diff options
Diffstat (limited to 'lib/sqlalchemy/pool/base.py')
| -rw-r--r-- | lib/sqlalchemy/pool/base.py | 178 |
1 files changed, 130 insertions, 48 deletions
diff --git a/lib/sqlalchemy/pool/base.py b/lib/sqlalchemy/pool/base.py index 41f2f03b2..18ff66e5d 100644 --- a/lib/sqlalchemy/pool/base.py +++ b/lib/sqlalchemy/pool/base.py @@ -13,6 +13,7 @@ from __future__ import annotations from collections import deque +import dataclasses from enum import Enum import threading import time @@ -46,6 +47,51 @@ if TYPE_CHECKING: 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.""" @@ -168,39 +214,46 @@ class Pool(log.Identified, event.EventTarget): 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`. - - 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 may be appropriate if the database / DBAPI - works in pure "autocommit" mode at all times, or if the - application uses the :class:`_engine.Engine` with consistent - connectivity patterns. See the section - :ref:`pool_reset_on_return` for more details. - - * ``False`` - same as None, this is here for - backwards compatibility. + 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 @@ -671,7 +724,9 @@ class _ConnectionRecord(ConnectionPoolEntry): rec.fairy_ref = ref = weakref.ref( fairy, - lambda ref: _finalize_fairy(None, rec, pool, ref, echo, True) + lambda ref: _finalize_fairy( + None, rec, pool, ref, echo, transaction_was_reset=False + ) if _finalize_fairy else None, ) @@ -864,7 +919,7 @@ def _finalize_fairy( weakref.ref[_ConnectionFairy] ], # this is None when called directly, not by the gc echo: Optional[log._EchoFlagType], - reset: bool = True, + transaction_was_reset: bool = False, fairy: Optional[_ConnectionFairy] = None, ) -> None: """Cleanup for a :class:`._ConnectionFairy` whether or not it's already @@ -906,11 +961,7 @@ def _finalize_fairy( if dbapi_connection is not None: if connection_record and echo: pool.logger.debug( - "Connection %r being returned to pool%s", - dbapi_connection, - ", transaction state was already reset by caller" - if not reset - else "", + "Connection %r being returned to pool", dbapi_connection ) try: @@ -923,8 +974,13 @@ def _finalize_fairy( echo, ) assert fairy.dbapi_connection is dbapi_connection - if reset and can_manipulate_connection: - fairy._reset(pool) + + fairy._reset( + pool, + transaction_was_reset=transaction_was_reset, + terminate_only=detach, + asyncio_safe=can_manipulate_connection, + ) if detach: if connection_record: @@ -1293,29 +1349,55 @@ class _ConnectionFairy(PoolProxiedConnection): def _checkout_existing(self) -> _ConnectionFairy: return _ConnectionFairy._checkout(self._pool, fairy=self) - def _checkin(self, reset: bool = True) -> None: + def _checkin(self, transaction_was_reset: bool = False) -> None: _finalize_fairy( self.dbapi_connection, self._connection_record, self._pool, None, self._echo, - reset=reset, + transaction_was_reset=transaction_was_reset, fairy=self, ) def _close(self) -> None: self._checkin() - def _reset(self, pool: Pool) -> None: + 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) + 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 self._echo: - pool.logger.debug( - "Connection %s rollback-on-return", self.dbapi_connection - ) - pool._dialect.do_rollback(self) + 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( @@ -1396,7 +1478,7 @@ class _ConnectionFairy(PoolProxiedConnection): if self._counter == 0: self._checkin() - def _close_no_reset(self) -> None: + def _close_special(self, transaction_reset: bool = False) -> None: self._counter -= 1 if self._counter == 0: - self._checkin(reset=False) + self._checkin(transaction_was_reset=transaction_reset) |