High load on python wsgi server causes sem_init: Too many open files

[ciarancourtney]

When running HTTP benchmarks, wrt in this case, against a few Django + WSGI Server combinations (aiohttp, cherrypy, waitress) this error always crops up after a few seconds and the unikernel will become unresponsive. The Techempower framework sets the open file limit to

Code can be viewed here

=== calling "python.bin" main() ===

STUB ``__fork'' called
STUB ``_sys___wait450'' called
Serving on http://0.0.0.0:8080
sem_init: Too many open files

vagrant@tfb-all:~/FrameworkBenchmarks$ ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 23600
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 65535
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 99
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 23600
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited
```