HAProxy — load balancing for web applications

Apache with mod_jk served as a load balancer, but with increasing traffic we looked for a better solution. HAProxy is the de facto standard — fast, reliable and with excellent configurability.

Why HAProxy¶

Better health checks, detailed statistics (real-time dashboard), lower resource footprint, better sticky session management. A dedicated load balancer vs. a web server with LB functionality.

Configuration¶

Frontend, backend, health check on the /health endpoint. Sticky sessions via the SERVERID cookie. Automatic failover.

Zero-downtime deployment¶

Rolling deployment: take server A out of the pool, upgrade it, put it back, then server B. CLI: set server state drain.

Conclusion¶

HAProxy is an excellent load balancer. The stats dashboard and CLI enable the operational flexibility that Apache doesn’t offer.