Graceful restarts with code reloading on Capistrano style deployed Python applications

gunicorn.conf.py

import os
import signal

bind = "127.0.0.1:8888"
errorlog = "%s/log/gunicorn.log" % (os.getcwd())
workers = 4
keepalive = 5
preload_app = True

def on_starting(server):
  server.START_CTX['cwd'] = "/var/webapps/application/current"

def when_ready(server):
  server.log.info("Master ready in %s" % os.getcwd())
  # Quit the old unicorn process
  old_pid = "/var/webapps/application/shared/pids/gunicorn.pid.oldbin"
  if os.path.isfile(old_pid):
    try:
      pid = open(old_pid).read().split()[0]
      os.kill(int(pid), signal.SIGQUIT)
    except Exception as e:
      server.log.exception("Error cleaning up %s" % e)