That's actually our prod setup; we do that now and it's a pretty robust. As a bonus is gives you a nice "wiretap point" you can use tcpdump for debugging.
In our limited tests with HaProxy -unixDomainSocket-> Tomcat, we saw a significant increase in throughput and decrease in latency (when it worked). It got rid of our wiretap point though which is pretty handy, and we didn't _really_ need the performance increase. If I were to speculate, HaProxy is a rocket and beats even the mature codebase of Tomcat it seems when parsing http, and probably takes advantage of kernel features that haven't made its way into Tomcat yet. It wasn't prod-worthy stable, sometimes execution threads seemed to hang.
In our limited tests with HaProxy -unixDomainSocket-> Tomcat, we saw a significant increase in throughput and decrease in latency (when it worked). It got rid of our wiretap point though which is pretty handy, and we didn't _really_ need the performance increase. If I were to speculate, HaProxy is a rocket and beats even the mature codebase of Tomcat it seems when parsing http, and probably takes advantage of kernel features that haven't made its way into Tomcat yet. It wasn't prod-worthy stable, sometimes execution threads seemed to hang.