# 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):
if mode is _WRITER:
self._writer()
elif mode is _ASYNC_READER:
self._async_reader()
else:
self._reader()
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):
if self.mode is None:
self.mode = _READER
elif self.mode is _ASYNC_READER:
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):
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
@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 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) 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)