花了快一天，才搞出来的一个client-go的demo

用来直接获取所有service的annotaion里有ambassador的东东。

或者，watch集群事件。

package main

import (
	"fmt"
	"os"
	//"time"
	"strings"

	//"k8s.io/apimachinery/pkg/api/errors"
	"k8s.io/api/core/v1"
    	//"k8s.io/apimachinery/pkg/labels"
    	//"k8s.io/apimachinery/pkg/watch"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/rest"
	//
	// Uncomment to load all auth plugins
	// _ "k8s.io/client-go/plugin/pkg/client/auth"
	//
	// Or uncomment to load specific auth plugins
	// _ "k8s.io/client-go/plugin/pkg/client/auth/azure"
	// _ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
	// _ "k8s.io/client-go/plugin/pkg/client/auth/oidc"
	// _ "k8s.io/client-go/plugin/pkg/client/auth/openstack"
)

func main() {
	// creates the in-cluster config
	config, err := rest.InClusterConfig()
	if err != nil {
		panic(err.Error())
	}
	// creates the clientset
	clientset, err := kubernetes.NewForConfig(config)
	if err != nil {
		panic(err.Error())
	}

		// get pods in all the namespaces by omitting namespace
		// Or specify namespace to get pods in particular namespace
		services, err := clientset.CoreV1().Services("").List(metav1.ListOptions{})
		if err != nil {
			panic(err.Error())
		}
		for i:=0; i < len(services.Items); i++ {
			item := services.Items[i].Annotations
			for k, v := range item {
				if strings.Contains(k, "getambassador") && strings.Contains(v, "ambassador") && strings.Contains(v, "Mapping"){
					fmt.Println(v)
					fmt.Println("@@@@@@@@@@@@@@@@@@@@@@@")
				}
			}
		}

		//time.Sleep(10 * time.Second)
		handleNewServices(clientset)

}

func handleNewServices(clientset *kubernetes.Clientset) {
    for {
        serviceStreamWatcher, err := clientset.CoreV1().Services("").Watch(metav1.ListOptions{})
        if err != nil {
            panic(err.Error())
        }
        fmt.Printf("%T\n", serviceStreamWatcher)
        for {
            select {
        	case event := <-serviceStreamWatcher.ResultChan():           

            	    service := event.Object.(*v1.Service)		                                                                                              

            	    for key, value := range service.Annotations {
                	if strings.Contains(key, "getambassador") && strings.Contains(value, "ambassador") && strings.Contains(value, "Mapping"){
			    toFileStr := fmt.Sprintf("%s\n%s\n=============\n", event.Type, value)
                            //fmt.Println(toFileStr)
			    _appendToFile("/app/k8s-ambassador",  toFileStr)
                        }
            	    }
            }
    	}
    }
}

func _appendToFile(file, str string) {
        f, err := os.OpenFile(file, os.O_CREATE|os.O_APPEND|os.O_RDWR, 0664)
        if err != nil {
                fmt.Printf("Cannot open file %s!\n", file)
                return
        }
        defer f.Close()
        f.WriteString(str)
}