diff options
Diffstat (limited to 'oslo_concurrency/lockutils.py')
| -rw-r--r-- | oslo_concurrency/lockutils.py | 54 |
1 files changed, 44 insertions, 10 deletions
diff --git a/oslo_concurrency/lockutils.py b/oslo_concurrency/lockutils.py index 67cf41e..1a9abe8 100644 --- a/oslo_concurrency/lockutils.py +++ b/oslo_concurrency/lockutils.py @@ -206,15 +206,35 @@ def remove_external_lock_file(name, lock_file_prefix=None, lock_path=None, {'file': lock_file_path}) -def internal_lock(name, semaphores=None): +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 - return semaphores.get(name) + 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): + 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 @@ -247,6 +267,10 @@ def lock(name, lock_file_prefix=None, external=False, lock_path=None, :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. @@ -257,17 +281,23 @@ def lock(name, lock_file_prefix=None, external=False, lock_path=None, if semaphores is not None: raise NotImplementedError(_('Specifying semaphores is not ' 'supported when using fair locks.')) - # The fastners module specifies that write_lock() provides fairness. + 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) + int_lock = internal_lock(name, semaphores=semaphores, + blocking=blocking) 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) - ext_lock.acquire(delay=delay) + 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}) @@ -314,7 +344,7 @@ def lock_with_prefix(lock_file_prefix): def synchronized(name, lock_file_prefix=None, external=False, lock_path=None, - semaphores=None, delay=0.01, fair=False): + semaphores=None, delay=0.01, fair=False, blocking=True): """Synchronization decorator. Decorating a method like so:: @@ -347,10 +377,11 @@ def synchronized(name, lock_file_prefix=None, external=False, lock_path=None, def inner(*args, **kwargs): t1 = timeutils.now() t2 = None + gotten = True try: with lock(name, lock_file_prefix, external, lock_path, do_log=False, semaphores=semaphores, delay=delay, - fair=fair): + fair=fair, blocking=blocking): t2 = timeutils.now() LOG.debug('Lock "%(name)s" acquired by "%(function)s" :: ' 'waited %(wait_secs)0.3fs', @@ -358,15 +389,18 @@ def synchronized(name, lock_file_prefix=None, external=False, lock_path=None, 'function': reflection.get_callable_name(f), '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" released by "%(function)s" :: held ' - '%(held_secs)s', + LOG.debug('Lock "%(name)s" "%(gotten)s" by "%(function)s" ::' + ' held %(held_secs)s', {'name': name, + 'gotten': 'released' if gotten else 'unacquired', 'function': reflection.get_callable_name(f), 'held_secs': held_secs}) return inner |