wrk
Modern HTTP benchmarking tool
...An optional LuaJIT script can perform HTTP request generation, response processing, and custom reporting. Details are available in SCRIPTING and several examples are located in scripts. The machine running wrk must have a sufficient number of ephemeral ports available and closed sockets should be recycled quickly. To handle the initial connection burst the server's listen(2) backlog should be greater than the number of concurrent connections being tested.