/usr/lib/python3.7/asyncio/unix_events.py is in libpython3.7-stdlib 3.7.0~b3-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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import errno
import io
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 futures
from . import selector_events
from . import transports
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
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 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(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 not (1 <= sig < signal.NSIG):
raise ValueError(f'sig {sig} out of range(1, {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)
async 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:
await waiter
except Exception:
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()
return server
async def _sock_sendfile_native(self, sock, file, offset, count):
try:
os.sendfile
except AttributeError as exc:
raise events.SendfileNotAvailableError(
"os.sendfile() is not available")
try:
fileno = file.fileno()
except (AttributeError, io.UnsupportedOperation) as err:
raise events.SendfileNotAvailableError("not a regular file")
try:
fsize = os.fstat(fileno).st_size
except OSError as err:
raise events.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 = events.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 Exception 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
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):
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)
def __del__(self):
if self._pipe is not None:
warnings.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 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 __del__(self):
if self._pipe is not None:
warnings.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, 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
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()
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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