haproxy - HA-Proxy is a TCP/HTTP reverse proxy for high availability environments
HAProxy is a free, fast and reliable solution offering high
availability, load balancing, and proxying for TCP and HTTP-based
applications. It is particularly suited for web sites crawling under
very high loads while needing persistence or Layer7 processing.
Supporting tens of thousands of connections is clearly realistic with
modern hardware. Its mode of operation makes integration with existing
architectures very easy and riskless, while still offering the
possibility not to expose fragile web servers to the net.