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      1 #
      2 # Module providing the `Process` class which emulates `threading.Thread`
      3 #
      4 # multiprocessing/process.py
      5 #
      6 # Copyright (c) 2006-2008, R Oudkerk
      7 # All rights reserved.
      8 #
      9 # Redistribution and use in source and binary forms, with or without
     10 # modification, are permitted provided that the following conditions
     11 # are met:
     12 #
     13 # 1. Redistributions of source code must retain the above copyright
     14 #    notice, this list of conditions and the following disclaimer.
     15 # 2. Redistributions in binary form must reproduce the above copyright
     16 #    notice, this list of conditions and the following disclaimer in the
     17 #    documentation and/or other materials provided with the distribution.
     18 # 3. Neither the name of author nor the names of any contributors may be
     19 #    used to endorse or promote products derived from this software
     20 #    without specific prior written permission.
     21 #
     22 # THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
     23 # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     24 # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     25 # ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     26 # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     27 # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     28 # OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     29 # HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     30 # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     31 # OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     32 # SUCH DAMAGE.
     33 #
     34 
     35 __all__ = ['Process', 'current_process', 'active_children']
     36 
     37 #
     38 # Imports
     39 #
     40 
     41 import os
     42 import sys
     43 import signal
     44 import itertools
     45 
     46 #
     47 #
     48 #
     49 
     50 try:
     51     ORIGINAL_DIR = os.path.abspath(os.getcwd())
     52 except OSError:
     53     ORIGINAL_DIR = None
     54 
     55 #
     56 # Public functions
     57 #
     58 
     59 def current_process():
     60     '''
     61     Return process object representing the current process
     62     '''
     63     return _current_process
     64 
     65 def active_children():
     66     '''
     67     Return list of process objects corresponding to live child processes
     68     '''
     69     _cleanup()
     70     return list(_current_process._children)
     71 
     72 #
     73 #
     74 #
     75 
     76 def _cleanup():
     77     # check for processes which have finished
     78     for p in list(_current_process._children):
     79         if p._popen.poll() is not None:
     80             _current_process._children.discard(p)
     81 
     82 #
     83 # The `Process` class
     84 #
     85 
     86 class Process(object):
     87     '''
     88     Process objects represent activity that is run in a separate process
     89 
     90     The class is analagous to `threading.Thread`
     91     '''
     92     _Popen = None
     93 
     94     def __init__(self, group=None, target=None, name=None, args=(), kwargs={}):
     95         assert group is None, 'group argument must be None for now'
     96         count = _current_process._counter.next()
     97         self._identity = _current_process._identity + (count,)
     98         self._authkey = _current_process._authkey
     99         self._daemonic = _current_process._daemonic
    100         self._tempdir = _current_process._tempdir
    101         self._parent_pid = os.getpid()
    102         self._popen = None
    103         self._target = target
    104         self._args = tuple(args)
    105         self._kwargs = dict(kwargs)
    106         self._name = name or type(self).__name__ + '-' + \
    107                      ':'.join(str(i) for i in self._identity)
    108 
    109     def run(self):
    110         '''
    111         Method to be run in sub-process; can be overridden in sub-class
    112         '''
    113         if self._target:
    114             self._target(*self._args, **self._kwargs)
    115 
    116     def start(self):
    117         '''
    118         Start child process
    119         '''
    120         assert self._popen is None, 'cannot start a process twice'
    121         assert self._parent_pid == os.getpid(), \
    122                'can only start a process object created by current process'
    123         assert not _current_process._daemonic, \
    124                'daemonic processes are not allowed to have children'
    125         _cleanup()
    126         if self._Popen is not None:
    127             Popen = self._Popen
    128         else:
    129             from .forking import Popen
    130         self._popen = Popen(self)
    131         _current_process._children.add(self)
    132 
    133     def terminate(self):
    134         '''
    135         Terminate process; sends SIGTERM signal or uses TerminateProcess()
    136         '''
    137         self._popen.terminate()
    138 
    139     def join(self, timeout=None):
    140         '''
    141         Wait until child process terminates
    142         '''
    143         assert self._parent_pid == os.getpid(), 'can only join a child process'
    144         assert self._popen is not None, 'can only join a started process'
    145         res = self._popen.wait(timeout)
    146         if res is not None:
    147             _current_process._children.discard(self)
    148 
    149     def is_alive(self):
    150         '''
    151         Return whether process is alive
    152         '''
    153         if self is _current_process:
    154             return True
    155         assert self._parent_pid == os.getpid(), 'can only test a child process'
    156         if self._popen is None:
    157             return False
    158         self._popen.poll()
    159         return self._popen.returncode is None
    160 
    161     @property
    162     def name(self):
    163         return self._name
    164 
    165     @name.setter
    166     def name(self, name):
    167         assert isinstance(name, basestring), 'name must be a string'
    168         self._name = name
    169 
    170     @property
    171     def daemon(self):
    172         '''
    173         Return whether process is a daemon
    174         '''
    175         return self._daemonic
    176 
    177     @daemon.setter
    178     def daemon(self, daemonic):
    179         '''
    180         Set whether process is a daemon
    181         '''
    182         assert self._popen is None, 'process has already started'
    183         self._daemonic = daemonic
    184 
    185     @property
    186     def authkey(self):
    187         return self._authkey
    188 
    189     @authkey.setter
    190     def authkey(self, authkey):
    191         '''
    192         Set authorization key of process
    193         '''
    194         self._authkey = AuthenticationString(authkey)
    195 
    196     @property
    197     def exitcode(self):
    198         '''
    199         Return exit code of process or `None` if it has yet to stop
    200         '''
    201         if self._popen is None:
    202             return self._popen
    203         return self._popen.poll()
    204 
    205     @property
    206     def ident(self):
    207         '''
    208         Return identifier (PID) of process or `None` if it has yet to start
    209         '''
    210         if self is _current_process:
    211             return os.getpid()
    212         else:
    213             return self._popen and self._popen.pid
    214 
    215     pid = ident
    216 
    217     def __repr__(self):
    218         if self is _current_process:
    219             status = 'started'
    220         elif self._parent_pid != os.getpid():
    221             status = 'unknown'
    222         elif self._popen is None:
    223             status = 'initial'
    224         else:
    225             if self._popen.poll() is not None:
    226                 status = self.exitcode
    227             else:
    228                 status = 'started'
    229 
    230         if type(status) is int:
    231             if status == 0:
    232                 status = 'stopped'
    233             else:
    234                 status = 'stopped[%s]' % _exitcode_to_name.get(status, status)
    235 
    236         return '<%s(%s, %s%s)>' % (type(self).__name__, self._name,
    237                                    status, self._daemonic and ' daemon' or '')
    238 
    239     ##
    240 
    241     def _bootstrap(self):
    242         from . import util
    243         global _current_process
    244 
    245         try:
    246             self._children = set()
    247             self._counter = itertools.count(1)
    248             try:
    249                 sys.stdin.close()
    250                 sys.stdin = open(os.devnull)
    251             except (OSError, ValueError):
    252                 pass
    253             _current_process = self
    254             util._finalizer_registry.clear()
    255             util._run_after_forkers()
    256             util.info('child process calling self.run()')
    257             try:
    258                 self.run()
    259                 exitcode = 0
    260             finally:
    261                 util._exit_function()
    262         except SystemExit, e:
    263             if not e.args:
    264                 exitcode = 1
    265             elif isinstance(e.args[0], int):
    266                 exitcode = e.args[0]
    267             else:
    268                 sys.stderr.write(str(e.args[0]) + '\n')
    269                 sys.stderr.flush()
    270                 exitcode = 0 if isinstance(e.args[0], str) else 1
    271         except:
    272             exitcode = 1
    273             import traceback
    274             sys.stderr.write('Process %s:\n' % self.name)
    275             sys.stderr.flush()
    276             traceback.print_exc()
    277 
    278         util.info('process exiting with exitcode %d' % exitcode)
    279         return exitcode
    280 
    281 #
    282 # We subclass bytes to avoid accidental transmission of auth keys over network
    283 #
    284 
    285 class AuthenticationString(bytes):
    286     def __reduce__(self):
    287         from .forking import Popen
    288         if not Popen.thread_is_spawning():
    289             raise TypeError(
    290                 'Pickling an AuthenticationString object is '
    291                 'disallowed for security reasons'
    292                 )
    293         return AuthenticationString, (bytes(self),)
    294 
    295 #
    296 # Create object representing the main process
    297 #
    298 
    299 class _MainProcess(Process):
    300 
    301     def __init__(self):
    302         self._identity = ()
    303         self._daemonic = False
    304         self._name = 'MainProcess'
    305         self._parent_pid = None
    306         self._popen = None
    307         self._counter = itertools.count(1)
    308         self._children = set()
    309         self._authkey = AuthenticationString(os.urandom(32))
    310         self._tempdir = None
    311 
    312 _current_process = _MainProcess()
    313 del _MainProcess
    314 
    315 #
    316 # Give names to some return codes
    317 #
    318 
    319 _exitcode_to_name = {}
    320 
    321 for name, signum in signal.__dict__.items():
    322     if name[:3]=='SIG' and '_' not in name:
    323         _exitcode_to_name[-signum] = name
    324