mirror of
https://github.com/python/cpython.git
synced 2025-08-27 04:05:34 +00:00
asyncio: Refactor SIGCHLD handling. By Anthony Baire.
This commit is contained in:
Guido van Rossum
parent
ccea08462b
commit
0eaa5ac9b5
5 changed files with 1315 additions and 199 deletions
|
|
@ -8,6 +8,7 @@ import socket
|
|||
import stat
|
||||
import subprocess
|
||||
import sys
|
||||
import threading
|
||||
|
||||
|
||||
from . import base_subprocess
|
||||
|
|
@ -20,7 +21,10 @@ from . import transports
|
|||
from .log import logger
|
||||
|
||||
|
||||
__all__ = ['SelectorEventLoop', 'STDIN', 'STDOUT', 'STDERR']
|
||||
__all__ = ['SelectorEventLoop', 'STDIN', 'STDOUT', 'STDERR',
|
||||
'AbstractChildWatcher', 'SafeChildWatcher',
|
||||
'FastChildWatcher', 'DefaultEventLoopPolicy',
|
||||
]
|
||||
|
||||
STDIN = 0
|
||||
STDOUT = 1
|
||||
|
|
@ -31,7 +35,7 @@ if sys.platform == 'win32': # pragma: no cover
|
|||
raise ImportError('Signals are not really supported on Windows')
|
||||
|
||||
|
||||
class SelectorEventLoop(selector_events.BaseSelectorEventLoop):
|
||||
class _UnixSelectorEventLoop(selector_events.BaseSelectorEventLoop):
|
||||
"""Unix event loop
|
||||
|
||||
Adds signal handling to SelectorEventLoop
|
||||
|
|
@ -40,17 +44,10 @@ class SelectorEventLoop(selector_events.BaseSelectorEventLoop):
|
|||
def __init__(self, selector=None):
|
||||
super().__init__(selector)
|
||||
self._signal_handlers = {}
|
||||
self._subprocesses = {}
|
||||
|
||||
def _socketpair(self):
|
||||
return socket.socketpair()
|
||||
|
||||
def close(self):
|
||||
handler = self._signal_handlers.get(signal.SIGCHLD)
|
||||
if handler is not None:
|
||||
self.remove_signal_handler(signal.SIGCHLD)
|
||||
super().close()
|
||||
|
||||
def add_signal_handler(self, sig, callback, *args):
|
||||
"""Add a handler for a signal. UNIX only.
|
||||
|
||||
|
|
@ -152,49 +149,20 @@ class SelectorEventLoop(selector_events.BaseSelectorEventLoop):
|
|||
def _make_subprocess_transport(self, protocol, args, shell,
|
||||
stdin, stdout, stderr, bufsize,
|
||||
extra=None, **kwargs):
|
||||
self._reg_sigchld()
|
||||
transp = _UnixSubprocessTransport(self, protocol, args, shell,
|
||||
stdin, stdout, stderr, bufsize,
|
||||
extra=None, **kwargs)
|
||||
self._subprocesses[transp.get_pid()] = transp
|
||||
with events.get_child_watcher() as watcher:
|
||||
transp = _UnixSubprocessTransport(self, protocol, args, shell,
|
||||
stdin, stdout, stderr, bufsize,
|
||||
extra=None, **kwargs)
|
||||
watcher.add_child_handler(transp.get_pid(),
|
||||
self._child_watcher_callback, transp)
|
||||
yield from transp._post_init()
|
||||
return transp
|
||||
|
||||
def _reg_sigchld(self):
|
||||
if signal.SIGCHLD not in self._signal_handlers:
|
||||
self.add_signal_handler(signal.SIGCHLD, self._sig_chld)
|
||||
def _child_watcher_callback(self, pid, returncode, transp):
|
||||
self.call_soon_threadsafe(transp._process_exited, returncode)
|
||||
|
||||
def _sig_chld(self):
|
||||
try:
|
||||
# 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:
|
||||
break # No more child processes exist.
|
||||
if pid == 0:
|
||||
break # All remaining child processes are still alive.
|
||||
elif os.WIFSIGNALED(status):
|
||||
# A child process died because of a signal.
|
||||
returncode = -os.WTERMSIG(status)
|
||||
elif os.WIFEXITED(status):
|
||||
# A child process exited (e.g. sys.exit()).
|
||||
returncode = os.WEXITSTATUS(status)
|
||||
else:
|
||||
# A 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.
|
||||
returncode = status
|
||||
transp = self._subprocesses.get(pid)
|
||||
if transp is not None:
|
||||
transp._process_exited(returncode)
|
||||
except Exception:
|
||||
logger.exception('Unknown exception in SIGCHLD handler')
|
||||
|
||||
def _subprocess_closed(self, transport):
|
||||
pid = transport.get_pid()
|
||||
self._subprocesses.pop(pid, None)
|
||||
def _subprocess_closed(self, transp):
|
||||
pass
|
||||
|
||||
|
||||
def _set_nonblocking(fd):
|
||||
|
|
@ -423,3 +391,335 @@ class _UnixSubprocessTransport(base_subprocess.BaseSubprocessTransport):
|
|||
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 set_loop(self, loop):
|
||||
"""Reattach the watcher to another event 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, loop):
|
||||
self._loop = None
|
||||
self._callbacks = {}
|
||||
|
||||
self.set_loop(loop)
|
||||
|
||||
def close(self):
|
||||
self.set_loop(None)
|
||||
self._callbacks.clear()
|
||||
|
||||
def _do_waitpid(self, expected_pid):
|
||||
raise NotImplementedError()
|
||||
|
||||
def _do_waitpid_all(self):
|
||||
raise NotImplementedError()
|
||||
|
||||
def set_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 remove_child_handler(self, pid):
|
||||
try:
|
||||
del self._callbacks[pid]
|
||||
return True
|
||||
except KeyError:
|
||||
return False
|
||||
|
||||
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 __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 _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, loop):
|
||||
super().__init__(loop)
|
||||
|
||||
self._lock = threading.Lock()
|
||||
self._zombies = {}
|
||||
self._forks = 0
|
||||
|
||||
def close(self):
|
||||
super().close()
|
||||
self._zombies.clear()
|
||||
|
||||
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"
|
||||
|
||||
self._callbacks[pid] = callback, args
|
||||
|
||||
try:
|
||||
# Ensure that the child is not already terminated.
|
||||
# (raise KeyError if still alive)
|
||||
returncode = self._zombies.pop(pid)
|
||||
|
||||
# Child is dead, therefore we can fire the callback immediately.
|
||||
# First we remove it from the dict.
|
||||
# (raise KeyError if .remove_child_handler() was called in-between)
|
||||
del self._callbacks[pid]
|
||||
except KeyError:
|
||||
pass
|
||||
else:
|
||||
callback(pid, returncode, *args)
|
||||
|
||||
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)
|
||||
|
||||
try:
|
||||
callback, args = self._callbacks.pop(pid)
|
||||
except KeyError:
|
||||
# unknown child
|
||||
with self._lock:
|
||||
if self._forks:
|
||||
# It may not be registered yet.
|
||||
self._zombies[pid] = returncode
|
||||
continue
|
||||
|
||||
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
|
||||
if isinstance(threading.current_thread(),
|
||||
threading._MainThread):
|
||||
self._watcher = SafeChildWatcher(self._local._loop)
|
||||
else:
|
||||
self._watcher = SafeChildWatcher(None)
|
||||
|
||||
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 .set_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.set_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
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue