Kubernetes Architecture

Understanding control plane components, node components, and networking

Overview

Kubernetes is a distributed system composed of multiple components working together. This section covers the architecture of a Kubernetes cluster, including the control plane, node components, optional services, and networking model.

Architecture Diagram

┌─────────────────────────────────────────────────────────────────┐
│                      Kubernetes Cluster                         │
│  ┌──────────────────────────────────────────────────────────┐  │
│  │                    Control Plane                         │  │
│  │  ┌──────────┐ ┌────────────┐ ┌─────────────┐            │  │
│  │  │  API     │ │ etcd       │ │  Scheduler  │            │  │
│  │  │  Server  │ │ (Key-Value)│ │             │            │  │
│  │  └──────────┘ └────────────┘ └─────────────┘            │  │
│  │  ┌──────────────┐  ┌──────────────┐                     │  │
│  │  │  Controller  │ │  Cloud       │                     │  │
│  │  │  Manager     │ │  Controller  │                     │  │
│  │  └──────────────┘  └──────────────┘                     │  │
│  └──────────────────────────────────────────────────────────┘  │
│                            ↓                                   │
│  ┌──────────────────────────────────────────────────────────┐  │
│  │                    Worker Nodes                          │  │
│  │  ┌───────────────┐  ┌───────────────┐  ┌───────────────┐│  │
│  │  │   Node 1      │  │   Node 2      │  │   Node 3      ││  │
│  │  │ ┌───────────┐  │  │ ┌───────────┐  │  │ ┌───────────┐  ││  │
│  │  │ │  Kubelet  │  │  │ │  Kubelet  │  │  │ │  Kubelet  │  ││  │
│  │  │ └───────────┘  │  │ └───────────┘  │  │ └───────────┘  ││  │
│  │  │ ┌───────────┐  │  │ ┌───────────┐  │  │ ┌───────────┐  ││  │
│  │  │ │kube-proxy│  │  │ │kube-proxy│  │  │ │kube-proxy│  ││  │
│  │  │ └───────────┘  │  │ └───────────┘  │  │ └───────────┘  ││  │
│  │  │ ┌───────────┐  │  │ ┌───────────┐  │  │ ┌───────────┐  ││  │
│  │  │ │Container │  │  │ │Container │  │  │ │Container │  ││  │
│  │  │ │ Runtime  │  │  │ │ Runtime  │  │  │ │ Runtime  │  ││  │
│  │  │ └───────────┘  │  │ └───────────┘  │  │ └───────────┘  ││  │
│  │  └───────────────┘  └───────────────┘  └───────────────┘│  │
│  └──────────────────────────────────────────────────────────┘  │
└─────────────────────────────────────────────────────────────────┘

Study Path

1. Control Plane - API Server, etcd, Scheduler, Controller Manager
2. Node Components - Kubelet, kube-proxy, Container Runtime
3. Optional Services - DNS, Dashboard, Ingress Controller
4. Networking Model - Pod networking, Services, Network Policies

Control Plane Components

Component	Purpose
kube-apiserver	Front-end for all API operations
etcd	Consistent key-value store for cluster data
kube-scheduler	Assigns pods to nodes
kube-controller-manager	Runs controller processes

Node Components

Component	Purpose
kubelet	Agent that runs on each node
kube-proxy	Network proxy on each node
Container Runtime	Runs containers (Docker, containerd, CRI-O)

Quick Reference

Check Cluster Components

# Check all control plane pods
kubectl get pods -n kube-system

# Check nodes
kubectl get nodes -o wide

# Check cluster info
kubectl cluster-info

# Check component status
kubectl get componentstatuses

Check Control Plane

# API server
kubectl get pods -n kube-system -l component=kube-apiserver

# Scheduler
kubectl get pods -n kube-system -l component=kube-scheduler

# Controller manager
kubectl get pods -n kube-system -l component=kube-controller-manager

# etcd
kubectl get pods -n kube-system -l component=etcd

Next Steps

1. Learn Control Plane: Control Plane
2. Understand Node Components: Node Components
3. Study Networking: Networking Model

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Continue Learning:

• Control Plane
• Node Components
• Networking Model

Return to: Overview | K8s for MLOps