Ejemplo n.º 1
0
    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 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
Ejemplo n.º 3
0
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)
Ejemplo n.º 4
0
        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