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Edit File : unix_events.py \| Size : 36.39 KB
"""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() if not sys.is_finalizing(): for sig in list(self._signal_handlers): self.remove_signal_handler(sig) else: if self._signal_handlers: warnings.warn(f"Closing the loop {self!r} " f"on interpreter shutdown " f"stage, skipping signal handlers removal", ResourceWarning, source=self) self._signal_handlers.clear() 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.type)): 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.type)): 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 Back

Edit File : unix_events.py | Size : 36.39 KB

"""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()
        if not sys.is_finalizing():
            for sig in list(self._signal_handlers):
                self.remove_signal_handler(sig)
        else:
            if self._signal_handlers:
                warnings.warn(f"Closing the loop {self!r} "
                              f"on interpreter shutdown "
                              f"stage, skipping signal handlers removal",
                              ResourceWarning,
                              source=self)
                self._signal_handlers.clear()

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.type)):
                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.type)):
                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()

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)

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

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