As a small follow-on, there is also Barrage [1], which is more of a framework than anything else. kellabyte wrote it to benchmark changes to Haywire [2], so it's geared towards configuring your client and server, and then collecting all of the metrics from both the client side, and the server side, and displaying them in an easy-to-digest format.

This obviously isn't terribly useful if you're just trying to gauge request rates, or apply load, but it's very useful if you need a repeatable way to not only measure request rates but see how your server is doing under load.

[1] https://github.com/kellabyte/barrage

[2] https://github.com/kellabyte/Haywire