How to get logs from kubernetes using golang?

Question

I\'m looking for the solution of how to get logs from a pod in Kubernetes cluster using golang. I\'ve looked at \"https://github.com/kubernetes/client-go\" and \"https://god

Answer 1

Here is what we came up with eventually using client-go library:

func getPodLogs(pod corev1.Pod) string {
    podLogOpts := corev1.PodLogOptions{}
    config, err := rest.InClusterConfig()
    if err != nil {
        return "error in getting config"
    }
    // creates the clientset
    clientset, err := kubernetes.NewForConfig(config)
    if err != nil {
        return "error in getting access to K8S"
    }
    req := clientset.CoreV1().Pods(pod.Namespace).GetLogs(pod.Name, &podLogOpts)
    podLogs, err := req.Stream()
    if err != nil {
        return "error in opening stream"
    }
    defer podLogs.Close()

    buf := new(bytes.Buffer)
    _, err = io.Copy(buf, podLogs)
    if err != nil {
        return "error in copy information from podLogs to buf"
    }
    str := buf.String()

    return str
}

I hope it will help someone. Please share your thoughts or solutions of how you get logs from pods in Kubernetes.

Answer 2

And if you want read stream in client-go v11.0.0+, the code is like this, feel free for create clientset by yourself:

func GetPodLogs(namespace string, podName string, containerName string, follow bool) error {
    count := int64(100)
    podLogOptions := v1.PodLogOptions{
        Container: containerName,
        Follow:    follow,
        TailLines: &count,
    }

    podLogRequest := clientSet.CoreV1().
        Pods(namespace).
        GetLogs(podName, &podLogOptions)
    stream, err := podLogRequest.Stream(context.TODO())
    if err != nil {
        return err
    }
    defer stream.Close()

    for {
        buf := make([]byte, 2000)
        numBytes, err := stream.Read(buf)
        if numBytes == 0 {
            continue
        }
        if err == io.EOF {
            break
        }
        if err != nil {
            return err
        }
        message := string(buf[:numBytes])
        fmt.Print(message)
    }
    return nil
}

Answer 3

@Emixam23

I believe you will find this snippet useful.

How to get the dynamic name of a pod?

import  metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"

    labelSelector := metav1.LabelSelector{MatchLabels: map[string]string{<LABEL_KEY>: <LABEL_VALUE>}}
    listOptions := metav1.ListOptions{
        LabelSelector: labels.Set(labelSelector.MatchLabels).String(),
    }
    pod, err := k8sClient.CoreV1().Pods(<NAMESPACE>).List(listOptions)
    podName := pod.Items[0].ObjectMeta.Name

Answer 4

The controller-runtime client library does not yet support subresources other than /status, so you would have to use client-go as shown in the other question.