OpenStack Study: storage_users.py

**** CubicPower OpenStack Study ****

def register_storage_use(storage_path, hostname):

    """Identify the id of this instance storage."""

    # NOTE(morganfainberg): config option import is avoided here since it is

    # explicitly imported from compute.manager and may cause issues with

    # defining options after config has been processed with the

    # wrapped-function style used here.

    LOCK_PATH = os.path.join(CONF.instances_path, 'locks')

    @utils.synchronized('storage-registry-lock', external=True,

                        lock_path=LOCK_PATH)

    def do_register_storage_use(storage_path, hostname):

        # NOTE(mikal): this is required to determine if the instance storage is

        # shared, which is something that the image cache manager needs to

        # know. I can imagine other uses as well though.

        d = {}

        id_path = os.path.join(storage_path, 'compute_nodes')

        if os.path.exists(id_path):

            with open(id_path) as f:

                try:

                    d = json.loads(f.read())

                except ValueError:

                    LOG.warning(_("Cannot decode JSON from %(id_path)s"),

                                {"id_path": id_path})

        d[hostname] = time.time()

        with open(id_path, 'w') as f:

            f.write(json.dumps(d))

    return do_register_storage_use(storage_path, hostname)

# NOTE(morganfainberg): Due to circular import dependencies, the use of the

# CONF.instances_path needs to be wrapped so that it can be resolved at the

# appropriate time. Because compute.manager imports this file, we end up in

# a rather ugly dependency loop without moving this into a wrapped function.

# This issue mostly stems from the use of a decorator for the lock

# synchronize and the implications of how decorators wrap the wrapped function

# or method.  If this needs to be used outside of compute.manager, it should

# be refactored to eliminate this circular dependency loop.

**** CubicPower OpenStack Study ****

def get_storage_users(storage_path):

    """Get a list of all the users of this storage path."""

    # NOTE(morganfainberg): config option import is avoided here since it is

    # explicitly imported from compute.manager and may cause issues with

    # defining options after config has been processed with the

    # wrapped-function style used here.

    LOCK_PATH = os.path.join(CONF.instances_path, 'locks')

    @utils.synchronized('storage-registry-lock', external=True,

                        lock_path=LOCK_PATH)

    def do_get_storage_users(storage_path):

        d = {}

        id_path = os.path.join(storage_path, 'compute_nodes')

        if os.path.exists(id_path):

            with open(id_path) as f:

                try:

                    d = json.loads(f.read())

                except ValueError:

                    LOG.warning(_("Cannot decode JSON from %(id_path)s"),

                                {"id_path": id_path})

        recent_users = []

        for node in d:

            if time.time() - d[node] < TWENTY_FOUR_HOURS:

                recent_users.append(node)

        return recent_users

    return do_get_storage_users(storage_path)