I have an Rails (3.2) app that runs on nginx and unicorn on a cloud platform. The "box" is running on Ubuntu 12.04. When the system load is at about 70% or above, nginx abruptly (and seemingly randomly) starts throwing 502 Bad gateway errors; when load is less there's nothing like it. I have experimented with various number of cores (4, 6, 10 - I can "change hardware" as it's on cloud platform), a