Kubernetes筆記（6）—— kubectl程式碼分析（1）

這是一個建立於 的文章，其中的資訊可能已經有所發展或是發生改變。

kubectl實際啟動並執行函數（k8s.io/kubernetes/pkg/kubectl/app/kubectl.go）：

func Run() error {    cmd := cmd.NewKubectlCommand(cmdutil.NewFactory(nil), os.Stdin, os.Stdout, os.Stderr)    return cmd.Execute()}

NewKubectlCommand的代碼（k8s.io/kubernetes/pkg/kubectl/cmd/cmd.go）：

// NewKubectlCommand creates the `kubectl` command and its nested children.func NewKubectlCommand(f *cmdutil.Factory, in io.Reader, out, err io.Writer) *cobra.Command {    // Parent command to which all subcommands are added.    cmds := &cobra.Command{        Use:   "kubectl",        Short: "kubectl controls the Kubernetes cluster manager",        Long: `kubectl controls the Kubernetes cluster manager.Find more information at https://github.com/kubernetes/kubernetes.`,        Run: runHelp,        BashCompletionFunction: bash_completion_func,    }    f.BindFlags(cmds.PersistentFlags())    // From this point and forward we get warnings on flags that contain "_" separators    cmds.SetGlobalNormalizationFunc(util.WarnWordSepNormalizeFunc)    cmds.AddCommand(NewCmdGet(f, out))    cmds.AddCommand(NewCmdDescribe(f, out))    cmds.AddCommand(NewCmdCreate(f, out))    ......    return &cmds}

所以cmd := cmd.NewKubectlCommand(cmdutil.NewFactory(nil), os.Stdin, os.Stdout, os.Stderr)得到的cmd是一個指向cobra.Command的指標。

cmdutil.NewFactory代碼（k8s.io/kubernetes/pkg/kubectl/cmd/util/factory.go）：

// NewFactory creates a factory with the default Kubernetes resources defined// if optionalClientConfig is nil, then flags will be bound to a new clientcmd.ClientConfig.// if optionalClientConfig is not nil, then this factory will make use of it.func NewFactory(optionalClientConfig clientcmd.ClientConfig) *Factory {    mapper := kubectl.ShortcutExpander{RESTMapper: api.RESTMapper}    flags := pflag.NewFlagSet("", pflag.ContinueOnError)    flags.SetNormalizeFunc(util.WarnWordSepNormalizeFunc) // Warn for "_" flags    generators := map[string]kubectl.Generator{        "run/v1":                          kubectl.BasicReplicationController{},        "run-pod/v1":                      kubectl.BasicPod{},        "service/v1":                      kubectl.ServiceGeneratorV1{},        "service/v2":                      kubectl.ServiceGeneratorV2{},        "horizontalpodautoscaler/v1beta1": kubectl.HorizontalPodAutoscalerV1Beta1{},        "deployment/v1beta1":              kubectl.DeploymentV1Beta1{},        "job/v1beta1":                     kubectl.JobV1Beta1{},    }    clientConfig := optionalClientConfig    if optionalClientConfig == nil {        clientConfig = DefaultClientConfig(flags)    }    clients := NewClientCache(clientConfig)    return &Factory{        ......    }

因為cmdutil.NewFactory(nil)參數為nil，所以調用的是DefaultClientConfig函數。

clientcmd.ClientConfig定義在k8s.io/kubernetes/pkg/client/unversioned/clientcmd/client_config.go檔案：

// ClientConfig is used to make it easy to get an api server clienttype ClientConfig interface {    // RawConfig returns the merged result of all overrides    RawConfig() (clientcmdapi.Config, error)    // ClientConfig returns a complete client config    ClientConfig() (*client.Config, error)    // Namespace returns the namespace resulting from the merged    // result of all overrides and a boolean indicating if it was    // overridden    Namespace() (string, bool, error)}

DefaultClientConfig代碼（k8s.io/kubernetes/pkg/kubectl/cmd/util/factory.go）：

func DefaultClientConfig(flags *pflag.FlagSet) clientcmd.ClientConfig {    loadingRules := clientcmd.NewDefaultClientConfigLoadingRules()    flags.StringVar(&loadingRules.ExplicitPath, "kubeconfig", "", "Path to the kubeconfig file to use for CLI requests.")    overrides := &clientcmd.ConfigOverrides{}    flagNames := clientcmd.RecommendedConfigOverrideFlags("")    // short flagnames are disabled by default.  These are here for compatibility with existing scripts    flagNames.ClusterOverrideFlags.APIServer.ShortName = "s"    clientcmd.BindOverrideFlags(overrides, flags, flagNames)    clientConfig := clientcmd.NewInteractiveDeferredLoadingClientConfig(loadingRules, overrides, os.Stdin)    return clientConfig}

最後返回一個DeferredLoadingClientConfig結構體（定義在k8s.io/kubernetes/pkg/client/unversioned/clientcmd/merged_client_builder.go）:

// DeferredLoadingClientConfig is a ClientConfig interface that is backed by a set of loading rules// It is used in cases where the loading rules may change after you've instantiated them and you want to be sure that// the most recent rules are used.  This is useful in cases where you bind flags to loading rule parameters before// the parse happens and you want your calling code to be ignorant of how the values are being mutated to avoid// passing extraneous information down a call stacktype DeferredLoadingClientConfig struct {    loadingRules   *ClientConfigLoadingRules    overrides      *ConfigOverrides    fallbackReader io.Reader}