CODEWITHSUNDEEP
gokubernetes
David Wer
David Wer

Reputation: 418

Watch all changes in pod status

I'm trying to write code that behaves like kubectl get pods --watch. This way I'm triggered every time the status of the pod changes.

I created a go project (that runs in the cluster) and added the following code:

podsWatcher, err := restAPIClient.CoreV1().Pods("").Watch(globalHTTPContext, metav1.ListOptions{Watch: true})
if err != nil {
    // do something
}
podsChan := podsWatcher.ResultChan()
for event := range podsChan {
    switch event.Type {
    case watch.Added:
        // do something
    case watch.Modified:
        // do something
    case watch.Deleted:
        // do something
    case watch.Bookmark:
        // do something
    case watch.Error:
        // do something
    }
}

I receive an event every time I make a major change in the pod, but not for all of the events. (events).

How can I get a trigger of every change that happened in the status of the pods (like the --watch flag)?

Upvotes: 2

Views: 9015

Answers (1)

David Wer
David Wer

Reputation: 418

Apparently the watch is triggered by every change (made in pod describe) and I was looking at the pod.status.phase instead of looking at the pod.Status.ContainerStatuses, that is why I thought I did not receive every event.

I added a function that will handle the events as following:

// get ContainerStatuses. If there is no containerStatus, return the pod phase
func getPodStatus(pod *core.Pod) string {
    containerStatuses := pod.Status.ContainerStatuses
    status := ""
    if len(containerStatuses) > 0 {
        for i := range containerStatuses {
            if containerStatuses[i].State.Terminated != nil {
                status = containerStatuses[i].State.Terminated.Reason
            }
            if containerStatuses[i].State.Waiting != nil {
                status = containerStatuses[i].State.Waiting.Reason
            }
            if containerStatuses[i].State.Running != nil {
                if status == "" { // if none of the containers report an error
                    status = "Running"
                }
            }
        }
    }
    if status == "" {
        status = string(pod.Status.Phase)
    }
    return status
}

// PodWatch watch pod changes in all namespaces
func PodWatch() error {
    podsWatcher, err := restAPIClient.CoreV1().Pods("").Watch(globalHTTPContext, metav1.ListOptions{Watch: true})
    if err != nil {
        return err
    }
    podsChan := podsWatcher.ResultChan()
    for event := range podsChan {
        pod, err := event.Object.(*core.Pod)
        if err != nil {
            return err
        }
        switch event.Type {
        case watch.Added:
            fmt.Println(getPodStatus(pod))
        case watch.Modified:
            fmt.Println(getPodStatus(pod))
        case watch.Deleted:
            fmt.Println(getPodStatus(pod))
        case watch.Bookmark:
            fmt.Println(getPodStatus(pod))
        case watch.Error:
            fmt.Println(getPodStatus(pod))
        }
    }
}

This solution suits my needs, if you wish to implement the --watch like the kubectl, you can find the implementation here.

Upvotes: 2

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