Load Balancing: Traffic intelligent verteilen

Load Balancer verteilen Anfragen auf mehrere Server. Lernen Sie die verschiedenen Strategien und ihre Einsatzgebiete.

Warum Load Balancing?

Ohne Load Balancer:
┌──────────┐
│  Client  │───────────────────► Server (überlastet!)
└──────────┘

Mit Load Balancer:
┌──────────┐      ┌─────────────┐      ┌──────────┐
│  Client  │─────►│ Load Balancer│────►│ Server 1 │
└──────────┘      └─────────────┘  │   ├──────────┤
                        │          └──►│ Server 2 │
                        │              ├──────────┤
                        └─────────────►│ Server 3 │
                                       └──────────┘

Load Balancing Algorithmen

Nginx als Load Balancer

# /etc/nginx/nginx.conf

# Upstream definieren
upstream backend {
    # Round Robin (Standard)
    server 10.0.0.1:8080;
    server 10.0.0.2:8080;
    server 10.0.0.3:8080;
}

# Mit Gewichtung
upstream backend_weighted {
    server 10.0.0.1:8080 weight=3;  # 3x mehr Traffic
    server 10.0.0.2:8080 weight=2;
    server 10.0.0.3:8080 weight=1;
}

# Least Connections
upstream backend_least {
    least_conn;
    server 10.0.0.1:8080;
    server 10.0.0.2:8080;
    server 10.0.0.3:8080;
}

# IP Hash (Session Affinity)
upstream backend_sticky {
    ip_hash;
    server 10.0.0.1:8080;
    server 10.0.0.2:8080;
    server 10.0.0.3:8080;
}

server {
    listen 80;

    location / {
        proxy_pass http://backend;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}

Health Checks

upstream backend {
    server 10.0.0.1:8080 max_fails=3 fail_timeout=30s;
    server 10.0.0.2:8080 max_fails=3 fail_timeout=30s;
    server 10.0.0.3:8080 backup;  # Nur wenn andere ausfallen
}

# Nginx Plus (kostenpflichtig) - Active Health Checks
upstream backend {
    zone backend 64k;
    server 10.0.0.1:8080;
    server 10.0.0.2:8080;

    health_check interval=5s fails=3 passes=2;
}

HAProxy Konfiguration

# /etc/haproxy/haproxy.cfg
global
    maxconn 50000
    log /dev/log local0

defaults
    mode http
    timeout connect 5s
    timeout client 30s
    timeout server 30s
    option httplog

frontend http_front
    bind *:80
    bind *:443 ssl crt /etc/ssl/certs/cert.pem
    redirect scheme https if !{ ssl_fc }
    default_backend servers

backend servers
    balance roundrobin
    option httpchk GET /health
    http-check expect status 200

    server server1 10.0.0.1:8080 check weight 3
    server server2 10.0.0.2:8080 check weight 2
    server server3 10.0.0.3:8080 check weight 1 backup

# Stats Page
listen stats
    bind *:8404
    stats enable
    stats uri /stats
    stats auth admin:password

Docker Swarm Load Balancing

# docker-compose.yml
version: '3.8'

services:
  web:
    image: nginx
    deploy:
      replicas: 3
      update_config:
        parallelism: 1
        delay: 10s
      restart_policy:
        condition: on-failure
    ports:
      - "80:80"

# Swarm erstellt automatisch Load Balancing
# Intern über ingress network

Kubernetes Services

# ClusterIP: Internes Load Balancing
apiVersion: v1
kind: Service
metadata:
  name: my-service
spec:
  selector:
    app: my-app
  ports:
    - port: 80
      targetPort: 8080
  type: ClusterIP

# LoadBalancer: Externes Load Balancing
apiVersion: v1
kind: Service
metadata:
  name: my-service-external
spec:
  selector:
    app: my-app
  ports:
    - port: 80
      targetPort: 8080
  type: LoadBalancer

Session Persistence (Sticky Sessions)

# Nginx - Cookie-basiert
upstream backend {
    server 10.0.0.1:8080;
    server 10.0.0.2:8080;
    sticky cookie srv_id expires=1h;
}

# HAProxy - Cookie
backend servers
    balance roundrobin
    cookie SERVERID insert indirect nocache
    server server1 10.0.0.1:8080 cookie s1
    server server2 10.0.0.2:8080 cookie s2

# Besser: Stateless Design!
# Sessions in Redis/Memcached statt auf Server

SSL Termination

# Load Balancer terminiert SSL
┌────────┐ HTTPS  ┌────────────┐ HTTP  ┌────────┐
│ Client │───────►│Load Balancer│──────►│ Server │
└────────┘        └────────────┘       └────────┘
                  └── SSL hier ──┘

# Nginx SSL Termination
server {
    listen 443 ssl;
    ssl_certificate /etc/ssl/cert.pem;
    ssl_certificate_key /etc/ssl/key.pem;

    location / {
        proxy_pass http://backend;  # HTTP intern
        proxy_set_header X-Forwarded-Proto $scheme;
    }
}

Weitere Informationen

• 🔄 HAProxy Konfiguration
• 🌐 Nginx Reverse Proxy
• ☸️ Kubernetes Services