Configuring Load Balancers

Overview

Configure load balancers across AWS (ALB, NLB), GCP (HTTP(S) LB, TCP/UDP LB), Nginx, and HAProxy. Generate production-ready configurations with health checks, SSL/TLS termination, path-based and host-based routing, sticky sessions, rate limiting, and traffic distribution rules for high-availability deployments.

Prerequisites

• Backend servers identified with IPs, DNS names, and ports

• Load balancer type determined: L4 (NLB, HAProxy TCP) or L7 (ALB, Nginx, HAProxy HTTP)

• SSL/TLS certificates available (ACM, Let's Encrypt, or self-signed) if using HTTPS

• Health check endpoints defined on backend services (e.g., /health returning 200)

• Cloud provider CLI installed for managed load balancers (aws , gcloud )

Instructions

• Select load balancer type based on requirements: ALB for HTTP/HTTPS with path routing, NLB for TCP/UDP with static IPs, Nginx for on-prem reverse proxy, HAProxy for high-performance TCP/HTTP

• Define the backend pool: list all backend server addresses, ports, and weights for weighted distribution

• Configure health checks with appropriate interval (10-30s), timeout (5s), healthy threshold (3), and unhealthy threshold (2)

• Set up SSL/TLS termination: configure certificates, redirect HTTP to HTTPS, set minimum TLS version to 1.2

• Define routing rules: path-based routing (/api -> API pool, /static -> CDN), host-based routing (api.example.com -> API)

• Enable session persistence (sticky sessions) using cookies or source IP affinity where needed for stateful applications

• Add connection draining to gracefully handle backend removal during deployments

• Configure logging and monitoring: access logs to S3/CloudWatch, request metrics, error rate dashboards

• Test the configuration: validate syntax (nginx -t , HAProxy config check), verify traffic distribution, and confirm failover behavior

Output

• Nginx configuration files (nginx.conf , site configs) with upstream blocks and server directives

• HAProxy configuration (haproxy.cfg ) with frontend/backend sections

• Terraform HCL for AWS ALB/NLB with target groups, listeners, and rules

• GCP load balancer Terraform with backend services, URL maps, and health checks

• SSL certificate configuration and renewal automation

Error Handling

Error Cause Solution

502 Bad Gateway

Backend server unreachable or not responding Verify backend IPs, ports, and firewall rules; check backend service health

SSL certificate verify failed

Certificate expired, wrong chain, or key mismatch Verify certificate validity and chain with openssl s_client ; regenerate if needed

Target is unhealthy

Health check endpoint returning non-200 or timing out Verify health check path returns 200; increase timeout if backend is slow to respond

nginx: configuration file test failed

Syntax error in Nginx configuration Run nginx -t to identify the specific error line; fix syntax and test again

Session persistence not working

Cookie-based stickiness misconfigured or client not sending cookies Verify cookie name matches; use IP-based affinity as fallback for non-browser clients

Examples

• "Configure an AWS ALB with HTTPS listener, path-based routing to two target groups (/api and /web), and health checks on /health."

• "Generate an Nginx reverse proxy config with upstream servers, sticky sessions via cookie, and rate limiting at 100 req/s per IP."

• "Create a HAProxy configuration for TCP load balancing across 4 database read replicas with health checks and connection draining."

Resources

• Nginx load balancing: https://nginx.org/en/docs/http/load_balancing.html

• HAProxy configuration: https://www.haproxy.org/download/2.8/doc/configuration.txt

• AWS ALB: https://docs.aws.amazon.com/elasticloadbalancing/latest/application/

• GCP Load Balancing: https://cloud.google.com/load-balancing/docs

• See ${CLAUDE_SKILL_DIR}/references/errors.md for additional error handling patterns