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#
# Module providing the `Process` class which emulates `threading.Thread`
#
# multiprocessing/process.py
#
# Copyright (c) 2006-2008, R Oudkerk
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution.
# 3. Neither the name of author nor the names of any contributors may be
# used to endorse or promote products derived from this software
# without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
#
from __future__ import absolute_import
__all__ = ['Process', 'current_process', 'active_children']
#
# Imports
#
import os
import sys
import signal
import itertools
import binascii
from .compat import bytes
try:
from _weakrefset import WeakSet
except ImportError:
WeakSet = None # noqa
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(_current_process._children)
def _cleanup():
# check for processes which have finished
for p in list(_current_process._children):
if p._popen.poll() is not None:
_current_process._children.discard(p)
class Process(object):
'''
Process objects represent activity that is run in a separate process
The class is analagous to `threading.Thread`
'''
_Popen = None
def __init__(self, group=None, target=None, name=None, args=(), kwargs={},
daemon=None, **_kw):
assert group is None, 'group argument must be None for now'
count = _current_process._counter.next()
self._identity = _current_process._identity + (count,)
self._authkey = _current_process._authkey
if daemon is not None:
self._daemonic = daemon
else:
self._daemonic = _current_process._daemonic
self._tempdir = _current_process._tempdir
self._semprefix = _current_process._semprefix
self._unlinkfd = _current_process._unlinkfd
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 _dangling is not None:
_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._daemonic, \
'daemonic processes are not allowed to have children'
_cleanup()
if self._Popen is not None:
Popen = self._Popen
else:
from .forking import Popen
self._popen = Popen(self)
self._sentinel = self._popen.sentinel
_current_process._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:
_current_process._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
self._popen.poll()
return self._popen.returncode is None
def _get_name(self):
return self._name
def _set_name(self, value):
assert isinstance(name, basestring), 'name must be a string'
self._name = value
name = property(_get_name, _set_name)
def _get_daemon(self):
return self._daemonic
def _set_daemon(self, daemonic):
assert self._popen is None, 'process has already started'
self._daemonic = daemonic
daemon = property(_get_daemon, _set_daemon)
def _get_authkey(self):
return self._authkey
def _set_authkey(self, authkey):
self._authkey = AuthenticationString(authkey)
authkey = property(_get_authkey, _set_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._daemonic and ' daemon' or '')
##
def _bootstrap(self):
from . import util
global _current_process
try:
self._children = set()
self._counter = itertools.count(1)
if sys.stdin is not None:
try:
sys.stdin.close()
sys.stdin = open(os.devnull)
except (OSError, ValueError):
pass
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, e:
if not e.args:
exitcode = 1
elif type(e.args[0]) is int:
exitcode = e.args[0]
else:
sys.stderr.write(e.args[0] + '\n')
exitcode = 1
except:
exitcode = 1
if not util.error('Process %s', self.name, exc_info=True):
import traceback
sys.stderr.write('Process %s:\n' % self.name)
traceback.print_exc()
finally:
util.info('process exiting with exitcode %d', exitcode)
sys.stdout.flush()
sys.stderr.flush()
return exitcode
#
# We subclass bytes to avoid accidental transmission of auth keys over network
#
class AuthenticationString(bytes):
def __reduce__(self):
from .forking import Popen
if not Popen.thread_is_spawning():
raise TypeError(
'Pickling an AuthenticationString object is '
'disallowed for security reasons')
return AuthenticationString, (bytes(self),)
#
# Create object representing the main process
#
class _MainProcess(Process):
def __init__(self):
self._identity = ()
self._daemonic = False
self._name = 'MainProcess'
self._parent_pid = None
self._popen = None
self._counter = itertools.count(1)
self._children = set()
self._authkey = AuthenticationString(os.urandom(32))
self._tempdir = None
self._semprefix = 'mp-' + binascii.hexlify(
os.urandom(4)).decode('ascii')
self._unlinkfd = None
_current_process = _MainProcess()
del _MainProcess
#
# Give names to some return codes
#
_exitcode_to_name = {}
for name, signum in signal.__dict__.items():
if name[:3] == 'SIG' and '_' not in name:
_exitcode_to_name[-signum] = name
_dangling = WeakSet() if WeakSet is not None else None
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