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📁 ..	-	2026-03-21 15:45
📄 __init__.py # sqlalchemy/pool/__init__.py # Copyright (C) 2005-2021 the SQLAlchemy authors and contributors # <see AUTHORS file> # # This module is part of SQLAlchemy and is released under # the MIT License: http://www.opensource.org/licenses/mit-license.php """Connection pooling for DB-API connections. Provides a number of connection pool implementations for a variety of usage scenarios and thread behavior requirements imposed by the application, DB-API or database itself. Also provides a DB-API 2.0 connection proxying mechanism allowing regular DB-API connect() methods to be transparently managed by a SQLAlchemy connection pool. """ from .base import _ConnectionFairy # noqa from .base import _ConnectionRecord # noqa from .base import _finalize_fairy # noqa from .base import _refs # noqa from .base import Pool from .base import reset_commit from .base import reset_none from .base import reset_rollback from .dbapi_proxy import clear_managers from .dbapi_proxy import manage from .impl import AssertionPool from .impl import NullPool from .impl import QueuePool from .impl import SingletonThreadPool from .impl import StaticPool __all__ = [ "Pool", "reset_commit", "reset_none", "reset_rollback", "clear_managers", "manage", "AssertionPool", "NullPool", "QueuePool", "SingletonThreadPool", "StaticPool", ] # as these are likely to be used in various test suites, debugging # setups, keep them in the sqlalchemy.pool namespace	1.45 KB	2026-01-20 12:58
📁 __pycache__	-	2026-03-21 15:45
📄 base.py # sqlalchemy/pool.py # Copyright (C) 2005-2021 the SQLAlchemy authors and contributors # <see AUTHORS file> # # This module is part of SQLAlchemy and is released under # the MIT License: http://www.opensource.org/licenses/mit-license.php """Base constructs for connection pools. """ from collections import deque import time import weakref from .. import event from .. import exc from .. import interfaces from .. import log from .. import util from ..util import threading reset_rollback = util.symbol("reset_rollback") reset_commit = util.symbol("reset_commit") reset_none = util.symbol("reset_none") class _ConnDialect(object): """partial implementation of :class:`.Dialect` which provides DBAPI connection methods. When a :class:`_pool.Pool` is combined with an :class:`_engine.Engine`, the :class:`_engine.Engine` replaces this with its own :class:`.Dialect`. """ def do_rollback(self, dbapi_connection): dbapi_connection.rollback() def do_commit(self, dbapi_connection): dbapi_connection.commit() def do_close(self, dbapi_connection): dbapi_connection.close() def do_ping(self, dbapi_connection): raise NotImplementedError( "The ping feature requires that a dialect is " "passed to the connection pool." ) class Pool(log.Identified): """Abstract base class for connection pools.""" _dialect = _ConnDialect() @util.deprecated_params( use_threadlocal=( "1.3", "The :paramref:`_pool.Pool.use_threadlocal` parameter is " "deprecated and will be removed in a future release.", ), listeners=( "0.7", ":class:`.PoolListener` is deprecated in favor of the " ":class:`_events.PoolEvents` listener interface. The " ":paramref:`_pool.Pool.listeners` parameter will be removed in a " "future release.", ), ) def __init__( self, creator, recycle=-1, echo=None, use_threadlocal=False, logging_name=None, reset_on_return=True, listeners=None, events=None, dialect=None, pre_ping=False, _dispatch=None, ): """ Construct a Pool. :param creator: a callable function that returns a DB-API connection object. The function will be called with parameters. :param recycle: If set to a value other than -1, number of seconds between connection recycling, which means upon checkout, if this timeout is surpassed the connection will be closed and replaced with a newly opened connection. Defaults to -1. :param logging_name: String identifier which will be used within the "name" field of logging records generated within the "sqlalchemy.pool" logger. Defaults to a hexstring of the object's id. :param echo: if True, the connection pool will log informational output such as when connections are invalidated as well as when connections are recycled to the default log handler, which defaults to ``sys.stdout`` for output.. If set to the string ``"debug"``, the logging will include pool checkouts and checkins. The :paramref:`_pool.Pool.echo` parameter can also be set from the :func:`_sa.create_engine` call by using the :paramref:`_sa.create_engine.echo_pool` parameter. .. seealso:: :ref:`dbengine_logging` - further detail on how to configure logging. :param use_threadlocal: If set to True, repeated calls to :meth:`connect` within the same application thread will be guaranteed to return the same connection object that is already checked out. This is a legacy use case and the flag has no effect when using the pool with a :class:`_engine.Engine` object. :param reset_on_return: Determine steps to take on connections as they are returned to the pool. reset_on_return can have any of these values: * ``"rollback"`` - call rollback() on the connection, to release locks and transaction resources. This is the default value. The vast majority of use cases should leave this value set. * ``True`` - same as 'rollback', this is here for backwards compatibility. * ``"commit"`` - call commit() on the connection, to release locks and transaction resources. A commit here may be desirable for databases that cache query plans if a commit is emitted, such as Microsoft SQL Server. However, this value is more dangerous than 'rollback' because any data changes present on the transaction are committed unconditionally. * ``None`` - don't do anything on the connection. This setting should generally only be made on a database that has no transaction support at all, namely MySQL MyISAM; when used on this backend, performance can be improved as the "rollback" call is still expensive on MySQL. It is strongly recommended that this setting not be used for transaction-supporting databases in conjunction with a persistent pool such as :class:`.QueuePool`, as it opens the possibility for connections still in a transaction to be idle in the pool. The setting may be appropriate in the case of :class:`.NullPool` or special circumstances where the connection pool in use is not being used to maintain connection lifecycle. * ``False`` - same as None, this is here for backwards compatibility. :param events: a list of 2-tuples, each of the form ``(callable, target)`` which will be passed to :func:`.event.listen` upon construction. Provided here so that event listeners can be assigned via :func:`_sa.create_engine` before dialect-level listeners are applied. :param listeners: A list of :class:`.PoolListener`-like objects or dictionaries of callables that receive events when DB-API connections are created, checked out and checked in to the pool. :param dialect: a :class:`.Dialect` that will handle the job of calling rollback(), close(), or commit() on DBAPI connections. If omitted, a built-in "stub" dialect is used. Applications that make use of :func:`_sa.create_engine` should not use this parameter as it is handled by the engine creation strategy. .. versionadded:: 1.1 - ``dialect`` is now a public parameter to the :class:`_pool.Pool`. :param pre_ping: if True, the pool will emit a "ping" (typically "SELECT 1", but is dialect-specific) on the connection upon checkout, to test if the connection is alive or not. If not, the connection is transparently re-connected and upon success, all other pooled connections established prior to that timestamp are invalidated. Requires that a dialect is passed as well to interpret the disconnection error. .. versionadded:: 1.2 """ if logging_name: self.logging_name = self._orig_logging_name = logging_name else: self._orig_logging_name = None log.instance_logger(self, echoflag=echo) self._threadconns = threading.local() self._creator = creator self._recycle = recycle self._invalidate_time = 0 self._use_threadlocal = use_threadlocal self._pre_ping = pre_ping self._reset_on_return = util.symbol.parse_user_argument( reset_on_return, { reset_rollback: ["rollback", True], reset_none: ["none", None, False], reset_commit: ["commit"], }, "reset_on_return", resolve_symbol_names=False, ) self.echo = echo if _dispatch: self.dispatch._update(_dispatch, only_propagate=False) if dialect: self._dialect = dialect if events: for fn, target in events: event.listen(self, target, fn) if listeners: for l in listeners: self.add_listener(l) @property def _creator(self): return self.__dict__["_creator"] @_creator.setter def _creator(self, creator): self.__dict__["_creator"] = creator self._invoke_creator = self._should_wrap_creator(creator) def _should_wrap_creator(self, creator): """Detect if creator accepts a single argument, or is sent as a legacy style no-arg function. """ try: argspec = util.get_callable_argspec(self._creator, no_self=True) except TypeError: return lambda crec: creator() defaulted = argspec[3] is not None and len(argspec[3]) or 0 positionals = len(argspec[0]) - defaulted # look for the exact arg signature that DefaultStrategy # sends us if (argspec[0], argspec[3]) == (["connection_record"], (None,)): return creator # or just a single positional elif positionals == 1: return creator # all other cases, just wrap and assume legacy "creator" callable # thing else: return lambda crec: creator() def _close_connection(self, connection): self.logger.debug("Closing connection %r", connection) try: self._dialect.do_close(connection) except Exception: self.logger.error( "Exception closing connection %r", connection, exc_info=True ) @util.deprecated( "0.7", "The :meth:`_pool.Pool.add_listener` method is deprecated and " "will be removed in a future release. Please use the " ":class:`_events.PoolEvents` listener interface.", ) def add_listener(self, listener): """Add a :class:`.PoolListener`-like object to this pool. ``listener`` may be an object that implements some or all of PoolListener, or a dictionary of callables containing implementations of some or all of the named methods in PoolListener. """ interfaces.PoolListener._adapt_listener(self, listener) def unique_connection(self): """Produce a DBAPI connection that is not referenced by any thread-local context. This method is equivalent to :meth:`_pool.Pool.connect` when the :paramref:`_pool.Pool.use_threadlocal` flag is not set to True. When :paramref:`_pool.Pool.use_threadlocal` is True, the :meth:`_pool.Pool.unique_connection` method provides a means of bypassing the threadlocal context. """ return _ConnectionFairy._checkout(self) def _create_connection(self): """Called by subclasses to create a new ConnectionRecord.""" return _ConnectionRecord(self) def _invalidate(self, connection, exception=None, _checkin=True): """Mark all connections established within the generation of the given connection as invalidated. If this pool's last invalidate time is before when the given connection was created, update the timestamp til now. Otherwise, no action is performed. Connections with a start time prior to this pool's invalidation time will be recycled upon next checkout. """ rec = getattr(connection, "_connection_record", None) if not rec or self._invalidate_time < rec.starttime: self._invalidate_time = time.time() if _checkin and getattr(connection, "is_valid", False): connection.invalidate(exception) def recreate(self): """Return a new :class:`_pool.Pool`, of the same class as this one and configured with identical creation arguments. This method is used in conjunction with :meth:`dispose` to close out an entire :class:`_pool.Pool` and create a new one in its place. """ raise NotImplementedError() def dispose(self): """Dispose of this pool. This method leaves the possibility of checked-out connections remaining open, as it only affects connections that are idle in the pool. .. seealso:: :meth:`Pool.recreate` """ raise NotImplementedError() def connect(self): """Return a DBAPI connection from the pool. The connection is instrumented such that when its ``close()`` method is called, the connection will be returned to the pool. """ if not self._use_threadlocal: return _ConnectionFairy._checkout(self) try: rec = self._threadconns.current() except AttributeError: pass else: if rec is not None: return rec._checkout_existing() return _ConnectionFairy._checkout(self, self._threadconns) def _return_conn(self, record): """Given a _ConnectionRecord, return it to the :class:`_pool.Pool`. This method is called when an instrumented DBAPI connection has its ``close()`` method called. """ if self._use_threadlocal: try: del self._threadconns.current except AttributeError: pass self._do_return_conn(record) def _do_get(self): """Implementation for :meth:`get`, supplied by subclasses.""" raise NotImplementedError() def _do_return_conn(self, conn): """Implementation for :meth:`return_conn`, supplied by subclasses.""" raise NotImplementedError() def status(self): raise NotImplementedError() class _ConnectionRecord(object): """Internal object which maintains an individual DBAPI connection referenced by a :class:`_pool.Pool`. The :class:`._ConnectionRecord` object always exists for any particular DBAPI connection whether or not that DBAPI connection has been "checked out". This is in contrast to the :class:`._ConnectionFairy` which is only a public facade to the DBAPI connection while it is checked out. A :class:`._ConnectionRecord` may exist for a span longer than that of a single DBAPI connection. For example, if the :meth:`._ConnectionRecord.invalidate` method is called, the DBAPI connection associated with this :class:`._ConnectionRecord` will be discarded, but the :class:`._ConnectionRecord` may be used again, in which case a new DBAPI connection is produced when the :class:`_pool.Pool` next uses this record. The :class:`._ConnectionRecord` is delivered along with connection pool events, including :meth:`_events.PoolEvents.connect` and :meth:`_events.PoolEvents.checkout`, however :class:`._ConnectionRecord` still remains an internal object whose API and internals may change. .. seealso:: :class:`._ConnectionFairy` """ def __init__(self, pool, connect=True): self.__pool = pool if connect: self.__connect(first_connect_check=True) self.finalize_callback = deque() fairy_ref = None starttime = None connection = None """A reference to the actual DBAPI connection being tracked. May be ``None`` if this :class:`._ConnectionRecord` has been marked as invalidated; a new DBAPI connection may replace it if the owning pool calls upon this :class:`._ConnectionRecord` to reconnect. """ _soft_invalidate_time = 0 @util.memoized_property def info(self): """The ``.info`` dictionary associated with the DBAPI connection. This dictionary is shared among the :attr:`._ConnectionFairy.info` and :attr:`_engine.Connection.info` accessors. .. note:: The lifespan of this dictionary is linked to the DBAPI connection itself, meaning that it is discarded each time the DBAPI connection is closed and/or invalidated. The :attr:`._ConnectionRecord.record_info` dictionary remains persistent throughout the lifespan of the :class:`._ConnectionRecord` container. """ return {} @util.memoized_property def record_info(self): """An "info' dictionary associated with the connection record itself. Unlike the :attr:`._ConnectionRecord.info` dictionary, which is linked to the lifespan of the DBAPI connection, this dictionary is linked to the lifespan of the :class:`._ConnectionRecord` container itself and will remain persistent throughout the life of the :class:`._ConnectionRecord`. .. versionadded:: 1.1 """ return {} @classmethod def checkout(cls, pool): rec = pool._do_get() try: dbapi_connection = rec.get_connection() except Exception as err: with util.safe_reraise(): rec._checkin_failed(err) echo = pool._should_log_debug() fairy = _ConnectionFairy(dbapi_connection, rec, echo) rec.fairy_ref = weakref.ref( fairy, lambda ref: _finalize_fairy and _finalize_fairy(None, rec, pool, ref, echo), ) _refs.add(rec) if echo: pool.logger.debug( "Connection %r checked out from pool", dbapi_connection ) return fairy def _checkin_failed(self, err): self.invalidate(e=err) self.checkin(_no_fairy_ref=True) def checkin(self, _no_fairy_ref=False): if self.fairy_ref is None and not _no_fairy_ref: util.warn("Double checkin attempted on %s" % self) return self.fairy_ref = None connection = self.connection pool = self.__pool while self.finalize_callback: finalizer = self.finalize_callback.pop() finalizer(connection) if pool.dispatch.checkin: pool.dispatch.checkin(connection, self) pool._return_conn(self) @property def in_use(self): return self.fairy_ref is not None @property def last_connect_time(self): return self.starttime def close(self): if self.connection is not None: self.__close() def invalidate(self, e=None, soft=False): """Invalidate the DBAPI connection held by this :class:`._ConnectionRecord`. This method is called for all connection invalidations, including when the :meth:`._ConnectionFairy.invalidate` or :meth:`_engine.Connection.invalidate` methods are called, as well as when any so-called "automatic invalidation" condition occurs. :param e: an exception object indicating a reason for the invalidation. :param soft: if True, the connection isn't closed; instead, this connection will be recycled on next checkout. .. versionadded:: 1.0.3 .. seealso:: :ref:`pool_connection_invalidation` """ # already invalidated if self.connection is None: return if soft: self.__pool.dispatch.soft_invalidate(self.connection, self, e) else: self.__pool.dispatch.invalidate(self.connection, self, e) if e is not None: self.__pool.logger.info( "%sInvalidate connection %r (reason: %s:%s)", "Soft " if soft else "", self.connection, e.__class__.__name__, e, ) else: self.__pool.logger.info( "%sInvalidate connection %r", "Soft " if soft else "", self.connection, ) if soft: self._soft_invalidate_time = time.time() else: self.__close() self.connection = None def get_connection(self): recycle = False # NOTE: the various comparisons here are assuming that measurable time # passes between these state changes. however, time.time() is not # guaranteed to have sub-second precision. comparisons of # "invalidation time" to "starttime" should perhaps use >= so that the # state change can take place assuming no measurable time has passed, # however this does not guarantee correct behavior here as if time # continues to not pass, it will try to reconnect repeatedly until # these timestamps diverge, so in that sense using > is safer. Per # https://stackoverflow.com/a/1938096/34549, Windows time.time() may be # within 16 milliseconds accuracy, so unit tests for connection # invalidation need a sleep of at least this long between initial start # time and invalidation for the logic below to work reliably. if self.connection is None: self.info.clear() self.__connect() elif ( self.__pool._recycle > -1 and time.time() - self.starttime > self.__pool._recycle ): self.__pool.logger.info( "Connection %r exceeded timeout; recycling", self.connection ) recycle = True elif self.__pool._invalidate_time > self.starttime: self.__pool.logger.info( "Connection %r invalidated due to pool invalidation; " + "recycling", self.connection, ) recycle = True elif self._soft_invalidate_time > self.starttime: self.__pool.logger.info( "Connection %r invalidated due to local soft invalidation; " + "recycling", self.connection, ) recycle = True if recycle: self.__close() self.info.clear() self.__connect() return self.connection def __close(self): self.finalize_callback.clear() if self.__pool.dispatch.close: self.__pool.dispatch.close(self.connection, self) self.__pool._close_connection(self.connection) self.connection = None def __connect(self, first_connect_check=False): pool = self.__pool # ensure any existing connection is removed, so that if # creator fails, this attribute stays None self.connection = None try: self.starttime = time.time() connection = pool._invoke_creator(self) pool.logger.debug("Created new connection %r", connection) self.connection = connection except Exception as e: with util.safe_reraise(): pool.logger.debug("Error on connect(): %s", e) else: if first_connect_check: pool.dispatch.first_connect.for_modify( pool.dispatch ).exec_once_unless_exception(self.connection, self) if pool.dispatch.connect: pool.dispatch.connect(self.connection, self) def _finalize_fairy( connection, connection_record, pool, ref, echo, fairy=None ): """Cleanup for a :class:`._ConnectionFairy` whether or not it's already been garbage collected. """ _refs.discard(connection_record) if ref is not None: if connection_record.fairy_ref is not ref: return assert connection is None connection = connection_record.connection if connection is not None: if connection_record and echo: pool.logger.debug( "Connection %r being returned to pool", connection ) try: fairy = fairy or _ConnectionFairy( connection, connection_record, echo ) assert fairy.connection is connection fairy._reset(pool) # Immediately close detached instances if not connection_record: if pool.dispatch.close_detached: pool.dispatch.close_detached(connection) pool._close_connection(connection) except BaseException as e: pool.logger.error( "Exception during reset or similar", exc_info=True ) if connection_record: connection_record.invalidate(e=e) if not isinstance(e, Exception): raise if connection_record and connection_record.fairy_ref is not None: connection_record.checkin() _refs = set() class _ConnectionFairy(object): """Proxies a DBAPI connection and provides return-on-dereference support. This is an internal object used by the :class:`_pool.Pool` implementation to provide context management to a DBAPI connection delivered by that :class:`_pool.Pool`. The name "fairy" is inspired by the fact that the :class:`._ConnectionFairy` object's lifespan is transitory, as it lasts only for the length of a specific DBAPI connection being checked out from the pool, and additionally that as a transparent proxy, it is mostly invisible. .. seealso:: :class:`._ConnectionRecord` """ def __init__(self, dbapi_connection, connection_record, echo): self.connection = dbapi_connection self._connection_record = connection_record self._echo = echo connection = None """A reference to the actual DBAPI connection being tracked.""" _connection_record = None """A reference to the :class:`._ConnectionRecord` object associated with the DBAPI connection. This is currently an internal accessor which is subject to change. """ _reset_agent = None """Refer to an object with a ``.commit()`` and ``.rollback()`` method; if non-None, the "reset-on-return" feature will call upon this object rather than directly against the dialect-level do_rollback() and do_commit() methods. In practice, a :class:`_engine.Connection` assigns a :class:`.Transaction` object to this variable when one is in scope so that the :class:`.Transaction` takes the job of committing or rolling back on return if :meth:`_engine.Connection.close` is called while the :class:`.Transaction` still exists. This is essentially an "event handler" of sorts but is simplified as an instance variable both for performance/simplicity as well as that there can only be one "reset agent" at a time. """ @classmethod def _checkout(cls, pool, threadconns=None, fairy=None): if not fairy: fairy = _ConnectionRecord.checkout(pool) fairy._pool = pool fairy._counter = 0 if threadconns is not None: threadconns.current = weakref.ref(fairy) if fairy.connection is None: raise exc.InvalidRequestError("This connection is closed") fairy._counter += 1 if ( not pool.dispatch.checkout and not pool._pre_ping ) or fairy._counter != 1: return fairy # Pool listeners can trigger a reconnection on checkout, as well # as the pre-pinger. # there are three attempts made here, but note that if the database # is not accessible from a connection standpoint, those won't proceed # here. attempts = 2 while attempts > 0: try: if pool._pre_ping: if fairy._echo: pool.logger.debug( "Pool pre-ping on connection %s", fairy.connection ) result = pool._dialect.do_ping(fairy.connection) if not result: if fairy._echo: pool.logger.debug( "Pool pre-ping on connection %s failed, " "will invalidate pool", fairy.connection, ) raise exc.InvalidatePoolError() pool.dispatch.checkout( fairy.connection, fairy._connection_record, fairy ) return fairy except exc.DisconnectionError as e: if e.invalidate_pool: pool.logger.info( "Disconnection detected on checkout, " "invalidating all pooled connections prior to " "current timestamp (reason: %r)", e, ) fairy._connection_record.invalidate(e) pool._invalidate(fairy, e, _checkin=False) else: pool.logger.info( "Disconnection detected on checkout, " "invalidating individual connection %s (reason: %r)", fairy.connection, e, ) fairy._connection_record.invalidate(e) try: fairy.connection = ( fairy._connection_record.get_connection() ) except Exception as err: with util.safe_reraise(): fairy._connection_record._checkin_failed(err) attempts -= 1 pool.logger.info("Reconnection attempts exhausted on checkout") fairy.invalidate() raise exc.InvalidRequestError("This connection is closed") def _checkout_existing(self): return _ConnectionFairy._checkout(self._pool, fairy=self) def _checkin(self): _finalize_fairy( self.connection, self._connection_record, self._pool, None, self._echo, fairy=self, ) self.connection = None self._connection_record = None _close = _checkin def _reset(self, pool): if pool.dispatch.reset: pool.dispatch.reset(self, self._connection_record) if pool._reset_on_return is reset_rollback: if self._echo: pool.logger.debug( "Connection %s rollback-on-return%s", self.connection, ", via agent" if self._reset_agent else "", ) if self._reset_agent: if not self._reset_agent.is_active: util.warn( "Reset agent is not active. " "This should not occur unless there was already " "a connectivity error in progress." ) pool._dialect.do_rollback(self) else: self._reset_agent.rollback() else: pool._dialect.do_rollback(self) elif pool._reset_on_return is reset_commit: if self._echo: pool.logger.debug( "Connection %s commit-on-return%s", self.connection, ", via agent" if self._reset_agent else "", ) if self._reset_agent: if not self._reset_agent.is_active: util.warn( "Reset agent is not active. " "This should not occur unless there was already " "a connectivity error in progress." ) pool._dialect.do_commit(self) else: self._reset_agent.commit() else: pool._dialect.do_commit(self) @property def _logger(self): return self._pool.logger @property def is_valid(self): """Return True if this :class:`._ConnectionFairy` still refers to an active DBAPI connection.""" return self.connection is not None @util.memoized_property def info(self): """Info dictionary associated with the underlying DBAPI connection referred to by this :class:`.ConnectionFairy`, allowing user-defined data to be associated with the connection. The data here will follow along with the DBAPI connection including after it is returned to the connection pool and used again in subsequent instances of :class:`._ConnectionFairy`. It is shared with the :attr:`._ConnectionRecord.info` and :attr:`_engine.Connection.info` accessors. The dictionary associated with a particular DBAPI connection is discarded when the connection itself is discarded. """ return self._connection_record.info @property def record_info(self): """Info dictionary associated with the :class:`._ConnectionRecord container referred to by this :class:`.ConnectionFairy`. Unlike the :attr:`._ConnectionFairy.info` dictionary, the lifespan of this dictionary is persistent across connections that are disconnected and/or invalidated within the lifespan of a :class:`._ConnectionRecord`. .. versionadded:: 1.1 """ if self._connection_record: return self._connection_record.record_info else: return None def invalidate(self, e=None, soft=False): """Mark this connection as invalidated. This method can be called directly, and is also called as a result of the :meth:`_engine.Connection.invalidate` method. When invoked, the DBAPI connection is immediately closed and discarded from further use by the pool. The invalidation mechanism proceeds via the :meth:`._ConnectionRecord.invalidate` internal method. :param e: an exception object indicating a reason for the invalidation. :param soft: if True, the connection isn't closed; instead, this connection will be recycled on next checkout. .. versionadded:: 1.0.3 .. seealso:: :ref:`pool_connection_invalidation` """ if self.connection is None: util.warn("Can't invalidate an already-closed connection.") return if self._connection_record: self._connection_record.invalidate(e=e, soft=soft) if not soft: self.connection = None self._checkin() def cursor(self, args, kwargs): """Return a new DBAPI cursor for the underlying connection. This method is a proxy for the ``connection.cursor()`` DBAPI method. """ return self.connection.cursor(args, **kwargs) def __getattr__(self, key): return getattr(self.connection, key) def detach(self): """Separate this connection from its Pool. This means that the connection will no longer be returned to the pool when closed, and will instead be literally closed. The containing ConnectionRecord is separated from the DB-API connection, and will create a new connection when next used. Note that any overall connection limiting constraints imposed by a Pool implementation may be violated after a detach, as the detached connection is removed from the pool's knowledge and control. """ if self._connection_record is not None: rec = self._connection_record _refs.remove(rec) rec.fairy_ref = None rec.connection = None # TODO: should this be _return_conn? self._pool._do_return_conn(self._connection_record) self.info = self.info.copy() self._connection_record = None if self._pool.dispatch.detach: self._pool.dispatch.detach(self.connection, rec) def close(self): self._counter -= 1 if self._counter == 0: self._checkin()	35.67 KB	2026-01-20 12:58
📄 dbapi_proxy.py # sqlalchemy/pool/dbapi_proxy.py # Copyright (C) 2005-2021 the SQLAlchemy authors and contributors # <see AUTHORS file> # # This module is part of SQLAlchemy and is released under # the MIT License: http://www.opensource.org/licenses/mit-license.php """DBAPI proxy utility. Provides transparent connection pooling on top of a Python DBAPI. This is legacy SQLAlchemy functionality that is not typically used today. """ from .impl import QueuePool from .. import util from ..util import threading proxies = {} @util.deprecated( "1.3", "The :func:`.pool.manage` function is deprecated, and will be " "removed in a future release.", ) def manage(module, params): r"""Return a proxy for a DB-API module that automatically pools connections. Given a DB-API 2.0 module and pool management parameters, returns a proxy for the module that will automatically pool connections, creating new connection pools for each distinct set of connection arguments sent to the decorated module's connect() function. :param module: a DB-API 2.0 database module :param poolclass: the class used by the pool module to provide pooling. Defaults to :class:`.QueuePool`. :param \params: will be passed through to poolclass """ try: return proxies[module] except KeyError: return proxies.setdefault(module, _DBProxy(module, params)) def clear_managers(): """Remove all current DB-API 2.0 managers. All pools and connections are disposed. """ for manager in proxies.values(): manager.close() proxies.clear() class _DBProxy(object): """Layers connection pooling behavior on top of a standard DB-API module. Proxies a DB-API 2.0 connect() call to a connection pool keyed to the specific connect parameters. Other functions and attributes are delegated to the underlying DB-API module. """ def __init__(self, module, poolclass=QueuePool, kw): """Initializes a new proxy. module a DB-API 2.0 module poolclass a Pool class, defaulting to QueuePool Other parameters are sent to the Pool object's constructor. """ self.module = module self.kw = kw self.poolclass = poolclass self.pools = {} self._create_pool_mutex = threading.Lock() def close(self): for key in list(self.pools): del self.pools[key] def __del__(self): self.close() def __getattr__(self, key): return getattr(self.module, key) def get_pool(self, args, kw): key = self._serialize(args, *kw) try: return self.pools[key] except KeyError: self._create_pool_mutex.acquire() try: if key not in self.pools: kw.pop("sa_pool_key", None) pool = self.poolclass( lambda: self.module.connect(args, kw), self.kw ) self.pools[key] = pool return pool else: return self.pools[key] finally: self._create_pool_mutex.release() def connect(self, args, kw): """Activate a connection to the database. Connect to the database using this DBProxy's module and the given connect arguments. If the arguments match an existing pool, the connection will be returned from the pool's current thread-local connection instance, or if there is no thread-local connection instance it will be checked out from the set of pooled connections. If the pool has no available connections and allows new connections to be created, a new database connection will be made. """ return self.get_pool(args, *kw).connect() def dispose(self, args, *kw): """Dispose the pool referenced by the given connect arguments.""" key = self._serialize(args, *kw) try: del self.pools[key] except KeyError: pass def _serialize(self, args, **kw): if "sa_pool_key" in kw: return kw["sa_pool_key"] return tuple(list(args) + [(k, kw[k]) for k in sorted(kw)])	4.22 KB	2026-01-20 12:58
📄 impl.py # sqlalchemy/pool.py # Copyright (C) 2005-2021 the SQLAlchemy authors and contributors # <see AUTHORS file> # # This module is part of SQLAlchemy and is released under # the MIT License: http://www.opensource.org/licenses/mit-license.php """Pool implementation classes. """ import traceback import weakref from .base import _ConnectionFairy from .base import _ConnectionRecord from .base import Pool from .. import exc from .. import util from ..util import chop_traceback from ..util import queue as sqla_queue from ..util import threading class QueuePool(Pool): """A :class:`_pool.Pool` that imposes a limit on the number of open connections. :class:`.QueuePool` is the default pooling implementation used for all :class:`_engine.Engine` objects, unless the SQLite dialect is in use. """ def __init__( self, creator, pool_size=5, max_overflow=10, timeout=30, use_lifo=False, kw ): r""" Construct a QueuePool. :param creator: a callable function that returns a DB-API connection object, same as that of :paramref:`_pool.Pool.creator`. :param pool_size: The size of the pool to be maintained, defaults to 5. This is the largest number of connections that will be kept persistently in the pool. Note that the pool begins with no connections; once this number of connections is requested, that number of connections will remain. ``pool_size`` can be set to 0 to indicate no size limit; to disable pooling, use a :class:`~sqlalchemy.pool.NullPool` instead. :param max_overflow: The maximum overflow size of the pool. When the number of checked-out connections reaches the size set in pool_size, additional connections will be returned up to this limit. When those additional connections are returned to the pool, they are disconnected and discarded. It follows then that the total number of simultaneous connections the pool will allow is pool_size + `max_overflow`, and the total number of "sleeping" connections the pool will allow is pool_size. `max_overflow` can be set to -1 to indicate no overflow limit; no limit will be placed on the total number of concurrent connections. Defaults to 10. :param timeout: The number of seconds to wait before giving up on returning a connection. Defaults to 30. :param use_lifo: use LIFO (last-in-first-out) when retrieving connections instead of FIFO (first-in-first-out). Using LIFO, a server-side timeout scheme can reduce the number of connections used during non-peak periods of use. When planning for server-side timeouts, ensure that a recycle or pre-ping strategy is in use to gracefully handle stale connections. .. versionadded:: 1.3 .. seealso:: :ref:`pool_use_lifo` :ref:`pool_disconnects` :param \kw: Other keyword arguments including :paramref:`_pool.Pool.recycle`, :paramref:`_pool.Pool.echo`, :paramref:`_pool.Pool.reset_on_return` and others are passed to the :class:`_pool.Pool` constructor. """ Pool.__init__(self, creator, kw) self._pool = sqla_queue.Queue(pool_size, use_lifo=use_lifo) self._overflow = 0 - pool_size self._max_overflow = max_overflow self._timeout = timeout self._overflow_lock = threading.Lock() def _do_return_conn(self, conn): try: self._pool.put(conn, False) except sqla_queue.Full: try: conn.close() finally: self._dec_overflow() def _do_get(self): use_overflow = self._max_overflow > -1 try: wait = use_overflow and self._overflow >= self._max_overflow return self._pool.get(wait, self._timeout) except sqla_queue.Empty: # don't do things inside of "except Empty", because when we say # we timed out or can't connect and raise, Python 3 tells # people the real error is queue.Empty which it isn't. pass if use_overflow and self._overflow >= self._max_overflow: if not wait: return self._do_get() else: raise exc.TimeoutError( "QueuePool limit of size %d overflow %d reached, " "connection timed out, timeout %d" % (self.size(), self.overflow(), self._timeout), code="3o7r", ) if self._inc_overflow(): try: return self._create_connection() except: with util.safe_reraise(): self._dec_overflow() else: return self._do_get() def _inc_overflow(self): if self._max_overflow == -1: self._overflow += 1 return True with self._overflow_lock: if self._overflow < self._max_overflow: self._overflow += 1 return True else: return False def _dec_overflow(self): if self._max_overflow == -1: self._overflow -= 1 return True with self._overflow_lock: self._overflow -= 1 return True def recreate(self): self.logger.info("Pool recreating") return self.__class__( self._creator, pool_size=self._pool.maxsize, max_overflow=self._max_overflow, pre_ping=self._pre_ping, use_lifo=self._pool.use_lifo, timeout=self._timeout, recycle=self._recycle, echo=self.echo, logging_name=self._orig_logging_name, use_threadlocal=self._use_threadlocal, reset_on_return=self._reset_on_return, _dispatch=self.dispatch, dialect=self._dialect, ) def dispose(self): while True: try: conn = self._pool.get(False) conn.close() except sqla_queue.Empty: break self._overflow = 0 - self.size() self.logger.info("Pool disposed. %s", self.status()) def status(self): return ( "Pool size: %d Connections in pool: %d " "Current Overflow: %d Current Checked out " "connections: %d" % ( self.size(), self.checkedin(), self.overflow(), self.checkedout(), ) ) def size(self): return self._pool.maxsize def timeout(self): return self._timeout def checkedin(self): return self._pool.qsize() def overflow(self): return self._overflow def checkedout(self): return self._pool.maxsize - self._pool.qsize() + self._overflow class NullPool(Pool): """A Pool which does not pool connections. Instead it literally opens and closes the underlying DB-API connection per each connection open/close. Reconnect-related functions such as ``recycle`` and connection invalidation are not supported by this Pool implementation, since no connections are held persistently. """ def status(self): return "NullPool" def _do_return_conn(self, conn): conn.close() def _do_get(self): return self._create_connection() def recreate(self): self.logger.info("Pool recreating") return self.__class__( self._creator, recycle=self._recycle, echo=self.echo, logging_name=self._orig_logging_name, use_threadlocal=self._use_threadlocal, reset_on_return=self._reset_on_return, pre_ping=self._pre_ping, _dispatch=self.dispatch, dialect=self._dialect, ) def dispose(self): pass class SingletonThreadPool(Pool): """A Pool that maintains one connection per thread. Maintains one connection per each thread, never moving a connection to a thread other than the one which it was created in. .. warning:: the :class:`.SingletonThreadPool` will call ``.close()`` on arbitrary connections that exist beyond the size setting of ``pool_size``, e.g. if more unique thread identities than what ``pool_size`` states are used. This cleanup is non-deterministic and not sensitive to whether or not the connections linked to those thread identities are currently in use. :class:`.SingletonThreadPool` may be improved in a future release, however in its current status it is generally used only for test scenarios using a SQLite ``:memory:`` database and is not recommended for production use. Options are the same as those of :class:`_pool.Pool`, as well as: :param pool_size: The number of threads in which to maintain connections at once. Defaults to five. :class:`.SingletonThreadPool` is used by the SQLite dialect automatically when a memory-based database is used. See :ref:`sqlite_toplevel`. """ def __init__(self, creator, pool_size=5, kw): Pool.__init__(self, creator, *kw) self._conn = threading.local() self._fairy = threading.local() self._all_conns = set() self.size = pool_size def recreate(self): self.logger.info("Pool recreating") return self.__class__( self._creator, pool_size=self.size, recycle=self._recycle, echo=self.echo, pre_ping=self._pre_ping, logging_name=self._orig_logging_name, use_threadlocal=self._use_threadlocal, reset_on_return=self._reset_on_return, _dispatch=self.dispatch, dialect=self._dialect, ) def dispose(self): """Dispose of this pool.""" for conn in self._all_conns: try: conn.close() except Exception: # pysqlite won't even let you close a conn from a thread # that didn't create it pass self._all_conns.clear() def _cleanup(self): while len(self._all_conns) >= self.size: c = self._all_conns.pop() c.close() def status(self): return "SingletonThreadPool id:%d size: %d" % ( id(self), len(self._all_conns), ) def _do_return_conn(self, conn): pass def _do_get(self): try: c = self._conn.current() if c: return c except AttributeError: pass c = self._create_connection() self._conn.current = weakref.ref(c) if len(self._all_conns) >= self.size: self._cleanup() self._all_conns.add(c) return c def connect(self): # vendored from Pool to include use_threadlocal behavior try: rec = self._fairy.current() except AttributeError: pass else: if rec is not None: return rec._checkout_existing() return _ConnectionFairy._checkout(self, self._fairy) def _return_conn(self, record): try: del self._fairy.current except AttributeError: pass self._do_return_conn(record) class StaticPool(Pool): """A Pool of exactly one connection, used for all requests. Reconnect-related functions such as ``recycle`` and connection invalidation (which is also used to support auto-reconnect) are not currently supported by this Pool implementation but may be implemented in a future release. """ @util.memoized_property def _conn(self): return self._creator() @util.memoized_property def connection(self): return _ConnectionRecord(self) def status(self): return "StaticPool" def dispose(self): if "_conn" in self.__dict__: self._conn.close() self._conn = None def recreate(self): self.logger.info("Pool recreating") return self.__class__( creator=self._creator, recycle=self._recycle, use_threadlocal=self._use_threadlocal, reset_on_return=self._reset_on_return, pre_ping=self._pre_ping, echo=self.echo, logging_name=self._orig_logging_name, _dispatch=self.dispatch, dialect=self._dialect, ) def _create_connection(self): return self._conn def _do_return_conn(self, conn): pass def _do_get(self): return self.connection class AssertionPool(Pool): """A :class:`_pool.Pool` that allows at most one checked out connection at any given time. This will raise an exception if more than one connection is checked out at a time. Useful for debugging code that is using more connections than desired. """ def __init__(self, args, *kw): self._conn = None self._checked_out = False self._store_traceback = kw.pop("store_traceback", True) self._checkout_traceback = None Pool.__init__(self, args, **kw) def status(self): return "AssertionPool" def _do_return_conn(self, conn): if not self._checked_out: raise AssertionError("connection is not checked out") self._checked_out = False assert conn is self._conn def dispose(self): self._checked_out = False if self._conn: self._conn.close() def recreate(self): self.logger.info("Pool recreating") return self.__class__( self._creator, echo=self.echo, pre_ping=self._pre_ping, recycle=self._recycle, reset_on_return=self._reset_on_return, logging_name=self._orig_logging_name, _dispatch=self.dispatch, dialect=self._dialect, ) def _do_get(self): if self._checked_out: if self._checkout_traceback: suffix = " at:\n%s" % "".join( chop_traceback(self._checkout_traceback) ) else: suffix = "" raise AssertionError("connection is already checked out" + suffix) if not self._conn: self._conn = self._create_connection() self._checked_out = True if self._store_traceback: self._checkout_traceback = traceback.format_stack() return self._conn	14.61 KB	2026-01-20 12:58

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