MultiprocessApplication2.py

import os
import tornado.httpserver
import tornado.ioloop
import tornado.web
from multiprocessing import Pipe

class HelloHandler(tornado.web.RequestHandler):
    def get(self):
        self.write(self.application.communicate('hello world'))

class MultiprocessApplication(tornado.web.Application):
    def __init__(self, *args, **kwargs):
        tornado.web.Application.__init__(self, *args, **kwargs)

    def fork(self, fork_num):
        if fork_num == 0:
            self._pipes = {0: Pipe()}
        conns = Pipe()
        pid = os.fork()
        if pid == 0:
            self._pid = os.getpid()
        self._pipes[pid or self._pid] = conns
        return pid

    def setup(self, ioloop, is_main_process):
        self.is_main_process = is_main_process
        if is_main_process:
            ioloop.add_handler(self._pipes[0][0].fileno(),
                               self._handle_child_event,
                               ioloop.READ)
    
    def communicate(self, data):
        to_send = (self._pid, data)
        self._pipes[0][1].send(to_send)
        return self._pipes[self._pid][0].recv()

    def _handle_child_event(self, fd, events):
        child_pid, data = self._pipes[0][0].recv()
        data = "pid %s says: %s" % (child_pid, data)
        self._pipes[child_pid][1].send(data)

app = MultiprocessApplication([
    (r"/", HelloHandler),
])

http_server = tornado.httpserver.HTTPServer(app)
http_server.bind(8889)
is_main = http_server.start(2, wait=False, fork_callback=app.fork)
ioloop = tornado.ioloop.IOLoop.instance()
app.setup(ioloop, is_main)
ioloop.start()

# Patch for tornado/httpserver.py
#
#diff --git a/tornado/httpserver.py b/tornado/httpserver.py
#index 2f0fa04..1568d60 100644
#--- a/tornado/httpserver.py
#+++ b/tornado/httpserver.py
#@@ -150,7 +150,7 @@ class HTTPServer(object):
#         self._socket.bind((address, port))
#         self._socket.listen(128)
# 
#-    def start(self, num_processes=None):
#+    def start(self, num_processes=None, wait=True, fork_callback=None):
#         """Starts this server in the IOLoop.
# 
#         By default, we detect the number of cores available on this machine
#@@ -181,19 +181,22 @@ class HTTPServer(object):
#         if num_processes > 1:
#             logging.info("Pre-forking %d server processes", num_processes)
#             for i in range(num_processes):
#-                if os.fork() == 0:
#+                pid = fork_callback(i) if fork_callback else os.fork()
#+                if pid == 0:
#                     self.io_loop = ioloop.IOLoop.instance()
#                     self.io_loop.add_handler(
#                         self._socket.fileno(), self._handle_events,
#                         ioloop.IOLoop.READ)
#-                    return
#-            os.waitpid(-1, 0)
#+                    return False
#+            if wait:
#+                os.waitpid(-1, 0)
#         else:
#             if not self.io_loop:
#                 self.io_loop = ioloop.IOLoop.instance()
#             self.io_loop.add_handler(self._socket.fileno(),
#                                      self._handle_events,
#                                      ioloop.IOLoop.READ)
#+        return True
# 
#     def stop(self):
#       self.io_loop.remove_handler(self._socket.fileno())