kubectl源码分析之port-forward

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原创最新推荐文章于 2026-11-12 13:28:24 发布 2k 阅读 AI 写同款· GEO 优化 ›

kubectl滚动更新资源 rollout Manage the rollout of a resource. Valid resource types include: * deployments * daemonsets * statefulsets Examples: # Rollback to the previous deployment kubectl rollout undo deployment/abc # Check the rollout status of a da 阅读详情

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目前刚开始写一个月，一共写了18篇原创文章，文章目录如下：

istio多集群探秘，部署了50次多集群后我得出的结论

istio多集群链路追踪，附实操视频

istio防故障利器，你知道几个,istio新手不要读，太难！

istio业务权限控制，原来可以这么玩

istio实现非侵入压缩，微服务之间如何实现压缩

不懂envoyfilter也敢说精通istio系列-http-rbac-不要只会用AuthorizationPolicy配置权限

不懂envoyfilter也敢说精通istio系列-02-http-corsFilter-不要只会vs

不懂envoyfilter也敢说精通istio系列-03-http-csrf filter-再也不用再代码里写csrf逻辑了

不懂envoyfilter也敢说精通istio系列http-jwt_authn-不要只会RequestAuthorization

不懂envoyfilter也敢说精通istio系列-05-fault-filter-故障注入不止是vs

不懂envoyfilter也敢说精通istio系列-06-http-match-配置路由不只是vs

不懂envoyfilter也敢说精通istio系列-07-负载均衡配置不止是dr

不懂envoyfilter也敢说精通istio系列-08-连接池和断路器

不懂envoyfilter也敢说精通istio系列-09-http-route filter

不懂envoyfilter也敢说精通istio系列-network filter-redis proxy

不懂envoyfilter也敢说精通istio系列-network filter-HttpConnectionManager

不懂envoyfilter也敢说精通istio系列-ratelimit-istio ratelimit完全手册

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type PortForwardOptions struct {//port-forward结构体
	Namespace     string
	PodName       string
	RESTClient    *restclient.RESTClient
	Config        *restclient.Config
	PodClient     corev1client.PodsGetter
	Address       []string
	Ports         []string
	PortForwarder portForwarder
	StopChannel   chan struct{}
	ReadyChannel  chan struct{}
}

//创建port-forward命令
func NewCmdPortForward(f cmdutil.Factory, streams genericclioptions.IOStreams) *cobra.Command {
	opts := &PortForwardOptions{//初始化结构体
		PortForwarder: &defaultPortForwarder{
			IOStreams: streams,
		},
	}
	cmd := &cobra.Command{//创建cobra命令
		Use:                   "port-forward TYPE/NAME [options] [LOCAL_PORT:]REMOTE_PORT [...[LOCAL_PORT_N:]REMOTE_PORT_N]",
		DisableFlagsInUseLine: true,
		Short:                 i18n.T("Forward one or more local ports to a pod"),
		Long:                  portforwardLong,
		Example:               portforwardExample,
		Run: func(cmd *cobra.Command, args []string) {
			if err := opts.Complete(f, cmd, args); err != nil {//先准备
				cmdutil.CheckErr(err)
			}
			if err := opts.Validate(); err != nil {//校验
				cmdutil.CheckErr(cmdutil.UsageErrorf(cmd, "%v", err.Error()))
			}
			if err := opts.RunPortForward(); err != nil {//运行
				cmdutil.CheckErr(err)
			}
		},
	}
	cmdutil.AddPodRunningTimeoutFlag(cmd, defaultPodPortForwardWaitTimeout)//pod-running-timeout选项
	cmd.Flags().StringSliceVar(&opts.Address, "address", []string{"localhost"}, "Addresses to listen on (comma separated). Only accepts IP addresses or localhost as a value. When localhost is supplied, kubectl will try to bind on both 127.0.0.1 and ::1 and will fail if neither of these addresses are available to bind.")//address选项
	// TODO support UID
	return cmd
}

//准备函数
func (o *PortForwardOptions) Complete(f cmdutil.Factory, cmd *cobra.Command, args []string) error {
	var err error
	if len(args) < 2 {//参数小于2个报错
		return cmdutil.UsageErrorf(cmd, "TYPE/NAME and list of ports are required for port-forward")
	}

	o.Namespace, _, err = f.ToRawKubeConfigLoader().Namespace()//设置namespace
	if err != nil {
		return err
	}

	builder := f.NewBuilder().
		WithScheme(scheme.Scheme, scheme.Scheme.PrioritizedVersionsAllGroups()...).
		ContinueOnError().
		NamespaceParam(o.Namespace).DefaultNamespace()//构造result对象

	getPodTimeout, err := cmdutil.GetPodRunningTimeoutFlag(cmd)//获取pod-running-timeout选项
	if err != nil {
		return cmdutil.UsageErrorf(cmd, err.Error())
	}

	resourceName := args[0]//获取资源
	builder.ResourceNames("pods", resourceName)

	obj, err := builder.Do().Object()//从result获取obj
	if err != nil {
		return err
	}

	forwardablePod, err := polymorphichelpers.AttachablePodForObjectFn(f, obj, getPodTimeout)//从obj获取forward的pod
	if err != nil {
		return err
	}

	o.PodName = forwardablePod.Name//设置pod名称

	// handle service port mapping to target port if needed
	switch t := obj.(type) {//断言obj类型
	case *corev1.Service://如果是service
		o.Ports, err = translateServicePortToTargetPort(args[1:], *t, *forwardablePod)//转换service的port
		if err != nil {
			return err
		}
	default://默认
		o.Ports, err = convertPodNamedPortToNumber(args[1:], *forwardablePod)//转换pod的port
		if err != nil {
			return err
		}
	}

	clientset, err := f.KubernetesClientSet()//获取clientset
	if err != nil {
		return err
	}

	o.PodClient = clientset.CoreV1()//从clientset获取podclient

	o.Config, err = f.ToRESTConfig()//设置restconfig
	if err != nil {
		return err
	}
	o.RESTClient, err = f.RESTClient()//设置restClient
	if err != nil {
		return err
	}

	o.StopChannel = make(chan struct{}, 1)//定义通道
	o.ReadyChannel = make(chan struct{})
	return nil
}

//校验
func (o PortForwardOptions) Validate() error {
	if len(o.PodName) == 0 {//pod名称不能为空
		return fmt.Errorf("pod name or resource type/name must be specified")
	}

	if len(o.Ports) < 1 {//端口不能小于个
		return fmt.Errorf("at least 1 PORT is required for port-forward")
	}

	if o.PortForwarder == nil || o.PodClient == nil || o.RESTClient == nil || o.Config == nil {//这四个对象不能为空
		return fmt.Errorf("client, client config, restClient, and portforwarder must be provided")
	}
	return nil
}

//运行
func (o PortForwardOptions) RunPortForward() error {
	pod, err := o.PodClient.Pods(o.Namespace).Get(o.PodName, metav1.GetOptions{})//获取pod
	if err != nil {
		return err
	}

	if pod.Status.Phase != corev1.PodRunning {//pod状态不为running返回错误
		return fmt.Errorf("unable to forward port because pod is not running. Current status=%v", pod.Status.Phase)
	}

	signals := make(chan os.Signal, 1)
	signal.Notify(signals, os.Interrupt)
	defer signal.Stop(signals)

	go func() {
		<-signals
		if o.StopChannel != nil {
			close(o.StopChannel)
		}
	}()

	req := o.RESTClient.Post().
		Resource("pods").
		Namespace(o.Namespace).
		Name(pod.Name).
		SubResource("portforward")//通过restclient的post方法后去request

	return o.PortForwarder.ForwardPorts("POST", req.URL(), o)//执行forward
}

//执行forward
func (f *defaultPortForwarder) ForwardPorts(method string, url *url.URL, opts PortForwardOptions) error {
	transport, upgrader, err := spdy.RoundTripperFor(opts.Config)//获取transport
	if err != nil {
		return err
	}
	dialer := spdy.NewDialer(upgrader, &http.Client{Transport: transport}, method, url)//获取dialer
	fw, err := portforward.NewOnAddresses(dialer, opts.Address, opts.Ports, opts.StopChannel, opts.ReadyChannel, f.Out, f.ErrOut)//构造forwarder
	if err != nil {
		return err
	}
	return fw.ForwardPorts()//执行forward
}

//拆分port
func splitPort(port string) (local, remote string) {
	parts := strings.Split(port, ":")//用冒号分割
	if len(parts) == 2 {//有两个
		return parts[0], parts[1]
	}

	return parts[0], parts[0]
}

//翻译svc port到target port
func translateServicePortToTargetPort(ports []string, svc corev1.Service, pod corev1.Pod) ([]string, error) {
	var translated []string
	for _, port := range ports {//遍历ports
		localPort, remotePort := splitPort(port)//分割port

		portnum, err := strconv.Atoi(remotePort)//把远程port转为整数
		if err != nil {//如果转换失败
			svcPort, err := util.LookupServicePortNumberByName(svc, remotePort)//通过名称查找service的port
			if err != nil {
				return nil, err
			}
			portnum = int(svcPort)//把svcPort转整数

			if localPort == remotePort {//如果本地port和远程port相等
				localPort = strconv.Itoa(portnum)
			}
		}
		containerPort, err := util.LookupContainerPortNumberByServicePort(svc, pod, int32(portnum))//后去svc的target-port
		if err != nil {
			// can't resolve a named port, or Service did not declare this port, return an error
			return nil, err
		}

		if int32(portnum) != containerPort {//如果容器的port的贝蒂svc的port不同则，
			translated = append(translated, fmt.Sprintf("%s:%d", localPort, containerPort))
		} else {
			translated = append(translated, port)
		}
	}
	return translated, nil
}

func convertPodNamedPortToNumber(ports []string, pod corev1.Pod) ([]string, error) {
	var converted []string
	for _, port := range ports {//遍历ports
		localPort, remotePort := splitPort(port)//分割port

		containerPortStr := remotePort
		_, err := strconv.Atoi(remotePort)//转换remoteport为整形
		if err != nil {
			containerPort, err := util.LookupContainerPortNumberByName(pod, remotePort)//从pod里查找port
			if err != nil {
				return nil, err
			}

			containerPortStr = strconv.Itoa(int(containerPort))
		}

		if localPort != remotePort {//如果本地port不等于远程port
			converted = append(converted, fmt.Sprintf("%s:%s", localPort, containerPortStr))
		} else {
			converted = append(converted, containerPortStr)
		}
	}

	return converted, nil
}