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Load Balancing

Load balancing is the process of distributing network traffic across multiple servers to ensure no single server becomes overwhelmed.

Types of Load Balancers​

Hardware Load Balancers​

  • Dedicated physical devices
  • High performance
  • Expensive
  • Examples: F5 BIG-IP, Citrix ADC

Software Load Balancers​

  • Run on standard hardware
  • More flexible
  • Cost-effective
  • Examples: Nginx, HAProxy, Apache

Cloud Load Balancers​

  • Managed service
  • Auto-scaling
  • Pay-as-you-go
  • Examples: AWS ELB, GCP Load Balancer, Azure Load Balancer

Load Balancing Algorithms​

Round Robin​

  • Requests distributed sequentially
  • Simple to implement
  • Doesn't consider server load

Least Connections​

  • Sends requests to server with fewest active connections
  • Better for long-lived connections
  • More complex to implement

IP Hash​

  • Client IP determines server selection
  • Ensures same client goes to same server
  • Good for session persistence

Best Practices​

  1. Health Checks

    • Regular server monitoring
    • Automatic failover
    • Graceful degradation

  2. Session Management

    • Sticky sessions
    • Session replication
    • Stateless design

  3. Security

    • SSL termination
    • DDoS protection
    • Access control

Implementation Examples​

Nginx Configuration​

http {
    upstream backend {
        server backend1.example.com;
        server backend2.example.com;
        server backend3.example.com;
    }

    server {
        listen 80;
        location / {
            proxy_pass http://backend;
        }
    }
}

AWS ELB Setup​

# Create load balancer
aws elb create-load-balancer \
    --load-balancer-name my-load-balancer \
    --listeners "Protocol=HTTP,LoadBalancerPort=80,InstanceProtocol=HTTP,InstancePort=80" \
    --subnets subnet-12345678 subnet-87654321

Common Challenges​

  • Session persistence
  • SSL termination
  • Health monitoring
  • Auto-scaling integration

Further Reading​