# Licensed under the Apache License, Version 2.0 (the "License"); you may # not use this file except in compliance with the License. You may obtain # a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the # License for the specific language governing permissions and limitations # under the License. import contextlib import functools import operator import threading import warnings from oslo_config import cfg from oslo_db import exception from oslo_db import options from oslo_db.sqlalchemy import engines from oslo_db.sqlalchemy import orm class _symbol(object): """represent a fixed symbol.""" __slots__ = 'name', def __init__(self, name): self.name = name def __repr__(self): return "symbol(%r)" % self.name _ASYNC_READER = _symbol('ASYNC_READER') """Represent the transaction state of "async reader". This state indicates that the transaction is a read-only and is safe to use on an asynchronously updated slave database. """ _READER = _symbol('READER') """Represent the transaction state of "reader". This state indicates that the transaction is a read-only and is only safe to use on a synchronously updated slave database; otherwise the master database should be used. """ _WRITER = _symbol('WRITER') """Represent the transaction state of "writer". This state indicates that the transaction writes data and should be directed at the master database. """ class _Default(object): """Mark a value as a default value. A value in the local configuration dictionary wrapped with _Default() will not take precedence over a value that is specified in cfg.CONF. Values that are set after the fact using configure() will supersede those in cfg.CONF. """ __slots__ = 'value', _notset = _symbol("NOTSET") def __init__(self, value=_notset): self.value = value @classmethod def resolve(cls, value): if isinstance(value, _Default): v = value.value if v is cls._notset: return None else: return v else: return value @classmethod def resolve_w_conf(cls, value, conf_namespace, key): if isinstance(value, _Default): v = getattr(conf_namespace, key, value.value) if v is cls._notset: return None else: return v else: return value @classmethod def is_set(cls, value): return not isinstance(value, _Default) or \ value.value is not cls._notset @classmethod def is_set_w_conf(cls, value, conf_namespace, key): return not isinstance(value, _Default) or \ value.value is not cls._notset or \ hasattr(conf_namespace, key) class _TransactionFactory(object): """A factory for :class:`._TransactionContext` objects. By default, there is just one of these, set up based on CONF, however instance-level :class:`._TransactionFactory` objects can be made, as is the case with the :class:`._TestTransactionFactory` subclass used by the oslo.db test suite. """ def __init__(self): self._url_cfg = { 'connection': _Default(), 'slave_connection': _Default(), } self._engine_cfg = { 'sqlite_fk': _Default(False), 'mysql_sql_mode': _Default('TRADITIONAL'), 'idle_timeout': _Default(3600), 'connection_debug': _Default(0), 'max_pool_size': _Default(), 'max_overflow': _Default(), 'pool_timeout': _Default(), 'sqlite_synchronous': _Default(True), 'connection_trace': _Default(False), 'max_retries': _Default(10), 'retry_interval': _Default(10), 'thread_checkin': _Default(True) } self._maker_cfg = { 'expire_on_commit': _Default(False), '__autocommit': True } self._transaction_ctx_cfg = { 'rollback_reader_sessions': False, } self._facade_cfg = { 'synchronous_reader': True } # other options that are defined in oslo.db.options.database_opts # but do not apply to the standard enginefacade arguments # (most seem to apply to api.DBAPI). self._ignored_cfg = dict( (k, _Default(None)) for k in [ 'db_max_retries', 'db_inc_retry_interval', 'use_db_reconnect', 'db_retry_interval', 'min_pool_size', 'db_max_retry_interval', 'sqlite_db', 'backend']) self._started = False self._legacy_facade = None self._start_lock = threading.Lock() def configure_defaults(self, **kw): """Apply default configurational options. This method can only be called before any specific transaction-beginning methods have been called. Configurational options are within a fixed set of keys, and fall under three categories: URL configuration, engine configuration, and session configuration. Each key given will be tested against these three configuration sets to see which one is applicable; if it is not applicable to any set, an exception is raised. The configurational options given here act as **defaults** when the :class:`._TransactionFactory` is configured using a :class:`oslo_config.cfg.ConfigOpts` object; the options present within the :class:`oslo_config.cfg.ConfigOpts` **take precedence** versus the arguments passed here. By default, the :class:`._TransactionFactory` loads in the configuration from :data:`oslo_config.cfg.CONF`, after applying the :data:`oslo_db.options.database_opts` configurational defaults to it. .. seealso:: :meth:`._TransactionFactory.configure` """ self._configure(True, kw) def configure(self, **kw): """Apply configurational options. This method can only be called before any specific transaction-beginning methods have been called. Behavior here is the same as that of :meth:`._TransactionFactory.configure_defaults`, with the exception that values specified here will **supersede** those setup in the :class:`oslo_config.cfg.ConfigOpts` options. .. seealso:: :meth:`._TransactionFactory.configure_defaults` """ self._configure(False, kw) def _configure(self, as_defaults, kw): if self._started: raise TypeError("this TransactionFactory is already started") not_supported = [] for k, v in kw.items(): for dict_ in ( self._url_cfg, self._engine_cfg, self._maker_cfg, self._ignored_cfg, self._facade_cfg, self._transaction_ctx_cfg): if k in dict_: dict_[k] = _Default(v) if as_defaults else v break else: not_supported.append(k) if not_supported: # would like to raise ValueError here, but there are just # too many unrecognized (obsolete?) configuration options # coming in from projects warnings.warn( "Configuration option(s) %r not supported" % sorted(not_supported), exception.NotSupportedWarning ) def get_legacy_facade(self): """Return a :class:`.LegacyEngineFacade` for this factory. This facade will make use of the same engine and sessionmaker as this factory, however will not share the same transaction context; the legacy facade continues to work the old way of returning a new Session each time get_session() is called. """ if not self._legacy_facade: self._legacy_facade = LegacyEngineFacade(None, _factory=self) if not self._started: self._start() return self._legacy_facade def _create_connection(self, mode): if not self._started: self._start() if mode is _WRITER: return self._writer_engine.connect() elif self.synchronous_reader or mode is _ASYNC_READER: return self._reader_engine.connect() else: return self._writer_engine.connect() def _create_session(self, mode, bind=None): if not self._started: self._start() kw = {} # don't pass 'bind' if bind is None; the sessionmaker # already has a bind to the engine. if bind: kw['bind'] = bind if mode is _WRITER: return self._writer_maker(**kw) elif self.synchronous_reader or mode is _ASYNC_READER: return self._reader_maker(**kw) else: return self._writer_maker(**kw) def _args_for_conf(self, default_cfg, conf): if conf is None: return dict( (key, _Default.resolve(value)) for key, value in default_cfg.items() if _Default.is_set(value) ) else: return dict( (key, _Default.resolve_w_conf(value, conf.database, key)) for key, value in default_cfg.items() if _Default.is_set_w_conf(value, conf.database, key) ) def _url_args_for_conf(self, conf): return self._args_for_conf(self._url_cfg, conf) def _engine_args_for_conf(self, conf): return self._args_for_conf(self._engine_cfg, conf) def _maker_args_for_conf(self, conf): return self._args_for_conf(self._maker_cfg, conf) def _start(self, conf=False, connection=None, slave_connection=None): with self._start_lock: # self._started has been checked on the outside # when _start() was called. Within the lock, # check the flag once more to detect the case where # the start process proceeded while this thread was waiting # for the lock. if self._started: return if conf is False: conf = cfg.CONF # perform register_opts() local to actually using # the cfg.CONF to maintain exact compatibility with # the EngineFacade design. This can be changed if needed. if conf is not None: conf.register_opts(options.database_opts, 'database') url_args = self._url_args_for_conf(conf) if connection: url_args['connection'] = connection if slave_connection: url_args['slave_connection'] = slave_connection engine_args = self._engine_args_for_conf(conf) maker_args = self._maker_args_for_conf(conf) maker_args['autocommit'] = maker_args.pop('__autocommit') self._writer_engine, self._writer_maker = \ self._setup_for_connection( url_args['connection'], engine_args, maker_args) if url_args.get('slave_connection'): self._reader_engine, self._reader_maker = \ self._setup_for_connection( url_args['slave_connection'], engine_args, maker_args) else: self._reader_engine, self._reader_maker = \ self._writer_engine, self._writer_maker self.synchronous_reader = self._facade_cfg['synchronous_reader'] # set up _started last, so that in case of exceptions # we try the whole thing again and report errors # correctly self._started = True def _setup_for_connection( self, sql_connection, engine_kwargs, maker_kwargs): if sql_connection is None: raise exception.CantStartEngineError( "No sql_connection parameter is established") engine = engines.create_engine( sql_connection=sql_connection, **engine_kwargs) sessionmaker = orm.get_maker(engine=engine, **maker_kwargs) return engine, sessionmaker class _TestTransactionFactory(_TransactionFactory): """A :class:`._TransactionFactory` used by test suites. This is a :class:`._TransactionFactory` that can be directly injected with an existing engine and sessionmaker. Note that while this is used by oslo.db's own tests of the enginefacade system, it is also exported for use by the test suites of other projects, first as an element of the oslo_db.sqlalchemy.test_base module, and secondly may be used by external test suites directly. Includes a feature to inject itself temporarily as the factory within the global :class:`._TransactionContextManager`. """ def __init__(self, engine, maker, apply_global, synchronous_reader): self._reader_engine = self._writer_engine = engine self._reader_maker = self._writer_maker = maker self._started = True self._legacy_facade = None self.synchronous_reader = synchronous_reader self._facade_cfg = _context_manager._factory._facade_cfg self._transaction_ctx_cfg = \ _context_manager._factory._transaction_ctx_cfg if apply_global: self.existing_factory = _context_manager._factory _context_manager._root_factory = self def dispose_global(self): _context_manager._root_factory = self.existing_factory class _TransactionContext(object): """Represent a single database transaction in progress.""" def __init__( self, factory, global_factory=None, rollback_reader_sessions=False): """Construct a new :class:`.TransactionContext`. :param factory: the :class:`.TransactionFactory` which will serve as a source of connectivity. :param global_factory: the "global" factory which will be used by the global ``_context_manager`` for new ``_TransactionContext`` objects created under this one. When left as None the actual "global" factory is used. :param rollback_reader_sessions: if True, a :class:`.Session` object will have its :meth:`.Session.rollback` method invoked at the end of a ``@reader`` block, actively rolling back the transaction and expiring the objects within, before the :class:`.Session` moves on to be closed, which has the effect of releasing connection resources back to the connection pool and detaching all objects. If False, the :class:`.Session` is not affected at the end of a ``@reader`` block; the underlying connection referred to by this :class:`.Session` will still be released in the enclosing context via the :meth:`.Session.close` method, which still ensures that the DBAPI connection is rolled back, however the objects associated with the :class:`.Session` retain their database-persisted contents after they are detached. .. seealso:: http://docs.sqlalchemy.org/en/rel_0_9/glossary.html#term-released\ SQLAlchemy documentation on what "releasing resources" means. """ self.factory = factory self.global_factory = global_factory self.mode = None self.session = None self.connection = None self.transaction = None kw = self.factory._transaction_ctx_cfg self.rollback_reader_sessions = kw['rollback_reader_sessions'] @contextlib.contextmanager def _connection(self, savepoint=False): if self.connection is None: try: if self.session is not None: # use existing session, which is outer to us self.connection = self.session.connection() if savepoint: with self.connection.begin_nested(): yield self.connection else: yield self.connection else: # is outermost self.connection = self.factory._create_connection( mode=self.mode) self.transaction = self.connection.begin() try: yield self.connection self._end_connection_transaction(self.transaction) except Exception: self.transaction.rollback() # TODO(zzzeek) do we need save_and_reraise() here, # or do newer eventlets not have issues? we are using # raw "raise" in many other places in oslo.db already # (and one six.reraise()). raise finally: self.transaction = None self.connection.close() finally: self.connection = None else: # use existing connection, which is outer to us if savepoint: with self.connection.begin_nested(): yield self.connection else: yield self.connection @contextlib.contextmanager def _session(self, savepoint=False): if self.session is None: self.session = self.factory._create_session( bind=self.connection, mode=self.mode) try: self.session.begin() yield self.session self._end_session_transaction(self.session) except Exception: self.session.rollback() # TODO(zzzeek) do we need save_and_reraise() here, # or do newer eventlets not have issues? we are using # raw "raise" in many other places in oslo.db already # (and one six.reraise()). raise finally: self.session.close() self.session = None else: # use existing session, which is outer to us if savepoint: with self.session.begin_nested(): yield self.session else: yield self.session def _end_session_transaction(self, session): if self.mode is _WRITER: session.commit() elif self.rollback_reader_sessions: session.rollback() # In the absense of calling session.rollback(), # the next call is session.close(). This releases all # objects from the session into the detached state, and # releases the connection as well; the connection when returned # to the pool is either rolled back in any case, or closed fully. def _end_connection_transaction(self, transaction): if self.mode is _WRITER: transaction.commit() else: transaction.rollback() def _produce_block(self, mode, connection, savepoint, allow_async=False): if mode is _WRITER: self._writer() elif mode is _ASYNC_READER: self._async_reader() else: self._reader(allow_async) if connection: return self._connection(savepoint) else: return self._session(savepoint) def _writer(self): if self.mode is None: self.mode = _WRITER elif self.mode is _READER: raise TypeError( "Can't upgrade a READER transaction " "to a WRITER mid-transaction") elif self.mode is _ASYNC_READER: raise TypeError( "Can't upgrade an ASYNC_READER transaction " "to a WRITER mid-transaction") def _reader(self, allow_async=False): if self.mode is None: self.mode = _READER elif self.mode is _ASYNC_READER and not allow_async: raise TypeError( "Can't upgrade an ASYNC_READER transaction " "to a READER mid-transaction") def _async_reader(self): if self.mode is None: self.mode = _ASYNC_READER class _TransactionContextTLocal(threading.local): def __deepcopy__(self, memo): return self def __reduce__(self): return _TransactionContextTLocal, () class _TransactionContextManager(object): """Provide context-management and decorator patterns for transactions. This object integrates user-defined "context" objects with the :class:`._TransactionContext` class, on behalf of a contained :class:`._TransactionFactory`. """ def __init__( self, root=None, mode=None, independent=False, savepoint=False, connection=False, replace_global_factory=None, _is_global_manager=False, allow_async=False): if root is None: self._root = self self._root_factory = _TransactionFactory() else: self._root = root self._replace_global_factory = replace_global_factory self._is_global_manager = _is_global_manager self._mode = mode self._independent = independent self._savepoint = savepoint if self._savepoint and self._independent: raise TypeError( "setting savepoint and independent makes no sense.") self._connection = connection self._allow_async = allow_async @property def _factory(self): """The :class:`._TransactionFactory` associated with this context.""" return self._root._root_factory def configure(self, **kw): """Apply configurational options to the factory. This method can only be called before any specific transaction-beginning methods have been called. """ self._factory.configure(**kw) def get_legacy_facade(self): """Return a :class:`.LegacyEngineFacade` for factory from this context. This facade will make use of the same engine and sessionmaker as this factory, however will not share the same transaction context; the legacy facade continues to work the old way of returning a new Session each time get_session() is called. """ return self._factory.get_legacy_facade() @property def replace(self): """Modifier to replace the global transaction factory with this one.""" return self._clone(replace_global_factory=self._factory) @property def writer(self): """Modifier to set the transaction to WRITER.""" return self._clone(mode=_WRITER) @property def reader(self): """Modifier to set the transaction to READER.""" return self._clone(mode=_READER) @property def allow_async(self): """Modifier to allow async operations Allows async operations if asynchronous session is already started in this context. Marking DB API methods with READER would make it impossible to use them in ASYNC_READER transactions, and marking them with ASYNC_READER would require a modification of all the places these DB API methods are called to force READER mode, where the latest DB state is required. In Nova DB API methods should have a 'safe' default (i.e. READER), so that they can start sessions on their own, but it would also be useful for them to be able to participate in an existing ASYNC_READER session, if one was started up the stack. """ if self._mode is _WRITER: raise TypeError("Setting async on a WRITER makes no sense") return self._clone(allow_async=True) @property def independent(self): """Modifier to start a transaction independent from any enclosing.""" return self._clone(independent=True) @property def savepoint(self): """Modifier to start a SAVEPOINT if a transaction already exists.""" return self._clone(savepoint=True) @property def connection(self): """Modifier to return a core Connection object instead of Session.""" return self._clone(connection=True) @property def async(self): """Modifier to set a READER operation to ASYNC_READER.""" if self._mode is _WRITER: raise TypeError("Setting async on a WRITER makes no sense") return self._clone(mode=_ASYNC_READER) def using(self, context): """Provide a context manager block that will use the given context.""" return self._transaction_scope(context) def __call__(self, fn): """Decorate a function.""" @functools.wraps(fn) def wrapper(*args, **kwargs): context = args[0] with self._transaction_scope(context): return fn(*args, **kwargs) return wrapper def _clone(self, **kw): default_kw = { "independent": self._independent, "mode": self._mode, "connection": self._connection } default_kw.update(kw) return _TransactionContextManager(root=self._root, **default_kw) @contextlib.contextmanager def _transaction_scope(self, context): new_transaction = self._independent transaction_contexts_by_thread = \ _transaction_contexts_by_thread(context) current = restore = getattr( transaction_contexts_by_thread, "current", None) use_factory = self._factory global_factory = None if self._replace_global_factory: use_factory = global_factory = self._replace_global_factory elif current is not None and current.global_factory: global_factory = current.global_factory if self._root._is_global_manager: use_factory = global_factory if current is not None and ( new_transaction or current.factory is not use_factory ): current = None if current is None: current = transaction_contexts_by_thread.current = \ _TransactionContext( use_factory, global_factory=global_factory, **use_factory._transaction_ctx_cfg) try: if self._mode is not None: with current._produce_block( mode=self._mode, connection=self._connection, savepoint=self._savepoint, allow_async=self._allow_async) as resource: yield resource else: yield finally: if restore is None: del transaction_contexts_by_thread.current elif current is not restore: transaction_contexts_by_thread.current = restore def _context_descriptor(attr=None): getter = operator.attrgetter(attr) def _property_for_context(context): try: transaction_context = context.transaction_ctx except exception.NoEngineContextEstablished: raise exception.NoEngineContextEstablished( "No TransactionContext is established for " "this %s object within the current thread; " "the %r attribute is unavailable." % (context, attr) ) else: result = getter(transaction_context) if result is None: raise exception.ContextNotRequestedError( "The '%s' context attribute was requested but " "it has not been established for this context." % attr ) return result return property(_property_for_context) def _transaction_ctx_for_context(context): by_thread = _transaction_contexts_by_thread(context) try: return by_thread.current except AttributeError: raise exception.NoEngineContextEstablished( "No TransactionContext is established for " "this %s object within the current thread. " % context ) def _transaction_contexts_by_thread(context): transaction_contexts_by_thread = getattr( context, '_enginefacade_context', None) if transaction_contexts_by_thread is None: transaction_contexts_by_thread = \ context._enginefacade_context = _TransactionContextTLocal() return transaction_contexts_by_thread def transaction_context_provider(klass): """Decorate a class with ``session`` and ``connection`` attributes.""" setattr( klass, 'transaction_ctx', property(_transaction_ctx_for_context)) # Graft transaction context attributes as context properties for attr in ('session', 'connection', 'transaction'): setattr(klass, attr, _context_descriptor(attr)) return klass _context_manager = _TransactionContextManager(_is_global_manager=True) """default context manager.""" def transaction_context(): """Construct a local transaction context. """ return _TransactionContextManager() def configure(**kw): """Apply configurational options to the global factory. This method can only be called before any specific transaction-beginning methods have been called. .. seealso:: :meth:`._TransactionFactory.configure` """ _context_manager._factory.configure(**kw) def get_legacy_facade(): """Return a :class:`.LegacyEngineFacade` for the global factory. This facade will make use of the same engine and sessionmaker as this factory, however will not share the same transaction context; the legacy facade continues to work the old way of returning a new Session each time get_session() is called. """ return _context_manager.get_legacy_facade() reader = _context_manager.reader """The global 'reader' starting point.""" writer = _context_manager.writer """The global 'writer' starting point.""" class LegacyEngineFacade(object): """A helper class for removing of global engine instances from oslo.db. .. deprecated:: 1.12.0 Please use :mod:`oslo_db.sqlalchemy.enginefacade` for new development. As a library, oslo.db can't decide where to store/when to create engine and sessionmaker instances, so this must be left for a target application. On the other hand, in order to simplify the adoption of oslo.db changes, we'll provide a helper class, which creates engine and sessionmaker on its instantiation and provides get_engine()/get_session() methods that are compatible with corresponding utility functions that currently exist in target projects, e.g. in Nova. engine/sessionmaker instances will still be global (and they are meant to be global), but they will be stored in the app context, rather that in the oslo.db context. Two important things to remember: 1. An Engine instance is effectively a pool of DB connections, so it's meant to be shared (and it's thread-safe). 2. A Session instance is not meant to be shared and represents a DB transactional context (i.e. it's not thread-safe). sessionmaker is a factory of sessions. :param sql_connection: the connection string for the database to use :type sql_connection: string :param slave_connection: the connection string for the 'slave' database to use. If not provided, the master database will be used for all operations. Note: this is meant to be used for offloading of read operations to asynchronously replicated slaves to reduce the load on the master database. :type slave_connection: string :param sqlite_fk: enable foreign keys in SQLite :type sqlite_fk: bool :param autocommit: use autocommit mode for created Session instances :type autocommit: bool :param expire_on_commit: expire session objects on commit :type expire_on_commit: bool Keyword arguments: :keyword mysql_sql_mode: the SQL mode to be used for MySQL sessions. (defaults to TRADITIONAL) :keyword idle_timeout: timeout before idle sql connections are reaped (defaults to 3600) :keyword connection_debug: verbosity of SQL debugging information. -1=Off, 0=None, 100=Everything (defaults to 0) :keyword max_pool_size: maximum number of SQL connections to keep open in a pool (defaults to SQLAlchemy settings) :keyword max_overflow: if set, use this value for max_overflow with sqlalchemy (defaults to SQLAlchemy settings) :keyword pool_timeout: if set, use this value for pool_timeout with sqlalchemy (defaults to SQLAlchemy settings) :keyword sqlite_synchronous: if True, SQLite uses synchronous mode (defaults to True) :keyword connection_trace: add python stack traces to SQL as comment strings (defaults to False) :keyword max_retries: maximum db connection retries during startup. (setting -1 implies an infinite retry count) (defaults to 10) :keyword retry_interval: interval between retries of opening a sql connection (defaults to 10) :keyword thread_checkin: boolean that indicates that between each engine checkin event a sleep(0) will occur to allow other greenthreads to run (defaults to True) """ def __init__(self, sql_connection, slave_connection=None, sqlite_fk=False, autocommit=True, expire_on_commit=False, _conf=None, _factory=None, **kwargs): warnings.warn( "EngineFacade is deprecated; please use " "oslo_db.sqlalchemy.enginefacade", exception.OsloDBDeprecationWarning, stacklevel=2) if _factory: self._factory = _factory else: self._factory = _TransactionFactory() self._factory.configure( sqlite_fk=sqlite_fk, __autocommit=autocommit, expire_on_commit=expire_on_commit, **kwargs ) # make sure passed-in urls are favored over that # of config self._factory._start( _conf, connection=sql_connection, slave_connection=slave_connection) def _check_factory_started(self): if not self._factory._started: self._factory._start() def get_engine(self, use_slave=False): """Get the engine instance (note, that it's shared). :param use_slave: if possible, use 'slave' database for this engine. If the connection string for the slave database wasn't provided, 'master' engine will be returned. (defaults to False) :type use_slave: bool """ self._check_factory_started() if use_slave: return self._factory._reader_engine else: return self._factory._writer_engine def get_session(self, use_slave=False, **kwargs): """Get a Session instance. :param use_slave: if possible, use 'slave' database connection for this session. If the connection string for the slave database wasn't provided, a session bound to the 'master' engine will be returned. (defaults to False) :type use_slave: bool Keyword arugments will be passed to a sessionmaker instance as is (if passed, they will override the ones used when the sessionmaker instance was created). See SQLAlchemy Session docs for details. """ self._check_factory_started() if use_slave: return self._factory._reader_maker(**kwargs) else: return self._factory._writer_maker(**kwargs) def get_sessionmaker(self, use_slave=False): """Get the sessionmaker instance used to create a Session. This can be called for those cases where the sessionmaker() is to be temporarily injected with some state such as a specific connection. """ self._check_factory_started() if use_slave: return self._factory._reader_maker else: return self._factory._writer_maker @classmethod def from_config(cls, conf, sqlite_fk=False, autocommit=True, expire_on_commit=False): """Initialize EngineFacade using oslo.config config instance options. :param conf: oslo.config config instance :type conf: oslo_config.cfg.ConfigOpts :param sqlite_fk: enable foreign keys in SQLite :type sqlite_fk: bool :param autocommit: use autocommit mode for created Session instances :type autocommit: bool :param expire_on_commit: expire session objects on commit :type expire_on_commit: bool """ return cls( None, sqlite_fk=sqlite_fk, autocommit=autocommit, expire_on_commit=expire_on_commit, _conf=conf)