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Editing: unix_events.py
"""Selector event loop for Unix with signal handling.""" import errno import io import itertools import os import selectors import signal import socket import stat import subprocess import sys import threading import warnings from . import base_events from . import base_subprocess from . import constants from . import coroutines from . import events from . import exceptions from . import futures from . import selector_events from . import tasks from . import transports from .log import logger __all__ = ( 'SelectorEventLoop', 'AbstractChildWatcher', 'SafeChildWatcher', 'FastChildWatcher', 'MultiLoopChildWatcher', 'ThreadedChildWatcher', '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 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 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, None) self._signal_handlers[sig] = handle try: # Register a dummy signal handler to ask Python to write the signal # number in the wakeup 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(f'sig {sig} cannot be caught') 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(f'sig {sig} cannot be caught') 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(f'sig must be an int, not {sig!r}') if sig not in signal.valid_signals(): raise ValueError(f'invalid signal number {sig}') 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) async def _make_subprocess_transport(self, protocol, args, shell, stdin, stdout, stderr, bufsize, extra=None, **kwargs): with events.get_child_watcher() as watcher: if not watcher.is_active(): # Check early. # Raising exception before process creation # prevents subprocess execution if the watcher # is not ready to handle it. raise RuntimeError("asyncio.get_child_watcher() is not activated, " "subprocess support is not installed.") 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: await waiter except (SystemExit, KeyboardInterrupt): raise except BaseException: transp.close() await transp._wait() raise return transp def _child_watcher_callback(self, pid, returncode, transp): self.call_soon_threadsafe(transp._process_exited, returncode) async def create_unix_connection( self, protocol_factory, path=None, *, ssl=None, sock=None, server_hostname=None, ssl_handshake_timeout=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 ssl_handshake_timeout is not None: raise ValueError( 'ssl_handshake_timeout 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') path = os.fspath(path) sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM, 0) try: sock.setblocking(False) await 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 sock.type != socket.SOCK_STREAM): raise ValueError( f'A UNIX Domain Stream Socket was expected, got {sock!r}') sock.setblocking(False) transport, protocol = await self._create_connection_transport( sock, protocol_factory, ssl, server_hostname, ssl_handshake_timeout=ssl_handshake_timeout) return transport, protocol async def create_unix_server( self, protocol_factory, path=None, *, sock=None, backlog=100, ssl=None, ssl_handshake_timeout=None, start_serving=True): if isinstance(ssl, bool): raise TypeError('ssl argument must be an SSLContext or None') if ssl_handshake_timeout is not None and not ssl: raise ValueError( 'ssl_handshake_timeout 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') path = os.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 = f'Address {path!r} is already in use' 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 sock.type != socket.SOCK_STREAM): raise ValueError( f'A UNIX Domain Stream Socket was expected, got {sock!r}') sock.setblocking(False) server = base_events.Server(self, [sock], protocol_factory, ssl, backlog, ssl_handshake_timeout) if start_serving: server._start_serving() # Skip one loop iteration so that all 'loop.add_reader' # go through. await tasks.sleep(0, loop=self) return server async def _sock_sendfile_native(self, sock, file, offset, count): try: os.sendfile except AttributeError as exc: raise exceptions.SendfileNotAvailableError( "os.sendfile() is not available") try: fileno = file.fileno() except (AttributeError, io.UnsupportedOperation) as err: raise exceptions.SendfileNotAvailableError("not a regular file") try: fsize = os.fstat(fileno).st_size except OSError as err: raise exceptions.SendfileNotAvailableError("not a regular file") blocksize = count if count else fsize if not blocksize: return 0 # empty file fut = self.create_future() self._sock_sendfile_native_impl(fut, None, sock, fileno, offset, count, blocksize, 0) return await fut def _sock_sendfile_native_impl(self, fut, registered_fd, sock, fileno, offset, count, blocksize, total_sent): fd = sock.fileno() if registered_fd is not None: # Remove the callback early. It should be rare that the # selector says the fd is ready but the call still returns # EAGAIN, and I am willing to take a hit in that case in # order to simplify the common case. self.remove_writer(registered_fd) if fut.cancelled(): self._sock_sendfile_update_filepos(fileno, offset, total_sent) return if count: blocksize = count - total_sent if blocksize <= 0: self._sock_sendfile_update_filepos(fileno, offset, total_sent) fut.set_result(total_sent) return try: sent = os.sendfile(fd, fileno, offset, blocksize) except (BlockingIOError, InterruptedError): if registered_fd is None: self._sock_add_cancellation_callback(fut, sock) self.add_writer(fd, self._sock_sendfile_native_impl, fut, fd, sock, fileno, offset, count, blocksize, total_sent) except OSError as exc: if (registered_fd is not None and exc.errno == errno.ENOTCONN and type(exc) is not ConnectionError): # If we have an ENOTCONN and this isn't a first call to # sendfile(), i.e. the connection was closed in the middle # of the operation, normalize the error to ConnectionError # to make it consistent across all Posix systems. new_exc = ConnectionError( "socket is not connected", errno.ENOTCONN) new_exc.__cause__ = exc exc = new_exc if total_sent == 0: # We can get here for different reasons, the main # one being 'file' is not a regular mmap(2)-like # file, in which case we'll fall back on using # plain send(). err = exceptions.SendfileNotAvailableError( "os.sendfile call failed") self._sock_sendfile_update_filepos(fileno, offset, total_sent) fut.set_exception(err) else: self._sock_sendfile_update_filepos(fileno, offset, total_sent) fut.set_exception(exc) except (SystemExit, KeyboardInterrupt): raise except BaseException as exc: self._sock_sendfile_update_filepos(fileno, offset, total_sent) fut.set_exception(exc) else: if sent == 0: # EOF self._sock_sendfile_update_filepos(fileno, offset, total_sent) fut.set_result(total_sent) else: offset += sent total_sent += sent if registered_fd is None: self._sock_add_cancellation_callback(fut, sock) self.add_writer(fd, self._sock_sendfile_native_impl, fut, fd, sock, fileno, offset, count, blocksize, total_sent) def _sock_sendfile_update_filepos(self, fileno, offset, total_sent): if total_sent > 0: os.lseek(fileno, offset, os.SEEK_SET) def _sock_add_cancellation_callback(self, fut, sock): def cb(fut): if fut.cancelled(): fd = sock.fileno() if fd != -1: self.remove_writer(fd) fut.add_done_callback(cb) 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 self._paused = 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.") os.set_blocking(self._fileno, False) 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(f'fd={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 '<{}>'.format(' '.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): if self._closing or self._paused: return self._paused = True self._loop._remove_reader(self._fileno) if self._loop.get_debug(): logger.debug("%r pauses reading", self) def resume_reading(self): if self._closing or not self._paused: return self._paused = False self._loop._add_reader(self._fileno, self._read_ready) if self._loop.get_debug(): logger.debug("%r resumes reading", self) 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) def __del__(self, _warn=warnings.warn): if self._pipe is not None: _warn(f"unclosed transport {self!r}", 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") os.set_blocking(self._fileno, False) 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(f'fd={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(f'bufsize={bufsize}') elif self._pipe is not None: info.append('open') else: info.append('closed') return '<{}>'.format(' '.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 (SystemExit, KeyboardInterrupt): raise except BaseException 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 (SystemExit, KeyboardInterrupt): raise except BaseException 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 __del__(self, _warn=warnings.warn): if self._pipe is not None: _warn(f"unclosed transport {self!r}", 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, OSError): 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 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 = socket.socketpair() try: 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) stdin_w = None finally: if stdin_w is not None: stdin.close() stdin_w.close() 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 is_active(self): """Return ``True`` if the watcher is active and is used by the event loop. Return True if the watcher is installed and ready to handle process exit notifications. """ 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() def _compute_returncode(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 BaseChildWatcher(AbstractChildWatcher): def __init__(self): self._loop = None self._callbacks = {} def close(self): self.attach_loop(None) def is_active(self): return self._loop is not None and self._loop.is_running() 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 (SystemExit, KeyboardInterrupt): raise except BaseException 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, }) 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): 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 = _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" 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 = _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 MultiLoopChildWatcher(AbstractChildWatcher): """A watcher that doesn't require running loop in the main thread. This implementation registers a SIGCHLD signal handler on instantiation (which may conflict with other code that install own handler for this signal). The solution is safe but it has a significant overhead when handling a big number of processes (*O(n)* each time a SIGCHLD is received). """ # Implementation note: # The class keeps compatibility with AbstractChildWatcher ABC # To achieve this it has empty attach_loop() method # and doesn't accept explicit loop argument # for add_child_handler()/remove_child_handler() # but retrieves the current loop by get_running_loop() def __init__(self): self._callbacks = {} self._saved_sighandler = None def is_active(self): return self._saved_sighandler is not None def close(self): self._callbacks.clear() if self._saved_sighandler is None: return handler = signal.getsignal(signal.SIGCHLD) if handler != self._sig_chld: logger.warning("SIGCHLD handler was changed by outside code") else: signal.signal(signal.SIGCHLD, self._saved_sighandler) self._saved_sighandler = None def __enter__(self): return self def __exit__(self, exc_type, exc_val, exc_tb): pass def add_child_handler(self, pid, callback, *args): loop = events.get_running_loop() self._callbacks[pid] = (loop, 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 attach_loop(self, loop): # Don't save the loop but initialize itself if called first time # The reason to do it here is that attach_loop() is called from # unix policy only for the main thread. # Main thread is required for subscription on SIGCHLD signal if self._saved_sighandler is not None: return self._saved_sighandler = signal.signal(signal.SIGCHLD, self._sig_chld) if self._saved_sighandler is None: logger.warning("Previous SIGCHLD handler was set by non-Python code, " "restore to default handler on watcher close.") self._saved_sighandler = signal.SIG_DFL # Set SA_RESTART to limit EINTR occurrences. signal.siginterrupt(signal.SIGCHLD, 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) debug_log = False else: if pid == 0: # The child process is still alive. return returncode = _compute_returncode(status) debug_log = True try: loop, callback, args = self._callbacks.pop(pid) except KeyError: # pragma: no cover # May happen if .remove_child_handler() is called # after os.waitpid() returns. logger.warning("Child watcher got an unexpected pid: %r", pid, exc_info=True) else: if loop.is_closed(): logger.warning("Loop %r that handles pid %r is closed", loop, pid) else: if debug_log and loop.get_debug(): logger.debug('process %s exited with returncode %s', expected_pid, returncode) loop.call_soon_threadsafe(callback, pid, returncode, *args) def _sig_chld(self, signum, frame): try: self._do_waitpid_all() except (SystemExit, KeyboardInterrupt): raise except BaseException: logger.warning('Unknown exception in SIGCHLD handler', exc_info=True) class ThreadedChildWatcher(AbstractChildWatcher): """Threaded child watcher implementation. The watcher uses a thread per process for waiting for the process finish. It doesn't require subscription on POSIX signal but a thread creation is not free. The watcher has O(1) complexity, its performance doesn't depend on amount of spawn processes. """ def __init__(self): self._pid_counter = itertools.count(0) self._threads = {} def is_active(self): return True def close(self): self._join_threads() def _join_threads(self): """Internal: Join all non-daemon threads""" threads = [thread for thread in list(self._threads.values()) if thread.is_alive() and not thread.daemon] for thread in threads: thread.join() def __enter__(self): return self def __exit__(self, exc_type, exc_val, exc_tb): pass def __del__(self, _warn=warnings.warn): threads = [thread for thread in list(self._threads.values()) if thread.is_alive()] if threads: _warn(f"{self.__class__} has registered but not finished child processes", ResourceWarning, source=self) def add_child_handler(self, pid, callback, *args): loop = events.get_running_loop() thread = threading.Thread(target=self._do_waitpid, name=f"waitpid-{next(self._pid_counter)}", args=(loop, pid, callback, args), daemon=True) self._threads[pid] = thread thread.start() def remove_child_handler(self, pid): # asyncio never calls remove_child_handler() !!! # The method is no-op but is implemented because # abstract base classe requires it return True def attach_loop(self, loop): pass def _do_waitpid(self, loop, expected_pid, callback, args): assert expected_pid > 0 try: pid, status = os.waitpid(expected_pid, 0) 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: returncode = _compute_returncode(status) if loop.get_debug(): logger.debug('process %s exited with returncode %s', expected_pid, returncode) if loop.is_closed(): logger.warning("Loop %r that handles pid %r is closed", loop, pid) else: loop.call_soon_threadsafe(callback, pid, returncode, *args) self._threads.pop(expected_pid) 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 = ThreadedChildWatcher() 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 ThreadedChildWatcher 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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