ff1dc9544c
Added a SQLite backed backend API implementation that interfaces with the database using sqlalchemy. All of the unit tests associated are included as well. Change-Id: I0948fe85d381db4ef1305ed6234ca3e06f3c8760
112 lines
3.3 KiB
Python
112 lines
3.3 KiB
Python
# -*- coding: utf-8 -*-
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# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
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# Copyright (C) 2013 Rackspace Hosting 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 logging
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import sqlalchemy
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import sqlalchemy.engine
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import sqlalchemy.interfaces
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import sqlalchemy.orm
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from sqlalchemy.pool import NullPool
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from sqlalchemy import exc
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from taskflow.backends import api as b_api
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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=True):
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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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_MAKER = get_maker(get_engine(), autocommit, expire_on_commit)
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return _MAKER()
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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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"""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 exc.DisconnectionError("Database server went away")
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else:
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raise
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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(_get_sql_connection())
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engine_args = {
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"pool_recycle": _get_sql_idle_timeout(),
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"echo": False,
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"convert_unicode": True
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}
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if "sqlite" in connection_dict.drivername:
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engine_args['poolclass'] = NullPool
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_ENGINE = sqlalchemy.create_engine(_get_sql_connection(),
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**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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if 'sqlite' in connection_dict.drivername:
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sqlalchemy.event.listen(_ENGINE, 'connect',
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synchronous_switch_listener)
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# TODO(jharlow): Check to make sure engine connected
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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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def _get_sql_connection():
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return b_api.SQL_CONNECTION
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def _get_sql_idle_timeout():
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return b_api.SQL_IDLE_TIMEOUT
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