#
# Module providing the `Process` class which emulates `threading.Thread`
#
# multiprocessing/process.py
#
# Copyright (c) 2006-2008, R Oudkerk
# Licensed to PSF under a Contributor Agreement.
#
__all__ = ['BaseProcess', 'current_process', 'active_children']
#
# Imports
#
import os
import sys
import signal
import itertools
from _weakrefset import WeakSet
#
#
#
try:
ORIGINAL_DIR = os.path.abspath(os.getcwd())
except OSError:
ORIGINAL_DIR = None
#
# Public functions
#
def current_process():
'''
Return process object representing the current process
'''
return _current_process
def active_children():
'''
Return list of process objects corresponding to live child processes
'''
_cleanup()
return list(_children)
#
#
#
def _cleanup():
# check for processes which have finished
for p in list(_children):
if p._popen.poll() is not None:
_children.discard(p)
#
# The `Process` class
#
class BaseProcess(object):
'''
Process objects represent activity that is run in a separate process
The class is analogous to `threading.Thread`
'''
def _Popen(self):
raise NotImplementedError
def __init__(self, group=None, target=None, name=None, args=(), kwargs={},
*, daemon=None):
assert group is None, 'group argument must be None for now'
count = next(_process_counter)
self._identity = _current_process._identity + (count,)
self._config = _current_process._config.copy()
self._parent_pid = os.getpid()
self._popen = None
self._target = target
self._args = tuple(args)
self._kwargs = dict(kwargs)
self._name = name or type(self).__name__ + '-' + \
':'.join(str(i) for i in self._identity)
if daemon is not None:
self.daemon = daemon
_dangling.add(self)
def run(self):
'''
Method to be run in sub-process; can be overridden in sub-class
'''
if self._target:
self._target(*self._args, **self._kwargs)
def start(self):
'''
Start child process
'''
assert self._popen is None, 'cannot start a process twice'
assert self._parent_pid == os.getpid(), \
'can only start a process object created by current process'
assert not _current_process._config.get('daemon'), \
'daemonic processes are not allowed to have children'
_cleanup()
self._popen = self._Popen(self)
self._sentinel = self._popen.sentinel
# Avoid a refcycle if the target function holds an indirect
# reference to the process object (see bpo-30775)
del self._target, self._args, self._kwargs
_children.add(self)
def terminate(self):
'''
Terminate process; sends SIGTERM signal or uses TerminateProcess()
'''
self._popen.terminate()
def join(self, timeout=None):
'''
Wait until child process terminates
'''
assert self._parent_pid == os.getpid(), 'can only join a child process'
assert self._popen is not None, 'can only join a started process'
res = self._popen.wait(timeout)
if res is not None:
_children.discard(self)
def is_alive(self):
'''
Return whether process is alive
'''
if self is _current_process:
return True
assert self._parent_pid == os.getpid(), 'can only test a child process'
if self._popen is None:
return False
returncode = self._popen.poll()
if returncode is None:
return True
else:
_children.discard(self)
return False
@property
def name(self):
return self._name
@name.setter
def name(self, name):
assert isinstance(name, str), 'name must be a string'
self._name = name
@property
def daemon(self):
'''
Return whether process is a daemon
'''
return self._config.get('daemon', False)
@daemon.setter
def daemon(self, daemonic):
'''
Set whether process is a daemon
'''
assert self._popen is None, 'process has already started'
self._config['daemon'] = daemonic
@property
def authkey(self):
return self._config['authkey']
@authkey.setter
def authkey(self, authkey):
'''
Set authorization key of process
'''
self._config['authkey'] = AuthenticationString(authkey)
@property
def exitcode(self):
'''
Return exit code of process or `None` if it has yet to stop
'''
if self._popen is None:
return self._popen
return self._popen.poll()
@property
def ident(self):
'''
Return identifier (PID) of process or `None` if it has yet to start
'''
if self is _current_process:
return os.getpid()
else:
return self._popen and self._popen.pid
pid = ident
@property
def sentinel(self):
'''
Return a file descriptor (Unix) or handle (Windows) suitable for
waiting for process termination.
'''
try:
return self._sentinel
except AttributeError:
raise ValueError("process not started")
def __repr__(self):
if self is _current_process:
status = 'started'
elif self._parent_pid != os.getpid():
status = 'unknown'
elif self._popen is None:
status = 'initial'
else:
if self._popen.poll() is not None:
status = self.exitcode
else:
status = 'started'
if type(status) is int:
if status == 0:
status = 'stopped'
else:
status = 'stopped[%s]' % _exitcode_to_name.get(status, status)
return '<%s(%s, %s%s)>' % (type(self).__name__, self._name,
status, self.daemon and ' daemon' or '')
##
def _bootstrap(self):
from . import util, context
global _current_process, _process_counter, _children
try:
if self._start_method is not None:
context._force_start_method(self._start_method)
_process_counter = itertools.count(1)
_children = set()
util._close_stdin()
old_process = _current_process
_current_process = self
try:
util._finalizer_registry.clear()
util._run_after_forkers()
finally:
# delay finalization of the old process object until after
# _run_after_forkers() is executed
del old_process
util.info('child process calling self.run()')
try:
self.run()
exitcode = 0
finally:
util._exit_function()
except SystemExit as e:
if not e.args:
exitcode = 1
elif isinstance(e.args[0], int):
exitcode = e.args[0]
else:
sys.stderr.write(str(e.args[0]) + '\n')
exitcode = 1
except:
exitcode = 1
import traceback
sys.stderr.write('Process %s:\n' % self.name)
traceback.print_exc()
finally:
util.info('process exiting with exitcode %d' % exitcode)
util._flush_std_streams()
return exitcode
#
# We subclass bytes to avoid accidental transmission of auth keys over network
#
class AuthenticationString(bytes):
def __reduce__(self):
from .context import get_spawning_popen
if get_spawning_popen() is None:
raise TypeError(
'Pickling an AuthenticationString object is '
'disallowed for security reasons'
)
return AuthenticationString, (bytes(self),)
#
# Create object representing the main process
#
class _MainProcess(BaseProcess):
def __init__(self):
self._identity = ()
self._name = 'MainProcess'
self._parent_pid = None
self._popen = None
self._config = {'authkey': AuthenticationString(os.urandom(32)),
'semprefix': '/mp'}
# Note that some versions of FreeBSD only allow named
# semaphores to have names of up to 14 characters. Therefore
# we choose a short prefix.
#
# On MacOSX in a sandbox it may be necessary to use a
# different prefix -- see #19478.
#
# Everything in self._config will be inherited by descendant
# processes.
_current_process = _MainProcess()
_process_counter = itertools.count(1)
_children = set()
del _MainProcess
#
# Give names to some return codes
#
_exitcode_to_name = {}
for name, signum in list(signal.__dict__.items()):
if name[:3]=='SIG' and '_' not in name:
_exitcode_to_name[-signum] = name
# For debug and leak testing
_dangling = WeakSet()