sqlalchemy.pool.events.PoolEvents

class documentation

class PoolEvents(event.Events[Pool]): (source)

Available events for :class:`_pool.Pool`. The methods here define the name of an event as well as the names of members that are passed to listener functions. e.g.:: from sqlalchemy import event def my_on_checkout(dbapi_conn, connection_rec, connection_proxy): "handle an on checkout event" event.listen(Pool, 'checkout', my_on_checkout) In addition to accepting the :class:`_pool.Pool` class and :class:`_pool.Pool` instances, :class:`_events.PoolEvents` also accepts :class:`_engine.Engine` objects and the :class:`_engine.Engine` class as targets, which will be resolved to the ``.pool`` attribute of the given engine or the :class:`_pool.Pool` class:: engine = create_engine("postgresql+psycopg2://scott:tiger@localhost/test") # will associate with engine.pool event.listen(engine, 'checkout', my_on_checkout)

Method	`checkin`	Called when a connection returns to the pool.
Method	`checkout`	Called when a connection is retrieved from the Pool.
Method	`close`	Called when a DBAPI connection is closed.
Method	`close_detached`	Called when a detached DBAPI connection is closed.
Method	`connect`	Called at the moment a particular DBAPI connection is first created for a given :class:`_pool.Pool`.
Method	`detach`	Called when a DBAPI connection is "detached" from a pool.
Method	`first_connect`	Called exactly once for the first time a DBAPI connection is checked out from a particular :class:`_pool.Pool`.
Method	`invalidate`	Called when a DBAPI connection is to be "invalidated".
Method	`reset`	Called before the "reset" action occurs for a pooled connection.
Method	`soft_invalidate`	Called when a DBAPI connection is to be "soft invalidated".
Class Method	`_accept_with`	Undocumented
Class Method	`_listen`	Undocumented
Class Variable	`_target_class_doc`	Undocumented

Inherited from Events:

Class Method	`_clear`	Undocumented
Class Method	`_remove`	Undocumented

Inherited from _HasEventsDispatch (via Events):

Method	`__getattr__`	Undocumented
Method	`__init_subclass__`	Intercept new Event subclasses and create associated _Dispatch classes.
Class Variable	`dispatch`	reference back to the _Dispatch class.
Class Method	`_create_dispatcher_class`	Create a :class:`._Dispatch` class corresponding to an :class:`.Events` class.
Static Method	`_set_dispatch`	Undocumented
Class Variable	`_dispatch_target`	class which will receive the .dispatch collection

def checkin(self, dbapi_connection: DBAPIConnection, connection_record: ConnectionPoolEntry): (source) ¶

Called when a connection returns to the pool. Note that the connection may be closed, and may be None if the connection has been invalidated. ``checkin`` will not be called for detached connections. (They do not return to the pool.) :param dbapi_connection: a DBAPI connection. The :attr:`.ConnectionPoolEntry.dbapi_connection` attribute. :param connection_record: the :class:`.ConnectionPoolEntry` managing the DBAPI connection.

def checkout(self, dbapi_connection: DBAPIConnection, connection_record: ConnectionPoolEntry, connection_proxy: PoolProxiedConnection): (source) ¶

Called when a connection is retrieved from the Pool. :param dbapi_connection: a DBAPI connection. The :attr:`.ConnectionPoolEntry.dbapi_connection` attribute. :param connection_record: the :class:`.ConnectionPoolEntry` managing the DBAPI connection. :param connection_proxy: the :class:`.PoolProxiedConnection` object which will proxy the public interface of the DBAPI connection for the lifespan of the checkout. If you raise a :class:`~sqlalchemy.exc.DisconnectionError`, the current connection will be disposed and a fresh connection retrieved. Processing of all checkout listeners will abort and restart using the new connection. .. seealso:: :meth:`_events.ConnectionEvents.engine_connect` - a similar event which occurs upon creation of a new :class:`_engine.Connection`.

def close(self, dbapi_connection: DBAPIConnection, connection_record: ConnectionPoolEntry): (source) ¶

Called when a DBAPI connection is closed. The event is emitted before the close occurs. The close of a connection can fail; typically this is because the connection is already closed. If the close operation fails, the connection is discarded. The :meth:`.close` event corresponds to a connection that's still associated with the pool. To intercept close events for detached connections use :meth:`.close_detached`. .. versionadded:: 1.1 :param dbapi_connection: a DBAPI connection. The :attr:`.ConnectionPoolEntry.dbapi_connection` attribute. :param connection_record: the :class:`.ConnectionPoolEntry` managing the DBAPI connection.

def close_detached(self, dbapi_connection: DBAPIConnection): (source) ¶

Called when a detached DBAPI connection is closed. The event is emitted before the close occurs. The close of a connection can fail; typically this is because the connection is already closed. If the close operation fails, the connection is discarded. .. versionadded:: 1.1 :param dbapi_connection: a DBAPI connection. The :attr:`.ConnectionPoolEntry.dbapi_connection` attribute.

def connect(self, dbapi_connection: DBAPIConnection, connection_record: ConnectionPoolEntry): (source) ¶

Called at the moment a particular DBAPI connection is first created for a given :class:`_pool.Pool`. This event allows one to capture the point directly after which the DBAPI module-level ``.connect()`` method has been used in order to produce a new DBAPI connection. :param dbapi_connection: a DBAPI connection. The :attr:`.ConnectionPoolEntry.dbapi_connection` attribute. :param connection_record: the :class:`.ConnectionPoolEntry` managing the DBAPI connection.

def detach(self, dbapi_connection: DBAPIConnection, connection_record: ConnectionPoolEntry): (source) ¶

Called when a DBAPI connection is "detached" from a pool. This event is emitted after the detach occurs. The connection is no longer associated with the given connection record. .. versionadded:: 1.1 :param dbapi_connection: a DBAPI connection. The :attr:`.ConnectionPoolEntry.dbapi_connection` attribute. :param connection_record: the :class:`.ConnectionPoolEntry` managing the DBAPI connection.

def first_connect(self, dbapi_connection: DBAPIConnection, connection_record: ConnectionPoolEntry): (source) ¶

Called exactly once for the first time a DBAPI connection is checked out from a particular :class:`_pool.Pool`. The rationale for :meth:`_events.PoolEvents.first_connect` is to determine information about a particular series of database connections based on the settings used for all connections. Since a particular :class:`_pool.Pool` refers to a single "creator" function (which in terms of a :class:`_engine.Engine` refers to the URL and connection options used), it is typically valid to make observations about a single connection that can be safely assumed to be valid about all subsequent connections, such as the database version, the server and client encoding settings, collation settings, and many others. :param dbapi_connection: a DBAPI connection. The :attr:`.ConnectionPoolEntry.dbapi_connection` attribute. :param connection_record: the :class:`.ConnectionPoolEntry` managing the DBAPI connection.

def invalidate(self, dbapi_connection: DBAPIConnection, connection_record: ConnectionPoolEntry, exception: Optional[BaseException]): (source) ¶

Called when a DBAPI connection is to be "invalidated". This event is called any time the :meth:`.ConnectionPoolEntry.invalidate` method is invoked, either from API usage or via "auto-invalidation", without the ``soft`` flag. The event occurs before a final attempt to call ``.close()`` on the connection occurs. :param dbapi_connection: a DBAPI connection. The :attr:`.ConnectionPoolEntry.dbapi_connection` attribute. :param connection_record: the :class:`.ConnectionPoolEntry` managing the DBAPI connection. :param exception: the exception object corresponding to the reason for this invalidation, if any. May be ``None``. .. versionadded:: 0.9.2 Added support for connection invalidation listening. .. seealso:: :ref:`pool_connection_invalidation`

@event._legacy_signature('2.0', ['dbapi_connection', 'connection_record'], (lambda dbapi_connection, connection_record, reset_state: (dbapi_connecti...
def reset(self, dbapi_connection: DBAPIConnection, connection_record: ConnectionPoolEntry, reset_state: PoolResetState): (source) ¶

Called before the "reset" action occurs for a pooled connection. This event represents when the ``rollback()`` method is called on the DBAPI connection before it is returned to the pool or discarded. A custom "reset" strategy may be implemented using this event hook, which may also be combined with disabling the default "reset" behavior using the :paramref:`_pool.Pool.reset_on_return` parameter. The primary difference between the :meth:`_events.PoolEvents.reset` and :meth:`_events.PoolEvents.checkin` events are that :meth:`_events.PoolEvents.reset` is called not just for pooled connections that are being returned to the pool, but also for connections that were detached using the :meth:`_engine.Connection.detach` method as well as asyncio connections that are being discarded due to garbage collection taking place on connections before the connection was checked in. Note that the event **is not** invoked for connections that were invalidated using :meth:`_engine.Connection.invalidate`. These events may be intercepted using the :meth:`.PoolEvents.soft_invalidate` and :meth:`.PoolEvents.invalidate` event hooks, and all "connection close" events may be intercepted using :meth:`.PoolEvents.close`. The :meth:`_events.PoolEvents.reset` event is usually followed by the :meth:`_events.PoolEvents.checkin` event, except in those cases where the connection is discarded immediately after reset. :param dbapi_connection: a DBAPI connection. The :attr:`.ConnectionPoolEntry.dbapi_connection` attribute. :param connection_record: the :class:`.ConnectionPoolEntry` managing the DBAPI connection. :param reset_state: :class:`.PoolResetState` instance which provides information about the circumstances under which the connection is being reset. .. versionadded:: 2.0 .. seealso:: :ref:`pool_reset_on_return` :meth:`_events.ConnectionEvents.rollback` :meth:`_events.ConnectionEvents.commit`

def soft_invalidate(self, dbapi_connection: DBAPIConnection, connection_record: ConnectionPoolEntry, exception: Optional[BaseException]): (source) ¶

Called when a DBAPI connection is to be "soft invalidated". This event is called any time the :meth:`.ConnectionPoolEntry.invalidate` method is invoked with the ``soft`` flag. Soft invalidation refers to when the connection record that tracks this connection will force a reconnect after the current connection is checked in. It does not actively close the dbapi_connection at the point at which it is called. .. versionadded:: 1.0.3 :param dbapi_connection: a DBAPI connection. The :attr:`.ConnectionPoolEntry.dbapi_connection` attribute. :param connection_record: the :class:`.ConnectionPoolEntry` managing the DBAPI connection. :param exception: the exception object corresponding to the reason for this invalidation, if any. May be ``None``.

@util.preload_module('sqlalchemy.engine')
@classmethod
def _accept_with(cls, target: Union[Pool, Type[Pool], Engine, Type[Engine]], identifier: str) -> Optional[Union[Pool, Type[Pool]]]: (source) ¶

overrides sqlalchemy.event.base.Events._accept_with

Undocumented

@classmethod
def _listen(cls, event_key: event._EventKey[Pool], **kw: Any): (source) ¶

overrides sqlalchemy.event.base.Events._listen

Undocumented

_target_class_doc: str = (source) ¶

Undocumented