需要定义 KUBERNETES_SERVICE_HOST 和 KUBERNETES_SERVICE_PORT 以加载集群内配置

Kubernetes集群外部访问集群时，使用 `inclusterconfig` 获取集群配置会导致错误。需要在外部访问时使用 `clientcmd.BuildConfigFromFlags` 来获取配置。另外，需要设置 `KUBERNETES_SERVICE_HOST` 和 `KUBERNETES_SERVICE_PORT` 环境变量，以便加载集群内部配置。

我正在开发一个动态 kubernetes informer，以监视我的 kubernetes 集群的事件以及所有 kubernetes 组件的发现。

但是，当我尝试通过 inclusterconfig 方法访问 kubeconfig 时，出现以下错误：

// go run main.go
fata[0000] could not get config                          error="unable to load in-cluster configuration, kubernetes_service_host and kubernetes_service_port must be defined"
exit status 1

我在 github 上的 kubernetes repo 以及 stackoverflow 上发现了与此相关的各种类似问题，但找不到任何解决方案或解决方法。 [kubernetes问题，kubernetes问题，stackoverflow类似问题，stackoverflow类似问题]

以下是go代码和go.mod文件

go 代码：

package main

import (
    "os"
    "os/signal"

    "github.com/sirupsen/logrus"
    v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
    "k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
    "k8s.io/apimachinery/pkg/runtime/schema"
    "k8s.io/client-go/dynamic"
    "k8s.io/client-go/dynamic/dynamicinformer"
    "k8s.io/client-go/rest"
    "k8s.io/client-go/tools/cache"
    "k8s.io/client-go/tools/clientcmd"
)

func main() {
    cfg, err := restconfig()
    if err != nil {
        logrus.witherror(err).fatal("could not get config")
    }

    // grab a dynamic interface that we can create informers from
    dc, err := dynamic.newforconfig(cfg)
    if err != nil {
        logrus.witherror(err).fatal("could not generate dynamic client for config")
    }

    // create a factory object that we can say "hey, i need to watch this resource"
    // and it will give us back an informer for it
    f := dynamicinformer.newfiltereddynamicsharedinformerfactory(dc, 0, v1.namespaceall, nil)

    // retrieve a "groupversionresource" type that we need when generating our informer from our dynamic factory
    gvr, _ := schema.parseresourcearg("deployments.v1.apps")

    // finally, create our informer for deployments!
    i := f.forresource(*gvr)

    stopch := make(chan struct{})
    go startwatching(stopch, i.informer())

    sigch := make(chan os.signal, 0)
    signal.notify(sigch, os.kill, os.interrupt)

    <-sigch
    close(stopch)
}

func restconfig() (*rest.config, error) {
    kubecfg, err := rest.inclusterconfig()
    if kubeconfig := os.getenv("kubeconfig"); kubeconfig != "" {
        kubecfg, err = clientcmd.buildconfigfromflags("", kubeconfig)
    }

    // var kubecfg *string
    // if home := homedir.homedir(); home != "" {
    //  kubecfg = flag.string("kubeconfig", filepath.join(home, ".kube", "config"), "(optional) absolute path to the kubeconfig file")
    // } else {
    //  kubecfg = flag.string("kubeconfig", "", "absolute path to the kubeconfig file")
    // }
    // flag.parse()

    // kubecfg, err := clientcmd.buildconfigfromflags("", *kubeconfig)

    //testing-ends

    if err != nil {
        return nil, err
    }

    return kubecfg, nil
}

func startwatching(stopch <-chan struct{}, s cache.sharedindexinformer) {
    handlers := cache.resourceeventhandlerfuncs{
        addfunc: func(obj interface{}) {
            u := obj.(*unstructured.unstructured)

            logrus.withfields(logrus.fields{
                "name":      u.getname(),
                "namespace": u.getnamespace(),
                "labels":    u.getlabels(),
            }).info("received add event!")
        },
        updatefunc: func(oldobj, obj interface{}) {
            logrus.info("received update event!")
        },
        deletefunc: func(obj interface{}) {
            logrus.info("received update event!")
        },
    }

    s.addeventhandler(handlers)
    s.run(stopch)
}

go.mod 文件：

module discovery-test

go 1.15

require (
    github.com/googleapis/gnostic v0.5.3 // indirect
    github.com/gregjones/httpcache v0.0.0-20190611155906-901d90724c79 // indirect
    github.com/imdario/mergo v0.3.11 // indirect
    github.com/peterbourgon/diskv v2.0.1+incompatible // indirect
    github.com/sirupsen/logrus v1.7.0
    golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897 // indirect
    golang.org/x/net v0.0.0-20201029055024-942e2f445f3c // indirect
    golang.org/x/oauth2 v0.0.0-20200902213428-5d25da1a8d43 // indirect
    golang.org/x/time v0.0.0-20200630173020-3af7569d3a1e // indirect
    k8s.io/apimachinery v0.17.0
    k8s.io/client-go v0.17.0
    k8s.io/klog v1.0.0 // indirect
    k8s.io/utils v0.0.0-20201027101359-01387209bb0d // indirect
)

解决方案

首先，感谢@shudiptasharma。他的评论帮助我弄清楚我正在尝试从集群外部获取集群配置，该配置导致我无法访问集群的本地计算机（127.0.0.1）上的程序。

此外，我尝试弄清楚如何从集群外部访问集群，发现 inclusterconfig 用于在集群内部运行用例，当在集群外部运行时，可以使用如下所示的内容：

//go run main.go
package main

import (
    "os"
    "os/signal"
  //"context"
    "flag"
    //"fmt"
    "path/filepath"
    //"time"

    "github.com/sirupsen/logrus"
    v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
    "k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
    "k8s.io/apimachinery/pkg/runtime/schema"
    "k8s.io/client-go/dynamic"
    "k8s.io/client-go/dynamic/dynamicinformer"
    //"k8s.io/client-go/rest"
    "k8s.io/client-go/tools/cache"
    "k8s.io/client-go/tools/clientcmd"
  "k8s.io/client-go/util/homedir"
)

func main() {
  //kubeconfig := os.Getenv("KUBECONFIG")
  
  var kubeconfig *string
    if home := homedir.HomeDir(); home != "" {
        kubeconfig = flag.String("kubeconfig", filepath.Join(home, ".kube", "config"), "(optional) absolute path to the kubeconfig file")
    } else {
        kubeconfig = flag.String("kubeconfig", "", "absolute path to the kubeconfig file")
    }
    flag.Parse()
  
    cfg, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
    if err != nil {
        logrus.WithError(err).Fatal("could not get config")
    }

    // Grab a dynamic interface that we can create informers from
    dc, err := dynamic.NewForConfig(cfg)
    if err != nil {
        logrus.WithError(err).Fatal("could not generate dynamic client for config")
    }

    // Create a factory object that we can say "hey, I need to watch this resource"
    // and it will give us back an informer for it
    f := dynamicinformer.NewFilteredDynamicSharedInformerFactory(dc, 0, v1.NamespaceAll, nil)

    // Retrieve a "GroupVersionResource" type that we need when generating our informer from our dynamic factory
    gvr, _ := schema.ParseResourceArg("deployments.v1.apps")

    // Finally, create our informer for deployments!
    i := f.ForResource(*gvr)

    stopCh := make(chan struct{})
    go startWatching(stopCh, i.Informer())

    sigCh := make(chan os.Signal, 0)
    signal.Notify(sigCh, os.Kill, os.Interrupt)

    <-sigCh
    close(stopCh)
}

func startWatching(stopCh <-chan struct{}, s cache.SharedIndexInformer) {
    handlers := cache.ResourceEventHandlerFuncs{
        AddFunc: func(obj interface{}) {
            u := obj.(*unstructured.Unstructured)

            logrus.WithFields(logrus.Fields{
                "name":      u.GetName(),
                "namespace": u.GetNamespace(),
                "labels":    u.GetLabels(),
            }).Info("received add event!")
        },
        UpdateFunc: func(oldObj, obj interface{}) {
            logrus.Info("received update event!")
        },
        DeleteFunc: func(obj interface{}) {
            logrus.Info("received update event!")
        },
    }

    s.AddEventHandler(handlers)
    s.Run(stopCh)
}

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