426 lines
14 KiB
Python
426 lines
14 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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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', 'STDIN', 'STDOUT', 'STDERR']
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STDIN = 0
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STDOUT = 1
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STDERR = 2
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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 SelectorEventLoop(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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self._subprocesses = {}
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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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handler = self._signal_handlers.get(signal.SIGCHLD)
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if handler is not None:
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self.remove_signal_handler(signal.SIGCHLD)
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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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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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self._reg_sigchld()
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transp = _UnixSubprocessTransport(self, protocol, args, shell,
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stdin, stdout, stderr, bufsize,
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extra=None, **kwargs)
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self._subprocesses[transp.get_pid()] = transp
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yield from transp._post_init()
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return transp
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def _reg_sigchld(self):
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if signal.SIGCHLD not in self._signal_handlers:
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self.add_signal_handler(signal.SIGCHLD, self._sig_chld)
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def _sig_chld(self):
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try:
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# Because of signal coalescing, we must keep calling waitpid() as
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# long as we're able to reap a child.
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while True:
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try:
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pid, status = os.waitpid(-1, os.WNOHANG)
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except ChildProcessError:
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break # No more child processes exist.
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if pid == 0:
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break # All remaining child processes are still alive.
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elif os.WIFSIGNALED(status):
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# A child process died because of a signal.
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returncode = -os.WTERMSIG(status)
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elif os.WIFEXITED(status):
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# A child process exited (e.g. sys.exit()).
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returncode = os.WEXITSTATUS(status)
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else:
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# A 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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returncode = status
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transp = self._subprocesses.get(pid)
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if transp is not None:
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transp._process_exited(returncode)
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except Exception:
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logger.exception('Unknown exception in SIGCHLD handler')
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def _subprocess_closed(self, transport):
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pid = transport.get_pid()
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self._subprocesses.pop(pid, None)
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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 stat.S_ISSOCK(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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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(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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is_pipe = stat.S_ISFIFO(mode)
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if not (is_socket or is_pipe):
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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._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 _read_ready(self):
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# Pipe was closed by peer.
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self._close()
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def write(self, data):
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assert isinstance(data, bytes), repr(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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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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if 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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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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