/usr/lib/python3/dist-packages/pymongo/thread_util.py is in python3-pymongo 2.6.3-1build1.
This file is owned by root:root, with mode 0o644.
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#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Utilities to abstract the differences between threads and greenlets."""
import threading
import sys
import weakref
try:
from time import monotonic as _time
except ImportError:
from time import time as _time
have_gevent = True
try:
import greenlet
try:
# gevent-1.0rc2 and later.
from gevent.lock import BoundedSemaphore as GeventBoundedSemaphore
except ImportError:
from gevent.coros import BoundedSemaphore as GeventBoundedSemaphore
from gevent.greenlet import SpawnedLink
except ImportError:
have_gevent = False
from pymongo.errors import ExceededMaxWaiters
# Do we have to work around http://bugs.python.org/issue1868?
issue1868 = (sys.version_info[:3] <= (2, 7, 0))
class Ident(object):
def __init__(self):
self._refs = {}
def watching(self):
"""Is the current thread or greenlet being watched for death?"""
return self.get() in self._refs
def unwatch(self, tid):
self._refs.pop(tid, None)
def get(self):
"""An id for this thread or greenlet"""
raise NotImplementedError
def watch(self, callback):
"""Run callback when this thread or greenlet dies. callback takes
one meaningless argument.
"""
raise NotImplementedError
class ThreadIdent(Ident):
class _DummyLock(object):
def acquire(self):
pass
def release(self):
pass
def __init__(self):
super(ThreadIdent, self).__init__()
self._local = threading.local()
if issue1868:
self._lock = threading.Lock()
else:
self._lock = ThreadIdent._DummyLock()
# We watch for thread-death using a weakref callback to a thread local.
# Weakrefs are permitted on subclasses of object but not object() itself.
class ThreadVigil(object):
pass
def _make_vigil(self):
# Threadlocals in Python <= 2.7.0 have race conditions when setting
# attributes and possibly when getting them, too, leading to weakref
# callbacks not getting called later.
self._lock.acquire()
try:
vigil = getattr(self._local, 'vigil', None)
if not vigil:
self._local.vigil = vigil = ThreadIdent.ThreadVigil()
finally:
self._lock.release()
return vigil
def get(self):
return id(self._make_vigil())
def watch(self, callback):
vigil = self._make_vigil()
self._refs[id(vigil)] = weakref.ref(vigil, callback)
class GreenletIdent(Ident):
def get(self):
return id(greenlet.getcurrent())
def watch(self, callback):
current = greenlet.getcurrent()
tid = self.get()
if hasattr(current, 'link'):
# This is a Gevent Greenlet (capital G), which inherits from
# greenlet and provides a 'link' method to detect when the
# Greenlet exits.
link = SpawnedLink(callback)
current.rawlink(link)
self._refs[tid] = link
else:
# This is a non-Gevent greenlet (small g), or it's the main
# greenlet.
self._refs[tid] = weakref.ref(current, callback)
def unwatch(self, tid):
""" call unlink if link before """
link = self._refs.pop(tid, None)
current = greenlet.getcurrent()
if hasattr(current, 'unlink'):
# This is a Gevent enhanced Greenlet. Remove the SpawnedLink we
# linked to it.
current.unlink(link)
def create_ident(use_greenlets):
if use_greenlets:
return GreenletIdent()
else:
return ThreadIdent()
class Counter(object):
"""A thread- or greenlet-local counter.
"""
def __init__(self, use_greenlets):
self.ident = create_ident(use_greenlets)
self._counters = {}
def inc(self):
# Copy these references so on_thread_died needn't close over self
ident = self.ident
_counters = self._counters
tid = ident.get()
_counters.setdefault(tid, 0)
_counters[tid] += 1
if not ident.watching():
# Before the tid is possibly reused, remove it from _counters
def on_thread_died(ref):
ident.unwatch(tid)
_counters.pop(tid, None)
ident.watch(on_thread_died)
return _counters[tid]
def dec(self):
tid = self.ident.get()
if self._counters.get(tid, 0) > 0:
self._counters[tid] -= 1
return self._counters[tid]
else:
return 0
def get(self):
return self._counters.get(self.ident.get(), 0)
### Begin backport from CPython 3.2 for timeout support for Semaphore.acquire
class Semaphore:
# After Tim Peters' semaphore class, but not quite the same (no maximum)
def __init__(self, value=1):
if value < 0:
raise ValueError("semaphore initial value must be >= 0")
self._cond = threading.Condition(threading.Lock())
self._value = value
def acquire(self, blocking=True, timeout=None):
if not blocking and timeout is not None:
raise ValueError("can't specify timeout for non-blocking acquire")
rc = False
endtime = None
self._cond.acquire()
while self._value == 0:
if not blocking:
break
if timeout is not None:
if endtime is None:
endtime = _time() + timeout
else:
timeout = endtime - _time()
if timeout <= 0:
break
self._cond.wait(timeout)
else:
self._value = self._value - 1
rc = True
self._cond.release()
return rc
__enter__ = acquire
def release(self):
self._cond.acquire()
self._value = self._value + 1
self._cond.notify()
self._cond.release()
def __exit__(self, t, v, tb):
self.release()
@property
def counter(self):
return self._value
class BoundedSemaphore(Semaphore):
"""Semaphore that checks that # releases is <= # acquires"""
def __init__(self, value=1):
Semaphore.__init__(self, value)
self._initial_value = value
def release(self):
if self._value >= self._initial_value:
raise ValueError("Semaphore released too many times")
return Semaphore.release(self)
### End backport from CPython 3.2
class DummySemaphore(object):
def __init__(self, value=None):
pass
def acquire(self, blocking=True, timeout=None):
return True
def release(self):
pass
class MaxWaitersBoundedSemaphore(object):
def __init__(self, semaphore_class, value=1, max_waiters=1):
self.waiter_semaphore = semaphore_class(max_waiters)
self.semaphore = semaphore_class(value)
def acquire(self, blocking=True, timeout=None):
if not self.waiter_semaphore.acquire(False):
raise ExceededMaxWaiters()
try:
return self.semaphore.acquire(blocking, timeout)
finally:
self.waiter_semaphore.release()
def __getattr__(self, name):
return getattr(self.semaphore, name)
class MaxWaitersBoundedSemaphoreThread(MaxWaitersBoundedSemaphore):
def __init__(self, value=1, max_waiters=1):
MaxWaitersBoundedSemaphore.__init__(
self, BoundedSemaphore, value, max_waiters)
if have_gevent:
class MaxWaitersBoundedSemaphoreGevent(MaxWaitersBoundedSemaphore):
def __init__(self, value=1, max_waiters=1):
MaxWaitersBoundedSemaphore.__init__(
self, GeventBoundedSemaphore, value, max_waiters)
def create_semaphore(max_size, max_waiters, use_greenlets):
if max_size is None:
return DummySemaphore()
elif use_greenlets:
if max_waiters is None:
return GeventBoundedSemaphore(max_size)
else:
return MaxWaitersBoundedSemaphoreGevent(max_size, max_waiters)
else:
if max_waiters is None:
return BoundedSemaphore(max_size)
else:
return MaxWaitersBoundedSemaphoreThread(max_size, max_waiters)
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