<p>I have a demo golang program to list Pods without a particular label. I want to modify it so it also can add a label to each pod.</p>

<p>(I'm using the AWS hosted Kubernetes service, EKS so there's some boilerplate code specific to EKS )</p>

<pre class="lang-golang prettyprint-override"><code>package main

import (
    "fmt"
    eksauth "github.com/chankh/eksutil/pkg/auth"
    metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
)

func main() {
    cfg := &amp;eksauth.ClusterConfig{ClusterName: "my_cluster_name"}

    clientset, _ := eksauth.NewAuthClient(cfg)
    api := clientset.CoreV1()

    // Get all pods from all namespaces without the "sent_alert_emailed" label.
    pods, _ := api.Pods("").List(metav1.ListOptions{LabelSelector: "!sent_alert_emailed"})

    for i, pod := range pods.Items {
        fmt.Println(fmt.Sprintf("[%2d] %s, Phase: %s, Created: %s, HostIP: %s", i, pod.GetName(), string(pod.Status.Phase), pod.GetCreationTimestamp(), string(pod.Status.HostIP)))

        // Here I want to add a label to this pod
        // e.g. something like:
        // pod.addLabel("sent_alert_emailed=true")
    }
}
</code></pre>

<p>I know kubectl can be used to add labels, e.g.</p>

<pre><code>kubectl label pod my-pod new-label=awesome                 # Add a Label
kubectl label pod my-pod new-label=awesomer --overwrite    # Change a existing label
</code></pre>

<p>I was hoping there would be an equivalent method via the go-client?</p>

<p>I'm hoping there is a more elegant way, but until I learn about it, I managed to add a label to a Pod using <code>Patch</code>. Here is my demo code (again it has some EKS boilerplate stuff you may be able to ignore): </p>

<pre class="lang-golang prettyprint-override"><code>package main

import (
    "fmt"
    "encoding/json"
    "time"
    "k8s.io/apimachinery/pkg/types"

    eksauth "github.com/chankh/eksutil/pkg/auth"
    metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
)

type patchStringValue struct {
    Op    string `json:"op"`
    Path  string `json:"path"`
    Value string `json:"value"`
}

func main() {
    var updateErr error

    cfg := &amp;eksauth.ClusterConfig{ClusterName: "my cluster name"}
    clientset, _ := eksauth.NewAuthClient(cfg)
    api := clientset.CoreV1()

    // Get all pods from all namespaces without the "sent_alert_emailed" label.
    pods, _ := api.Pods("").List(metav1.ListOptions{LabelSelector: "!sent_alert_emailed"})

    for i, pod := range pods.Items {
        fmt.Println(fmt.Sprintf("[%2d] %s, Phase: %s, Created: %s, HostIP: %s", i, pod.GetName(), string(pod.Status.Phase), pod.GetCreationTimestamp(), string(pod.Status.HostIP)))

        payload := []patchStringValue{{
            Op:    "replace",
            Path:  "/metadata/labels/sent_alert_emailed",
            Value: time.Now().Format("2006-01-02_15.04.05"),
        }}
        payloadBytes, _ := json.Marshal(payload)

        _, updateErr = api.Pods(pod.GetNamespace()).Patch(pod.GetName(), types.JSONPatchType, payloadBytes)
        if updateErr == nil {
            fmt.Println(fmt.Sprintf("Pod %s labelled successfully.", pod.GetName()))
        } else {
            fmt.Println(updateErr)
        }
    }
}
</code></pre>
