435 lines
12 KiB
Python
435 lines
12 KiB
Python
#
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# Module providing the `Process` class which emulates `threading.Thread`
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#
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# multiprocessing/process.py
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#
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# Copyright (c) 2006-2008, R Oudkerk
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# Licensed to PSF under a Contributor Agreement.
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#
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#
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# Imports
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#
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import os
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import sys
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import signal
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import itertools
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import logging
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import threading
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from _weakrefset import WeakSet
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from multiprocessing import process as _mproc
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try:
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ORIGINAL_DIR = os.path.abspath(os.getcwd())
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except OSError:
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ORIGINAL_DIR = None
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__all__ = ['BaseProcess', 'Process', 'current_process', 'active_children']
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#
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# Public functions
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#
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def current_process():
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'''
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Return process object representing the current process
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'''
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return _current_process
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def _set_current_process(process):
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global _current_process
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_current_process = _mproc._current_process = process
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def _cleanup():
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# check for processes which have finished
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for p in list(_children):
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if p._popen.poll() is not None:
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_children.discard(p)
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def _maybe_flush(f):
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try:
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f.flush()
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except (AttributeError, EnvironmentError, NotImplementedError):
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pass
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def active_children(_cleanup=_cleanup):
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'''
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Return list of process objects corresponding to live child processes
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'''
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try:
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_cleanup()
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except TypeError:
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# called after gc collect so _cleanup does not exist anymore
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return []
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return list(_children)
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class BaseProcess:
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'''
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Process objects represent activity that is run in a separate process
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The class is analogous to `threading.Thread`
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'''
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def _Popen(self):
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raise NotImplementedError()
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def __init__(self, group=None, target=None, name=None,
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args=(), kwargs={}, daemon=None, **_kw):
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assert group is None, 'group argument must be None for now'
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count = next(_process_counter)
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self._identity = _current_process._identity + (count, )
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self._config = _current_process._config.copy()
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self._parent_pid = os.getpid()
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self._popen = None
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self._closed = False
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self._target = target
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self._args = tuple(args)
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self._kwargs = dict(kwargs)
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self._name = (
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name or type(self).__name__ + '-' +
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':'.join(str(i) for i in self._identity)
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)
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if daemon is not None:
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self.daemon = daemon
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if _dangling is not None:
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_dangling.add(self)
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self._controlled_termination = False
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def _check_closed(self):
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if self._closed:
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raise ValueError("process object is closed")
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def run(self):
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'''
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Method to be run in sub-process; can be overridden in sub-class
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'''
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if self._target:
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self._target(*self._args, **self._kwargs)
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def start(self):
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'''
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Start child process
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'''
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self._check_closed()
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assert self._popen is None, 'cannot start a process twice'
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assert self._parent_pid == os.getpid(), \
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'can only start a process object created by current process'
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_cleanup()
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self._popen = self._Popen(self)
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self._sentinel = self._popen.sentinel
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_children.add(self)
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def close(self):
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'''
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Close the Process object and release the resources it holds.
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It is an error to call this method while the child is still running.
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Other methods and properties then raise ValueError.
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'''
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if self._popen is not None:
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# poll() also reports None when the child was already reaped by
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# someone else (ECHILD, e.g. a SIGCHLD handler calling
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# waitpid(-1)), so such a process can never be closed; this is
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# the same in multiprocessing.
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if self._popen.poll() is None:
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raise ValueError(
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"Cannot close a process while it is still running. "
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"You should first call join() or terminate().")
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self._popen.close()
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self._popen = None
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del self._sentinel
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_children.discard(self)
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self._closed = True
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def terminate(self):
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'''
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Terminate process; sends SIGTERM signal or uses TerminateProcess()
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'''
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self._check_closed()
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self._popen.terminate()
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def terminate_controlled(self):
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self._controlled_termination = True
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self.terminate()
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def join(self, timeout=None):
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'''
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Wait until child process terminates
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'''
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self._check_closed()
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assert self._parent_pid == os.getpid(), 'can only join a child process'
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assert self._popen is not None, 'can only join a started process'
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res = self._popen.wait(timeout)
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if res is not None:
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_children.discard(self)
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# only release the sentinel: callers still read exitcode after join
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self._popen.close()
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def is_alive(self):
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'''
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Return whether process is alive
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'''
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self._check_closed()
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if self is _current_process:
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return True
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assert self._parent_pid == os.getpid(), 'can only test a child process'
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if self._popen is None:
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return False
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self._popen.poll()
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return self._popen.returncode is None
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def _is_alive(self):
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if self._popen is None:
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return False
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return self._popen.poll() is None
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@property
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def name(self):
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return self._name
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@name.setter
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def name(self, name): # noqa
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assert isinstance(name, str), 'name must be a string'
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self._name = name
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@property
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def daemon(self):
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'''
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Return whether process is a daemon
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'''
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return self._config.get('daemon', False)
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@daemon.setter # noqa
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def daemon(self, daemonic):
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'''
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Set whether process is a daemon
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'''
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assert self._popen is None, 'process has already started'
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self._config['daemon'] = daemonic
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@property
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def authkey(self):
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return self._config['authkey']
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@authkey.setter # noqa
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def authkey(self, authkey):
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'''
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Set authorization key of process
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'''
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self._config['authkey'] = AuthenticationString(authkey)
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@property
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def exitcode(self):
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'''
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Return exit code of process or `None` if it has yet to stop
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'''
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self._check_closed()
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if self._popen is None:
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return self._popen
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return self._popen.poll()
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@property
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def ident(self):
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'''
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Return identifier (PID) of process or `None` if it has yet to start
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'''
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self._check_closed()
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if self is _current_process:
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return os.getpid()
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else:
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return self._popen and self._popen.pid
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pid = ident
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@property
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def sentinel(self):
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'''
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Return a file descriptor (Unix) or handle (Windows) suitable for
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waiting for process termination.
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'''
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self._check_closed()
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try:
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return self._sentinel
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except AttributeError:
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raise ValueError("process not started")
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@property
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def _counter(self):
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# compat for 2.7
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return _process_counter
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@property
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def _children(self):
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# compat for 2.7
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return _children
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@property
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def _authkey(self):
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# compat for 2.7
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return self.authkey
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@property
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def _daemonic(self):
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# compat for 2.7
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return self.daemon
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@property
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def _tempdir(self):
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# compat for 2.7
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return self._config.get('tempdir')
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def __repr__(self):
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if self is _current_process:
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status = 'started'
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elif self._closed:
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status = 'closed'
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elif self._parent_pid != os.getpid():
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status = 'unknown'
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elif self._popen is None:
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status = 'initial'
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else:
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if self._popen.poll() is not None:
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status = self.exitcode
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else:
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status = 'started'
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if type(status) is int:
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if status == 0:
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status = 'stopped'
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else:
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status = 'stopped[%s]' % _exitcode_to_name.get(status, status)
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return '<%s(%s, %s%s)>' % (type(self).__name__, self._name,
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status, self.daemon and ' daemon' or '')
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##
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def _bootstrap(self):
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from . import util, context
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global _current_process, _process_counter, _children
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try:
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if self._start_method is not None:
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context._force_start_method(self._start_method)
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_process_counter = itertools.count(1)
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_children = set()
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if sys.stdin is not None:
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try:
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sys.stdin.close()
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sys.stdin = open(os.devnull)
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except (EnvironmentError, OSError, ValueError):
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pass
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old_process = _current_process
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_set_current_process(self)
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# Re-init logging system.
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# Workaround for https://bugs.python.org/issue6721/#msg140215
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# Python logging module uses RLock() objects which are broken
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# after fork. This can result in a deadlock (Celery Issue #496).
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loggerDict = logging.Logger.manager.loggerDict
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logger_names = list(loggerDict.keys())
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logger_names.append(None) # for root logger
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for name in logger_names:
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if not name or not isinstance(loggerDict[name],
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logging.PlaceHolder):
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for handler in logging.getLogger(name).handlers:
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handler.createLock()
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logging._lock = threading.RLock()
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try:
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util._finalizer_registry.clear()
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util._run_after_forkers()
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finally:
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# delay finalization of the old process object until after
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# _run_after_forkers() is executed
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del old_process
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util.info('child process %s calling self.run()', self.pid)
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try:
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self.run()
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exitcode = 0
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finally:
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util._exit_function()
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except SystemExit as exc:
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if not exc.args:
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exitcode = 1
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elif isinstance(exc.args[0], int):
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exitcode = exc.args[0]
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else:
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sys.stderr.write(str(exc.args[0]) + '\n')
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_maybe_flush(sys.stderr)
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exitcode = 0 if isinstance(exc.args[0], str) else 1
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except:
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exitcode = 1
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if not util.error('Process %s', self.name, exc_info=True):
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import traceback
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sys.stderr.write('Process %s:\n' % self.name)
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traceback.print_exc()
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finally:
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util.info('process %s exiting with exitcode %d',
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self.pid, exitcode)
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_maybe_flush(sys.stdout)
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_maybe_flush(sys.stderr)
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return exitcode
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#
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# We subclass bytes to avoid accidental transmission of auth keys over network
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#
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class AuthenticationString(bytes):
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def __reduce__(self):
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from .context import get_spawning_popen
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if get_spawning_popen() is None:
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raise TypeError(
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'Pickling an AuthenticationString object is '
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'disallowed for security reasons')
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return AuthenticationString, (bytes(self),)
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#
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# Create object representing the main process
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#
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class _MainProcess(BaseProcess):
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def __init__(self):
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self._identity = ()
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self._name = 'MainProcess'
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self._parent_pid = None
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self._popen = None
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self._closed = False
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self._config = {'authkey': AuthenticationString(os.urandom(32)),
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'semprefix': '/mp'}
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_current_process = _MainProcess()
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_process_counter = itertools.count(1)
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_children = set()
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del _MainProcess
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Process = BaseProcess
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#
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# Give names to some return codes
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#
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_exitcode_to_name = {}
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for name, signum in signal.__dict__.items():
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if name[:3] == 'SIG' and '_' not in name:
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_exitcode_to_name[-signum] = name
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# For debug and leak testing
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_dangling = WeakSet()
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