Comment 1 for bug 1742821

I attempted to do this locally in a devstack environment and I was not able to reproduce this at all. Setting the number of processes to launch to 10x the number of cores did not cause anything to fail. (I eventually exhausted all of my VM's memory but then the OOMkiller just killed things)

Looking at these steps my assumption is that something else is breaking and it just happens to coincide with you changing the uwsgi config and restarting glance. (or it maybe a side effect of misconfiguring your glance)This is kinda confirmed by the fact that nova list is also returning 500 because that call has nothing to do with glance at all. It's isolated to nova's DB and api service.

Additionally there aren't any service logs as to what's causing the 500. A 500 error normally means there is an unhandled exception in the api service, so there should be stacktraces in the logs that will show you what's wrong. My guess is though that you exhausted all of the ram on your machine and the oomkiller killed mysql.