74 lines
2.3 KiB
Python
74 lines
2.3 KiB
Python
# Copyright 2014 Rackspace
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import contextlib
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import time
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from sqlalchemy.sql.expression import select
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from oslo_config import cfg
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from oslo_db.sqlalchemy import session as db_session
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from oslo_log import log as logging
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from oslo_utils import excutils
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LOG = logging.getLogger(__name__)
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_FACADE = None
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def _create_facade_lazily():
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global _FACADE
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if _FACADE is None:
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_FACADE = db_session.EngineFacade.from_config(cfg.CONF, sqlite_fk=True)
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return _FACADE
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def get_engine():
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facade = _create_facade_lazily()
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return facade.get_engine()
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def get_session(expire_on_commit=True, autocommit=True):
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"""Helper method to grab session."""
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facade = _create_facade_lazily()
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return facade.get_session(expire_on_commit=expire_on_commit,
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autocommit=autocommit)
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@contextlib.contextmanager
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def get_lock_session():
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"""Context manager for using a locking (not auto-commit) session."""
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lock_session = get_session(autocommit=False)
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try:
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yield lock_session
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lock_session.commit()
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except Exception:
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with excutils.save_and_reraise_exception():
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lock_session.rollback()
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def wait_for_connection(exit_event):
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"""Helper method to wait for DB connection"""
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down = True
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while down and not exit_event.is_set():
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try:
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LOG.debug('Trying to re-establish connection to database.')
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get_engine().scalar(select([1]))
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down = False
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LOG.debug('Connection to database re-established.')
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except Exception:
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retry_interval = cfg.CONF.database.retry_interval
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LOG.exception('Connection to database failed. Retrying in %s '
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'seconds.', retry_interval)
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time.sleep(retry_interval)
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