Update README.md

[mvleandro]

Removing the know flaws section because when the watcher starts it picks up all the changes from the beginning, that is, if something happens between the end of the bootstrap and the start of the watcher, it will pick it up. There is no flaw.

[benlangfeld]

How do you define "the beginning"? Do you have a documentation reference?

[mvleandro]

How do you define "the beginning"? Do you have a documentation reference?

Yes, I have not only documentation, but I have tested it. This behavior comes from the Kubernetes API itself. Reference: https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.27/#watch-configmap-v1-core

You can run the code bellow on your machine and try It by yourself.

package main

import (
	"context"
	"flag"
	"fmt"
	"path/filepath"

	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
	_ "k8s.io/client-go/plugin/pkg/client/auth/oidc"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/clientcmd"
	"k8s.io/client-go/util/homedir"
)

func main() {
	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()

	var betaPXClient *kubernetes.Clientset
	//var betaHQClient *kubernetes.Clientset
	var config *rest.Config
	var err error

	// using `contextName` context in kubeConfig
	contextName := "app-beta-hq"
	config, err = buildConfigWithContextFromFlags(contextName, *kubeconfig)
	if err != nil {
		panic(err)
	}

	// // create the clientset
	// betaHQClient, err = kubernetes.NewForConfig(config)
	// if err != nil {
	// 	panic(err.Error())
	// }

	// using `contextName` context in kubeConfig
	contextName = "app-beta-px"
	config, err = buildConfigWithContextFromFlags(contextName, *kubeconfig)
	if err != nil {
		panic(err)
	}

	// create the clientset
	betaPXClient, err = kubernetes.NewForConfig(config)
	if err != nil {
		panic(err.Error())
	}

	pods, err := betaPXClient.CoreV1().Pods("monitoring").Watch(context.TODO(), metav1.ListOptions{})
	if err != nil {
		panic(err.Error())
	}

	for event := range pods.ResultChan() {
		pod := event.Object.(*corev1.Pod)

		fmt.Printf("Pod %s was %s on namespace %s.\n", pod.Name, event.Type, pod.Namespace)
	}
}

func buildConfigWithContextFromFlags(context string, kubeconfigPath string) (*rest.Config, error) {
	return clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
		&clientcmd.ClientConfigLoadingRules{ExplicitPath: kubeconfigPath},
		&clientcmd.ConfigOverrides{
			CurrentContext: context,
		}).ClientConfig()
}

[benlangfeld]

How do you define "the beginning"? Do you have a documentation reference?

Yes, I have not only documentation, but I have tested it. This behavior comes from the Kubernetes API itself. Reference: https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.27/#watch-configmap-v1-core

You can run the code bellow on your machine and try It by yourself.

package main

import (
	"context"
	"flag"
	"fmt"
	"path/filepath"

	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
	_ "k8s.io/client-go/plugin/pkg/client/auth/oidc"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/clientcmd"
	"k8s.io/client-go/util/homedir"
)

func main() {
	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()

	var betaPXClient *kubernetes.Clientset
	//var betaHQClient *kubernetes.Clientset
	var config *rest.Config
	var err error

	// using `contextName` context in kubeConfig
	contextName := "app-beta-hq"
	config, err = buildConfigWithContextFromFlags(contextName, *kubeconfig)
	if err != nil {
		panic(err)
	}

	// // create the clientset
	// betaHQClient, err = kubernetes.NewForConfig(config)
	// if err != nil {
	// 	panic(err.Error())
	// }

	// using `contextName` context in kubeConfig
	contextName = "app-beta-px"
	config, err = buildConfigWithContextFromFlags(contextName, *kubeconfig)
	if err != nil {
		panic(err)
	}

	// create the clientset
	betaPXClient, err = kubernetes.NewForConfig(config)
	if err != nil {
		panic(err.Error())
	}

	pods, err := betaPXClient.CoreV1().Pods("monitoring").Watch(context.TODO(), metav1.ListOptions{})
	if err != nil {
		panic(err.Error())
	}

	for event := range pods.ResultChan() {
		pod := event.Object.(*corev1.Pod)

		fmt.Printf("Pod %s was %s on namespace %s.\n", pod.Name, event.Type, pod.Namespace)
	}
}

func buildConfigWithContextFromFlags(context string, kubeconfigPath string) (*rest.Config, error) {
	return clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
		&clientcmd.ClientConfigLoadingRules{ExplicitPath: kubeconfigPath},
		&clientcmd.ConfigOverrides{
			CurrentContext: context,
		}).ClientConfig()
}

Does this work on the basis of the sendInitialEvents parameter?