Cluster Components and kubernetes Concepts

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kubernetes cluster  and components

A Kubernetes cluster is a set of nodes that run containerized applications. Kubernetes manages these applications efficiently, providing scalability, fault tolerance, and automation.

Kubernetes Cluster Components

A Kubernetes cluster consists of two main types of nodes:

1. Control Plane (Master Node)

The control plane manages the cluster, scheduling workloads, maintaining the desired state, and handling networking. It includes:

• API Server (kube-apiserver)

  • Acts as the front-end for Kubernetes.
  • Exposes REST APIs for interaction with the cluster.
  • Authenticates and processes requests.

• Controller Manager (kube-controller-manager)

  • Runs controllers that ensure the desired state of the cluster.
  • Types of controllers:
    • Node Controller (monitors node health)
    • Deployment Controller (manages deployments)
    • Service Controller (handles services)

• Scheduler (kube-scheduler)

  • Assigns workloads (pods) to worker nodes based on resource availability and constraints.

• etcd (Key-Value Store)

  • Stores cluster state and configuration data.
  • Distributed and fault-tolerant.

2. Worker Nodes

Worker nodes run the application workloads inside containers. Key components:

• Kubelet

  • Agent running on each node.
  • Communicates with the API server.
  • Ensures containers run as expected.

• Container Runtime (Docker, containerd, CRI-O, etc.)

  • Runs containers on the node.

• Kube Proxy

  • Manages networking, load balancing, and communication between services.

• Pods

  • The smallest deployable unit in Kubernetes.
  • A pod contains one or more containers that share storage, networking, and configuration.

3. Additional Components

• Network Plugins (CNI - Calico, Flannel, Cilium, etc.)

  • Enables networking between pods across nodes.

• Ingress Controller

  • Manages external access to services (e.g., NGINX Ingress, Traefik).

• CoreDNS

  • Provides DNS resolution for services within the cluster.