d51723fa64
The fallback was added 9 years ago, in 0.1.0 release[1].
[1] c98d5edc44
Change-Id: I3b66c5f9df58eaeea9fc51a6c0b83af2e39a525b
531 lines
17 KiB
Python
531 lines
17 KiB
Python
# Copyright 2011 OpenStack Foundation.
|
|
# All Rights Reserved.
|
|
#
|
|
# 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.
|
|
|
|
import contextlib
|
|
import errno
|
|
import functools
|
|
import logging
|
|
import os
|
|
import shutil
|
|
import subprocess
|
|
import sys
|
|
import tempfile
|
|
import threading
|
|
import weakref
|
|
|
|
import fasteners
|
|
from oslo_config import cfg
|
|
from oslo_utils import reflection
|
|
from oslo_utils import timeutils
|
|
|
|
from oslo_concurrency._i18n import _
|
|
|
|
try:
|
|
# import eventlet optionally
|
|
import eventlet
|
|
from eventlet import patcher as eventlet_patcher
|
|
except ImportError:
|
|
eventlet = None
|
|
eventlet_patcher = None
|
|
|
|
|
|
LOG = logging.getLogger(__name__)
|
|
|
|
|
|
_opts = [
|
|
cfg.BoolOpt('disable_process_locking', default=False,
|
|
help='Enables or disables inter-process locks.'),
|
|
cfg.StrOpt('lock_path',
|
|
default=os.environ.get("OSLO_LOCK_PATH"),
|
|
help='Directory to use for lock files. For security, the '
|
|
'specified directory should only be writable by the user '
|
|
'running the processes that need locking. '
|
|
'Defaults to environment variable OSLO_LOCK_PATH. '
|
|
'If external locks are used, a lock path must be set.')
|
|
]
|
|
|
|
|
|
def _register_opts(conf):
|
|
conf.register_opts(_opts, group='oslo_concurrency')
|
|
|
|
|
|
CONF = cfg.CONF
|
|
_register_opts(CONF)
|
|
|
|
|
|
def set_defaults(lock_path):
|
|
"""Set value for lock_path.
|
|
|
|
This can be used by tests to set lock_path to a temporary directory.
|
|
"""
|
|
cfg.set_defaults(_opts, lock_path=lock_path)
|
|
|
|
|
|
def get_lock_path(conf):
|
|
"""Return the path used for external file-based locks.
|
|
|
|
:param conf: Configuration object
|
|
:type conf: oslo_config.cfg.ConfigOpts
|
|
|
|
.. versionadded:: 1.8
|
|
"""
|
|
_register_opts(conf)
|
|
return conf.oslo_concurrency.lock_path
|
|
|
|
|
|
class ReaderWriterLock(fasteners.ReaderWriterLock):
|
|
"""A reader/writer lock.
|
|
|
|
.. versionadded:: 0.4
|
|
"""
|
|
def __init__(self, *args, **kwargs):
|
|
super().__init__(*args, **kwargs)
|
|
# Until https://github.com/eventlet/eventlet/issues/731 is resolved
|
|
# we need to use eventlet.getcurrent instead of
|
|
# threading.current_thread if we are running in a monkey patched
|
|
# environment
|
|
if eventlet is not None and eventlet_patcher is not None:
|
|
if eventlet_patcher.is_monkey_patched('thread'):
|
|
self._current_thread = eventlet.getcurrent
|
|
|
|
|
|
InterProcessLock = fasteners.InterProcessLock
|
|
|
|
|
|
class FairLocks(object):
|
|
"""A garbage collected container of fair locks.
|
|
|
|
With a fair lock, contending lockers will get the lock in the order in
|
|
which they tried to acquire it.
|
|
|
|
This collection internally uses a weak value dictionary so that when a
|
|
lock is no longer in use (by any threads) it will automatically be
|
|
removed from this container by the garbage collector.
|
|
"""
|
|
|
|
def __init__(self):
|
|
self._locks = weakref.WeakValueDictionary()
|
|
self._lock = threading.Lock()
|
|
|
|
def get(self, name):
|
|
"""Gets (or creates) a lock with a given name.
|
|
|
|
:param name: The lock name to get/create (used to associate
|
|
previously created names with the same lock).
|
|
|
|
Returns an newly constructed lock (or an existing one if it was
|
|
already created for the given name).
|
|
"""
|
|
with self._lock:
|
|
try:
|
|
return self._locks[name]
|
|
except KeyError:
|
|
# The fasteners module specifies that
|
|
# ReaderWriterLock.write_lock() will give FIFO behaviour,
|
|
# so we don't need to do anything special ourselves.
|
|
rwlock = ReaderWriterLock()
|
|
self._locks[name] = rwlock
|
|
return rwlock
|
|
|
|
|
|
_fair_locks = FairLocks()
|
|
|
|
|
|
def internal_fair_lock(name):
|
|
return _fair_locks.get(name)
|
|
|
|
|
|
class Semaphores(object):
|
|
"""A garbage collected container of semaphores.
|
|
|
|
This collection internally uses a weak value dictionary so that when a
|
|
semaphore is no longer in use (by any threads) it will automatically be
|
|
removed from this container by the garbage collector.
|
|
|
|
.. versionadded:: 0.3
|
|
"""
|
|
|
|
def __init__(self):
|
|
self._semaphores = weakref.WeakValueDictionary()
|
|
self._lock = threading.Lock()
|
|
|
|
def get(self, name):
|
|
"""Gets (or creates) a semaphore with a given name.
|
|
|
|
:param name: The semaphore name to get/create (used to associate
|
|
previously created names with the same semaphore).
|
|
|
|
Returns an newly constructed semaphore (or an existing one if it was
|
|
already created for the given name).
|
|
"""
|
|
with self._lock:
|
|
try:
|
|
return self._semaphores[name]
|
|
except KeyError:
|
|
sem = threading.Semaphore()
|
|
self._semaphores[name] = sem
|
|
return sem
|
|
|
|
def __len__(self):
|
|
"""Returns how many semaphores exist at the current time."""
|
|
return len(self._semaphores)
|
|
|
|
|
|
_semaphores = Semaphores()
|
|
|
|
|
|
def _get_lock_path(name, lock_file_prefix, lock_path=None):
|
|
# NOTE(mikal): the lock name cannot contain directory
|
|
# separators
|
|
name = name.replace(os.sep, '_')
|
|
if lock_file_prefix:
|
|
sep = '' if lock_file_prefix.endswith('-') else '-'
|
|
name = '%s%s%s' % (lock_file_prefix, sep, name)
|
|
|
|
local_lock_path = lock_path or CONF.oslo_concurrency.lock_path
|
|
|
|
if not local_lock_path:
|
|
raise cfg.RequiredOptError('lock_path', 'oslo_concurrency')
|
|
|
|
return os.path.join(local_lock_path, name)
|
|
|
|
|
|
def external_lock(name, lock_file_prefix=None, lock_path=None):
|
|
lock_file_path = _get_lock_path(name, lock_file_prefix, lock_path)
|
|
|
|
return InterProcessLock(lock_file_path)
|
|
|
|
|
|
def remove_external_lock_file(name, lock_file_prefix=None, lock_path=None,
|
|
semaphores=None):
|
|
"""Remove an external lock file when it's not used anymore
|
|
This will be helpful when we have a lot of lock files
|
|
"""
|
|
with internal_lock(name, semaphores=semaphores):
|
|
lock_file_path = _get_lock_path(name, lock_file_prefix, lock_path)
|
|
try:
|
|
os.remove(lock_file_path)
|
|
except OSError as exc:
|
|
if exc.errno != errno.ENOENT:
|
|
LOG.warning('Failed to remove file %(file)s',
|
|
{'file': lock_file_path})
|
|
|
|
|
|
class AcquireLockFailedException(Exception):
|
|
def __init__(self, lock_name):
|
|
self.message = "Failed to acquire the lock %s" % lock_name
|
|
|
|
def __str__(self):
|
|
return self.message
|
|
|
|
|
|
def internal_lock(name, semaphores=None, blocking=True):
|
|
@contextlib.contextmanager
|
|
def nonblocking(lock):
|
|
"""Try to acquire the internal lock without blocking."""
|
|
if not lock.acquire(blocking=False):
|
|
raise AcquireLockFailedException(name)
|
|
try:
|
|
yield lock
|
|
finally:
|
|
lock.release()
|
|
|
|
if semaphores is None:
|
|
semaphores = _semaphores
|
|
lock = semaphores.get(name)
|
|
|
|
return nonblocking(lock) if not blocking else lock
|
|
|
|
|
|
@contextlib.contextmanager
|
|
def lock(name, lock_file_prefix=None, external=False, lock_path=None,
|
|
do_log=True, semaphores=None, delay=0.01, fair=False, blocking=True):
|
|
"""Context based lock
|
|
|
|
This function yields a `threading.Semaphore` instance (if we don't use
|
|
eventlet.monkey_patch(), else `semaphore.Semaphore`) unless external is
|
|
True, in which case, it'll yield an InterProcessLock instance.
|
|
|
|
:param lock_file_prefix: The lock_file_prefix argument is used to provide
|
|
lock files on disk with a meaningful prefix.
|
|
|
|
:param external: The external keyword argument denotes whether this lock
|
|
should work across multiple processes. This means that if two different
|
|
workers both run a method decorated with @synchronized('mylock',
|
|
external=True), only one of them will execute at a time.
|
|
|
|
:param lock_path: The path in which to store external lock files. For
|
|
external locking to work properly, this must be the same for all
|
|
references to the lock.
|
|
|
|
:param do_log: Whether to log acquire/release messages. This is primarily
|
|
intended to reduce log message duplication when `lock` is used from the
|
|
`synchronized` decorator.
|
|
|
|
:param semaphores: Container that provides semaphores to use when locking.
|
|
This ensures that threads inside the same application can not collide,
|
|
due to the fact that external process locks are unaware of a processes
|
|
active threads.
|
|
|
|
:param delay: Delay between acquisition attempts (in seconds).
|
|
|
|
:param fair: Whether or not we want a "fair" lock where contending lockers
|
|
will get the lock in the order in which they tried to acquire it.
|
|
|
|
:param blocking: Whether to wait forever to try to acquire the lock.
|
|
Incompatible with fair locks because those provided by the fasteners
|
|
module doesn't implements a non-blocking behavior.
|
|
|
|
.. versionchanged:: 0.2
|
|
Added *do_log* optional parameter.
|
|
|
|
.. versionchanged:: 0.3
|
|
Added *delay* and *semaphores* optional parameters.
|
|
"""
|
|
if fair:
|
|
if semaphores is not None:
|
|
raise NotImplementedError(_('Specifying semaphores is not '
|
|
'supported when using fair locks.'))
|
|
if blocking is not True:
|
|
raise NotImplementedError(_('Disabling blocking is not supported '
|
|
'when using fair locks.'))
|
|
# The fasteners module specifies that write_lock() provides fairness.
|
|
int_lock = internal_fair_lock(name).write_lock()
|
|
else:
|
|
int_lock = internal_lock(name, semaphores=semaphores,
|
|
blocking=blocking)
|
|
if do_log:
|
|
LOG.debug('Acquiring lock "%s"', name)
|
|
with int_lock:
|
|
if do_log:
|
|
LOG.debug('Acquired lock "%(lock)s"', {'lock': name})
|
|
try:
|
|
if external and not CONF.oslo_concurrency.disable_process_locking:
|
|
ext_lock = external_lock(name, lock_file_prefix, lock_path)
|
|
gotten = ext_lock.acquire(delay=delay, blocking=blocking)
|
|
if not gotten:
|
|
raise AcquireLockFailedException(name)
|
|
if do_log:
|
|
LOG.debug('Acquired external semaphore "%(lock)s"',
|
|
{'lock': name})
|
|
try:
|
|
yield ext_lock
|
|
finally:
|
|
ext_lock.release()
|
|
else:
|
|
yield int_lock
|
|
finally:
|
|
if do_log:
|
|
LOG.debug('Releasing lock "%(lock)s"', {'lock': name})
|
|
|
|
|
|
def lock_with_prefix(lock_file_prefix):
|
|
"""Partial object generator for the lock context manager.
|
|
|
|
Redefine lock in each project like so::
|
|
|
|
(in nova/utils.py)
|
|
from oslo_concurrency import lockutils
|
|
|
|
_prefix = 'nova'
|
|
lock = lockutils.lock_with_prefix(_prefix)
|
|
lock_cleanup = lockutils.remove_external_lock_file_with_prefix(_prefix)
|
|
|
|
|
|
(in nova/foo.py)
|
|
from nova import utils
|
|
|
|
with utils.lock('mylock'):
|
|
...
|
|
|
|
Eventually clean up with::
|
|
|
|
lock_cleanup('mylock')
|
|
|
|
:param lock_file_prefix: A string used to provide lock files on disk with a
|
|
meaningful prefix. Will be separated from the lock name with a hyphen,
|
|
which may optionally be included in the lock_file_prefix (e.g.
|
|
``'nova'`` and ``'nova-'`` are equivalent).
|
|
"""
|
|
return functools.partial(lock, lock_file_prefix=lock_file_prefix)
|
|
|
|
|
|
def synchronized(name, lock_file_prefix=None, external=False, lock_path=None,
|
|
semaphores=None, delay=0.01, fair=False, blocking=True):
|
|
"""Synchronization decorator.
|
|
|
|
Decorating a method like so::
|
|
|
|
@synchronized('mylock')
|
|
def foo(self, *args):
|
|
...
|
|
|
|
ensures that only one thread will execute the foo method at a time.
|
|
|
|
Different methods can share the same lock::
|
|
|
|
@synchronized('mylock')
|
|
def foo(self, *args):
|
|
...
|
|
|
|
@synchronized('mylock')
|
|
def bar(self, *args):
|
|
...
|
|
|
|
This way only one of either foo or bar can be executing at a time.
|
|
|
|
.. versionchanged:: 0.3
|
|
Added *delay* and *semaphores* optional parameter.
|
|
"""
|
|
|
|
def wrap(f):
|
|
|
|
@functools.wraps(f)
|
|
def inner(*args, **kwargs):
|
|
t1 = timeutils.now()
|
|
t2 = None
|
|
gotten = True
|
|
f_name = reflection.get_callable_name(f)
|
|
try:
|
|
LOG.debug('Acquiring lock "%s" by "%s"', name, f_name)
|
|
with lock(name, lock_file_prefix, external, lock_path,
|
|
do_log=False, semaphores=semaphores, delay=delay,
|
|
fair=fair, blocking=blocking):
|
|
t2 = timeutils.now()
|
|
LOG.debug('Lock "%(name)s" acquired by "%(function)s" :: '
|
|
'waited %(wait_secs)0.3fs',
|
|
{'name': name,
|
|
'function': f_name,
|
|
'wait_secs': (t2 - t1)})
|
|
return f(*args, **kwargs)
|
|
except AcquireLockFailedException:
|
|
gotten = False
|
|
finally:
|
|
t3 = timeutils.now()
|
|
if t2 is None:
|
|
held_secs = "N/A"
|
|
else:
|
|
held_secs = "%0.3fs" % (t3 - t2)
|
|
LOG.debug('Lock "%(name)s" "%(gotten)s" by "%(function)s" ::'
|
|
' held %(held_secs)s',
|
|
{'name': name,
|
|
'gotten': 'released' if gotten else 'unacquired',
|
|
'function': f_name,
|
|
'held_secs': held_secs})
|
|
return inner
|
|
|
|
return wrap
|
|
|
|
|
|
def synchronized_with_prefix(lock_file_prefix):
|
|
"""Partial object generator for the synchronization decorator.
|
|
|
|
Redefine @synchronized in each project like so::
|
|
|
|
(in nova/utils.py)
|
|
from oslo_concurrency import lockutils
|
|
|
|
_prefix = 'nova'
|
|
synchronized = lockutils.synchronized_with_prefix(_prefix)
|
|
lock_cleanup = lockutils.remove_external_lock_file_with_prefix(_prefix)
|
|
|
|
|
|
(in nova/foo.py)
|
|
from nova import utils
|
|
|
|
@utils.synchronized('mylock')
|
|
def bar(self, *args):
|
|
...
|
|
|
|
Eventually clean up with::
|
|
|
|
lock_cleanup('mylock')
|
|
|
|
:param lock_file_prefix: A string used to provide lock files on disk with a
|
|
meaningful prefix. Will be separated from the lock name with a hyphen,
|
|
which may optionally be included in the lock_file_prefix (e.g.
|
|
``'nova'`` and ``'nova-'`` are equivalent).
|
|
"""
|
|
|
|
return functools.partial(synchronized, lock_file_prefix=lock_file_prefix)
|
|
|
|
|
|
def remove_external_lock_file_with_prefix(lock_file_prefix):
|
|
"""Partial object generator for the remove lock file function.
|
|
|
|
Redefine remove_external_lock_file_with_prefix in each project like so::
|
|
|
|
(in nova/utils.py)
|
|
from oslo_concurrency import lockutils
|
|
|
|
_prefix = 'nova'
|
|
synchronized = lockutils.synchronized_with_prefix(_prefix)
|
|
lock = lockutils.lock_with_prefix(_prefix)
|
|
lock_cleanup = lockutils.remove_external_lock_file_with_prefix(_prefix)
|
|
|
|
(in nova/foo.py)
|
|
from nova import utils
|
|
|
|
@utils.synchronized('mylock')
|
|
def bar(self, *args):
|
|
...
|
|
|
|
def baz(self, *args):
|
|
...
|
|
with utils.lock('mylock'):
|
|
...
|
|
...
|
|
|
|
<eventually call lock_cleanup('mylock') to clean up>
|
|
|
|
The lock_file_prefix argument is used to provide lock files on disk with a
|
|
meaningful prefix.
|
|
"""
|
|
return functools.partial(remove_external_lock_file,
|
|
lock_file_prefix=lock_file_prefix)
|
|
|
|
|
|
def _lock_wrapper(argv):
|
|
"""Create a dir for locks and pass it to command from arguments
|
|
|
|
This is exposed as a console script entry point named
|
|
lockutils-wrapper
|
|
|
|
If you run this:
|
|
lockutils-wrapper stestr run <etc>
|
|
|
|
a temporary directory will be created for all your locks and passed to all
|
|
your tests in an environment variable. The temporary dir will be deleted
|
|
afterwards and the return value will be preserved.
|
|
"""
|
|
|
|
lock_dir = tempfile.mkdtemp()
|
|
os.environ["OSLO_LOCK_PATH"] = lock_dir
|
|
try:
|
|
ret_val = subprocess.call(argv[1:])
|
|
finally:
|
|
shutil.rmtree(lock_dir, ignore_errors=True)
|
|
return ret_val
|
|
|
|
|
|
def main():
|
|
sys.exit(_lock_wrapper(sys.argv))
|
|
|
|
|
|
if __name__ == '__main__':
|
|
raise NotImplementedError(_('Calling lockutils directly is no longer '
|
|
'supported. Please use the '
|
|
'lockutils-wrapper console script instead.'))
|