cpython/Lib/asyncio/unix_events.py

753 lines
24 KiB
Python

"""Selector eventloop for Unix with signal handling."""
import errno
import fcntl
import os
import signal
import socket
import stat
import subprocess
import sys
import threading
from . import base_subprocess
from . import constants
from . import events
from . import protocols
from . import selector_events
from . import tasks
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')
class _UnixSelectorEventLoop(selector_events.BaseSelectorEventLoop):
"""Unix event loop
Adds signal handling to SelectorEventLoop
"""
def __init__(self, selector=None):
super().__init__(selector)
self._signal_handlers = {}
def _socketpair(self):
return socket.socketpair()
def close(self):
for sig in list(self._signal_handlers):
self.remove_signal_handler(sig)
super().close()
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.
"""
self._check_signal(sig)
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 as exc:
raise RuntimeError(str(exc))
handle = events.make_handle(callback, args)
self._signal_handlers[sig] = handle
try:
signal.signal(sig, self._handle_signal)
# 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 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, arg):
"""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 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)
@tasks.coroutine
def _make_subprocess_transport(self, protocol, args, shell,
stdin, stdout, stderr, bufsize,
extra=None, **kwargs):
with events.get_child_watcher() as watcher:
transp = _UnixSubprocessTransport(self, protocol, args, shell,
stdin, stdout, stderr, bufsize,
extra=extra, **kwargs)
yield from transp._post_init()
watcher.add_child_handler(transp.get_pid(),
self._child_watcher_callback, transp)
return transp
def _child_watcher_callback(self, pid, returncode, transp):
self.call_soon_threadsafe(transp._process_exited, returncode)
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 eventloop 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()
mode = os.fstat(self._fileno).st_mode
if not (stat.S_ISFIFO(mode) or
stat.S_ISSOCK(mode) or
stat.S_ISCHR(mode)):
raise ValueError("Pipe transport is for pipes/sockets only.")
_set_nonblocking(self._fileno)
self._protocol = protocol
self._closing = False
self._loop.add_reader(self._fileno, self._read_ready)
self._loop.call_soon(self._protocol.connection_made, self)
if waiter is not None:
self._loop.call_soon(waiter.set_result, None)
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)
else:
if data:
self._protocol.data_received(data)
else:
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 close(self):
if not self._closing:
self._close(None)
def _fatal_error(self, exc):
# should be called by exception handler only
if not (isinstance(exc, OSError) and exc.errno == errno.EIO):
logger.exception('Fatal error for %s', self)
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(selector_events._FlowControlMixin,
transports.WriteTransport):
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()
mode = os.fstat(self._fileno).st_mode
is_socket = stat.S_ISSOCK(mode)
if not (is_socket or
stat.S_ISFIFO(mode) or
stat.S_ISCHR(mode)):
raise ValueError("Pipe transport is only for "
"pipes, sockets and character devices")
_set_nonblocking(self._fileno)
self._protocol = protocol
self._buffer = []
self._conn_lost = 0
self._closing = False # Set when close() or write_eof() called.
# On AIX, the reader trick only works for sockets.
# On other platforms it works for pipes and sockets.
# (Exception: OS X 10.4? Issue #19294.)
if is_socket or not sys.platform.startswith("aix"):
self._loop.add_reader(self._fileno, self._read_ready)
self._loop.call_soon(self._protocol.connection_made, self)
if waiter is not None:
self._loop.call_soon(waiter.set_result, None)
def get_write_buffer_size(self):
return sum(len(data) for data in self._buffer)
def _read_ready(self):
# Pipe was closed by peer.
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)
return
if n == len(data):
return
elif n > 0:
data = data[n:]
self._loop.add_writer(self._fileno, self._write_ready)
self._buffer.append(data)
self._maybe_pause_protocol()
def _write_ready(self):
data = b''.join(self._buffer)
assert data, 'Data should not be empty'
self._buffer.clear()
try:
n = os.write(self._fileno, data)
except (BlockingIOError, InterruptedError):
self._buffer.append(data)
except Exception as exc:
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)
else:
if n == len(data):
self._loop.remove_writer(self._fileno)
self._maybe_resume_protocol() # May append to buffer.
if not self._buffer and self._closing:
self._loop.remove_reader(self._fileno)
self._call_connection_lost(None)
return
elif n > 0:
data = data[n:]
self._buffer.append(data) # Try again later.
def can_write_eof(self):
return True
# TODO: Make the relationships between write_eof(), close(),
# abort(), _fatal_error() and _close() more straightforward.
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 close(self):
if 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):
# should be called by exception handler only
if not isinstance(exc, (BrokenPipeError, ConnectionResetError)):
logger.exception('Fatal error for %s', self)
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 = self._loop._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(), 'rb', 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
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:
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:
logger.exception('Unknown exception in SIGCHLD handler')
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 __init__(self):
super().__init__()
self._callbacks = {}
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 = self._compute_returncode(status)
try:
callback, args = self._callbacks.pop(pid)
except KeyError: # pragma: no cover
# May happen if .remove_child_handler() is called
# after os.waitpid() returns.
pass
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._callbacks = {}
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 = 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
continue
callback = None
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):
"""XXX"""
_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 child watcher
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 child watcher"""
assert watcher is None or isinstance(watcher, AbstractChildWatcher)
if self._watcher is not None:
self._watcher.close()
self._watcher = watcher
SelectorEventLoop = _UnixSelectorEventLoop
DefaultEventLoopPolicy = _UnixDefaultEventLoopPolicy