#Docker Cluster Management

This chapter covers Docker cluster management technologies, including Docker Swarm and Kubernetes basics.

#Why Cluster Management?

Single-host Docker faces production challenges:

#Docker Swarm

Docker Swarm is Docker's built-in cluster management and orchestration tool.

#Architecture

┌─────────────────────────────────────────────┐
│              Docker Swarm Cluster            │
│                                             │
│  ┌──────────┐  ┌──────────┐  ┌──────────┐  │
│  │ Manager  │  │ Manager  │  │ Manager  │  │
│  │  Node 1  │  │  Node 2  │  │  Node 3  │  │
│  └────┬─────┘  └────┬─────┘  └────┬─────┘  │
│       │              │              │        │
│  ┌────▼─────┐  ┌────▼─────┐  ┌────▼─────┐  │
│  │ Worker   │  │ Worker   │  │ Worker   │  │
│  │  Node 1  │  │  Node 2  │  │  Node 3  │  │
│  └──────────┘  └──────────┘  └──────────┘  │
└─────────────────────────────────────────────┘

#Initialize Swarm

docker swarm init --advertise-addr <MANAGER-IP>
# Run the output join command on Worker nodes
docker node ls

#Deploy Services

docker service create --name web --replicas 3 -p 80:80 nginx:latest
docker service ls
docker service ps web
docker service scale web=5
docker service update --image nginx:1.25 web
docker service rm web

#Deploy with Stack

# docker-stack.yml
version: '3.8'
services:
  web:
    image: nginx:latest
    deploy:
      replicas: 3
      update_config:
        parallelism: 1
        delay: 10s
      restart_policy:
        condition: on-failure
    ports:
      - "80:80"

docker stack deploy -c docker-stack.yml myapp
docker stack ls
docker stack services myapp
docker stack rm myapp

#Kubernetes Introduction

Kubernetes (K8s) is the most popular container orchestration platform.

#Core Concepts

#Try K8s with Docker Desktop

1. Open Docker Desktop → Settings → Kubernetes
2. Check "Enable Kubernetes"
3. Click "Apply & Restart"

kubectl cluster-info
kubectl get nodes

#Basic Operations

kubectl create deployment web --image=nginx --replicas=3
kubectl expose deployment web --port=80 --type=NodePort
kubectl get pods
kubectl get services
kubectl scale deployment web --replicas=5
kubectl set image deployment/web nginx=nginx:1.25
kubectl logs <pod-name>
kubectl delete deployment web

#Docker Swarm vs Kubernetes

#Choosing

• Docker Swarm: Small-medium teams, quick setup, simple cluster needs
• Kubernetes: Large teams, complex microservices, rich ecosystem support needed

#Chapter Summary

Cluster management is key to running containerized applications in production. Docker Swarm offers simplicity, while Kubernetes is the industry standard for large-scale orchestration. Choose based on team size and business requirements.

#Further Reading

• Docker Swarm Documentation
• Kubernetes Official Documentation