~unity-2d-team/unity-2d/Shell-MultiMonitor

# Copyright (c) 2011 Canonical Ltd

#

# This program is free software: you can redistribute it and/or modify

# it under the terms of the GNU Affero General Public License as published by

# the Free Software Foundation, either version 3 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU Affero General Public License for more details.

#

# You should have received a copy of the GNU Affero General Public

# License along with this program. If not, see

# <http://www.gnu.org/licenses/>.

"""Things to ease working with cassandra."""

from pycassa.pool import InvalidRequestError

def workaround_1779(callable, *args, **kwargs):

    """Workaround cassandra not being able to do concurrent schema edits.

    The callable is tried until it does not raised InvalidRequestException

    with why = "Previous version mismatch. cannot apply."

    :param callable: The callable to call.

    :param args: The args for it.

    :param kwargs: The kwargs for it.

    :return: The result of calling the callable.

    """

    while True:

        # Workaround https://issues.apache.org/jira/browse/CASSANDRA-1779:

        # Cassandra cannot do concurrent schema changes.

        try:

            return callable(*args, **kwargs)

            break

        except InvalidRequestError as e:

            if e.why != 'Previous version mismatch. cannot apply.':

                raise