API Groups

Concept and Usage of API Groups

Refer to the Kubernetes API Reference (opens in a new tab) and Kubernetes API (opens in a new tab) for the complete list of API groups and resources.

In Kubernetes, we have some endpoints that are grouped together based on their functionality. These groups are called API groups.

• /version - Provides version information about the kube-apiserver or cluster.
• /healthz - Health check endpoint to verify if the kube-apiserver is running correctly.
• /metrics - Exposes metrics for monitoring and performance analysis.
• /logs - Provides access to the logs of the kube-apiserver or to integrate with third-party logging applications.
• /api - The core API group, which includes core resources such as pods, services, nodes, etc.
• /apis - The extended API group (named group), which includes additional resources and features.

The reason to understand this is that when you are working with RBAC (Role-Based Access Control) in Kubernetes, you need to specify the API group and resource to which the role applies.

There are two ways to access the API paths:

1. Use cluster IP and port 6443

   # View all API paths
   curl https://<cluster-ip>:6443
    
   # View the core API group
   curl https://<cluster-ip>:6443/api
    
   # View the named API group
   curl https://<cluster-ip>:6443/apis
    
   # View the kube-apiserver version
   curl https://<cluster-ip>:6443/version
    
   # Get the lists of pods
   curl https://<cluster-ip>:6443/api/v1/pods
    
   curl https://<cluster-ip>:6443 --key <path-to-key> --cert <path-to-cert> --cacert <path-to-ca-cert>

   You might need to provide authentication details to access the API paths.

2. Use kubectl proxy

   kubectl proxy
   curl http://localhost:8001

   This will create a proxy server that will forward the requests to the kube-apiserver, it will use the kubeconfig file to authenticate these requests.

   kube-proxy != kubectl proxy

   • kube-proxy is a network proxy that runs on each node in the cluster to enable network communication to the pods from the outside world.
   • kubectl proxy is a proxy server that forwards requests to the kube-apiserver.

Core API Group

The core API group is the default API group in Kubernetes. It includes the core resources such as pods, services, nodes, etc. The core API group is accessed using the /api/v1 endpoint.

Named API Group

The named API group is an extended API group that includes additional resources and features that can extend the Kubernetes functionality by adding custom resources. Besides, all the new resources and features are added to the named API group. The named API group is accessed using the /apis/<group>/<version> endpoint.

Each API group has its own set of resources and each resource has its own set of actions.