How to Use Go Client-go to Watch Kubernetes Service Events?

How to Watch Events on a Kubernetes Service Using Go Client

In Kubernetes, monitoring changes to services is crucial for maintaining application health. This article demonstrates how to implement event watching for Kubernetes services using the client-go library.

To start, establish a Kubernetes configuration by creating a config object using clientcmd.BuildConfigFromFlags():

import (
    "k8s.io/client-go/tools/clientcmd"
)

// ...

config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
if err != nil {
    panic(err.Error())
}

Use the configuration to create a new Kubernetes client:

import (
    "k8s.io/client-go/kubernetes"
)

// ...

clientset, err := kubernetes.NewForConfig(config)

Create a watchlist representing the services you wish to monitor:

import (
    "k8s.io/client-go/tools/cache"
    v1 "k8s.io/client-go/pkg/api/v1"
)

// ...

watchlist := cache.NewListWatchFromClient(clientset.Core().RESTClient(), "services", v1.NamespaceDefault,
    fields.Everything())

Establish an informer to handle incoming events:

informer := cache.NewInformer(
    watchlist,
    &v1.Service{},
    time.Second * 0,
    cache.ResourceEventHandlerFuncs{
        AddFunc: func(obj interface{}) {
            fmt.Printf("service added: %s \n", obj)
        },
        DeleteFunc: func(obj interface{}) {
            fmt.Printf("service deleted: %s \n", obj)
        },
        UpdateFunc: func(oldObj, newObj interface{}) {
            fmt.Printf("service changed \n")
        },
    },
)

Run the informer to start monitoring for events:

stop := make(chan struct{})
go informer.Run(stop)

Keep the program running indefinitely to continue monitoring for service events:

for {
    time.Sleep(time.Second)
}

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