dlecorfec

Take a look at Tengine, from Taobao. It's based on nginx.

woosh.

Damn game, because of it we are forced to use "golang" in search engines.

+1 for strace (and tcpdump)

A bit better, in case your API is down, maybe you could have a script that grab a strace (and maybe a gdb backtrace, see http://poormansprofiler.org/) of the usual suspect and join that to the alert.