Architecture & Control Plane Components:
- Definition: Kubernetes (K8s) is an open-source container orchestration platform that automates deployment, scaling, health management, and load balancing of containerized workloads across a cluster.
1. Control Plane Components (Cluster Brain):
- kube-apiserver: The central REST API gateway through which all cluster administration commands pass.
- etcd: Consistent, distributed, and highly available key-value datastore holding complete cluster state and configuration.
- kube-scheduler: Assigns newly created Pods to available Worker Nodes based on resource requests, affinities, and taints.
- kube-controller-manager: Runs reconciliation loops (DeploymentController, NodeController) that continuously steer the cluster toward the desired declared state.
2. Worker Node Components:
- kubelet: Primary node agent ensuring assigned Pods and containers are running and healthy per specification.
- kube-proxy: Maintains network rules on nodes to route traffic to Pod IP addresses and implement Services.
- Container Runtime: Low-level engine executing containers (e.g., containerd or CRI-O).
3. Core Abstractions: Pod (smallest deployable unit), Service (stable network endpoint), and Deployment (declarative rollout controller).