You can talk to Kubernetes API server in 3 ways.a
a. Using kubectl command
b. Kubernetes Dashboard
c. Any rest client like Postman, curl
API server provides REST Apis to communicate with it. You can create Kubernetes objects like Pods, ReplicaSets, Deployments, etc., by talking to API Server.
Let’s talk to Kubernetes using curl command-line tool.
Step 1: In order to communicate using curl, first you need to start kubectl proxy.
kubectl proxy --port=1234
Above command starts a proxy on port 1234.
$kubectl proxy --port=1234
Starting to serve on 127.0.0.1:1234
You can run the proxy in background by adding & at the end of the command.
kubectl proxy --port=1234 &
Step 2: Communicate to the proxy using curl.
Execute the command ‘curl http://localhost:1234’ to see all the APIs provided by kubectl proxy.
$curl http://localhost:1234
{
"paths": [
"/api",
"/api/v1",
"/apis",
"/apis/",
"/apis/admissionregistration.k8s.io",
"/apis/admissionregistration.k8s.io/v1",
"/apis/admissionregistration.k8s.io/v1beta1",
"/apis/apiextensions.k8s.io",
"/apis/apiextensions.k8s.io/v1",
"/apis/apiextensions.k8s.io/v1beta1",
"/apis/apiregistration.k8s.io",
"/apis/apiregistration.k8s.io/v1",
"/apis/apiregistration.k8s.io/v1beta1",
"/apis/apps",
"/apis/apps/v1",
"/apis/authentication.k8s.io",
"/apis/authentication.k8s.io/v1",
"/apis/authentication.k8s.io/v1beta1",
"/apis/authorization.k8s.io",
"/apis/authorization.k8s.io/v1",
"/apis/authorization.k8s.io/v1beta1",
"/apis/autoscaling",
"/apis/autoscaling/v1",
"/apis/autoscaling/v2beta1",
"/apis/autoscaling/v2beta2",
"/apis/batch",
"/apis/batch/v1",
"/apis/batch/v1beta1",
"/apis/certificates.k8s.io",
"/apis/certificates.k8s.io/v1beta1",
"/apis/coordination.k8s.io",
"/apis/coordination.k8s.io/v1",
"/apis/coordination.k8s.io/v1beta1",
"/apis/discovery.k8s.io",
"/apis/discovery.k8s.io/v1beta1",
"/apis/events.k8s.io",
"/apis/events.k8s.io/v1beta1",
"/apis/extensions",
"/apis/extensions/v1beta1",
"/apis/networking.k8s.io",
"/apis/networking.k8s.io/v1",
"/apis/networking.k8s.io/v1beta1",
"/apis/node.k8s.io",
"/apis/node.k8s.io/v1beta1",
"/apis/policy",
"/apis/policy/v1beta1",
"/apis/rbac.authorization.k8s.io",
"/apis/rbac.authorization.k8s.io/v1",
"/apis/rbac.authorization.k8s.io/v1beta1",
"/apis/scheduling.k8s.io",
"/apis/scheduling.k8s.io/v1",
"/apis/scheduling.k8s.io/v1beta1",
"/apis/storage.k8s.io",
"/apis/storage.k8s.io/v1",
"/apis/storage.k8s.io/v1beta1",
"/healthz",
"/healthz/autoregister-completion",
"/healthz/etcd",
"/healthz/log",
"/healthz/ping",
"/healthz/poststarthook/apiservice-openapi-controller",
"/healthz/poststarthook/apiservice-registration-controller",
"/healthz/poststarthook/apiservice-status-available-controller",
"/healthz/poststarthook/bootstrap-controller",
"/healthz/poststarthook/crd-informer-synced",
"/healthz/poststarthook/generic-apiserver-start-informers",
"/healthz/poststarthook/kube-apiserver-autoregistration",
"/healthz/poststarthook/rbac/bootstrap-roles",
"/healthz/poststarthook/scheduling/bootstrap-system-priority-classes",
"/healthz/poststarthook/start-apiextensions-controllers",
"/healthz/poststarthook/start-apiextensions-informers",
"/healthz/poststarthook/start-cluster-authentication-info-controller",
"/healthz/poststarthook/start-kube-aggregator-informers",
"/healthz/poststarthook/start-kube-apiserver-admission-initializer",
"/livez",
"/livez/autoregister-completion",
"/livez/etcd",
"/livez/log",
"/livez/ping",
"/livez/poststarthook/apiservice-openapi-controller",
"/livez/poststarthook/apiservice-registration-controller",
"/livez/poststarthook/apiservice-status-available-controller",
"/livez/poststarthook/bootstrap-controller",
"/livez/poststarthook/crd-informer-synced",
"/livez/poststarthook/generic-apiserver-start-informers",
"/livez/poststarthook/kube-apiserver-autoregistration",
"/livez/poststarthook/rbac/bootstrap-roles",
"/livez/poststarthook/scheduling/bootstrap-system-priority-classes",
"/livez/poststarthook/start-apiextensions-controllers",
"/livez/poststarthook/start-apiextensions-informers",
"/livez/poststarthook/start-cluster-authentication-info-controller",
"/livez/poststarthook/start-kube-aggregator-informers",
"/livez/poststarthook/start-kube-apiserver-admission-initializer",
"/logs",
"/metrics",
"/openapi/v2",
"/readyz",
"/readyz/autoregister-completion",
"/readyz/etcd",
"/readyz/log",
"/readyz/ping",
"/readyz/poststarthook/apiservice-openapi-controller",
"/readyz/poststarthook/apiservice-registration-controller",
"/readyz/poststarthook/apiservice-status-available-controller",
"/readyz/poststarthook/bootstrap-controller",
"/readyz/poststarthook/crd-informer-synced",
"/readyz/poststarthook/generic-apiserver-start-informers",
"/readyz/poststarthook/kube-apiserver-autoregistration",
"/readyz/poststarthook/rbac/bootstrap-roles",
"/readyz/poststarthook/scheduling/bootstrap-system-priority-classes",
"/readyz/poststarthook/start-apiextensions-controllers",
"/readyz/poststarthook/start-apiextensions-informers",
"/readyz/poststarthook/start-cluster-authentication-info-controller",
"/readyz/poststarthook/start-kube-aggregator-informers",
"/readyz/poststarthook/start-kube-apiserver-admission-initializer",
"/readyz/shutdown",
"/version"
]
}
curl http://localhost:1234/metrics
Give you the metrics
curl http://localhost:1234/version
Give you the version information.
$curl http://localhost:1234/version
{
"major": "1",
"minor": "18",
"gitVersion": "v1.18.0",
"gitCommit": "9e991415386e4cf155a24b1da15becaa390438d8",
"gitTreeState": "clean",
"buildDate": "2020-03-25T14:50:46Z",
"goVersion": "go1.13.8",
"compiler": "gc",
"platform": "linux/amd64"
}
curl http://localhost:1234/api/v1/namespaces
Give all the available namespaces.
curl http://localhost:1234/api/v1/namespaces/default/services
List all the services in the default namespace.
curl http://localhost:1234/api/v1/namespaces/default/pods
List all the available pods in the default namespace.
Let’s create a deployment and explore the API objects using curl tool.
Step 1: Create employeeServiceDeployment.yml with the below content.
employeeServiceDeployment.yml
metadata:
name: employee-service-deployment
labels:
app: employee-service-deployment
author: krishna
serviceType: webservice
spec:
template:
metadata:
name: employee-service
labels:
app: employee-service
author: krishna
serviceType: webservice
spec:
containers:
- name: employee-service-container
image: jboss/wildfly
replicas: 5
selector:
matchLabels:
app: employee-servic
As you see above definition, it creates 5 pods with the image ‘jboss/wildfly’.
Step 2: Create deployment by executing below command.
kubectl create -f employeeServiceDeployment.yml
$kubectl create -f employeeServiceDeployment.yml
deployment.apps/employee-service-deployment created
Step 3: You can query the pods information by executing below command.
curl http://localhost:1234/api/v1/namespaces/default/pods
I hope you got some basic idea and now you can go through Kubernetes documentation and explore the APIs.
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