python multiprocessing BaseManager registered class lost connection immediately after Ctrl-C

Question

I am experiencing some issues that I suspect is a limitation of my python program to handle correctly, my program is not been able to call methods of a registered class of BaseManager immediately after I hit Ctrl-C, even other process implemented as classes that inherit from multiprocessing.Process are affected. I have some methods that I would like to call from process that don't execute correctly after Ctrl-C.

For example the following code is not able to call the mt instance of TestClass after Ctrl-C.

from multiprocessing.managers import BaseManager, NamespaceProxy
import time

class TestClass(object):
    def __init__(self, a):
        self.a = a

    def b(self):
        print self.a

class MyManager(BaseManager): pass

class TestProxy(NamespaceProxy):
    # We need to expose the same __dunder__ methods as NamespaceProxy,
    # in addition to the b method.
    _exposed_ = ('__getattribute__', '__setattr__', '__delattr__', 'b')

    def b(self):
        callmethod = object.__getattribute__(self, '_callmethod')
        return callmethod('b')

MyManager.register('TestClass', TestClass, TestProxy)

if __name__ == '__main__':
    manager = MyManager()
    manager.start()
    t = TestClass(1)
    print t.a
    mt = manager.TestClass(2)
    print mt.a
    mt.a = 5
    mt.b()

    try:
        while 1:
            pass
    except (KeyboardInterrupt, SystemExit):
        time.sleep(0.1)
        mt.a = 7
        mt.b()
        print "bye"
        pass

Here is the console output

1
2
5
^CTraceback (most recent call last):
  File "testManager.py", line 38, in <module>
    mt.a = 7
  File "/usr/lib/python2.7/multiprocessing/managers.py", line 1028, in __setattr__
    return callmethod('__setattr__', (key, value))
  File "/usr/lib/python2.7/multiprocessing/managers.py", line 758, in _callmethod
    conn.send((self._id, methodname, args, kwds))
IOError: [Errno 32] Broken pipe

Do you have any suggestion? Is there any workaround or something wrong in my code?

Thanks in advance.

Answer 1

If someone happen to had this issue, I solved based on this answer https://stackoverflow.com/a/21106459/1667319 . Here is the working code

from multiprocessing.managers import SyncManager, NamespaceProxy
import time
import signal

#handle SIGINT from SyncManager object
def mgr_sig_handler(signal, frame):
    print 'not closing the mgr'

#initilizer for SyncManager
def mgr_init():
    signal.signal(signal.SIGINT, mgr_sig_handler)
    #signal.signal(signal.SIGINT, signal.SIG_IGN) # <- OR do this to just ignore the signal
    print 'initialized mananger'

class TestClass(object):
    def __init__(self, a):
        self.a = a

    def b(self):
        print self.a

class MyManager(SyncManager): pass

class TestProxy(NamespaceProxy):
    # We need to expose the same __dunder__ methods as NamespaceProxy,
    # in addition to the b method.
    _exposed_ = ('__getattribute__', '__setattr__', '__delattr__', 'b')

    def b(self):
        callmethod = object.__getattribute__(self, '_callmethod')
        return callmethod('b')

MyManager.register('TestClass', TestClass, TestProxy)

if __name__ == '__main__':
    manager = MyManager()
    manager.start(mgr_init)
    t = TestClass(1)
    print t.a
    mt = manager.TestClass(2)
    print mt.a
    mt.a = 5
    mt.b()
    try:
        while 1:
            pass
    except (KeyboardInterrupt, SystemExit):
        time.sleep(0.1)
        mt.a = 7
        mt.b()
        print "bye"
        pass

Cheers,

Answer 2

This is duplicate to question and I wrote there:

Simplest solution - start manager with

manager.start(signal.signal, (signal.SIGINT, signal.SIG_IGN))

instead of manager.start(). And check if signal module is in your imports (import signal).

This catch and ignore SIGINT (Ctrl-C) in manager process.