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# pool/base.py
# Copyright (C) 2005-2024 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:
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)