I have an application that uses both grequests
and multiprocessing.managers
for a combination of IPC communication and Asynchronous RESTful communications over HTTP.
It seems that grequests
, in using gevent.monkey
's patch_all()
method, breaks the multiprocessing.connection
module used by the multiprocessing.manager.SyncManager
class and its derivatives.
This is apparently not an isolated issue, but affects any use case that implements multiprocessing.connetion
, such as multiprocessing.pool
, for example.
Drilling down into the code in gevent/monkey.py
, I found that the swapping of the stdlib socket
module with gevent.socket
is what causes the breakage.
This can be found at line 115 in gevent/monkey.py
under the patch_socket()
function:
def patch_socket(dns=True, aggressive=True):
"""Replace the standard socket object with gevent's cooperative sockets.
...
_socket.socket = socket.socket # This line breaks multiprocessing.connection!
...
My question is then why does this swappage break multiprocessing.connection
, and what advantages are derived from using gevent.socket
instead of the stdlib's socket
module? That is, what performance loss, if any, will I incur from not patching the socket
module?
Traceback
Traceback (most recent call last):
File "clientWithGeventMonkeyPatch.py", line 49, in <module>
client = GetClient(host, port, authkey)
File "clientWithGeventMonkeyPatch.py", line 39, in GetClient
client.connect()
File "/usr/lib/python2.7/multiprocessing/managers.py", line 500, in connect
conn = Client(self._address, authkey=self._authkey)
File "/usr/lib/python2.7/multiprocessing/connection.py", line 175, in Client
answer_challenge(c, authkey)
File "/usr/lib/python2.7/multiprocessing/connection.py", line 414, in answer_challenge
response = connection.recv_bytes(256) # reject large message
IOError: [Errno 11] Resource temporarily unavailable
code to reproduce the error
(on ubuntu server 11.10, python2.7.3, with gevent, greenlet, and grequests installed)
manager.py
## manager.py
import multiprocessing
import multiprocessing.managers
import datetime
class LocalManager(multiprocessing.managers.SyncManager):
def __init__(self, *args, **kwargs):
multiprocessing.managers.SyncManager.__init__(self, *args, **kwargs)
self.__type__ = 'LocalManager'
def GetManager(host, port, authkey):
def getdatetime():
return '{}'.format(datetime.datetime.now())
LocalManager.register('getdatetime', callable = getdatetime)
manager = LocalManager(address = (host, port), authkey = authkey)
manager.start()
return manager
if __name__ == '__main__':
# define our manager connection parameters
port = 55555
host = 'localhost'
authkey = 'auth1234'
# start a manager
man = GetManager(host, port, authkey)
# wait for user input to shut down
raw_input('return to shutdown')
man.shutdown()
client.py
## client.py -- this one works
import time
import multiprocessing.managers
class RemoteClient(multiprocessing.managers.SyncManager):
def __init__(self, *args, **kwargs):
multiprocessing.managers.SyncManager.__init__(self, *args, **kwargs)
self.__type__ = 'RemoteClient'
def GetClient(host, port, authkey):
RemoteClient.register('getdatetime')
client = RemoteClient(address = (host, port), authkey = authkey)
client.connect()
return client
if __name__ == '__main__':
# define our client connection parameters
port = 55555
host = 'localhost'
authkey = 'auth1234'
# start a manager
client = GetClient(host, port, authkey)
print 'connected', client
print 'client.getdatetime()', client.getdatetime()
# wait a couple of seconds, then do it again
time.sleep(2)
print 'client.getdatetime()', client.getdatetime()
# exit...
clientWithGeventMonkeyPatch.py
## clientWithGeventMonkeyPatch.py -- breaks, depending on patch_all() parameters
import time
import multiprocessing.managers
# this part is copied from grequests
# bear in mind that it doesn't actually do anything in this module.
try:
import gevent
from gevent import monkey as curious_george
from gevent.pool import Pool
except ImportError:
raise RuntimeError('Gevent is required for grequests.')
# this line causes breakage of the multiprocessing.manager connection auth method:
# Monkey-patch.
# patch_all() parameters with default values: socket=True, dns=True, time=True, select=True, thread=True, os=True, ssl=True, aggressive=True
curious_george.patch_all(thread=False, select=False) # breaks
#~ curious_george.patch_all(thread=False, select=False, socket = False) # works!
#~ curious_george.patch_all(thread=False, select=False, socket = True, aggressive = True, dns = True) # same as (thread=False, select=False); breaks
#~ curious_george.patch_all(thread=False, select=False, socket = True, aggressive = True, dns = False) # breaks
#~ curious_george.patch_all(thread=False, select=False, socket = True, aggressive = False, dns = True) # breaks
#~ curious_george.patch_all(thread=False, select=False, socket = True, aggressive = False, dns = False) # breaks
class RemoteClient(multiprocessing.managers.SyncManager):
def __init__(self, *args, **kwargs):
multiprocessing.managers.SyncManager.__init__(self, *args, **kwargs)
self.__type__ = 'RemoteClient'
def GetClient(host, port, authkey):
RemoteClient.register('getdatetime')
client = RemoteClient(address = (host, port), authkey = authkey)
client.connect()
return client
if __name__ == '__main__':
# define our client connection parameters
port = 55555
host = 'localhost'
authkey = 'auth1234'
# start a manager
client = GetClient(host, port, authkey)
print 'connected', client
print 'client.getdatetime()', client.getdatetime()
# wait a couple of seconds, then do it again
time.sleep(2)
print 'client.getdatetime()', client.getdatetime()
# exit...