Monkey-patch prior to importing standard lib modules to prevent unnec…

…essary blockage

In production environments, I've seen a some threading.Lock acquire calls
killing the controller. I believe this patch should resolve that issue:

    A child intends to die, starting replacement before it dies
    Controller.spawn_children(number=1)
    Traceback (most recent call last):
    File "/usr/local/bin/spawning", line 8, in <module>
        load_entry_point('Spawning==0.9.5', 'console_scripts', 'spawning')()
    File "/usr/local/lib/python2.6/site-packages/spawning/spawning_controller.py", line 501, in main
        start_controller(sock, factory, factory_args)
    File "/usr/local/lib/python2.6/site-packages/spawning/spawning_controller.py", line 278, in start_controller
        c.run()
    File "/usr/local/lib/python2.6/site-packages/spawning/spawning_controller.py", line 236, in run
        self.runloop()
    File "/usr/local/lib/python2.6/site-packages/spawning/spawning_controller.py", line 158, in runloop
        eventlet.sleep(0.1)
    File "/usr/local/lib/python2.6/site-packages/eventlet/greenthread.py", line 30, in sleep
        hub.switch()
    File "/usr/local/lib/python2.6/site-packages/eventlet/hubs/hub.py", line 177, in switch
        return self.greenlet.switch()
    File "/usr/local/lib/python2.6/site-packages/eventlet/hubs/hub.py", line 226, in run
        self.wait(sleep_time)
    File "/usr/local/lib/python2.6/site-packages/eventlet/hubs/poll.py", line 84, in wait
        presult = self.do_poll(seconds)
    File "/usr/local/lib/python2.6/site-packages/eventlet/hubs/epolls.py", line 55, in do_poll
        return self.poll.poll(seconds)
    File "/usr/local/lib/python2.6/site-packages/spawning/spawning_controller.py", line 212, in handle_deadlychild
    File "/usr/local/lib/python2.6/site-packages/eventlet/hubs/poll.py", line 84, in wait
        presult = self.do_poll(seconds)
    File "/usr/local/lib/python2.6/site-packages/eventlet/hubs/epolls.py", line 55, in do_poll
        return self.poll.poll(seconds)
    File "/usr/local/lib/python2.6/site-packages/spawning/spawning_controller.py", line 212, in handle_deadlychild
        self.spawn_children(number=1)
    File "/usr/local/lib/python2.6/site-packages/spawning/spawning_controller.py", line 121, in spawn_children
        self.log.debug('Controller.spawn_children(number=%d)' % number)
    File "/usr/local/lib/python2.6/logging/__init__.py", line 1044, in debug
        self._log(DEBUG, msg, args, **kwargs)
    File "/usr/local/lib/python2.6/logging/__init__.py", line 1173, in _log
        self.handle(record)
    File "/usr/local/lib/python2.6/logging/__init__.py", line 1183, in handle
        self.callHandlers(record)
    File "/usr/local/lib/python2.6/logging/__init__.py", line 1220, in callHandlers
        hdlr.handle(record)
    File "/usr/local/lib/python2.6/logging/__init__.py", line 681, in handle
        self.release()
    File "/usr/local/lib/python2.6/logging/__init__.py", line 635, in release
        self.lock.release()
    File "/usr/local/lib/python2.6/threading.py", line 142, in release
        self.__block.release()
    File "/usr/local/lib/python2.6/site-packages/eventlet/semaphore.py", line 80, in release
        def release(self, blocking=True):
    File "/usr/local/lib/python2.6/site-packages/spawning/spawning_controller.py", line 211, in handle_deadlychild
        self.log.debug('A child intends to die, starting replacement before it dies')
    File "/usr/local/lib/python2.6/logging/__init__.py", line 1044, in debug
        self._log(DEBUG, msg, args, **kwargs)
    File "/usr/local/lib/python2.6/logging/__init__.py", line 1173, in _log
        self.handle(record)
    File "/usr/local/lib/python2.6/logging/__init__.py", line 1183, in handle
        self.callHandlers(record)
    File "/usr/local/lib/python2.6/logging/__init__.py", line 1220, in callHandlers
        hdlr.handle(record)
    File "/usr/local/lib/python2.6/logging/__init__.py", line 677, in handle
        self.acquire()
    File "/usr/local/lib/python2.6/logging/__init__.py", line 628, in acquire
        self.lock.acquire()
    File "/usr/local/lib/python2.6/threading.py", line 123, in acquire
        rc = self.__block.acquire(blocking)
    File "/usr/local/lib/python2.6/site-packages/eventlet/semaphore.py", line 71, in acquire
        hubs.get_hub().switch()
    File "/usr/local/lib/python2.6/site-packages/eventlet/hubs/hub.py", line 162, in switch
        assert cur is not self.greenlet, 'Cannot switch to MAINLOOP from MAINLOOP'
    AssertionError: Cannot switch to MAINLOOP from MAINLOOP

Change-Id: I18a63313279963ba51a18ee221137660be473c8f

src/spawning/spawning_controller.py

@@ -22,6 +22,9 @@
 # THE SOFTWARE.
 from __future__ import with_statement
 
+import eventlet
+eventlet.monkey_patch()
+
 import commands
 import datetime
 import errno
@@ -40,7 +43,6 @@
     import json
 
 
-import eventlet
 import eventlet.backdoor
 from eventlet.green import os