I know how to use the API to perform simple request such as display node information selecting node by labels value.

For example : curl http://localhost:8080/api/v1/nodes?labelSelector=kubernetes.io/role=worker3 Display informations about node whose role is worker3.

Is there a way to perform the same request using a JSON query ?

looked on the web to find a such example but did not find one.

CodePudding user response：

You can query with kubectl by label. The Roles of the node are just labels.

To return in yaml format

 kubectl get nodes -l node-role.kubernetes.io/worker -o yaml

To return in json format

 kubectl get nodes -l node-role.kubernetes.io/worker -o json

Update
Querying the api with json you can do like so:

curl http://localhost:8080/api/v1/nodes?{"node.kubernetes.io/worker01":"worker01"}

This in my case returns this:

{
  "kind": "NodeList",
  "apiVersion": "v1",
  "metadata": {
    "resourceVersion": "317238"
  },
  "items": [
    {
      "metadata": {
        "name": "worker01",
        "uid": "a2bec224-361f-49e9-8bba-b3b172816d6e",
        "resourceVersion": "316653",
        "creationTimestamp": "2022-12-24T11:04:43Z",
        "labels": {
          "beta.kubernetes.io/arch": "amd64",
          "beta.kubernetes.io/os": "linux",
          "kubernetes.io/arch": "amd64",
          "kubernetes.io/hostname": "worker01",
          "kubernetes.io/os": "linux",
          "microk8s.io/cluster": "true",
          "node.kubernetes.io/microk8s-worker": "microk8s-worker"
        },

............

As you can see it works, but you must analyse 2 things generally.

1. the api version (can be different to v1, depends on the kubernetes version)
2. the labels and property name.

The example above comes from microk8s, here i havent even Roles defined.

kubectl get node
NAME       STATUS   ROLES    AGE   VERSION
master     Ready    <none>   17d   v1.25.4
worker01   Ready    <none>   17d   v1.25.4

So i looked for some label that could extract the required data.