152 lines
5.0 KiB
Python
152 lines
5.0 KiB
Python
# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright 2010 United States Government as represented by the
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# Administrator of the National Aeronautics and Space Administration.
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# All Rights Reserved.
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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 Handling for SQLAlchemy backend."""
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import time
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from oslo.config import cfg
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from sqlalchemy.exc import DisconnectionError, OperationalError
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import sqlalchemy.interfaces
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import sqlalchemy.orm
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from sqlalchemy.pool import NullPool, StaticPool
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import manila.exception
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from manila.openstack.common import log as logging
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CONF = cfg.CONF
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LOG = logging.getLogger(__name__)
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_ENGINE = None
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_MAKER = None
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def get_session(autocommit=True, expire_on_commit=False):
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"""Return a SQLAlchemy session."""
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global _MAKER
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if _MAKER is None:
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engine = get_engine()
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_MAKER = get_maker(engine, autocommit, expire_on_commit)
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session = _MAKER()
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session.query = manila.exception.wrap_db_error(session.query)
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session.flush = manila.exception.wrap_db_error(session.flush)
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return session
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def synchronous_switch_listener(dbapi_conn, connection_rec):
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"""Switch sqlite connections to non-synchronous mode"""
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dbapi_conn.execute("PRAGMA synchronous = OFF")
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def ping_listener(dbapi_conn, connection_rec, connection_proxy):
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"""
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Ensures that MySQL connections checked out of the
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pool are alive.
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Borrowed from:
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http://groups.google.com/group/sqlalchemy/msg/a4ce563d802c929f
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"""
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try:
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dbapi_conn.cursor().execute('select 1')
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except dbapi_conn.OperationalError, ex:
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if ex.args[0] in (2006, 2013, 2014, 2045, 2055):
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LOG.warn(_('Got mysql server has gone away: %s'), ex)
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raise DisconnectionError("Database server went away")
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else:
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raise
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def is_db_connection_error(args):
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"""Return True if error in connecting to db."""
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# NOTE(adam_g): This is currently MySQL specific and needs to be extended
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# to support Postgres and others.
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conn_err_codes = ('2002', '2003', '2006')
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for err_code in conn_err_codes:
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if args.find(err_code) != -1:
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return True
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return False
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def get_engine():
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"""Return a SQLAlchemy engine."""
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global _ENGINE
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if _ENGINE is None:
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connection_dict = sqlalchemy.engine.url.make_url(CONF.sql_connection)
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engine_args = {
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"pool_recycle": CONF.sql_idle_timeout,
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"echo": False,
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'convert_unicode': True,
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}
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# Map our SQL debug level to SQLAlchemy's options
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if CONF.sql_connection_debug >= 100:
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engine_args['echo'] = 'debug'
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elif CONF.sql_connection_debug >= 50:
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engine_args['echo'] = True
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if "sqlite" in connection_dict.drivername:
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engine_args["poolclass"] = NullPool
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if CONF.sql_connection == "sqlite://":
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engine_args["poolclass"] = StaticPool
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engine_args["connect_args"] = {'check_same_thread': False}
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_ENGINE = sqlalchemy.create_engine(CONF.sql_connection, **engine_args)
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if 'mysql' in connection_dict.drivername:
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sqlalchemy.event.listen(_ENGINE, 'checkout', ping_listener)
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elif "sqlite" in connection_dict.drivername:
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if not CONF.sqlite_synchronous:
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sqlalchemy.event.listen(_ENGINE, 'connect',
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synchronous_switch_listener)
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try:
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_ENGINE.connect()
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except OperationalError, e:
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if not is_db_connection_error(e.args[0]):
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raise
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remaining = CONF.sql_max_retries
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if remaining == -1:
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remaining = 'infinite'
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while True:
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msg = _('SQL connection failed. %s attempts left.')
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LOG.warn(msg % remaining)
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if remaining != 'infinite':
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remaining -= 1
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time.sleep(CONF.sql_retry_interval)
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try:
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_ENGINE.connect()
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break
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except OperationalError, e:
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if ((remaining != 'infinite' and remaining == 0) or
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not is_db_connection_error(e.args[0])):
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raise
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return _ENGINE
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def get_maker(engine, autocommit=True, expire_on_commit=False):
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"""Return a SQLAlchemy sessionmaker using the given engine."""
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return sqlalchemy.orm.sessionmaker(bind=engine,
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autocommit=autocommit,
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expire_on_commit=expire_on_commit)
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