Kubernetes API - gets Pods on specific nodes

Question

Looking at http://kubernetes.io/docs/user-guide/labels/#selecting-sets-of-nodes it looks to be possible to select a certain range of pods based on labels. But in my case I w

Answer 1

kubectl describe node <node> will show all of the non-terminated pods running on that node

Answer 2

You also can query for all pods an a node with the following command

kubectl get pods -o wide --all-namespaces | grep <YOUR-NODE>

Answer 3

As mentioned in the accepted answer the PR is now merged and you can get pods by node as follows:

kubectl get pods --all-namespaces -o wide --field-selector spec.nodeName=<node>

Answer 4

I've gone through the same process with the Go Client and it uncovers a few shortcuts the CLI is taking.

func doNodesHavePods(clientset *kubernetes.Clientset) error {
    nodeLabelSelector := "nodelabel=interesting_nodes"
    nodes, err := clientset.CoreV1().Nodes().List(metav1.ListOptions{LabelSelector: nodeLabelSelector})

    if err != nil {
        return err
    }

    nodeNames := []string{}
    for _, node := range nodes.Items {
        nodeNames = append(nodeNames, node.Name)
    }
    // --all-namespaces -> listing and looping on namespaces
    namespaces, err := clientset.CoreV1().Namespaces().List(metav1.ListOptions{})

    if err != nil {
        return err
    }
    for _, namespace := range namespaces.Items {
        for _, name := range nodeNames {
            // pods need a namespace to be listed.
            pods, err := clientset.CoreV1().Pods(namespace.Name).List(metav1.ListOptions{FieldSelector: "spec.nodeName=" + name})
            if err != nil {
                println("%v", err)
            }
            for _, pod := range pods.Items {
                fmt.Println(pod.Namespace, pod.Name)
            }
        }
    }
    return nil
}

I've started to find that a lot of the questions I need to ask are becoming too complex for the CLI which is a great workhorse, but learning to use the Go Client can help you get the first answer you're looking for, but also dig deeper into questions that those answers raise.

Answer 5

Example sorting pods by nodeName:

kubectl get pods -o wide --sort-by="{.spec.nodeName}"

Example of getting pods on nodes using label filter:

for n in $(kubectl get nodes -l your_label_key=your_label_value --no-headers | cut -d " " -f1); do 
    kubectl get pods --all-namespaces  --no-headers --field-selector spec.nodeName=${n} 
done

or by number of restarts

kubectl get pods --sort-by="{.status.containerStatuses[:1].restartCount}"

Example filtering by nodeName using --template flag:

$ kubectl get nodes

NAME                         STATUS                     AGE
ip-10-0-90-30.ec2.internal   Ready                      2d
ip-10-0-90-35.ec2.internal   Ready                      2d
ip-10-0-90-50.ec2.internal   Ready,SchedulingDisabled   2d
ip-10-0-91-60.ec2.internal   Ready                      2d
ip-10-0-91-65.ec2.internal   Ready                      2d


$kubectl get pods --template '{{range .items}}{{if eq .spec.nodeName "ip-10-0-90-30.ec2.internal"}}{{.metadata.name}}{{"\n"}}{{end}}}{{end}}'

filebeat-pezch
app-5xole
node-exporter-6kfs8
prometheus-0
sso-359976856-wu8zt

Answer 6

What you want is supported in the Kubernetes API server-side like this:

curl --cacert ca.crt --cert apiserver.crt --key apiserver.key  https://<server>:<port>/api/v1/namespaces/<namespace>/pods?fieldSelector=spec.nodeName%3Dsomenodename

However that field selector option is not built into kubectl yet: https://github.com/kubernetes/kubernetes/pull/50140