How to kube-API Server Works

• User Interaction:
  • The user interacts with Kubernetes through the kubectl command-line interface.

Example: 

• Authentication and Validation:
  • The kube-API Server authenticates the user’s request and validates it to ensure compliance with Kubernetes API schemas and policies.
• Data Retrieval from ETCD:
  • Upon validation, the kube-API Server retrieves data from the ETCD cluster, which acts as the persistent storage for Kubernetes cluster state.
• Response to User:
  • The kube-API Server responds to the user with the requested information or performs the requested operation (e.g., creating a pod).
• kube-Scheduler Assignment:
  • If a user request involves creating a pod without specifying a node, the kube-Scheduler monitors the API-Server for new pod requests.
  • It then assigns the appropriate node for the pod to run on based on scheduling policies.
• Communication with Kubelet:
  • The kube-API Server updates the ETCD cluster with information about the newly created pod and its assigned node.
  • It then communicates this information to the kubelet running on the appropriate worker node.
• POD Creation by Kubelet:
  • The kubelet on the worker node receives instructions to create the pod.
  • It interacts with the container runtime engine (e.g., Docker) to deploy the application image and create the pod.
• Status Update:
  • Once the pod is created and running, the kubelet updates the pod’s status in the ETCD cluster via the kube-API Server.
• Continuous Process:
  • This workflow repeats for every user request or cluster state change, ensuring consistency and proper management of the Kubernetes cluster.