Run twisted wsgi like an old-school, socket sharing fcgi subprocess

run.py

# Many very old fcgi containers had a trick probably inherited from old 
# inetd, where a socket is syscall dup2'd onto fd 0 of a subprocess. 
# The parent creates and binds the socket while the children then just 
# listen on it.
#
# Something to note is that supervisord provides this facility with its
# [fcgi-program] configuration section. The benefit here is simple inet
# or fcgi style graceful restarts. Anyhow, here is how you grab a
# socket that is fd 0 and start your twisted wsgi container on it. The
# wsgi application here is `application`.
from twisted.internet import fdesc
from twisted.internet import reactor
from twisted.web.server import Site
from twisted.web.wsgi import WSGIResource

resource = WSGIResource(reactor, reactor.getThreadPool(), application)
site = Site(resource)
fdesc.setNonBlocking(0)
reactor.adoptStreamPort(0, socket.AF_INET, site)
reactor.run()