372 lines
14 KiB
Python
372 lines
14 KiB
Python
|
###############################################################################
|
||
|
|
# Server process to keep track of unlinked resources, like folders and
|
||
|
|
# semaphores and clean them.
|
||
|
|
#
|
||
|
|
# author: Thomas Moreau
|
||
|
|
#
|
||
|
|
# adapted from multiprocessing/semaphore_tracker.py (17/02/2017)
|
||
|
|
# * include custom spawnv_passfds to start the process
|
||
|
|
# * add some VERBOSE logging
|
||
|
|
#
|
||
|
|
# TODO: multiprocessing.resource_tracker was contributed to Python 3.8 so
|
||
|
|
# once loky drops support for Python 3.7 it might be possible to stop
|
||
|
|
# maintaining this loky-specific fork. As a consequence, it might also be
|
||
|
|
# possible to stop maintaining the loky.backend.synchronize fork of
|
||
|
|
# multiprocessing.synchronize.
|
||
|
|
|
||
|
|
#
|
||
|
|
# On Unix we run a server process which keeps track of unlinked
|
||
|
|
# resources. The server ignores SIGINT and SIGTERM and reads from a
|
||
|
|
# pipe. The resource_tracker implements a reference counting scheme: each time
|
||
|
|
# a Python process anticipates the shared usage of a resource by another
|
||
|
|
# process, it signals the resource_tracker of this shared usage, and in return,
|
||
|
|
# the resource_tracker increments the resource's reference count by 1.
|
||
|
|
# Similarly, when access to a resource is closed by a Python process, the
|
||
|
|
# process notifies the resource_tracker by asking it to decrement the
|
||
|
|
# resource's reference count by 1. When the reference count drops to 0, the
|
||
|
|
# resource_tracker attempts to clean up the underlying resource.
|
||
|
|
|
||
|
|
# Finally, every other process connected to the resource tracker has a copy of
|
||
|
|
# the writable end of the pipe used to communicate with it, so the resource
|
||
|
|
# tracker gets EOF when all other processes have exited. Then the
|
||
|
|
# resource_tracker process unlinks any remaining leaked resources (with
|
||
|
|
# reference count above 0)
|
||
|
|
|
||
|
|
# For semaphores, this is important because the system only supports a limited
|
||
|
|
# number of named semaphores, and they will not be automatically removed till
|
||
|
|
# the next reboot. Without this resource tracker process, "killall python"
|
||
|
|
# would probably leave unlinked semaphores.
|
||
|
|
|
||
|
|
# Note that this behavior differs from CPython's resource_tracker, which only
|
||
|
|
# implements list of shared resources, and not a proper refcounting scheme.
|
||
|
|
# Also, CPython's resource tracker will only attempt to cleanup those shared
|
||
|
|
# resources once all procsses connected to the resouce tracker have exited.
|
||
|
|
|
||
|
|
|
||
|
|
import os
|
||
|
|
import shutil
|
||
|
|
import sys
|
||
|
|
import signal
|
||
|
|
import warnings
|
||
|
|
import threading
|
||
|
|
from _multiprocessing import sem_unlink
|
||
|
|
from multiprocessing import util
|
||
|
|
|
||
|
|
from . import spawn
|
||
|
|
|
||
|
|
if sys.platform == "win32":
|
||
|
|
import _winapi
|
||
|
|
import msvcrt
|
||
|
|
from multiprocessing.reduction import duplicate
|
||
|
|
|
||
|
|
|
||
|
|
__all__ = ['ensure_running', 'register', 'unregister']
|
||
|
|
|
||
|
|
_HAVE_SIGMASK = hasattr(signal, 'pthread_sigmask')
|
||
|
|
_IGNORED_SIGNALS = (signal.SIGINT, signal.SIGTERM)
|
||
|
|
|
||
|
|
_CLEANUP_FUNCS = {
|
||
|
|
'folder': shutil.rmtree,
|
||
|
|
'file': os.unlink
|
||
|
|
}
|
||
|
|
|
||
|
|
if os.name == "posix":
|
||
|
|
_CLEANUP_FUNCS['semlock'] = sem_unlink
|
||
|
|
|
||
|
|
|
||
|
|
VERBOSE = False
|
||
|
|
|
||
|
|
|
||
|
|
class ResourceTracker:
|
||
|
|
|
||
|
|
def __init__(self):
|
||
|
|
self._lock = threading.Lock()
|
||
|
|
self._fd = None
|
||
|
|
self._pid = None
|
||
|
|
|
||
|
|
def getfd(self):
|
||
|
|
self.ensure_running()
|
||
|
|
return self._fd
|
||
|
|
|
||
|
|
def ensure_running(self):
|
||
|
|
'''Make sure that resource tracker process is running.
|
||
|
|
|
||
|
|
This can be run from any process. Usually a child process will use
|
||
|
|
the resource created by its parent.'''
|
||
|
|
with self._lock:
|
||
|
|
if self._fd is not None:
|
||
|
|
# resource tracker was launched before, is it still running?
|
||
|
|
if self._check_alive():
|
||
|
|
# => still alive
|
||
|
|
return
|
||
|
|
# => dead, launch it again
|
||
|
|
os.close(self._fd)
|
||
|
|
if os.name == "posix":
|
||
|
|
try:
|
||
|
|
# At this point, the resource_tracker process has been
|
||
|
|
# killed or crashed. Let's remove the process entry
|
||
|
|
# from the process table to avoid zombie processes.
|
||
|
|
os.waitpid(self._pid, 0)
|
||
|
|
except OSError:
|
||
|
|
# The process was terminated or is a child from an
|
||
|
|
# ancestor of the current process.
|
||
|
|
pass
|
||
|
|
self._fd = None
|
||
|
|
self._pid = None
|
||
|
|
|
||
|
|
warnings.warn('resource_tracker: process died unexpectedly, '
|
||
|
|
'relaunching. Some folders/sempahores might '
|
||
|
|
'leak.')
|
||
|
|
|
||
|
|
fds_to_pass = []
|
||
|
|
try:
|
||
|
|
fds_to_pass.append(sys.stderr.fileno())
|
||
|
|
except Exception:
|
||
|
|
pass
|
||
|
|
|
||
|
|
r, w = os.pipe()
|
||
|
|
if sys.platform == "win32":
|
||
|
|
_r = duplicate(msvcrt.get_osfhandle(r), inheritable=True)
|
||
|
|
os.close(r)
|
||
|
|
r = _r
|
||
|
|
|
||
|
|
cmd = f'from {main.__module__} import main; main({r}, {VERBOSE})'
|
||
|
|
try:
|
||
|
|
fds_to_pass.append(r)
|
||
|
|
# process will out live us, so no need to wait on pid
|
||
|
|
exe = spawn.get_executable()
|
||
|
|
args = [exe, *util._args_from_interpreter_flags(), '-c', cmd]
|
||
|
|
util.debug(f"launching resource tracker: {args}")
|
||
|
|
# bpo-33613: Register a signal mask that will block the
|
||
|
|
# signals. This signal mask will be inherited by the child
|
||
|
|
# that is going to be spawned and will protect the child from a
|
||
|
|
# race condition that can make the child die before it
|
||
|
|
# registers signal handlers for SIGINT and SIGTERM. The mask is
|
||
|
|
# unregistered after spawning the child.
|
||
|
|
try:
|
||
|
|
if _HAVE_SIGMASK:
|
||
|
|
signal.pthread_sigmask(signal.SIG_BLOCK,
|
||
|
|
_IGNORED_SIGNALS)
|
||
|
|
pid = spawnv_passfds(exe, args, fds_to_pass)
|
||
|
|
finally:
|
||
|
|
if _HAVE_SIGMASK:
|
||
|
|
signal.pthread_sigmask(signal.SIG_UNBLOCK,
|
||
|
|
_IGNORED_SIGNALS)
|
||
|
|
except BaseException:
|
||
|
|
os.close(w)
|
||
|
|
raise
|
||
|
|
else:
|
||
|
|
self._fd = w
|
||
|
|
self._pid = pid
|
||
|
|
finally:
|
||
|
|
if sys.platform == "win32":
|
||
|
|
_winapi.CloseHandle(r)
|
||
|
|
else:
|
||
|
|
os.close(r)
|
||
|
|
|
||
|
|
def _check_alive(self):
|
||
|
|
'''Check for the existence of the resource tracker process.'''
|
||
|
|
try:
|
||
|
|
self._send('PROBE', '', '')
|
||
|
|
except BrokenPipeError:
|
||
|
|
return False
|
||
|
|
else:
|
||
|
|
return True
|
||
|
|
|
||
|
|
def register(self, name, rtype):
|
||
|
|
'''Register a named resource, and increment its refcount.'''
|
||
|
|
self.ensure_running()
|
||
|
|
self._send('REGISTER', name, rtype)
|
||
|
|
|
||
|
|
def unregister(self, name, rtype):
|
||
|
|
'''Unregister a named resource with resource tracker.'''
|
||
|
|
self.ensure_running()
|
||
|
|
self._send('UNREGISTER', name, rtype)
|
||
|
|
|
||
|
|
def maybe_unlink(self, name, rtype):
|
||
|
|
'''Decrement the refcount of a resource, and delete it if it hits 0'''
|
||
|
|
self.ensure_running()
|
||
|
|
self._send("MAYBE_UNLINK", name, rtype)
|
||
|
|
|
||
|
|
def _send(self, cmd, name, rtype):
|
||
|
|
if len(name) > 512:
|
||
|
|
# posix guarantees that writes to a pipe of less than PIPE_BUF
|
||
|
|
# bytes are atomic, and that PIPE_BUF >= 512
|
||
|
|
raise ValueError('name too long')
|
||
|
|
msg = f'{cmd}:{name}:{rtype}\n'.encode('ascii')
|
||
|
|
nbytes = os.write(self._fd, msg)
|
||
|
|
assert nbytes == len(msg)
|
||
|
|
|
||
|
|
|
||
|
|
_resource_tracker = ResourceTracker()
|
||
|
|
ensure_running = _resource_tracker.ensure_running
|
||
|
|
register = _resource_tracker.register
|
||
|
|
maybe_unlink = _resource_tracker.maybe_unlink
|
||
|
|
unregister = _resource_tracker.unregister
|
||
|
|
getfd = _resource_tracker.getfd
|
||
|
|
|
||
|
|
|
||
|
|
def main(fd, verbose=0):
|
||
|
|
'''Run resource tracker.'''
|
||
|
|
# protect the process from ^C and "killall python" etc
|
||
|
|
if verbose:
|
||
|
|
util.log_to_stderr(level=util.DEBUG)
|
||
|
|
|
||
|
|
signal.signal(signal.SIGINT, signal.SIG_IGN)
|
||
|
|
signal.signal(signal.SIGTERM, signal.SIG_IGN)
|
||
|
|
|
||
|
|
if _HAVE_SIGMASK:
|
||
|
|
signal.pthread_sigmask(signal.SIG_UNBLOCK, _IGNORED_SIGNALS)
|
||
|
|
|
||
|
|
for f in (sys.stdin, sys.stdout):
|
||
|
|
try:
|
||
|
|
f.close()
|
||
|
|
except Exception:
|
||
|
|
pass
|
||
|
|
|
||
|
|
if verbose:
|
||
|
|
util.debug("Main resource tracker is running")
|
||
|
|
|
||
|
|
registry = {rtype: {} for rtype in _CLEANUP_FUNCS.keys()}
|
||
|
|
try:
|
||
|
|
# keep track of registered/unregistered resources
|
||
|
|
if sys.platform == "win32":
|
||
|
|
fd = msvcrt.open_osfhandle(fd, os.O_RDONLY)
|
||
|
|
with open(fd, 'rb') as f:
|
||
|
|
while True:
|
||
|
|
line = f.readline()
|
||
|
|
if line == b'': # EOF
|
||
|
|
break
|
||
|
|
try:
|
||
|
|
splitted = line.strip().decode('ascii').split(':')
|
||
|
|
# name can potentially contain separator symbols (for
|
||
|
|
# instance folders on Windows)
|
||
|
|
cmd, name, rtype = (
|
||
|
|
splitted[0], ':'.join(splitted[1:-1]), splitted[-1])
|
||
|
|
|
||
|
|
if cmd == 'PROBE':
|
||
|
|
continue
|
||
|
|
|
||
|
|
if rtype not in _CLEANUP_FUNCS:
|
||
|
|
raise ValueError(
|
||
|
|
f'Cannot register {name} for automatic cleanup: '
|
||
|
|
f'unknown resource type ({rtype}). Resource type '
|
||
|
|
'should be one of the following: '
|
||
|
|
f'{list(_CLEANUP_FUNCS.keys())}'
|
||
|
|
)
|
||
|
|
|
||
|
|
if cmd == 'REGISTER':
|
||
|
|
if name not in registry[rtype]:
|
||
|
|
registry[rtype][name] = 1
|
||
|
|
else:
|
||
|
|
registry[rtype][name] += 1
|
||
|
|
|
||
|
|
if verbose:
|
||
|
|
util.debug(
|
||
|
|
"[ResourceTracker] incremented refcount of "
|
||
|
|
f"{rtype} {name} "
|
||
|
|
f"(current {registry[rtype][name]})"
|
||
|
|
)
|
||
|
|
elif cmd == 'UNREGISTER':
|
||
|
|
del registry[rtype][name]
|
||
|
|
if verbose:
|
||
|
|
util.debug(
|
||
|
|
f"[ResourceTracker] unregister {name} {rtype}: "
|
||
|
|
f"registry({len(registry)})"
|
||
|
|
)
|
||
|
|
elif cmd == 'MAYBE_UNLINK':
|
||
|
|
registry[rtype][name] -= 1
|
||
|
|
if verbose:
|
||
|
|
util.debug(
|
||
|
|
"[ResourceTracker] decremented refcount of "
|
||
|
|
f"{rtype} {name} "
|
||
|
|
f"(current {registry[rtype][name]})"
|
||
|
|
)
|
||
|
|
|
||
|
|
if registry[rtype][name] == 0:
|
||
|
|
del registry[rtype][name]
|
||
|
|
try:
|
||
|
|
if verbose:
|
||
|
|
util.debug(
|
||
|
|
f"[ResourceTracker] unlink {name}"
|
||
|
|
)
|
||
|
|
_CLEANUP_FUNCS[rtype](name)
|
||
|
|
except Exception as e:
|
||
|
|
warnings.warn(
|
||
|
|
f'resource_tracker: {name}: {e!r}')
|
||
|
|
|
||
|
|
else:
|
||
|
|
raise RuntimeError(f'unrecognized command {cmd!r}')
|
||
|
|
except BaseException:
|
||
|
|
try:
|
||
|
|
sys.excepthook(*sys.exc_info())
|
||
|
|
except BaseException:
|
||
|
|
pass
|
||
|
|
finally:
|
||
|
|
# all processes have terminated; cleanup any remaining resources
|
||
|
|
def _unlink_resources(rtype_registry, rtype):
|
||
|
|
if rtype_registry:
|
||
|
|
try:
|
||
|
|
warnings.warn(
|
||
|
|
'resource_tracker: There appear to be '
|
||
|
|
f'{len(rtype_registry)} leaked {rtype} objects to '
|
||
|
|
'clean up at shutdown'
|
||
|
|
)
|
||
|
|
except Exception:
|
||
|
|
pass
|
||
|
|
for name in rtype_registry:
|
||
|
|
# For some reason the process which created and registered this
|
||
|
|
# resource has failed to unregister it. Presumably it has
|
||
|
|
# died. We therefore clean it up.
|
||
|
|
try:
|
||
|
|
_CLEANUP_FUNCS[rtype](name)
|
||
|
|
if verbose:
|
||
|
|
util.debug(f"[ResourceTracker] unlink {name}")
|
||
|
|
except Exception as e:
|
||
|
|
warnings.warn(f'resource_tracker: {name}: {e!r}')
|
||
|
|
|
||
|
|
for rtype, rtype_registry in registry.items():
|
||
|
|
if rtype == "folder":
|
||
|
|
continue
|
||
|
|
else:
|
||
|
|
_unlink_resources(rtype_registry, rtype)
|
||
|
|
|
||
|
|
# The default cleanup routine for folders deletes everything inside
|
||
|
|
# those folders recursively, which can include other resources tracked
|
||
|
|
# by the resource tracker). To limit the risk of the resource tracker
|
||
|
|
# attempting to delete twice a resource (once as part of a tracked
|
||
|
|
# folder, and once as a resource), we delete the folders after all
|
||
|
|
# other resource types.
|
||
|
|
if "folder" in registry:
|
||
|
|
_unlink_resources(registry["folder"], "folder")
|
||
|
|
|
||
|
|
if verbose:
|
||
|
|
util.debug("resource tracker shut down")
|
||
|
|
|
||
|
|
|
||
|
|
#
|
||
|
|
# Start a program with only specified fds kept open
|
||
|
|
#
|
||
|
|
|
||
|
|
def spawnv_passfds(path, args, passfds):
|
||
|
|
passfds = sorted(passfds)
|
||
|
|
if sys.platform != "win32":
|
||
|
|
errpipe_read, errpipe_write = os.pipe()
|
||
|
|
try:
|
||
|
|
from .reduction import _mk_inheritable
|
||
|
|
from .fork_exec import fork_exec
|
||
|
|
_pass = [_mk_inheritable(fd) for fd in passfds]
|
||
|
|
return fork_exec(args, _pass)
|
||
|
|
finally:
|
||
|
|
os.close(errpipe_read)
|
||
|
|
os.close(errpipe_write)
|
||
|
|
else:
|
||
|
|
cmd = ' '.join(f'"{x}"' for x in args)
|
||
|
|
try:
|
||
|
|
_, ht, pid, _ = _winapi.CreateProcess(
|
||
|
|
path, cmd, None, None, True, 0, None, None, None)
|
||
|
|
_winapi.CloseHandle(ht)
|
||
|
|
except BaseException:
|
||
|
|
pass
|
||
|
|
return pid
|