94 lines
2.6 KiB
Python
94 lines
2.6 KiB
Python
# Copyright (c) 2014 Mirantis, Inc.
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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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"""Session management functions."""
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import threading
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from oslo_config import cfg
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from oslo_db import exception
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from oslo_db import options
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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 timeutils
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from murano.db.models import Lock
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LOG = logging.getLogger(__name__)
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CONF = cfg.CONF
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options.set_defaults(CONF)
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_FACADE = None
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_LOCK = threading.Lock()
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MAX_LOCK_RETRIES = 10
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def _create_facade_lazily():
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global _LOCK, _FACADE
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if _FACADE is None:
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with _LOCK:
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if _FACADE is None:
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_FACADE = db_session.EngineFacade.from_config(CONF,
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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(**kwargs):
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facade = _create_facade_lazily()
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return facade.get_session(**kwargs)
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def get_lock(name, session=None):
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if session is None:
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session = get_session()
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nested = False
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else:
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nested = session.transaction is not None
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return _get_or_create_lock(name, session, nested)
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def _get_or_create_lock(name, session, nested, retry=0):
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if nested:
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session.begin_nested()
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else:
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session.begin()
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existing = session.query(Lock).get(name)
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if existing is None:
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try:
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# no lock found, creating a new one
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lock = Lock(id=name, ts=timeutils.utcnow())
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lock.save(session)
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return session.transaction
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# lock created and acquired
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except exception.DBDuplicateEntry:
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session.rollback()
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if retry >= MAX_LOCK_RETRIES:
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raise
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else:
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# other transaction has created a lock, repeat to acquire
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# via update
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return _get_or_create_lock(name, session, nested, retry + 1)
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else:
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# lock found, acquiring by doing update
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existing.ts = timeutils.utcnow()
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existing.save(session)
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return session.transaction
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