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# pool/base.py # Copyright (C) 2005-2025 the SQLAlchemy authors and contributors # <see AUTHORS file> # # This module is part of SQLAlchemy and is released under # the MIT License: https://www.opensource.org/licenses/mit-license.php """Base constructs for connection pools. """ from __future__ import annotations from collections import deque import dataclasses from enum import Enum import threading import time import typing from typing import Any from typing import Callable from typing import cast from typing import Deque from typing import Dict from typing import List from typing import Optional from typing import Tuple from typing import TYPE_CHECKING from typing import Union import weakref from .. import event from .. import exc from .. import log from .. import util from ..util.typing import Literal from ..util.typing import Protocol if TYPE_CHECKING: from ..engine.interfaces import DBAPIConnection from ..engine.interfaces import DBAPICursor from ..engine.interfaces import Dialect from ..event import _DispatchCommon from ..event import _ListenerFnType from ..event import dispatcher from ..sql._typing import _InfoType @dataclasses.dataclass(frozen=True) class PoolResetState: """describes the state of a DBAPI connection as it is being passed to the :meth:`.PoolEvents.reset` connection pool event. .. versionadded:: 2.0.0b3 """ __slots__ = ("transaction_was_reset", "terminate_only", "asyncio_safe") transaction_was_reset: bool """Indicates if the transaction on the DBAPI connection was already essentially "reset" back by the :class:`.Connection` object. This boolean is True if the :class:`.Connection` had transactional state present upon it, which was then not closed using the :meth:`.Connection.rollback` or :meth:`.Connection.commit` method; instead, the transaction was closed inline within the :meth:`.Connection.close` method so is guaranteed to remain non-present when this event is reached. """ terminate_only: bool """indicates if the connection is to be immediately terminated and not checked in to the pool. This occurs for connections that were invalidated, as well as asyncio connections that were not cleanly handled by the calling code that are instead being garbage collected. In the latter case, operations can't be safely run on asyncio connections within garbage collection as there is not necessarily an event loop present. """ asyncio_safe: bool """Indicates if the reset operation is occurring within a scope where an enclosing event loop is expected to be present for asyncio applications. Will be False in the case that the connection is being garbage collected. """ class ResetStyle(Enum): """Describe options for "reset on return" behaviors.""" reset_rollback = 0 reset_commit = 1 reset_none = 2 _ResetStyleArgType = Union[ ResetStyle, Literal[True, None, False, "commit", "rollback"], ] reset_rollback, reset_commit, reset_none = list(ResetStyle) class _ConnDialect: """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`. """ is_async = False has_terminate = False def do_rollback(self, dbapi_connection: PoolProxiedConnection) -> None: dbapi_connection.rollback() def do_commit(self, dbapi_connection: PoolProxiedConnection) -> None: dbapi_connection.commit() def do_terminate(self, dbapi_connection: DBAPIConnection) -> None: dbapi_connection.close() def do_close(self, dbapi_connection: DBAPIConnection) -> None: dbapi_connection.close() def _do_ping_w_event(self, dbapi_connection: DBAPIConnection) -> bool: raise NotImplementedError( "The ping feature requires that a dialect is " "passed to the connection pool." ) def get_driver_connection(self, connection: DBAPIConnection) -> Any: return connection class _AsyncConnDialect(_ConnDialect): is_async = True class _CreatorFnType(Protocol): def __call__(self) -> DBAPIConnection: ... class _CreatorWRecFnType(Protocol): def __call__(self, rec: ConnectionPoolEntry) -> DBAPIConnection: ... class Pool(log.Identified, event.EventTarget): """Abstract base class for connection pools.""" dispatch: dispatcher[Pool] echo: log._EchoFlagType _orig_logging_name: Optional[str] _dialect: Union[_ConnDialect, Dialect] = _ConnDialect() _creator_arg: Union[_CreatorFnType, _CreatorWRecFnType] _invoke_creator: _CreatorWRecFnType _invalidate_time: float def __init__( self, creator: Union[_CreatorFnType, _CreatorWRecFnType], recycle: int = -1, echo: log._EchoFlagType = None, logging_name: Optional[str] = None, reset_on_return: _ResetStyleArgType = True, events: Optional[List[Tuple[_ListenerFnType, str]]] = None, dialect: Optional[Union[_ConnDialect, Dialect]] = None, pre_ping: bool = False, _dispatch: Optional[_DispatchCommon[Pool]] = 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 reset_on_return: Determine steps to take on connections as they are returned to the pool, which were not otherwise handled by a :class:`_engine.Connection`. Available from :func:`_sa.create_engine` via the :paramref:`_sa.create_engine.pool_reset_on_return` parameter. :paramref:`_pool.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. * ``"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 may be appropriate if the database / DBAPI works in pure "autocommit" mode at all times, or if a custom reset handler is established using the :meth:`.PoolEvents.reset` event handler. * ``True`` - same as 'rollback', this is here for backwards compatibility. * ``False`` - same as None, this is here for backwards compatibility. For further customization of reset on return, the :meth:`.PoolEvents.reset` event hook may be used which can perform any connection activity desired on reset. .. seealso:: :ref:`pool_reset_on_return` :meth:`.PoolEvents.reset` :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 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. :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._creator = creator self._recycle = recycle self._invalidate_time = 0 self._pre_ping = pre_ping self._reset_on_return = util.parse_user_argument_for_enum( reset_on_return, { ResetStyle.reset_rollback: ["rollback", True], ResetStyle.reset_none: ["none", None, False], ResetStyle.reset_commit: ["commit"], }, "reset_on_return", ) 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) @util.hybridproperty def _is_asyncio(self) -> bool: return self._dialect.is_async @property def _creator(self) -> Union[_CreatorFnType, _CreatorWRecFnType]: return self._creator_arg @_creator.setter def _creator( self, creator: Union[_CreatorFnType, _CreatorWRecFnType] ) -> None: self._creator_arg = creator # mypy seems to get super confused assigning functions to # attributes self._invoke_creator = self._should_wrap_creator(creator) @_creator.deleter def _creator(self) -> None: # needed for mock testing del self._creator_arg del self._invoke_creator def _should_wrap_creator( self, creator: Union[_CreatorFnType, _CreatorWRecFnType] ) -> _CreatorWRecFnType: """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: creator_fn = cast(_CreatorFnType, creator) return lambda rec: creator_fn() if argspec.defaults is not None: defaulted = len(argspec.defaults) else: defaulted = 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 cast(_CreatorWRecFnType, creator) # or just a single positional elif positionals == 1: return cast(_CreatorWRecFnType, creator) # all other cases, just wrap and assume legacy "creator" callable # thing else: creator_fn = cast(_CreatorFnType, creator) return lambda rec: creator_fn() def _close_connection( self, connection: DBAPIConnection, *, terminate: bool = False ) -> None: self.logger.debug( "%s connection %r", "Hard-closing" if terminate else "Closing", connection, ) try: if terminate: self._dialect.do_terminate(connection) else: self._dialect.do_close(connection) except BaseException as e: self.logger.error( f"Exception {'terminating' if terminate else 'closing'} " f"connection %r", connection, exc_info=True, ) if not isinstance(e, Exception): raise def _create_connection(self) -> ConnectionPoolEntry: """Called by subclasses to create a new ConnectionRecord.""" return _ConnectionRecord(self) def _invalidate( self, connection: PoolProxiedConnection, exception: Optional[BaseException] = None, _checkin: bool = True, ) -> None: """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) -> Pool: """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) -> None: """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) -> PoolProxiedConnection: """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. """ return _ConnectionFairy._checkout(self) def _return_conn(self, record: ConnectionPoolEntry) -> None: """Given a _ConnectionRecord, return it to the :class:`_pool.Pool`. This method is called when an instrumented DBAPI connection has its ``close()`` method called. """ self._do_return_conn(record) def _do_get(self) -> ConnectionPoolEntry: """Implementation for :meth:`get`, supplied by subclasses.""" raise NotImplementedError() def _do_return_conn(self, record: ConnectionPoolEntry) -> None: """Implementation for :meth:`return_conn`, supplied by subclasses.""" raise NotImplementedError() def status(self) -> str: """Returns a brief description of the state of this pool.""" raise NotImplementedError() class ManagesConnection: """Common base for the two connection-management interfaces :class:`.PoolProxiedConnection` and :class:`.ConnectionPoolEntry`. These two objects are typically exposed in the public facing API via the connection pool event hooks, documented at :class:`.PoolEvents`. .. versionadded:: 2.0 """ __slots__ = () dbapi_connection: Optional[DBAPIConnection] """A reference to the actual DBAPI connection being tracked. This is a :pep:`249`-compliant object that for traditional sync-style dialects is provided by the third-party DBAPI implementation in use. For asyncio dialects, the implementation is typically an adapter object provided by the SQLAlchemy dialect itself; the underlying asyncio object is available via the :attr:`.ManagesConnection.driver_connection` attribute. SQLAlchemy's interface for the DBAPI connection is based on the :class:`.DBAPIConnection` protocol object .. seealso:: :attr:`.ManagesConnection.driver_connection` :ref:`faq_dbapi_connection` """ driver_connection: Optional[Any] """The "driver level" connection object as used by the Python DBAPI or database driver. For traditional :pep:`249` DBAPI implementations, this object will be the same object as that of :attr:`.ManagesConnection.dbapi_connection`. For an asyncio database driver, this will be the ultimate "connection" object used by that driver, such as the ``asyncpg.Connection`` object which will not have standard pep-249 methods. .. versionadded:: 1.4.24 .. seealso:: :attr:`.ManagesConnection.dbapi_connection` :ref:`faq_dbapi_connection` """ @util.ro_memoized_property def info(self) -> _InfoType: """Info dictionary associated with the underlying DBAPI connection referred to by this :class:`.ManagesConnection` instance, allowing user-defined data to be associated with the connection. The data in this dictionary is persistent for the lifespan of the DBAPI connection itself, including across pool checkins and checkouts. When the connection is invalidated and replaced with a new one, this dictionary is cleared. For a :class:`.PoolProxiedConnection` instance that's not associated with a :class:`.ConnectionPoolEntry`, such as if it were detached, the attribute returns a dictionary that is local to that :class:`.ConnectionPoolEntry`. Therefore the :attr:`.ManagesConnection.info` attribute will always provide a Python dictionary. .. seealso:: :attr:`.ManagesConnection.record_info` """ raise NotImplementedError() @util.ro_memoized_property def record_info(self) -> Optional[_InfoType]: """Persistent info dictionary associated with this :class:`.ManagesConnection`. Unlike the :attr:`.ManagesConnection.info` dictionary, the lifespan of this dictionary is that of the :class:`.ConnectionPoolEntry` which owns it; therefore this dictionary will persist across reconnects and connection invalidation for a particular entry in the connection pool. For a :class:`.PoolProxiedConnection` instance that's not associated with a :class:`.ConnectionPoolEntry`, such as if it were detached, the attribute returns None. Contrast to the :attr:`.ManagesConnection.info` dictionary which is never None. .. seealso:: :attr:`.ManagesConnection.info` """ raise NotImplementedError() def invalidate( self, e: Optional[BaseException] = None, soft: bool = False ) -> None: """Mark the managed connection as invalidated. :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. .. seealso:: :ref:`pool_connection_invalidation` """ raise NotImplementedError() class ConnectionPoolEntry(ManagesConnection): """Interface for the object that maintains an individual database connection on behalf of a :class:`_pool.Pool` instance. The :class:`.ConnectionPoolEntry` object represents the long term maintainance of a particular connection for a pool, including expiring or invalidating that connection to have it replaced with a new one, which will continue to be maintained by that same :class:`.ConnectionPoolEntry` instance. Compared to :class:`.PoolProxiedConnection`, which is the short-term, per-checkout connection manager, this object lasts for the lifespan of a particular "slot" within a connection pool. The :class:`.ConnectionPoolEntry` object is mostly visible to public-facing API code when it is delivered to connection pool event hooks, such as :meth:`_events.PoolEvents.connect` and :meth:`_events.PoolEvents.checkout`. .. versionadded:: 2.0 :class:`.ConnectionPoolEntry` provides the public facing interface for the :class:`._ConnectionRecord` internal class. """ __slots__ = () @property def in_use(self) -> bool: """Return True the connection is currently checked out""" raise NotImplementedError() def close(self) -> None: """Close the DBAPI connection managed by this connection pool entry.""" raise NotImplementedError() class _ConnectionRecord(ConnectionPoolEntry): """Maintains a position in a connection pool which references a pooled connection. This is an internal object used by the :class:`_pool.Pool` implementation to provide context management to a DBAPI connection maintained by that :class:`_pool.Pool`. The public facing interface for this class is described by the :class:`.ConnectionPoolEntry` class. See that class for public API details. .. seealso:: :class:`.ConnectionPoolEntry` :class:`.PoolProxiedConnection` """ __slots__ = ( "__pool", "fairy_ref", "finalize_callback", "fresh", "starttime", "dbapi_connection", "__weakref__", "__dict__", ) finalize_callback: Deque[Callable[[DBAPIConnection], None]] fresh: bool fairy_ref: Optional[weakref.ref[_ConnectionFairy]] starttime: float def __init__(self, pool: Pool, connect: bool = True): self.fresh = False self.fairy_ref = None self.starttime = 0 self.dbapi_connection = None self.__pool = pool if connect: self.__connect() self.finalize_callback = deque() dbapi_connection: Optional[DBAPIConnection] @property def driver_connection(self) -> Optional[Any]: # type: ignore[override] # mypy#4125 # noqa: E501 if self.dbapi_connection is None: return None else: return self.__pool._dialect.get_driver_connection( self.dbapi_connection ) @property @util.deprecated( "2.0", "The _ConnectionRecord.connection attribute is deprecated; " "please use 'driver_connection'", ) def connection(self) -> Optional[DBAPIConnection]: return self.dbapi_connection _soft_invalidate_time: float = 0 @util.ro_memoized_property def info(self) -> _InfoType: return {} @util.ro_memoized_property def record_info(self) -> Optional[_InfoType]: return {} @classmethod def checkout(cls, pool: Pool) -> _ConnectionFairy: if TYPE_CHECKING: rec = cast(_ConnectionRecord, pool._do_get()) else: rec = pool._do_get() try: dbapi_connection = rec.get_connection() except BaseException as err: with util.safe_reraise(): rec._checkin_failed(err, _fairy_was_created=False) # not reached, for code linters only raise echo = pool._should_log_debug() fairy = _ConnectionFairy(pool, dbapi_connection, rec, echo) rec.fairy_ref = ref = weakref.ref( fairy, lambda ref: ( _finalize_fairy( None, rec, pool, ref, echo, transaction_was_reset=False ) if _finalize_fairy is not None else None ), ) _strong_ref_connection_records[ref] = rec if echo: pool.logger.debug( "Connection %r checked out from pool", dbapi_connection ) return fairy def _checkin_failed( self, err: BaseException, _fairy_was_created: bool = True ) -> None: self.invalidate(e=err) self.checkin( _fairy_was_created=_fairy_was_created, ) def checkin(self, _fairy_was_created: bool = True) -> None: if self.fairy_ref is None and _fairy_was_created: # _fairy_was_created is False for the initial get connection phase; # meaning there was no _ConnectionFairy and we must unconditionally # do a checkin. # # otherwise, if fairy_was_created==True, if fairy_ref is None here # that means we were checked in already, so this looks like # a double checkin. util.warn("Double checkin attempted on %s" % self) return self.fairy_ref = None connection = self.dbapi_connection pool = self.__pool while self.finalize_callback: finalizer = self.finalize_callback.pop() if connection is not None: finalizer(connection) if pool.dispatch.checkin: pool.dispatch.checkin(connection, self) pool._return_conn(self) @property def in_use(self) -> bool: return self.fairy_ref is not None @property def last_connect_time(self) -> float: return self.starttime def close(self) -> None: if self.dbapi_connection is not None: self.__close() def invalidate( self, e: Optional[BaseException] = None, soft: bool = False ) -> None: # already invalidated if self.dbapi_connection is None: return if soft: self.__pool.dispatch.soft_invalidate( self.dbapi_connection, self, e ) else: self.__pool.dispatch.invalidate(self.dbapi_connection, self, e) if e is not None: self.__pool.logger.info( "%sInvalidate connection %r (reason: %s:%s)", "Soft " if soft else "", self.dbapi_connection, e.__class__.__name__, e, ) else: self.__pool.logger.info( "%sInvalidate connection %r", "Soft " if soft else "", self.dbapi_connection, ) if soft: self._soft_invalidate_time = time.time() else: self.__close(terminate=True) self.dbapi_connection = None def get_connection(self) -> DBAPIConnection: 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.dbapi_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.dbapi_connection, ) recycle = True elif self.__pool._invalidate_time > self.starttime: self.__pool.logger.info( "Connection %r invalidated due to pool invalidation; " + "recycling", self.dbapi_connection, ) recycle = True elif self._soft_invalidate_time > self.starttime: self.__pool.logger.info( "Connection %r invalidated due to local soft invalidation; " + "recycling", self.dbapi_connection, ) recycle = True if recycle: self.__close(terminate=True) self.info.clear() self.__connect() assert self.dbapi_connection is not None return self.dbapi_connection def _is_hard_or_soft_invalidated(self) -> bool: return ( self.dbapi_connection is None or self.__pool._invalidate_time > self.starttime or (self._soft_invalidate_time > self.starttime) ) def __close(self, *, terminate: bool = False) -> None: self.finalize_callback.clear() if self.__pool.dispatch.close: self.__pool.dispatch.close(self.dbapi_connection, self) assert self.dbapi_connection is not None self.__pool._close_connection( self.dbapi_connection, terminate=terminate ) self.dbapi_connection = None def __connect(self) -> None: pool = self.__pool # ensure any existing connection is removed, so that if # creator fails, this attribute stays None self.dbapi_connection = None try: self.starttime = time.time() self.dbapi_connection = connection = pool._invoke_creator(self) pool.logger.debug("Created new connection %r", connection) self.fresh = True except BaseException as e: with util.safe_reraise(): pool.logger.debug("Error on connect(): %s", e) else: # in SQLAlchemy 1.4 the first_connect event is not used by # the engine, so this will usually not be set if pool.dispatch.first_connect: pool.dispatch.first_connect.for_modify( pool.dispatch ).exec_once_unless_exception(self.dbapi_connection, self) # init of the dialect now takes place within the connect # event, so ensure a mutex is used on the first run pool.dispatch.connect.for_modify( pool.dispatch )._exec_w_sync_on_first_run(self.dbapi_connection, self) def _finalize_fairy( dbapi_connection: Optional[DBAPIConnection], connection_record: Optional[_ConnectionRecord], pool: Pool, ref: Optional[ weakref.ref[_ConnectionFairy] ], # this is None when called directly, not by the gc echo: Optional[log._EchoFlagType], transaction_was_reset: bool = False, fairy: Optional[_ConnectionFairy] = None, ) -> None: """Cleanup for a :class:`._ConnectionFairy` whether or not it's already been garbage collected. When using an async dialect no IO can happen here (without using a dedicated thread), since this is called outside the greenlet context and with an already running loop. In this case function will only log a message and raise a warning. """ is_gc_cleanup = ref is not None if is_gc_cleanup: assert ref is not None _strong_ref_connection_records.pop(ref, None) assert connection_record is not None if connection_record.fairy_ref is not ref: return assert dbapi_connection is None dbapi_connection = connection_record.dbapi_connection elif fairy: _strong_ref_connection_records.pop(weakref.ref(fairy), None) # null pool is not _is_asyncio but can be used also with async dialects dont_restore_gced = pool._dialect.is_async if dont_restore_gced: detach = connection_record is None or is_gc_cleanup can_manipulate_connection = not is_gc_cleanup can_close_or_terminate_connection = ( not pool._dialect.is_async or pool._dialect.has_terminate ) requires_terminate_for_close = ( pool._dialect.is_async and pool._dialect.has_terminate ) else: detach = connection_record is None can_manipulate_connection = can_close_or_terminate_connection = True requires_terminate_for_close = False if dbapi_connection is not None: if connection_record and echo: pool.logger.debug( "Connection %r being returned to pool", dbapi_connection ) try: if not fairy: assert connection_record is not None fairy = _ConnectionFairy( pool, dbapi_connection, connection_record, echo, ) assert fairy.dbapi_connection is dbapi_connection fairy._reset( pool, transaction_was_reset=transaction_was_reset, terminate_only=detach, asyncio_safe=can_manipulate_connection, ) if detach: if connection_record: fairy._pool = pool fairy.detach() if can_close_or_terminate_connection: if pool.dispatch.close_detached: pool.dispatch.close_detached(dbapi_connection) pool._close_connection( dbapi_connection, terminate=requires_terminate_for_close, ) 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 finally: if detach and is_gc_cleanup and dont_restore_gced: message = ( "The garbage collector is trying to clean up " f"non-checked-in connection {dbapi_connection!r}, " f"""which will be { 'dropped, as it cannot be safely terminated' if not can_close_or_terminate_connection else 'terminated' }. """ "Please ensure that SQLAlchemy pooled connections are " "returned to " "the pool explicitly, either by calling ``close()`` " "or by using appropriate context managers to manage " "their lifecycle." ) pool.logger.error(message) util.warn(message) if connection_record and connection_record.fairy_ref is not None: connection_record.checkin() # give gc some help. See # test/engine/test_pool.py::PoolEventsTest::test_checkin_event_gc[True] # which actually started failing when pytest warnings plugin was # turned on, due to util.warn() above if fairy is not None: fairy.dbapi_connection = None # type: ignore fairy._connection_record = None del dbapi_connection del connection_record del fairy # a dictionary of the _ConnectionFairy weakrefs to _ConnectionRecord, so that # GC under pypy will call ConnectionFairy finalizers. linked directly to the # weakref that will empty itself when collected so that it should not create # any unmanaged memory references. _strong_ref_connection_records: Dict[ weakref.ref[_ConnectionFairy], _ConnectionRecord ] = {} class PoolProxiedConnection(ManagesConnection): """A connection-like adapter for a :pep:`249` DBAPI connection, which includes additional methods specific to the :class:`.Pool` implementation. :class:`.PoolProxiedConnection` is the public-facing interface for the internal :class:`._ConnectionFairy` implementation object; users familiar with :class:`._ConnectionFairy` can consider this object to be equivalent. .. versionadded:: 2.0 :class:`.PoolProxiedConnection` provides the public- facing interface for the :class:`._ConnectionFairy` internal class. """ __slots__ = () if typing.TYPE_CHECKING: def commit(self) -> None: ... def cursor(self) -> DBAPICursor: ... def rollback(self) -> None: ... @property def is_valid(self) -> bool: """Return True if this :class:`.PoolProxiedConnection` still refers to an active DBAPI connection.""" raise NotImplementedError() @property def is_detached(self) -> bool: """Return True if this :class:`.PoolProxiedConnection` is detached from its pool.""" raise NotImplementedError() def detach(self) -> None: """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 associated :class:`.ConnectionPoolEntry` is de-associated from this DBAPI connection. 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. """ raise NotImplementedError() def close(self) -> None: """Release this connection back to the pool. The :meth:`.PoolProxiedConnection.close` method shadows the :pep:`249` ``.close()`` method, altering its behavior to instead :term:`release` the proxied connection back to the connection pool. Upon release to the pool, whether the connection stays "opened" and pooled in the Python process, versus actually closed out and removed from the Python process, is based on the pool implementation in use and its configuration and current state. """ raise NotImplementedError() class _AdhocProxiedConnection(PoolProxiedConnection): """provides the :class:`.PoolProxiedConnection` interface for cases where the DBAPI connection is not actually proxied. This is used by the engine internals to pass a consistent :class:`.PoolProxiedConnection` object to consuming dialects in response to pool events that may not always have the :class:`._ConnectionFairy` available. """ __slots__ = ("dbapi_connection", "_connection_record", "_is_valid") dbapi_connection: DBAPIConnection _connection_record: ConnectionPoolEntry def __init__( self, dbapi_connection: DBAPIConnection, connection_record: ConnectionPoolEntry, ): self.dbapi_connection = dbapi_connection self._connection_record = connection_record self._is_valid = True @property def driver_connection(self) -> Any: # type: ignore[override] # mypy#4125 return self._connection_record.driver_connection @property def connection(self) -> DBAPIConnection: return self.dbapi_connection @property def is_valid(self) -> bool: """Implement is_valid state attribute. for the adhoc proxied connection it's assumed the connection is valid as there is no "invalidate" routine. """ return self._is_valid def invalidate( self, e: Optional[BaseException] = None, soft: bool = False ) -> None: self._is_valid = False @util.ro_non_memoized_property def record_info(self) -> Optional[_InfoType]: return self._connection_record.record_info def cursor(self, *args: Any, **kwargs: Any) -> DBAPICursor: return self.dbapi_connection.cursor(*args, **kwargs) def __getattr__(self, key: Any) -> Any: return getattr(self.dbapi_connection, key) class _ConnectionFairy(PoolProxiedConnection): """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 public facing interface for this class is described by the :class:`.PoolProxiedConnection` class. See that class for public API details. 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:`.PoolProxiedConnection` :class:`.ConnectionPoolEntry` """ __slots__ = ( "dbapi_connection", "_connection_record", "_echo", "_pool", "_counter", "__weakref__", "__dict__", ) pool: Pool dbapi_connection: DBAPIConnection _echo: log._EchoFlagType def __init__( self, pool: Pool, dbapi_connection: DBAPIConnection, connection_record: _ConnectionRecord, echo: log._EchoFlagType, ): self._pool = pool self._counter = 0 self.dbapi_connection = dbapi_connection self._connection_record = connection_record self._echo = echo _connection_record: Optional[_ConnectionRecord] @property def driver_connection(self) -> Optional[Any]: # type: ignore[override] # mypy#4125 # noqa: E501 if self._connection_record is None: return None return self._connection_record.driver_connection @property @util.deprecated( "2.0", "The _ConnectionFairy.connection attribute is deprecated; " "please use 'driver_connection'", ) def connection(self) -> DBAPIConnection: return self.dbapi_connection @classmethod def _checkout( cls, pool: Pool, threadconns: Optional[threading.local] = None, fairy: Optional[_ConnectionFairy] = None, ) -> _ConnectionFairy: if not fairy: fairy = _ConnectionRecord.checkout(pool) if threadconns is not None: threadconns.current = weakref.ref(fairy) assert ( fairy._connection_record is not None ), "can't 'checkout' a detached connection fairy" assert ( fairy.dbapi_connection is not None ), "can't 'checkout' an invalidated connection fairy" 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: connection_is_fresh = fairy._connection_record.fresh fairy._connection_record.fresh = False try: if pool._pre_ping: if not connection_is_fresh: if fairy._echo: pool.logger.debug( "Pool pre-ping on connection %s", fairy.dbapi_connection, ) result = pool._dialect._do_ping_w_event( fairy.dbapi_connection ) if not result: if fairy._echo: pool.logger.debug( "Pool pre-ping on connection %s failed, " "will invalidate pool", fairy.dbapi_connection, ) raise exc.InvalidatePoolError() elif fairy._echo: pool.logger.debug( "Connection %s is fresh, skipping pre-ping", fairy.dbapi_connection, ) pool.dispatch.checkout( fairy.dbapi_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.dbapi_connection, e, ) fairy._connection_record.invalidate(e) try: fairy.dbapi_connection = ( fairy._connection_record.get_connection() ) except BaseException as err: with util.safe_reraise(): fairy._connection_record._checkin_failed( err, _fairy_was_created=True, ) # prevent _ConnectionFairy from being carried # in the stack trace. Do this after the # connection record has been checked in, so that # if the del triggers a finalize fairy, it won't # try to checkin a second time. del fairy # never called, this is for code linters raise attempts -= 1 except BaseException as be_outer: with util.safe_reraise(): rec = fairy._connection_record if rec is not None: rec._checkin_failed( be_outer, _fairy_was_created=True, ) # prevent _ConnectionFairy from being carried # in the stack trace, see above del fairy # never called, this is for code linters raise pool.logger.info("Reconnection attempts exhausted on checkout") fairy.invalidate() raise exc.InvalidRequestError("This connection is closed") def _checkout_existing(self) -> _ConnectionFairy: return _ConnectionFairy._checkout(self._pool, fairy=self) def _checkin(self, transaction_was_reset: bool = False) -> None: _finalize_fairy( self.dbapi_connection, self._connection_record, self._pool, None, self._echo, transaction_was_reset=transaction_was_reset, fairy=self, ) def _close(self) -> None: self._checkin() def _reset( self, pool: Pool, transaction_was_reset: bool, terminate_only: bool, asyncio_safe: bool, ) -> None: if pool.dispatch.reset: pool.dispatch.reset( self.dbapi_connection, self._connection_record, PoolResetState( transaction_was_reset=transaction_was_reset, terminate_only=terminate_only, asyncio_safe=asyncio_safe, ), ) if not asyncio_safe: return if pool._reset_on_return is reset_rollback: if transaction_was_reset: if self._echo: pool.logger.debug( "Connection %s reset, transaction already reset", self.dbapi_connection, ) else: if self._echo: pool.logger.debug( "Connection %s rollback-on-return", self.dbapi_connection, ) pool._dialect.do_rollback(self) elif pool._reset_on_return is reset_commit: if self._echo: pool.logger.debug( "Connection %s commit-on-return", self.dbapi_connection, ) pool._dialect.do_commit(self) @property def _logger(self) -> log._IdentifiedLoggerType: return self._pool.logger @property def is_valid(self) -> bool: return self.dbapi_connection is not None @property def is_detached(self) -> bool: return self._connection_record is None @util.ro_memoized_property def info(self) -> _InfoType: if self._connection_record is None: return {} else: return self._connection_record.info @util.ro_non_memoized_property def record_info(self) -> Optional[_InfoType]: if self._connection_record is None: return None else: return self._connection_record.record_info def invalidate( self, e: Optional[BaseException] = None, soft: bool = False ) -> None: if self.dbapi_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: # prevent any rollback / reset actions etc. on # the connection self.dbapi_connection = None # type: ignore # finalize self._checkin() def cursor(self, *args: Any, **kwargs: Any) -> DBAPICursor: assert self.dbapi_connection is not None return self.dbapi_connection.cursor(*args, **kwargs) def __getattr__(self, key: str) -> Any: return getattr(self.dbapi_connection, key) def detach(self) -> None: if self._connection_record is not None: rec = self._connection_record rec.fairy_ref = None rec.dbapi_connection = None # TODO: should this be _return_conn? self._pool._do_return_conn(self._connection_record) # can't get the descriptor assignment to work here # in pylance. mypy is OK w/ it self.info = self.info.copy() # type: ignore self._connection_record = None if self._pool.dispatch.detach: self._pool.dispatch.detach(self.dbapi_connection, rec) def close(self) -> None: self._counter -= 1 if self._counter == 0: self._checkin() def _close_special(self, transaction_reset: bool = False) -> None: self._counter -= 1 if self._counter == 0: self._checkin(transaction_was_reset=transaction_reset)