def acquire(self):
basedir = os.path.dirname(self.fname)
if not os.path.exists(basedir):
fileutils.ensure_tree(basedir)
LOG.info(_LI('Created lock path: %s'), basedir)
self.lockfile = open(self.fname, 'w')
while True:
try:
# Using non-blocking locks since green threads are not
# patched to deal with blocking locking calls.
# Also upon reading the MSDN docs for locking(), it seems
# to have a laughable 10 attempts "blocking" mechanism.
self.trylock()
LOG.debug('Got file lock "%s"', self.fname)
return True
except IOError as e:
if e.errno in (errno.EACCES, errno.EAGAIN):
# external locks synchronise things like iptables
# updates - give it some time to prevent busy spinning
time.sleep(0.01)
else:
raise threading.ThreadError(_("Unable to acquire lock on"
" `%(filename)s` due to"
" %(exception)s") %
{
'filename': self.fname,
'exception': e,
})
def lock(name, lock_file_prefix=None, external=False, lock_path=None):
"""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 a method decorated with @synchronized('mylock',
external=True), only one of them will execute at a time.
:param lock_path: The lock_path keyword argument is used to specify a
special location for external lock files to live. If nothing is set, then
CONF.lock_path is used as a default.
"""
with _semaphores_lock:
try:
sem = _semaphores[name]
except KeyError:
sem = threading.Semaphore()
_semaphores[name] = sem
with sem:
LOG.debug(_('Got semaphore "%(lock)s"'), {"lock": name})
# NOTE(mikal): I know this looks odd
if not hasattr(local.strong_store, "locks_held"):
local.strong_store.locks_held = []
local.strong_store.locks_held.append(name)
try:
if external and not CONF.disable_process_locking:
LOG.debug(_('Attempting to grab file lock "%(lock)s"'), {"lock": name})
# We need a copy of lock_path because it is non-local
local_lock_path = lock_path or CONF.lock_path
if not local_lock_path:
raise cfg.RequiredOptError("lock_path")
if not os.path.exists(local_lock_path):
fileutils.ensure_tree(local_lock_path)
LOG.info(_("Created lock path: %s"), local_lock_path)
def add_prefix(name, prefix):
if not prefix:
return name
sep = "" if prefix.endswith("-") else "-"
return "%s%s%s" % (prefix, sep, name)
# NOTE(mikal): the lock name cannot contain directory
# separators
lock_file_name = add_prefix(name.replace(os.sep, "_"), lock_file_prefix)
lock_file_path = os.path.join(local_lock_path, lock_file_name)
try:
lock = InterProcessLock(lock_file_path)
with lock as lock:
LOG.debug(_('Got file lock "%(lock)s" at %(path)s'), {"lock": name, "path": lock_file_path})
yield lock
finally:
LOG.debug(_('Released file lock "%(lock)s" at %(path)s'), {"lock": name, "path": lock_file_path})
else:
yield sem
finally:
local.strong_store.locks_held.remove(name)
def inner(*args, **kwargs):
# NOTE(soren): If we ever go natively threaded, this will be racy.
# See http://stackoverflow.com/questions/5390569/dyn
# amically-allocating-and-destroying-mutexes
sem = _semaphores.get(name, semaphore.Semaphore())
if name not in _semaphores:
# this check is not racy - we're already holding ref locally
# so GC won't remove the item and there was no IO switch
# (only valid in greenthreads)
_semaphores[name] = sem
with sem:
LOG.debug(_('Got semaphore "%(lock)s" for method '
'"%(method)s"...'), {'lock': name,
'method': f.__name__})
# NOTE(mikal): I know this looks odd
if not hasattr(local.strong_store, 'locks_held'):
local.strong_store.locks_held = []
local.strong_store.locks_held.append(name)
try:
if external and not CONF.disable_process_locking:
LOG.debug(_('Attempting to grab file lock "%(lock)s" '
'for method "%(method)s"...'),
{'lock': name, 'method': f.__name__})
cleanup_dir = False
# We need a copy of lock_path because it is non-local
local_lock_path = lock_path
if not local_lock_path:
local_lock_path = CONF.lock_path
if not local_lock_path:
cleanup_dir = True
local_lock_path = tempfile.mkdtemp()
if not os.path.exists(local_lock_path):
fileutils.ensure_tree(local_lock_path)
# NOTE(mikal): the lock name cannot contain directory
# separators
safe_name = name.replace(os.sep, '_')
lock_file_name = '%s%s' % (lock_file_prefix, safe_name)
lock_file_path = os.path.join(local_lock_path,
lock_file_name)
try:
lock = InterProcessLock(lock_file_path)
with lock:
LOG.debug(_('Got file lock "%(lock)s" at '
'%(path)s for method '
'"%(method)s"...'),
{'lock': name,
'path': lock_file_path,
'method': f.__name__})
retval = f(*args, **kwargs)
finally:
LOG.debug(_('Released file lock "%(lock)s" at '
'%(path)s for method "%(method)s"...'),
{'lock': name,
'path': lock_file_path,
'method': f.__name__})
# NOTE(vish): This removes the tempdir if we needed
# to create one. This is used to
# cleanup the locks left behind by unit
# tests.
if cleanup_dir:
shutil.rmtree(local_lock_path)
else:
retval = f(*args, **kwargs)
finally:
local.strong_store.locks_held.remove(name)
return retval
