Kubernetes notes (6)--KUBECTL Code Analysis (1)

This is a creation in Article, where the information may have evolved or changed.

kubectlFunctions that are actually running ( 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()}

NewKubectlCommandThe code ( 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 is added. Cmds: = &cobra. command{use: "Kubectl", Short: "Kubectl controls the Kubernetes Cluster Manager", Long: ' Kubectl C Ontrols the Kubernetes cluster Manager. Find more information at https://github.com/kubernetes/kubernetes. ', Run:runhelp, bashcompletionfunction:b Ash_completion_func,} f.bindflags (Cmds. Persistentflags ())//From this point and forward we get warnings on the 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}  

So cmd := cmd.NewKubectlCommand(cmdutil.NewFactory(nil), os.Stdin, os.Stdout, os.Stderr) what you get cmd is a cobra.Command pointer to it.

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

Newfactory creates a factory with the default Kubernetes resources defined//if optionalclientconfig are nil, then flags 'll is bound to a new clientcmd. clientconfig.//if Optionalclientconfig is not nil and then this factory would make use of It.func newfactory (Optionalclientco Nfig 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 = Defau Ltclientconfig (Flags)} Clients: = Newclientcache (clientconfig) return &factory{...}

Because the cmdutil.NewFactory(nil) parameter is nil , the function is called DefaultClientConfig .

clientcmd.ClientConfigDefined in the k8s.io/kubernetes/pkg/client/unversioned/clientcmd/client_config.go file:

// 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)}

DefaultClientConfigCode ( 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}

Finally, a DeferredLoadingClientConfig struct (defined in) is returned 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}