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Edit File: unix_events.py
"""Selector event loop for Unix with signal handling.""" import errno import os import signal import socket import stat import subprocess import sys import threading import warnings from . import base_events from . import base_subprocess from . import compat from . import constants from . import coroutines from . import events from . import futures from . import selector_events from . import selectors from . import transports from .coroutines import coroutine from .log import logger __all__ = ['SelectorEventLoop', 'AbstractChildWatcher', 'SafeChildWatcher', 'FastChildWatcher', 'DefaultEventLoopPolicy', ] if sys.platform == 'win32': # pragma: no cover raise ImportError('Signals are not really supported on Windows') def _sighandler_noop(signum, frame): """Dummy signal handler.""" pass try: _fspath = os.fspath except AttributeError: # Python 3.5 or earlier _fspath = lambda path: path class _UnixSelectorEventLoop(selector_events.BaseSelectorEventLoop): """Unix event loop. Adds signal handling and UNIX Domain Socket support to SelectorEventLoop. """ def __init__(self, selector=None): super().__init__(selector) self._signal_handlers = {} def _socketpair(self): return socket.socketpair() def close(self): super().close() for sig in list(self._signal_handlers): self.remove_signal_handler(sig) def _process_self_data(self, data): for signum in data: if not signum: # ignore null bytes written by _write_to_self() continue self._handle_signal(signum) def add_signal_handler(self, sig, callback, *args): """Add a handler for a signal. UNIX only. Raise ValueError if the signal number is invalid or uncatchable. Raise RuntimeError if there is a problem setting up the handler. """ if (coroutines.iscoroutine(callback) or coroutines.iscoroutinefunction(callback)): raise TypeError("coroutines cannot be used " "with add_signal_handler()") self._check_signal(sig) self._check_closed() try: # set_wakeup_fd() raises ValueError if this is not the # main thread. By calling it early we ensure that an # event loop running in another thread cannot add a signal # handler. signal.set_wakeup_fd(self._csock.fileno()) except (ValueError, OSError) as exc: raise RuntimeError(str(exc)) handle = events.Handle(callback, args, self) self._signal_handlers[sig] = handle try: # Register a dummy signal handler to ask Python to write the signal # number in the wakup file descriptor. _process_self_data() will # read signal numbers from this file descriptor to handle signals. signal.signal(sig, _sighandler_noop) # Set SA_RESTART to limit EINTR occurrences. signal.siginterrupt(sig, False) except OSError as exc: del self._signal_handlers[sig] if not self._signal_handlers: try: signal.set_wakeup_fd(-1) except (ValueError, OSError) as nexc: logger.info('set_wakeup_fd(-1) failed: %s', nexc) if exc.errno == errno.EINVAL: raise RuntimeError('sig {} cannot be caught'.format(sig)) else: raise def _handle_signal(self, sig): """Internal helper that is the actual signal handler.""" handle = self._signal_handlers.get(sig) if handle is None: return # Assume it's some race condition. if handle._cancelled: self.remove_signal_handler(sig) # Remove it properly. else: self._add_callback_signalsafe(handle) def remove_signal_handler(self, sig): """Remove a handler for a signal. UNIX only. Return True if a signal handler was removed, False if not. """ self._check_signal(sig) try: del self._signal_handlers[sig] except KeyError: return False if sig == signal.SIGINT: handler = signal.default_int_handler else: handler = signal.SIG_DFL try: signal.signal(sig, handler) except OSError as exc: if exc.errno == errno.EINVAL: raise RuntimeError('sig {} cannot be caught'.format(sig)) else: raise if not self._signal_handlers: try: signal.set_wakeup_fd(-1) except (ValueError, OSError) as exc: logger.info('set_wakeup_fd(-1) failed: %s', exc) return True def _check_signal(self, sig): """Internal helper to validate a signal. Raise ValueError if the signal number is invalid or uncatchable. Raise RuntimeError if there is a problem setting up the handler. """ if not isinstance(sig, int): raise TypeError('sig must be an int, not {!r}'.format(sig)) if not (1 <= sig < signal.NSIG): raise ValueError( 'sig {} out of range(1, {})'.format(sig, signal.NSIG)) def _make_read_pipe_transport(self, pipe, protocol, waiter=None, extra=None): return _UnixReadPipeTransport(self, pipe, protocol, waiter, extra) def _make_write_pipe_transport(self, pipe, protocol, waiter=None, extra=None): return _UnixWritePipeTransport(self, pipe, protocol, waiter, extra) @coroutine def _make_subprocess_transport(self, protocol, args, shell, stdin, stdout, stderr, bufsize, extra=None, **kwargs): with events.get_child_watcher() as watcher: waiter = self.create_future() transp = _UnixSubprocessTransport(self, protocol, args, shell, stdin, stdout, stderr, bufsize, waiter=waiter, extra=extra, **kwargs) watcher.add_child_handler(transp.get_pid(), self._child_watcher_callback, transp) try: yield from waiter except Exception as exc: # Workaround CPython bug #23353: using yield/yield-from in an # except block of a generator doesn't clear properly # sys.exc_info() err = exc else: err = None if err is not None: transp.close() yield from transp._wait() raise err return transp def _child_watcher_callback(self, pid, returncode, transp): self.call_soon_threadsafe(transp._process_exited, returncode) @coroutine def create_unix_connection(self, protocol_factory, path, *, ssl=None, sock=None, server_hostname=None): assert server_hostname is None or isinstance(server_hostname, str) if ssl: if server_hostname is None: raise ValueError( 'you have to pass server_hostname when using ssl') else: if server_hostname is not None: raise ValueError('server_hostname is only meaningful with ssl') if path is not None: if sock is not None: raise ValueError( 'path and sock can not be specified at the same time') sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM, 0) try: sock.setblocking(False) yield from self.sock_connect(sock, path) except: sock.close() raise else: if sock is None: raise ValueError('no path and sock were specified') if (sock.family != socket.AF_UNIX or not base_events._is_stream_socket(sock)): raise ValueError( 'A UNIX Domain Stream Socket was expected, got {!r}' .format(sock)) sock.setblocking(False) transport, protocol = yield from self._create_connection_transport( sock, protocol_factory, ssl, server_hostname) return transport, protocol @coroutine def create_unix_server(self, protocol_factory, path=None, *, sock=None, backlog=100, ssl=None): if isinstance(ssl, bool): raise TypeError('ssl argument must be an SSLContext or None') if path is not None: if sock is not None: raise ValueError( 'path and sock can not be specified at the same time') path = _fspath(path) sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM) # Check for abstract socket. `str` and `bytes` paths are supported. if path[0] not in (0, '\x00'): try: if stat.S_ISSOCK(os.stat(path).st_mode): os.remove(path) except FileNotFoundError: pass except OSError as err: # Directory may have permissions only to create socket. logger.error('Unable to check or remove stale UNIX socket %r: %r', path, err) try: sock.bind(path) except OSError as exc: sock.close() if exc.errno == errno.EADDRINUSE: # Let's improve the error message by adding # with what exact address it occurs. msg = 'Address {!r} is already in use'.format(path) raise OSError(errno.EADDRINUSE, msg) from None else: raise except: sock.close() raise else: if sock is None: raise ValueError( 'path was not specified, and no sock specified') if (sock.family != socket.AF_UNIX or not base_events._is_stream_socket(sock)): raise ValueError( 'A UNIX Domain Stream Socket was expected, got {!r}' .format(sock)) server = base_events.Server(self, [sock]) sock.listen(backlog) sock.setblocking(False) self._start_serving(protocol_factory, sock, ssl, server) return server if hasattr(os, 'set_blocking'): def _set_nonblocking(fd): os.set_blocking(fd, False) else: import fcntl def _set_nonblocking(fd): flags = fcntl.fcntl(fd, fcntl.F_GETFL) flags = flags | os.O_NONBLOCK fcntl.fcntl(fd, fcntl.F_SETFL, flags) class _UnixReadPipeTransport(transports.ReadTransport): max_size = 256 * 1024 # max bytes we read in one event loop iteration def __init__(self, loop, pipe, protocol, waiter=None, extra=None): super().__init__(extra) self._extra['pipe'] = pipe self._loop = loop self._pipe = pipe self._fileno = pipe.fileno() self._protocol = protocol self._closing = False mode = os.fstat(self._fileno).st_mode if not (stat.S_ISFIFO(mode) or stat.S_ISSOCK(mode) or stat.S_ISCHR(mode)): self._pipe = None self._fileno = None self._protocol = None raise ValueError("Pipe transport is for pipes/sockets only.") _set_nonblocking(self._fileno) self._loop.call_soon(self._protocol.connection_made, self) # only start reading when connection_made() has been called self._loop.call_soon(self._loop._add_reader, self._fileno, self._read_ready) if waiter is not None: # only wake up the waiter when connection_made() has been called self._loop.call_soon(futures._set_result_unless_cancelled, waiter, None) def __repr__(self): info = [self.__class__.__name__] if self._pipe is None: info.append('closed') elif self._closing: info.append('closing') info.append('fd=%s' % self._fileno) selector = getattr(self._loop, '_selector', None) if self._pipe is not None and selector is not None: polling = selector_events._test_selector_event( selector, self._fileno, selectors.EVENT_READ) if polling: info.append('polling') else: info.append('idle') elif self._pipe is not None: info.append('open') else: info.append('closed') return '<%s>' % ' '.join(info) def _read_ready(self): try: data = os.read(self._fileno, self.max_size) except (BlockingIOError, InterruptedError): pass except OSError as exc: self._fatal_error(exc, 'Fatal read error on pipe transport') else: if data: self._protocol.data_received(data) else: if self._loop.get_debug(): logger.info("%r was closed by peer", self) self._closing = True self._loop._remove_reader(self._fileno) self._loop.call_soon(self._protocol.eof_received) self._loop.call_soon(self._call_connection_lost, None) def pause_reading(self): self._loop._remove_reader(self._fileno) def resume_reading(self): self._loop._add_reader(self._fileno, self._read_ready) def set_protocol(self, protocol): self._protocol = protocol def get_protocol(self): return self._protocol def is_closing(self): return self._closing def close(self): if not self._closing: self._close(None) # On Python 3.3 and older, objects with a destructor part of a reference # cycle are never destroyed. It's not more the case on Python 3.4 thanks # to the PEP 442. if compat.PY34: def __del__(self): if self._pipe is not None: warnings.warn("unclosed transport %r" % self, ResourceWarning, source=self) self._pipe.close() def _fatal_error(self, exc, message='Fatal error on pipe transport'): # should be called by exception handler only if (isinstance(exc, OSError) and exc.errno == errno.EIO): if self._loop.get_debug(): logger.debug("%r: %s", self, message, exc_info=True) else: self._loop.call_exception_handler({ 'message': message, 'exception': exc, 'transport': self, 'protocol': self._protocol, }) self._close(exc) def _close(self, exc): self._closing = True self._loop._remove_reader(self._fileno) self._loop.call_soon(self._call_connection_lost, exc) def _call_connection_lost(self, exc): try: self._protocol.connection_lost(exc) finally: self._pipe.close() self._pipe = None self._protocol = None self._loop = None class _UnixWritePipeTransport(transports._FlowControlMixin, transports.WriteTransport): def __init__(self, loop, pipe, protocol, waiter=None, extra=None): super().__init__(extra, loop) self._extra['pipe'] = pipe self._pipe = pipe self._fileno = pipe.fileno() self._protocol = protocol self._buffer = bytearray() self._conn_lost = 0 self._closing = False # Set when close() or write_eof() called. mode = os.fstat(self._fileno).st_mode is_char = stat.S_ISCHR(mode) is_fifo = stat.S_ISFIFO(mode) is_socket = stat.S_ISSOCK(mode) if not (is_char or is_fifo or is_socket): self._pipe = None self._fileno = None self._protocol = None raise ValueError("Pipe transport is only for " "pipes, sockets and character devices") _set_nonblocking(self._fileno) self._loop.call_soon(self._protocol.connection_made, self) # On AIX, the reader trick (to be notified when the read end of the # socket is closed) only works for sockets. On other platforms it # works for pipes and sockets. (Exception: OS X 10.4? Issue #19294.) if is_socket or (is_fifo and not sys.platform.startswith("aix")): # only start reading when connection_made() has been called self._loop.call_soon(self._loop._add_reader, self._fileno, self._read_ready) if waiter is not None: # only wake up the waiter when connection_made() has been called self._loop.call_soon(futures._set_result_unless_cancelled, waiter, None) def __repr__(self): info = [self.__class__.__name__] if self._pipe is None: info.append('closed') elif self._closing: info.append('closing') info.append('fd=%s' % self._fileno) selector = getattr(self._loop, '_selector', None) if self._pipe is not None and selector is not None: polling = selector_events._test_selector_event( selector, self._fileno, selectors.EVENT_WRITE) if polling: info.append('polling') else: info.append('idle') bufsize = self.get_write_buffer_size() info.append('bufsize=%s' % bufsize) elif self._pipe is not None: info.append('open') else: info.append('closed') return '<%s>' % ' '.join(info) def get_write_buffer_size(self): return len(self._buffer) def _read_ready(self): # Pipe was closed by peer. if self._loop.get_debug(): logger.info("%r was closed by peer", self) if self._buffer: self._close(BrokenPipeError()) else: self._close() def write(self, data): assert isinstance(data, (bytes, bytearray, memoryview)), repr(data) if isinstance(data, bytearray): data = memoryview(data) if not data: return if self._conn_lost or self._closing: if self._conn_lost >= constants.LOG_THRESHOLD_FOR_CONNLOST_WRITES: logger.warning('pipe closed by peer or ' 'os.write(pipe, data) raised exception.') self._conn_lost += 1 return if not self._buffer: # Attempt to send it right away first. try: n = os.write(self._fileno, data) except (BlockingIOError, InterruptedError): n = 0 except Exception as exc: self._conn_lost += 1 self._fatal_error(exc, 'Fatal write error on pipe transport') return if n == len(data): return elif n > 0: data = memoryview(data)[n:] self._loop._add_writer(self._fileno, self._write_ready) self._buffer += data self._maybe_pause_protocol() def _write_ready(self): assert self._buffer, 'Data should not be empty' try: n = os.write(self._fileno, self._buffer) except (BlockingIOError, InterruptedError): pass except Exception as exc: self._buffer.clear() self._conn_lost += 1 # Remove writer here, _fatal_error() doesn't it # because _buffer is empty. self._loop._remove_writer(self._fileno) self._fatal_error(exc, 'Fatal write error on pipe transport') else: if n == len(self._buffer): self._buffer.clear() self._loop._remove_writer(self._fileno) self._maybe_resume_protocol() # May append to buffer. if self._closing: self._loop._remove_reader(self._fileno) self._call_connection_lost(None) return elif n > 0: del self._buffer[:n] def can_write_eof(self): return True def write_eof(self): if self._closing: return assert self._pipe self._closing = True if not self._buffer: self._loop._remove_reader(self._fileno) self._loop.call_soon(self._call_connection_lost, None) def set_protocol(self, protocol): self._protocol = protocol def get_protocol(self): return self._protocol def is_closing(self): return self._closing def close(self): if self._pipe is not None and not self._closing: # write_eof is all what we needed to close the write pipe self.write_eof() # On Python 3.3 and older, objects with a destructor part of a reference # cycle are never destroyed. It's not more the case on Python 3.4 thanks # to the PEP 442. if compat.PY34: def __del__(self): if self._pipe is not None: warnings.warn("unclosed transport %r" % self, ResourceWarning, source=self) self._pipe.close() def abort(self): self._close(None) def _fatal_error(self, exc, message='Fatal error on pipe transport'): # should be called by exception handler only if isinstance(exc, base_events._FATAL_ERROR_IGNORE): if self._loop.get_debug(): logger.debug("%r: %s", self, message, exc_info=True) else: self._loop.call_exception_handler({ 'message': message, 'exception': exc, 'transport': self, 'protocol': self._protocol, }) self._close(exc) def _close(self, exc=None): self._closing = True if self._buffer: self._loop._remove_writer(self._fileno) self._buffer.clear() self._loop._remove_reader(self._fileno) self._loop.call_soon(self._call_connection_lost, exc) def _call_connection_lost(self, exc): try: self._protocol.connection_lost(exc) finally: self._pipe.close() self._pipe = None self._protocol = None self._loop = None if hasattr(os, 'set_inheritable'): # Python 3.4 and newer _set_inheritable = os.set_inheritable else: import fcntl def _set_inheritable(fd, inheritable): cloexec_flag = getattr(fcntl, 'FD_CLOEXEC', 1) old = fcntl.fcntl(fd, fcntl.F_GETFD) if not inheritable: fcntl.fcntl(fd, fcntl.F_SETFD, old | cloexec_flag) else: fcntl.fcntl(fd, fcntl.F_SETFD, old & ~cloexec_flag) class _UnixSubprocessTransport(base_subprocess.BaseSubprocessTransport): def _start(self, args, shell, stdin, stdout, stderr, bufsize, **kwargs): stdin_w = None if stdin == subprocess.PIPE: # Use a socket pair for stdin, since not all platforms # support selecting read events on the write end of a # socket (which we use in order to detect closing of the # other end). Notably this is needed on AIX, and works # just fine on other platforms. stdin, stdin_w = self._loop._socketpair() # Mark the write end of the stdin pipe as non-inheritable, # needed by close_fds=False on Python 3.3 and older # (Python 3.4 implements the PEP 446, socketpair returns # non-inheritable sockets) _set_inheritable(stdin_w.fileno(), False) self._proc = subprocess.Popen( args, shell=shell, stdin=stdin, stdout=stdout, stderr=stderr, universal_newlines=False, bufsize=bufsize, **kwargs) if stdin_w is not None: stdin.close() self._proc.stdin = open(stdin_w.detach(), 'wb', buffering=bufsize) class AbstractChildWatcher: """Abstract base class for monitoring child processes. Objects derived from this class monitor a collection of subprocesses and report their termination or interruption by a signal. New callbacks are registered with .add_child_handler(). Starting a new process must be done within a 'with' block to allow the watcher to suspend its activity until the new process if fully registered (this is needed to prevent a race condition in some implementations). Example: with watcher: proc = subprocess.Popen("sleep 1") watcher.add_child_handler(proc.pid, callback) Notes: Implementations of this class must be thread-safe. Since child watcher objects may catch the SIGCHLD signal and call waitpid(-1), there should be only one active object per process. """ def add_child_handler(self, pid, callback, *args): """Register a new child handler. Arrange for callback(pid, returncode, *args) to be called when process 'pid' terminates. Specifying another callback for the same process replaces the previous handler. Note: callback() must be thread-safe. """ raise NotImplementedError() def remove_child_handler(self, pid): """Removes the handler for process 'pid'. The function returns True if the handler was successfully removed, False if there was nothing to remove.""" raise NotImplementedError() def attach_loop(self, loop): """Attach the watcher to an event loop. If the watcher was previously attached to an event loop, then it is first detached before attaching to the new loop. Note: loop may be None. """ raise NotImplementedError() def close(self): """Close the watcher. This must be called to make sure that any underlying resource is freed. """ raise NotImplementedError() def __enter__(self): """Enter the watcher's context and allow starting new processes This function must return self""" raise NotImplementedError() def __exit__(self, a, b, c): """Exit the watcher's context""" raise NotImplementedError() class BaseChildWatcher(AbstractChildWatcher): def __init__(self): self._loop = None self._callbacks = {} def close(self): self.attach_loop(None) def _do_waitpid(self, expected_pid): raise NotImplementedError() def _do_waitpid_all(self): raise NotImplementedError() def attach_loop(self, loop): assert loop is None or isinstance(loop, events.AbstractEventLoop) if self._loop is not None and loop is None and self._callbacks: warnings.warn( 'A loop is being detached ' 'from a child watcher with pending handlers', RuntimeWarning) if self._loop is not None: self._loop.remove_signal_handler(signal.SIGCHLD) self._loop = loop if loop is not None: loop.add_signal_handler(signal.SIGCHLD, self._sig_chld) # Prevent a race condition in case a child terminated # during the switch. self._do_waitpid_all() def _sig_chld(self): try: self._do_waitpid_all() except Exception as exc: # self._loop should always be available here # as '_sig_chld' is added as a signal handler # in 'attach_loop' self._loop.call_exception_handler({ 'message': 'Unknown exception in SIGCHLD handler', 'exception': exc, }) def _compute_returncode(self, status): if os.WIFSIGNALED(status): # The child process died because of a signal. return -os.WTERMSIG(status) elif os.WIFEXITED(status): # The child process exited (e.g sys.exit()). return os.WEXITSTATUS(status) else: # The child exited, but we don't understand its status. # This shouldn't happen, but if it does, let's just # return that status; perhaps that helps debug it. return status class SafeChildWatcher(BaseChildWatcher): """'Safe' child watcher implementation. This implementation avoids disrupting other code spawning processes by polling explicitly each process in the SIGCHLD handler instead of calling os.waitpid(-1). This is a safe solution but it has a significant overhead when handling a big number of children (O(n) each time SIGCHLD is raised) """ def close(self): self._callbacks.clear() super().close() def __enter__(self): return self def __exit__(self, a, b, c): pass def add_child_handler(self, pid, callback, *args): if self._loop is None: raise RuntimeError( "Cannot add child handler, " "the child watcher does not have a loop attached") self._callbacks[pid] = (callback, args) # Prevent a race condition in case the child is already terminated. self._do_waitpid(pid) def remove_child_handler(self, pid): try: del self._callbacks[pid] return True except KeyError: return False def _do_waitpid_all(self): for pid in list(self._callbacks): self._do_waitpid(pid) def _do_waitpid(self, expected_pid): assert expected_pid > 0 try: pid, status = os.waitpid(expected_pid, os.WNOHANG) except ChildProcessError: # The child process is already reaped # (may happen if waitpid() is called elsewhere). pid = expected_pid returncode = 255 logger.warning( "Unknown child process pid %d, will report returncode 255", pid) else: if pid == 0: # The child process is still alive. return returncode = self._compute_returncode(status) if self._loop.get_debug(): logger.debug('process %s exited with returncode %s', expected_pid, returncode) try: callback, args = self._callbacks.pop(pid) except KeyError: # pragma: no cover # May happen if .remove_child_handler() is called # after os.waitpid() returns. if self._loop.get_debug(): logger.warning("Child watcher got an unexpected pid: %r", pid, exc_info=True) else: callback(pid, returncode, *args) class FastChildWatcher(BaseChildWatcher): """'Fast' child watcher implementation. This implementation reaps every terminated processes by calling os.waitpid(-1) directly, possibly breaking other code spawning processes and waiting for their termination. There is no noticeable overhead when handling a big number of children (O(1) each time a child terminates). """ def __init__(self): super().__init__() self._lock = threading.Lock() self._zombies = {} self._forks = 0 def close(self): self._callbacks.clear() self._zombies.clear() super().close() def __enter__(self): with self._lock: self._forks += 1 return self def __exit__(self, a, b, c): with self._lock: self._forks -= 1 if self._forks or not self._zombies: return collateral_victims = str(self._zombies) self._zombies.clear() logger.warning( "Caught subprocesses termination from unknown pids: %s", collateral_victims) def add_child_handler(self, pid, callback, *args): assert self._forks, "Must use the context manager" if self._loop is None: raise RuntimeError( "Cannot add child handler, " "the child watcher does not have a loop attached") with self._lock: try: returncode = self._zombies.pop(pid) except KeyError: # The child is running. self._callbacks[pid] = callback, args return # The child is dead already. We can fire the callback. callback(pid, returncode, *args) def remove_child_handler(self, pid): try: del self._callbacks[pid] return True except KeyError: return False def _do_waitpid_all(self): # Because of signal coalescing, we must keep calling waitpid() as # long as we're able to reap a child. while True: try: pid, status = os.waitpid(-1, os.WNOHANG) except ChildProcessError: # No more child processes exist. return else: if pid == 0: # A child process is still alive. return returncode = self._compute_returncode(status) with self._lock: try: callback, args = self._callbacks.pop(pid) except KeyError: # unknown child if self._forks: # It may not be registered yet. self._zombies[pid] = returncode if self._loop.get_debug(): logger.debug('unknown process %s exited ' 'with returncode %s', pid, returncode) continue callback = None else: if self._loop.get_debug(): logger.debug('process %s exited with returncode %s', pid, returncode) if callback is None: logger.warning( "Caught subprocess termination from unknown pid: " "%d -> %d", pid, returncode) else: callback(pid, returncode, *args) class _UnixDefaultEventLoopPolicy(events.BaseDefaultEventLoopPolicy): """UNIX event loop policy with a watcher for child processes.""" _loop_factory = _UnixSelectorEventLoop def __init__(self): super().__init__() self._watcher = None def _init_watcher(self): with events._lock: if self._watcher is None: # pragma: no branch self._watcher = SafeChildWatcher() if isinstance(threading.current_thread(), threading._MainThread): self._watcher.attach_loop(self._local._loop) def set_event_loop(self, loop): """Set the event loop. As a side effect, if a child watcher was set before, then calling .set_event_loop() from the main thread will call .attach_loop(loop) on the child watcher. """ super().set_event_loop(loop) if self._watcher is not None and \ isinstance(threading.current_thread(), threading._MainThread): self._watcher.attach_loop(loop) def get_child_watcher(self): """Get the watcher for child processes. If not yet set, a SafeChildWatcher object is automatically created. """ if self._watcher is None: self._init_watcher() return self._watcher def set_child_watcher(self, watcher): """Set the watcher for child processes.""" assert watcher is None or isinstance(watcher, AbstractChildWatcher) if self._watcher is not None: self._watcher.close() self._watcher = watcher SelectorEventLoop = _UnixSelectorEventLoop DefaultEventLoopPolicy = _UnixDefaultEventLoopPolicy