753 lines
24 KiB
Python
753 lines
24 KiB
Python
"""Selector eventloop for Unix with signal handling."""
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import errno
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import fcntl
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import os
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import signal
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import socket
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import stat
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import subprocess
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import sys
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import threading
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from . import base_subprocess
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from . import constants
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from . import events
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from . import protocols
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from . import selector_events
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from . import tasks
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from . import transports
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from .log import logger
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__all__ = ['SelectorEventLoop',
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'AbstractChildWatcher', 'SafeChildWatcher',
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'FastChildWatcher', 'DefaultEventLoopPolicy',
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]
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if sys.platform == 'win32': # pragma: no cover
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raise ImportError('Signals are not really supported on Windows')
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class _UnixSelectorEventLoop(selector_events.BaseSelectorEventLoop):
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"""Unix event loop
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Adds signal handling to SelectorEventLoop
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"""
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def __init__(self, selector=None):
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super().__init__(selector)
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self._signal_handlers = {}
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def _socketpair(self):
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return socket.socketpair()
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def close(self):
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for sig in list(self._signal_handlers):
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self.remove_signal_handler(sig)
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super().close()
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def add_signal_handler(self, sig, callback, *args):
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"""Add a handler for a signal. UNIX only.
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Raise ValueError if the signal number is invalid or uncatchable.
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Raise RuntimeError if there is a problem setting up the handler.
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"""
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self._check_signal(sig)
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try:
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# set_wakeup_fd() raises ValueError if this is not the
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# main thread. By calling it early we ensure that an
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# event loop running in another thread cannot add a signal
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# handler.
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signal.set_wakeup_fd(self._csock.fileno())
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except ValueError as exc:
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raise RuntimeError(str(exc))
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handle = events.make_handle(callback, args)
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self._signal_handlers[sig] = handle
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try:
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signal.signal(sig, self._handle_signal)
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# Set SA_RESTART to limit EINTR occurrences.
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signal.siginterrupt(sig, False)
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except OSError as exc:
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del self._signal_handlers[sig]
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if not self._signal_handlers:
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try:
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signal.set_wakeup_fd(-1)
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except ValueError as nexc:
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logger.info('set_wakeup_fd(-1) failed: %s', nexc)
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if exc.errno == errno.EINVAL:
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raise RuntimeError('sig {} cannot be caught'.format(sig))
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else:
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raise
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def _handle_signal(self, sig, arg):
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"""Internal helper that is the actual signal handler."""
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handle = self._signal_handlers.get(sig)
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if handle is None:
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return # Assume it's some race condition.
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if handle._cancelled:
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self.remove_signal_handler(sig) # Remove it properly.
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else:
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self._add_callback_signalsafe(handle)
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def remove_signal_handler(self, sig):
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"""Remove a handler for a signal. UNIX only.
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Return True if a signal handler was removed, False if not.
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"""
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self._check_signal(sig)
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try:
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del self._signal_handlers[sig]
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except KeyError:
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return False
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if sig == signal.SIGINT:
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handler = signal.default_int_handler
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else:
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handler = signal.SIG_DFL
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try:
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signal.signal(sig, handler)
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except OSError as exc:
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if exc.errno == errno.EINVAL:
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raise RuntimeError('sig {} cannot be caught'.format(sig))
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else:
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raise
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if not self._signal_handlers:
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try:
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signal.set_wakeup_fd(-1)
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except ValueError as exc:
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logger.info('set_wakeup_fd(-1) failed: %s', exc)
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return True
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def _check_signal(self, sig):
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"""Internal helper to validate a signal.
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Raise ValueError if the signal number is invalid or uncatchable.
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Raise RuntimeError if there is a problem setting up the handler.
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"""
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if not isinstance(sig, int):
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raise TypeError('sig must be an int, not {!r}'.format(sig))
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if not (1 <= sig < signal.NSIG):
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raise ValueError(
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'sig {} out of range(1, {})'.format(sig, signal.NSIG))
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def _make_read_pipe_transport(self, pipe, protocol, waiter=None,
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extra=None):
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return _UnixReadPipeTransport(self, pipe, protocol, waiter, extra)
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def _make_write_pipe_transport(self, pipe, protocol, waiter=None,
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extra=None):
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return _UnixWritePipeTransport(self, pipe, protocol, waiter, extra)
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@tasks.coroutine
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def _make_subprocess_transport(self, protocol, args, shell,
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stdin, stdout, stderr, bufsize,
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extra=None, **kwargs):
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with events.get_child_watcher() as watcher:
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transp = _UnixSubprocessTransport(self, protocol, args, shell,
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stdin, stdout, stderr, bufsize,
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extra=extra, **kwargs)
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yield from transp._post_init()
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watcher.add_child_handler(transp.get_pid(),
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self._child_watcher_callback, transp)
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return transp
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def _child_watcher_callback(self, pid, returncode, transp):
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self.call_soon_threadsafe(transp._process_exited, returncode)
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def _set_nonblocking(fd):
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flags = fcntl.fcntl(fd, fcntl.F_GETFL)
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flags = flags | os.O_NONBLOCK
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fcntl.fcntl(fd, fcntl.F_SETFL, flags)
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class _UnixReadPipeTransport(transports.ReadTransport):
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max_size = 256 * 1024 # max bytes we read in one eventloop iteration
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def __init__(self, loop, pipe, protocol, waiter=None, extra=None):
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super().__init__(extra)
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self._extra['pipe'] = pipe
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self._loop = loop
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self._pipe = pipe
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self._fileno = pipe.fileno()
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mode = os.fstat(self._fileno).st_mode
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if not (stat.S_ISFIFO(mode) or
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stat.S_ISSOCK(mode) or
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stat.S_ISCHR(mode)):
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raise ValueError("Pipe transport is for pipes/sockets only.")
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_set_nonblocking(self._fileno)
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self._protocol = protocol
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self._closing = False
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self._loop.add_reader(self._fileno, self._read_ready)
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self._loop.call_soon(self._protocol.connection_made, self)
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if waiter is not None:
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self._loop.call_soon(waiter.set_result, None)
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def _read_ready(self):
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try:
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data = os.read(self._fileno, self.max_size)
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except (BlockingIOError, InterruptedError):
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pass
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except OSError as exc:
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self._fatal_error(exc)
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else:
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if data:
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self._protocol.data_received(data)
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else:
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self._closing = True
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self._loop.remove_reader(self._fileno)
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self._loop.call_soon(self._protocol.eof_received)
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self._loop.call_soon(self._call_connection_lost, None)
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def pause_reading(self):
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self._loop.remove_reader(self._fileno)
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def resume_reading(self):
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self._loop.add_reader(self._fileno, self._read_ready)
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def close(self):
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if not self._closing:
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self._close(None)
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def _fatal_error(self, exc):
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# should be called by exception handler only
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if not (isinstance(exc, OSError) and exc.errno == errno.EIO):
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logger.exception('Fatal error for %s', self)
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self._close(exc)
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def _close(self, exc):
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self._closing = True
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self._loop.remove_reader(self._fileno)
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self._loop.call_soon(self._call_connection_lost, exc)
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def _call_connection_lost(self, exc):
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try:
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self._protocol.connection_lost(exc)
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finally:
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self._pipe.close()
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self._pipe = None
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self._protocol = None
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self._loop = None
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class _UnixWritePipeTransport(selector_events._FlowControlMixin,
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transports.WriteTransport):
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def __init__(self, loop, pipe, protocol, waiter=None, extra=None):
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super().__init__(extra)
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self._extra['pipe'] = pipe
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self._loop = loop
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self._pipe = pipe
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self._fileno = pipe.fileno()
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mode = os.fstat(self._fileno).st_mode
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is_socket = stat.S_ISSOCK(mode)
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if not (is_socket or
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stat.S_ISFIFO(mode) or
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stat.S_ISCHR(mode)):
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raise ValueError("Pipe transport is only for "
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"pipes, sockets and character devices")
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_set_nonblocking(self._fileno)
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self._protocol = protocol
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self._buffer = []
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self._conn_lost = 0
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self._closing = False # Set when close() or write_eof() called.
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# On AIX, the reader trick only works for sockets.
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# On other platforms it works for pipes and sockets.
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# (Exception: OS X 10.4? Issue #19294.)
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if is_socket or not sys.platform.startswith("aix"):
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self._loop.add_reader(self._fileno, self._read_ready)
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self._loop.call_soon(self._protocol.connection_made, self)
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if waiter is not None:
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self._loop.call_soon(waiter.set_result, None)
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def get_write_buffer_size(self):
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return sum(len(data) for data in self._buffer)
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def _read_ready(self):
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# Pipe was closed by peer.
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if self._buffer:
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self._close(BrokenPipeError())
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else:
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self._close()
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def write(self, data):
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assert isinstance(data, (bytes, bytearray, memoryview)), repr(data)
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if isinstance(data, bytearray):
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data = memoryview(data)
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if not data:
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return
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if self._conn_lost or self._closing:
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if self._conn_lost >= constants.LOG_THRESHOLD_FOR_CONNLOST_WRITES:
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logger.warning('pipe closed by peer or '
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'os.write(pipe, data) raised exception.')
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self._conn_lost += 1
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return
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if not self._buffer:
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# Attempt to send it right away first.
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try:
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n = os.write(self._fileno, data)
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except (BlockingIOError, InterruptedError):
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n = 0
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except Exception as exc:
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self._conn_lost += 1
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self._fatal_error(exc)
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return
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if n == len(data):
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return
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elif n > 0:
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data = data[n:]
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self._loop.add_writer(self._fileno, self._write_ready)
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self._buffer.append(data)
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self._maybe_pause_protocol()
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def _write_ready(self):
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data = b''.join(self._buffer)
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assert data, 'Data should not be empty'
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self._buffer.clear()
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try:
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n = os.write(self._fileno, data)
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except (BlockingIOError, InterruptedError):
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self._buffer.append(data)
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except Exception as exc:
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self._conn_lost += 1
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# Remove writer here, _fatal_error() doesn't it
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# because _buffer is empty.
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self._loop.remove_writer(self._fileno)
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self._fatal_error(exc)
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else:
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if n == len(data):
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self._loop.remove_writer(self._fileno)
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self._maybe_resume_protocol() # May append to buffer.
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if not self._buffer and self._closing:
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self._loop.remove_reader(self._fileno)
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self._call_connection_lost(None)
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return
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elif n > 0:
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data = data[n:]
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self._buffer.append(data) # Try again later.
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def can_write_eof(self):
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return True
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# TODO: Make the relationships between write_eof(), close(),
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# abort(), _fatal_error() and _close() more straightforward.
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def write_eof(self):
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if self._closing:
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return
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assert self._pipe
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self._closing = True
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if not self._buffer:
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self._loop.remove_reader(self._fileno)
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self._loop.call_soon(self._call_connection_lost, None)
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def close(self):
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if not self._closing:
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# write_eof is all what we needed to close the write pipe
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self.write_eof()
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def abort(self):
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self._close(None)
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def _fatal_error(self, exc):
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# should be called by exception handler only
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if not isinstance(exc, (BrokenPipeError, ConnectionResetError)):
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logger.exception('Fatal error for %s', self)
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self._close(exc)
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def _close(self, exc=None):
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self._closing = True
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if self._buffer:
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self._loop.remove_writer(self._fileno)
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self._buffer.clear()
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self._loop.remove_reader(self._fileno)
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self._loop.call_soon(self._call_connection_lost, exc)
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def _call_connection_lost(self, exc):
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try:
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self._protocol.connection_lost(exc)
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finally:
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self._pipe.close()
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self._pipe = None
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self._protocol = None
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self._loop = None
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class _UnixSubprocessTransport(base_subprocess.BaseSubprocessTransport):
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def _start(self, args, shell, stdin, stdout, stderr, bufsize, **kwargs):
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stdin_w = None
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if stdin == subprocess.PIPE:
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# Use a socket pair for stdin, since not all platforms
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# support selecting read events on the write end of a
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# socket (which we use in order to detect closing of the
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# other end). Notably this is needed on AIX, and works
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# just fine on other platforms.
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stdin, stdin_w = self._loop._socketpair()
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self._proc = subprocess.Popen(
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args, shell=shell, stdin=stdin, stdout=stdout, stderr=stderr,
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universal_newlines=False, bufsize=bufsize, **kwargs)
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if stdin_w is not None:
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stdin.close()
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self._proc.stdin = open(stdin_w.detach(), 'rb', buffering=bufsize)
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class AbstractChildWatcher:
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"""Abstract base class for monitoring child processes.
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Objects derived from this class monitor a collection of subprocesses and
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report their termination or interruption by a signal.
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New callbacks are registered with .add_child_handler(). Starting a new
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process must be done within a 'with' block to allow the watcher to suspend
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its activity until the new process if fully registered (this is needed to
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prevent a race condition in some implementations).
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Example:
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with watcher:
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proc = subprocess.Popen("sleep 1")
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watcher.add_child_handler(proc.pid, callback)
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Notes:
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Implementations of this class must be thread-safe.
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Since child watcher objects may catch the SIGCHLD signal and call
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waitpid(-1), there should be only one active object per process.
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"""
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def add_child_handler(self, pid, callback, *args):
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"""Register a new child handler.
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Arrange for callback(pid, returncode, *args) to be called when
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process 'pid' terminates. Specifying another callback for the same
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process replaces the previous handler.
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Note: callback() must be thread-safe
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"""
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raise NotImplementedError()
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def remove_child_handler(self, pid):
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"""Removes the handler for process 'pid'.
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The function returns True if the handler was successfully removed,
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False if there was nothing to remove."""
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raise NotImplementedError()
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def attach_loop(self, loop):
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"""Attach the watcher to an event loop.
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If the watcher was previously attached to an event loop, then it is
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first detached before attaching to the new loop.
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Note: loop may be None.
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"""
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raise NotImplementedError()
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def close(self):
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"""Close the watcher.
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This must be called to make sure that any underlying resource is freed.
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"""
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raise NotImplementedError()
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def __enter__(self):
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"""Enter the watcher's context and allow starting new processes
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This function must return self"""
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raise NotImplementedError()
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def __exit__(self, a, b, c):
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"""Exit the watcher's context"""
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raise NotImplementedError()
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class BaseChildWatcher(AbstractChildWatcher):
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def __init__(self):
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self._loop = None
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def close(self):
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self.attach_loop(None)
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def _do_waitpid(self, expected_pid):
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raise NotImplementedError()
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def _do_waitpid_all(self):
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raise NotImplementedError()
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def attach_loop(self, loop):
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assert loop is None or isinstance(loop, events.AbstractEventLoop)
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if self._loop is not None:
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self._loop.remove_signal_handler(signal.SIGCHLD)
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self._loop = loop
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if loop is not None:
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loop.add_signal_handler(signal.SIGCHLD, self._sig_chld)
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# Prevent a race condition in case a child terminated
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# during the switch.
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self._do_waitpid_all()
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def _sig_chld(self):
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try:
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self._do_waitpid_all()
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except Exception:
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logger.exception('Unknown exception in SIGCHLD handler')
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def _compute_returncode(self, status):
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if os.WIFSIGNALED(status):
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# The child process died because of a signal.
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return -os.WTERMSIG(status)
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elif os.WIFEXITED(status):
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# The child process exited (e.g sys.exit()).
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return os.WEXITSTATUS(status)
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else:
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# The child exited, but we don't understand its status.
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# This shouldn't happen, but if it does, let's just
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# return that status; perhaps that helps debug it.
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return status
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class SafeChildWatcher(BaseChildWatcher):
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"""'Safe' child watcher implementation.
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This implementation avoids disrupting other code spawning processes by
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polling explicitly each process in the SIGCHLD handler instead of calling
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os.waitpid(-1).
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This is a safe solution but it has a significant overhead when handling a
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big number of children (O(n) each time SIGCHLD is raised)
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"""
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def __init__(self):
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super().__init__()
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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
|