how to display nodes information with a JSON request? - kubernetes

Question

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%3Dworker3
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.

Answer 1

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.
the api version (can be different to v1, depends on the kubernetes version)
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.