 
	    //取kubectl后的参数，例如 apply -f test.yaml
		cmdPathPieces := o.Arguments[1:] 

		// only look for suitable extension executables if
		// the specified command does not already exist
		//通过Find去匹配命令，如果命令不存在，则寻找合适的扩展可执行文件
		if _, _, err := cmd.Find(cmdPathPieces); err != nil {
			// Also check the commands that will be added by Cobra.
			// These commands are only added once rootCmd.Execute() is called, so we
			// need to check them explicitly here.
			var cmdName string // first "non-flag" arguments
			for _, arg := range cmdPathPieces {
				if !strings.HasPrefix(arg, "-") {
					cmdName = arg
					break
				}
			}

			switch cmdName {
			case "help", cobra.ShellCompRequestCmd, cobra.ShellCompNoDescRequestCmd:
				// Don't search for a plugin
			default:
				if err := HandlePluginCommand(o.PluginHandler, cmdPathPieces); err != nil {
					fmt.Fprintf(o.IOStreams.ErrOut, "Error: %v\n", err)
					os.Exit(1)
				}
			}
		}
	}

	return cmd
}

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// NewKubectlCommand creates the `kubectl` command and its nested children.
func NewKubectlCommand(o KubectlOptions) *cobra.Command {
	warningHandler := rest.NewWarningWriter(o.IOStreams.ErrOut, rest.WarningWriterOptions{Deduplicate: true, Color: term.AllowsColorOutput(o.IOStreams.ErrOut)})
	warningsAsErrors := false
	// Parent command to which all subcommands are added.
	//创建主命令
	cmds := &cobra.Command{
		Use:   "kubectl",
		Short: i18n.T("kubectl controls the Kubernetes cluster manager"),
		Long: templates.LongDesc(`
      kubectl controls the Kubernetes cluster manager.

      Find more information at:
            https://kubernetes.io/docs/reference/kubectl/`),
		Run: runHelp,
		// Hook before and after Run initialize and write profiles to disk,
		// respectively.
		//初始化后，在运行指令前的钩子
		PersistentPreRunE: func(*cobra.Command, []string) error {
			rest.SetDefaultWarningHandler(warningHandler)
			//这里是做pprof性能分析，跳转到对应代码可以看到，我们可以用参数 --profile xxx 来采集性能指标，默认保存在当前目录下的profile.pprof中
			return initProfiling()
		},
		//运行指令后的钩子
		PersistentPostRunE: func(*cobra.Command, []string) error {
			if err := flushProfiling(); err != nil {
				return err
			}
			if warningsAsErrors {
				count := warningHandler.WarningCount()
				switch count {
				case 0:
					// no warnings
				case 1:
					return fmt.Errorf("%d warning received", count)
				default:
					return fmt.Errorf("%d warnings received", count)
				}
			}
			return nil
		},
	}
	// From this point and forward we get warnings on flags that contain "_" separators
	// when adding them with hyphen instead of the original name.
	//初始化设置cmds命令
	cmds.SetGlobalNormalizationFunc(cliflag.WarnWordSepNormalizeFunc)

	flags := cmds.PersistentFlags()

	addProfilingFlags(flags)

	flags.BoolVar(&warningsAsErrors, "warnings-as-errors", warningsAsErrors, "Treat warnings received from the server as errors and exit with a non-zero exit code")

	kubeConfigFlags := o.ConfigFlags
	if kubeConfigFlags == nil {
		kubeConfigFlags = defaultConfigFlags
	}
	kubeConfigFlags.AddFlags(flags)
	matchVersionKubeConfigFlags := cmdutil.NewMatchVersionFlags(kubeConfigFlags)
	matchVersionKubeConfigFlags.AddFlags(flags)
	// Updates hooks to add kubectl command headers: SIG CLI KEP 859.
	addCmdHeaderHooks(cmds, kubeConfigFlags)

    //初始化一个工厂
	f := cmdutil.NewFactory(matchVersionKubeConfigFlags)

	// Sending in 'nil' for the getLanguageFn() results in using
	// the LANG environment variable.
	//
	// TODO: Consider adding a flag or file preference for setting
	// the language, instead of just loading from the LANG env. variable.
	i18n.LoadTranslations("kubectl", nil)

	// Proxy command is incompatible with CommandHeaderRoundTripper, so
	// clear the WrapConfigFn before running proxy command.
	proxyCmd := proxy.NewCmdProxy(f, o.IOStreams)
	proxyCmd.PreRun = func(cmd *cobra.Command, args []string) {
		kubeConfigFlags.WrapConfigFn = nil
	}

	// Avoid import cycle by setting ValidArgsFunction here instead of in NewCmdGet()
	getCmd := get.NewCmdGet("kubectl", f, o.IOStreams)
	getCmd.ValidArgsFunction = utilcomp.ResourceTypeAndNameCompletionFunc(f)
    //kubectl定义了7类命令，Message为分类标签
	groups := templates.CommandGroups{
		{
			Message: "Basic Commands (Beginner):",
			Commands: []*cobra.Command{
				create.NewCmdCreate(f, o.IOStreams),
				expose.NewCmdExposeService(f, o.IOStreams),
				run.NewCmdRun(f, o.IOStreams),
				set.NewCmdSet(f, o.IOStreams),
			},
		},
		{
			Message: "Basic Commands (Intermediate):",
			Commands: []*cobra.Command{
				explain.NewCmdExplain("kubectl", f, o.IOStreams),
				getCmd,
				edit.NewCmdEdit(f, o.IOStreams),
				delete.NewCmdDelete(f, o.IOStreams),
			},
		},
		{
			Message: "Deploy Commands:",
			Commands: []*cobra.Command{
				rollout.NewCmdRollout(f, o.IOStreams),
				scale.NewCmdScale(f, o.IOStreams),
				autoscale.NewCmdAutoscale(f, o.IOStreams),
			},
		},
		{
			Message: "Cluster Management Commands:",
			Commands: []*cobra.Command{
				certificates.NewCmdCertificate(f, o.IOStreams),
				clusterinfo.NewCmdClusterInfo(f, o.IOStreams),
				top.NewCmdTop(f, o.IOStreams),
				drain.NewCmdCordon(f, o.IOStreams),
				drain.NewCmdUncordon(f, o.IOStreams),
				drain.NewCmdDrain(f, o.IOStreams),
				taint.NewCmdTaint(f, o.IOStreams),
			},
		},
		{
			Message: "Troubleshooting and Debugging Commands:",
			Commands: []*cobra.Command{
				describe.NewCmdDescribe("kubectl", f, o.IOStreams),
				logs.NewCmdLogs(f, o.IOStreams),
				attach.NewCmdAttach(f, o.IOStreams),
				cmdexec.NewCmdExec(f, o.IOStreams),
				portforward.NewCmdPortForward(f, o.IOStreams),
				proxyCmd,
				cp.NewCmdCp(f, o.IOStreams),
				auth.NewCmdAuth(f, o.IOStreams),
				debug.NewCmdDebug(f, o.IOStreams),
			},
		},
		{
			Message: "Advanced Commands:",
			Commands: []*cobra.Command{
				diff.NewCmdDiff(f, o.IOStreams),
				apply.NewCmdApply("kubectl", f, o.IOStreams),
				patch.NewCmdPatch(f, o.IOStreams),
				replace.NewCmdReplace(f, o.IOStreams),
				wait.NewCmdWait(f, o.IOStreams),
				kustomize.NewCmdKustomize(o.IOStreams),
			},
		},
		{
			Message: "Settings Commands:",
			Commands: []*cobra.Command{
				label.NewCmdLabel(f, o.IOStreams),
				annotate.NewCmdAnnotate("kubectl", f, o.IOStreams),
				completion.NewCmdCompletion(o.IOStreams.Out, ""),
			},
		},
	}
	groups.Add(cmds)

	filters := []string{"options"}

	// Hide the "alpha" subcommand if there are no alpha commands in this build.
	//如果在这个版本中没有alpha命令，隐藏“alpha”子命令
	alpha := NewCmdAlpha(f, o.IOStreams)
	if !alpha.HasSubCommands() {
		filters = append(filters, alpha.Name())
	}

	templates.ActsAsRootCommand(cmds, filters, groups...)

	utilcomp.SetFactoryForCompletion(f)
	registerCompletionFuncForGlobalFlags(cmds, f)

    //添加其余子命令，包括alpha/config/plugin/version/api-versions/api-resources/options
	cmds.AddCommand(alpha)
	cmds.AddCommand(cmdconfig.NewCmdConfig(clientcmd.NewDefaultPathOptions(), o.IOStreams))
	// 增加plugin子命令
	cmds.AddCommand(plugin.NewCmdPlugin(o.IOStreams))
	cmds.AddCommand(version.NewCmdVersion(f, o.IOStreams))
	cmds.AddCommand(apiresources.NewCmdAPIVersions(f, o.IOStreams))
	cmds.AddCommand(apiresources.NewCmdAPIResources(f, o.IOStreams))
	cmds.AddCommand(options.NewCmdOptions(o.IOStreams.Out))

	// Stop warning about normalization of flags. That makes it possible to
	// add the klog flags later.
	cmds.SetGlobalNormalizationFunc(cliflag.WordSepNormalizeFunc)
	return cmds
}

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// NewCmdCreate returns new initialized instance of create sub command
func NewCmdCreate(f cmdutil.Factory, ioStreams genericclioptions.IOStreams) *cobra.Command {
    //create子命令的相关选项
	o := NewCreateOptions(ioStreams)

    //create子命令
	cmd := &cobra.Command{
		Use:                   "create -f FILENAME",
		DisableFlagsInUseLine: true,
		Short:                 i18n.T("Create a resource from a file or from stdin"),
		Long:                  createLong,
		Example:               createExample,
		Run: func(cmd *cobra.Command, args []string) {
		    //验证参数
			if cmdutil.IsFilenameSliceEmpty(o.FilenameOptions.Filenames, o.FilenameOptions.Kustomize) {
				ioStreams.ErrOut.Write([]byte("Error: must specify one of -f and -k\n\n"))
				defaultRunFunc := cmdutil.DefaultSubCommandRun(ioStreams.ErrOut)
				defaultRunFunc(cmd, args)
				return
			}
			cmdutil.CheckErr(o.Complete(f, cmd, args))
			cmdutil.CheckErr(o.Validate())
			//执行逻辑是在这里的RunCreate
			cmdutil.CheckErr(o.RunCreate(f, cmd))
		},
	}

	// bind flag structs
	o.RecordFlags.AddFlags(cmd)

	usage := "to use to create the resource"
	//加入文件名选项的flag -f，保存到o.FilenameOptions.Filenames中，对应上面
	cmdutil.AddFilenameOptionFlags(cmd, &o.FilenameOptions, usage)
	cmdutil.AddValidateFlags(cmd)
	cmd.Flags().BoolVar(&o.EditBeforeCreate, "edit", o.EditBeforeCreate, "Edit the API resource before creating")
	cmd.Flags().Bool("windows-line-endings", runtime.GOOS == "windows",
		"Only relevant if --edit=true. Defaults to the line ending native to your platform.")
	cmdutil.AddApplyAnnotationFlags(cmd)
	cmdutil.AddDryRunFlag(cmd)
	cmdutil.AddLabelSelectorFlagVar(cmd, &o.Selector)
	cmd.Flags().StringVar(&o.Raw, "raw", o.Raw, "Raw URI to POST to the server.  Uses the transport specified by the kubeconfig file.")
	cmdutil.AddFieldManagerFlagVar(cmd, &o.fieldManager, "kubectl-create")

	o.PrintFlags.AddFlags(cmd)

	// create subcommands
	//create的子命令
	cmd.AddCommand(NewCmdCreateNamespace(f, ioStreams))
	cmd.AddCommand(NewCmdCreateQuota(f, ioStreams))
	cmd.AddCommand(NewCmdCreateSecret(f, ioStreams))
	cmd.AddCommand(NewCmdCreateConfigMap(f, ioStreams))
	cmd.AddCommand(NewCmdCreateServiceAccount(f, ioStreams))
	cmd.AddCommand(NewCmdCreateService(f, ioStreams))
	cmd.AddCommand(NewCmdCreateDeployment(f, ioStreams))
	cmd.AddCommand(NewCmdCreateClusterRole(f, ioStreams))
	cmd.AddCommand(NewCmdCreateClusterRoleBinding(f, ioStreams))
	cmd.AddCommand(NewCmdCreateRole(f, ioStreams))
	cmd.AddCommand(NewCmdCreateRoleBinding(f, ioStreams))
	cmd.AddCommand(NewCmdCreatePodDisruptionBudget(f, ioStreams))
	cmd.AddCommand(NewCmdCreatePriorityClass(f, ioStreams))
	cmd.AddCommand(NewCmdCreateJob(f, ioStreams))
	cmd.AddCommand(NewCmdCreateCronJob(f, ioStreams))
	cmd.AddCommand(NewCmdCreateIngress(f, ioStreams))
	cmd.AddCommand(NewCmdCreateToken(f, ioStreams))
	return cmd
}

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// RunCreate performs the creation
func (o *CreateOptions) RunCreate(f cmdutil.Factory, cmd *cobra.Command) error {
     // f为传入的Factory，主要是封装了与kube-apiserver交互客户端
	// raw only makes sense for a single file resource multiple objects aren't likely to do what you want.
	// the validator enforces this, so
	if len(o.Raw) > 0 {
		restClient, err := f.RESTClient()
		if err != nil {
			return err
		}
		return rawhttp.RawPost(restClient, o.IOStreams, o.Raw, o.FilenameOptions.Filenames[0])
	}

	if o.EditBeforeCreate {
		return RunEditOnCreate(f, o.PrintFlags, o.RecordFlags, o.IOStreams, cmd, &o.FilenameOptions, o.fieldManager)
	}

	schema, err := f.Validator(o.ValidationDirective, o.FieldValidationVerifier)
	if err != nil {
		return err
	}

	cmdNamespace, enforceNamespace, err := f.ToRawKubeConfigLoader().Namespace()
	if err != nil {
		return err
	}

    //实例化Builder
	r := f.NewBuilder().
		Unstructured().
		Schema(schema).
		ContinueOnError().
		NamespaceParam(cmdNamespace).DefaultNamespace().
		//读取文件信息，发现除了支持简单的本地文件，也支持标准输入和http/https协议访问的文件，保存为Visitor
		FilenameParam(enforceNamespace, &o.FilenameOptions).
		LabelSelectorParam(o.Selector).
		Flatten().
		Do()
	err = r.Err()
	if err != nil {
		return err
	}

	count := 0
	//调用visit函数，创建资源
	err = r.Visit(func(info *resource.Info, err error) error {
		if err != nil {
			return err
		}
		if err := util.CreateOrUpdateAnnotation(cmdutil.GetFlagBool(cmd, cmdutil.ApplyAnnotationsFlag), info.Object, scheme.DefaultJSONEncoder()); err != nil {
			return cmdutil.AddSourceToErr("creating", info.Source, err)
		}

		if err := o.Recorder.Record(info.Object); err != nil {
			klog.V(4).Infof("error recording current command: %v", err)
		}

		if o.DryRunStrategy != cmdutil.DryRunClient {
			if o.DryRunStrategy == cmdutil.DryRunServer {
				if err := o.DryRunVerifier.HasSupport(info.Mapping.GroupVersionKind); err != nil {
					return cmdutil.AddSourceToErr("creating", info.Source, err)
				}
			}
			obj, err := resource.
				NewHelper(info.Client, info.Mapping).
				DryRun(o.DryRunStrategy == cmdutil.DryRunServer).
				WithFieldManager(o.fieldManager).
				WithFieldValidation(o.ValidationDirective).
				Create(info.Namespace, true, info.Object)
			if err != nil {
				return cmdutil.AddSourceToErr("creating", info.Source, err)
			}
			info.Refresh(obj, true)
		}

		count++

		return o.PrintObj(info.Object)
	})
	if err != nil {
		return err
	}
	if count == 0 {
		return fmt.Errorf("no objects passed to create")
	}
	return nil
}

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if len(o.Arguments) > 1 {
		cmdPathPieces := o.Arguments[1:]

		// only look for suitable extension executables if
		// the specified command does not already exist
		if _, _, err := cmd.Find(cmdPathPieces); err != nil {
			// Also check the commands that will be added by Cobra.
			// These commands are only added once rootCmd.Execute() is called, so we
			// need to check them explicitly here.
			var cmdName string // first "non-flag" arguments
			for _, arg := range cmdPathPieces {
				if !strings.HasPrefix(arg, "-") {
					cmdName = arg
					break
				}
			}

			switch cmdName {
			case "help", cobra.ShellCompRequestCmd, cobra.ShellCompNoDescRequestCmd:
				// Don't search for a plugin
			default:
				if err := HandlePluginCommand(o.PluginHandler, cmdPathPieces); err != nil {
					fmt.Fprintf(o.IOStreams.ErrOut, "Error: %v\n", err)
					os.Exit(1)
				}
			}
		}
	}

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func NewCmdPlugin(streams genericclioptions.IOStreams) *cobra.Command {
	cmd := &cobra.Command{
		Use:                   "plugin [flags]",
		DisableFlagsInUseLine: true,
		Short:                 i18n.T("Provides utilities for interacting with plugins"),
		Long:                  pluginLong,
		Run: func(cmd *cobra.Command, args []string) {
			cmdutil.DefaultSubCommandRun(streams.ErrOut)(cmd, args)
		},
	}

	cmd.AddCommand(NewCmdPluginList(streams)) // li
	return cmd
}

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// NewCmdPluginList provides a way to list all plugin executables visible to kubectl
func NewCmdPluginList(streams genericclioptions.IOStreams) *cobra.Command {
	o := &PluginListOptions{
		IOStreams: streams,
	}

	cmd := &cobra.Command{
		Use:     "list",
		Short:   i18n.T("List all visible plugin executables on a user's PATH"),
		Example: pluginExample,
		Long:    pluginListLong,
		Run: func(cmd *cobra.Command, args []string) {
			cmdutil.CheckErr(o.Complete(cmd))
			cmdutil.CheckErr(o.Run())
		},
	}

	cmd.Flags().BoolVar(&o.NameOnly, "name-only", o.NameOnly, "If true, display only the binary name of each plugin, rather than its full path")
	return cmd
}

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func (o *PluginListOptions) Complete(cmd *cobra.Command) error {
	o.Verifier = &CommandOverrideVerifier{
		root:        cmd.Root(),
		seenPlugins: make(map[string]string),
	}

	o.PluginPaths = filepath.SplitList(os.Getenv("PATH"))
	return nil
}

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func (o *PluginListOptions) Run() error {
	pluginsFound := false
	isFirstFile := true
	pluginErrors := []error{}
	pluginWarnings := 0

	for _, dir := range uniquePathsList(o.PluginPaths) {
		if len(strings.TrimSpace(dir)) == 0 {
			continue
		}

		files, err := ioutil.ReadDir(dir)
		if err != nil {
			if _, ok := err.(*os.PathError); ok {
				fmt.Fprintf(o.ErrOut, "Unable to read directory %q from your PATH: %v. Skipping...\n", dir, err)
				continue
			}

			pluginErrors = append(pluginErrors, fmt.Errorf("error: unable to read directory %q in your PATH: %v", dir, err))
			continue
		}

		for _, f := range files {
			if f.IsDir() {
				continue
			}
			if !hasValidPrefix(f.Name(), ValidPluginFilenamePrefixes) {
				continue
			}

			if isFirstFile {
				fmt.Fprintf(o.Out, "The following compatible plugins are available:\n\n")
				pluginsFound = true
				isFirstFile = false
			}

			pluginPath := f.Name()
			if !o.NameOnly {
				pluginPath = filepath.Join(dir, pluginPath)
			}

			fmt.Fprintf(o.Out, "%s\n", pluginPath)
			if errs := o.Verifier.Verify(filepath.Join(dir, f.Name())); len(errs) != 0 {
				for _, err := range errs {
					fmt.Fprintf(o.ErrOut, "  - %s\n", err)
					pluginWarnings++
				}
			}
		}
	}

	if !pluginsFound {
		pluginErrors = append(pluginErrors, fmt.Errorf("error: unable to find any kubectl plugins in your PATH"))
	}

	if pluginWarnings > 0 {
		if pluginWarnings == 1 {
			pluginErrors = append(pluginErrors, fmt.Errorf("error: one plugin warning was found"))
		} else {
			pluginErrors = append(pluginErrors, fmt.Errorf("error: %v plugin warnings were found", pluginWarnings))
		}
	}
	if len(pluginErrors) > 0 {
		errs := bytes.NewBuffer(nil)
		for _, e := range pluginErrors {
			fmt.Fprintln(errs, e)
		}
		return fmt.Errorf("%s", errs.String())
	}

	return nil
}

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// HandlePluginCommand receives a pluginHandler and command-line arguments and attempts to find
// a plugin executable on the PATH that satisfies the given arguments.
func HandlePluginCommand(pluginHandler PluginHandler, cmdArgs []string) error {
	var remainingArgs []string // all "non-flag" arguments
	for _, arg := range cmdArgs {
		if strings.HasPrefix(arg, "-") {
			break
		}
		remainingArgs = append(remainingArgs, strings.Replace(arg, "-", "_", -1))
	}

	if len(remainingArgs) == 0 {
		// the length of cmdArgs is at least 1
		return fmt.Errorf("flags cannot be placed before plugin name: %s", cmdArgs[0])
	}

	foundBinaryPath := ""

	// attempt to find binary, starting at longest possible name with given cmdArgs
	for len(remainingArgs) > 0 {
	    //获取插件全路径
		path, found := pluginHandler.Lookup(strings.Join(remainingArgs, "-"))
		if !found {
			remainingArgs = remainingArgs[:len(remainingArgs)-1]
			continue
		}

		foundBinaryPath = path
		break
	}

	if len(foundBinaryPath) == 0 {
		return nil
	}

	// invoke cmd binary relaying the current environment and args given
	//执行
	if err := pluginHandler.Execute(foundBinaryPath, cmdArgs[len(remainingArgs):], os.Environ()); err != nil {
		return err
	}

	return nil
}

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// Lookup implements PluginHandler
func (h *DefaultPluginHandler) Lookup(filename string) (string, bool) {
	for _, prefix := range h.ValidPrefixes {
		path, err := exec.LookPath(fmt.Sprintf("%s-%s", prefix, filename))
		if err != nil || len(path) == 0 {
			continue
		}
		return path, true
	}

	return "", false
}

// Execute implements PluginHandler
func (h *DefaultPluginHandler) Execute(executablePath string, cmdArgs, environment []string) error {

	// Windows does not support exec syscall.
	if runtime.GOOS == "windows" {
		cmd := exec.Command(executablePath, cmdArgs...)
		cmd.Stdout = os.Stdout
		cmd.Stderr = os.Stderr
		cmd.Stdin = os.Stdin
		cmd.Env = environment
		err := cmd.Run()
		if err == nil {
			os.Exit(0)
		}
		return err
	}

	// invoke cmd binary relaying the environment and args given
	// append executablePath to cmdArgs, as execve will make first argument the "binary name".
	return syscall.Exec(executablePath, append([]string{executablePath}, cmdArgs...), environment)
}