Source code for multiprocessing.context

import os
import sys
import threading

from . import process
from . import reduction

__all__ = []            # things are copied from here to

# Exceptions

class ProcessError(Exception):

[docs]class BufferTooShort(ProcessError): pass
class TimeoutError(ProcessError): pass
[docs]class AuthenticationError(ProcessError): pass
# # Base type for contexts # class BaseContext(object): ProcessError = ProcessError BufferTooShort = BufferTooShort TimeoutError = TimeoutError AuthenticationError = AuthenticationError current_process = staticmethod(process.current_process) active_children = staticmethod(process.active_children) def cpu_count(self): '''Returns the number of CPUs in the system''' num = os.cpu_count() if num is None: raise NotImplementedError('cannot determine number of cpus') else: return num def Manager(self): '''Returns a manager associated with a running server process The managers methods such as `Lock()`, `Condition()` and `Queue()` can be used to create shared objects. ''' from .managers import SyncManager m = SyncManager(ctx=self.get_context()) m.start() return m def Pipe(self, duplex=True): '''Returns two connection object connected by a pipe''' from .connection import Pipe return Pipe(duplex) def Lock(self): '''Returns a non-recursive lock object''' from .synchronize import Lock return Lock(ctx=self.get_context()) def RLock(self): '''Returns a recursive lock object''' from .synchronize import RLock return RLock(ctx=self.get_context()) def Condition(self, lock=None): '''Returns a condition object''' from .synchronize import Condition return Condition(lock, ctx=self.get_context()) def Semaphore(self, value=1): '''Returns a semaphore object''' from .synchronize import Semaphore return Semaphore(value, ctx=self.get_context()) def BoundedSemaphore(self, value=1): '''Returns a bounded semaphore object''' from .synchronize import BoundedSemaphore return BoundedSemaphore(value, ctx=self.get_context()) def Event(self): '''Returns an event object''' from .synchronize import Event return Event(ctx=self.get_context()) def Barrier(self, parties, action=None, timeout=None): '''Returns a barrier object''' from .synchronize import Barrier return Barrier(parties, action, timeout, ctx=self.get_context()) def Queue(self, maxsize=0): '''Returns a queue object''' from .queues import Queue return Queue(maxsize, ctx=self.get_context()) def JoinableQueue(self, maxsize=0): '''Returns a queue object''' from .queues import JoinableQueue return JoinableQueue(maxsize, ctx=self.get_context()) def SimpleQueue(self): '''Returns a queue object''' from .queues import SimpleQueue return SimpleQueue(ctx=self.get_context()) def Pool(self, processes=None, initializer=None, initargs=(), maxtasksperchild=None): '''Returns a process pool object''' from .pool import Pool return Pool(processes, initializer, initargs, maxtasksperchild, context=self.get_context()) def RawValue(self, typecode_or_type, *args): '''Returns a shared object''' from .sharedctypes import RawValue return RawValue(typecode_or_type, *args) def RawArray(self, typecode_or_type, size_or_initializer): '''Returns a shared array''' from .sharedctypes import RawArray return RawArray(typecode_or_type, size_or_initializer) def Value(self, typecode_or_type, *args, lock=True): '''Returns a synchronized shared object''' from .sharedctypes import Value return Value(typecode_or_type, *args, lock=lock, ctx=self.get_context()) def Array(self, typecode_or_type, size_or_initializer, *, lock=True): '''Returns a synchronized shared array''' from .sharedctypes import Array return Array(typecode_or_type, size_or_initializer, lock=lock, ctx=self.get_context()) def freeze_support(self): '''Check whether this is a fake forked process in a frozen executable. If so then run code specified by commandline and exit. ''' if sys.platform == 'win32' and getattr(sys, 'frozen', False): from .spawn import freeze_support freeze_support() def get_logger(self): '''Return package logger -- if it does not already exist then it is created. ''' from .util import get_logger return get_logger() def log_to_stderr(self, level=None): '''Turn on logging and add a handler which prints to stderr''' from .util import log_to_stderr return log_to_stderr(level) def allow_connection_pickling(self): '''Install support for sending connections and sockets between processes ''' # This is undocumented. In previous versions of multiprocessing # its only effect was to make socket objects inheritable on Windows. from . import connection def set_executable(self, executable): '''Sets the path to a python.exe or pythonw.exe binary used to run child processes instead of sys.executable when using the 'spawn' start method. Useful for people embedding Python. ''' from .spawn import set_executable set_executable(executable) def set_forkserver_preload(self, module_names): '''Set list of module names to try to load in forkserver process. This is really just a hint. ''' from .forkserver import set_forkserver_preload set_forkserver_preload(module_names) def get_context(self, method=None): if method is None: return self try: ctx = _concrete_contexts[method] except KeyError: raise ValueError('cannot find context for %r' % method) ctx._check_available() return ctx def get_start_method(self, allow_none=False): return self._name def set_start_method(self, method=None): raise ValueError('cannot set start method of concrete context') @property def reducer(self): '''Controls how objects will be reduced to a form that can be shared with other processes.''' return globals().get('reduction') @reducer.setter def reducer(self, reduction): globals()['reduction'] = reduction def _check_available(self): pass # # Type of default context -- underlying context can be set at most once #
[docs]class Process(process.BaseProcess): _start_method = None @staticmethod def _Popen(process_obj): return _default_context.get_context().Process._Popen(process_obj)
class DefaultContext(BaseContext): Process = Process def __init__(self, context): self._default_context = context self._actual_context = None def get_context(self, method=None): if method is None: if self._actual_context is None: self._actual_context = self._default_context return self._actual_context else: return super().get_context(method) def set_start_method(self, method, force=False): if self._actual_context is not None and not force: raise RuntimeError('context has already been set') if method is None and force: self._actual_context = None return self._actual_context = self.get_context(method) def get_start_method(self, allow_none=False): if self._actual_context is None: if allow_none: return None self._actual_context = self._default_context return self._actual_context._name def get_all_start_methods(self): if sys.platform == 'win32': return ['spawn'] else: if reduction.HAVE_SEND_HANDLE: return ['fork', 'spawn', 'forkserver'] else: return ['fork', 'spawn'] DefaultContext.__all__ = list(x for x in dir(DefaultContext) if x[0] != '_') # # Context types for fixed start method # if sys.platform != 'win32': class ForkProcess(process.BaseProcess): _start_method = 'fork' @staticmethod def _Popen(process_obj): from .popen_fork import Popen return Popen(process_obj) class SpawnProcess(process.BaseProcess): _start_method = 'spawn' @staticmethod def _Popen(process_obj): from .popen_spawn_posix import Popen return Popen(process_obj) class ForkServerProcess(process.BaseProcess): _start_method = 'forkserver' @staticmethod def _Popen(process_obj): from .popen_forkserver import Popen return Popen(process_obj) class ForkContext(BaseContext): _name = 'fork' Process = ForkProcess class SpawnContext(BaseContext): _name = 'spawn' Process = SpawnProcess class ForkServerContext(BaseContext): _name = 'forkserver' Process = ForkServerProcess def _check_available(self): if not reduction.HAVE_SEND_HANDLE: raise ValueError('forkserver start method not available') _concrete_contexts = { 'fork': ForkContext(), 'spawn': SpawnContext(), 'forkserver': ForkServerContext(), } _default_context = DefaultContext(_concrete_contexts['fork']) else: class SpawnProcess(process.BaseProcess): _start_method = 'spawn' @staticmethod def _Popen(process_obj): from .popen_spawn_win32 import Popen return Popen(process_obj) class SpawnContext(BaseContext): _name = 'spawn' Process = SpawnProcess _concrete_contexts = { 'spawn': SpawnContext(), } _default_context = DefaultContext(_concrete_contexts['spawn']) # # Force the start method # def _force_start_method(method): _default_context._actual_context = _concrete_contexts[method] # # Check that the current thread is spawning a child process # _tls = threading.local() def get_spawning_popen(): return getattr(_tls, 'spawning_popen', None) def set_spawning_popen(popen): _tls.spawning_popen = popen def assert_spawning(obj): if get_spawning_popen() is None: raise RuntimeError( '%s objects should only be shared between processes' ' through inheritance' % type(obj).__name__ )