How to set up a load balancer for web servers

· Category: Networking

Short answer

A load balancer distributes incoming network traffic across multiple backend servers. It prevents any single server from becoming a bottleneck and improves fault tolerance.

Steps

  1. Choose a solution: Use hardware load balancers like F5, cloud solutions like AWS ALB/NLB, or software options like NGINX and HAProxy.

  2. Define the backend pool: Register your web servers with their IP addresses and health check endpoints.

  3. Select an algorithm: Common choices include Round Robin, Least Connections, and IP Hash.

  4. Configure health checks: Set up HTTP or TCP checks so the load balancer removes failed servers from the pool automatically.

  5. Configure SSL termination: Offload TLS encryption to the load balancer to reduce backend CPU usage.

  6. Set session persistence: Use sticky sessions if your application requires clients to hit the same backend server.

Tips

  • Use autoscaling groups with cloud load balancers for dynamic capacity.
  • Enable access logs to analyze traffic patterns and detect anomalies.
  • Keep backend servers in private subnets for security.

Common issues

  • Unhealthy servers remaining in the pool due to misconfigured health checks.
  • SSL certificate mismatches when terminating TLS at the balancer.
  • Uneven distribution caused by session stickiness on asymmetric workloads.