# sqlalchemy/pool/events.py # Copyright (C) 2005-2021 the SQLAlchemy authors and contributors # # # This module is part of SQLAlchemy and is released under # the MIT License: http://www.opensource.org/licenses/mit-license.php from .base import Pool from .. import event from ..engine.base import Engine class PoolEvents(event.Events): """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://scott:tiger@localhost/test") # will associate with engine.pool event.listen(engine, 'checkout', my_on_checkout) """ _target_class_doc = "SomeEngineOrPool" _dispatch_target = Pool @classmethod def _accept_with(cls, target): if isinstance(target, type): if issubclass(target, Engine): return Pool elif issubclass(target, Pool): return target elif isinstance(target, Engine): return target.pool else: return target @classmethod def _listen(cls, event_key, **kw): target = event_key.dispatch_target kw.setdefault("asyncio", target._is_asyncio) event_key.base_listen(**kw) def connect(self, dbapi_connection, connection_record): """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. :param connection_record: the :class:`._ConnectionRecord` managing the DBAPI connection. """ def first_connect(self, dbapi_connection, connection_record): """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. :param connection_record: the :class:`._ConnectionRecord` managing the DBAPI connection. """ def checkout(self, dbapi_connection, connection_record, connection_proxy): """Called when a connection is retrieved from the Pool. :param dbapi_connection: a DBAPI connection. :param connection_record: the :class:`._ConnectionRecord` managing the DBAPI connection. :param connection_proxy: the :class:`._ConnectionFairy` 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 checkin(self, dbapi_connection, connection_record): """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. :param connection_record: the :class:`._ConnectionRecord` managing the DBAPI connection. """ def reset(self, dbapi_connection, connection_record): """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. The behavior of "reset" can be controlled, including disabled, using the ``reset_on_return`` pool argument. The :meth:`_events.PoolEvents.reset` event is usually followed by the :meth:`_events.PoolEvents.checkin` event is called, except in those cases where the connection is discarded immediately after reset. :param dbapi_connection: a DBAPI connection. :param connection_record: the :class:`._ConnectionRecord` managing the DBAPI connection. .. seealso:: :meth:`_events.ConnectionEvents.rollback` :meth:`_events.ConnectionEvents.commit` """ def invalidate(self, dbapi_connection, connection_record, exception): """Called when a DBAPI connection is to be "invalidated". This event is called any time the :meth:`._ConnectionRecord.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. :param connection_record: the :class:`._ConnectionRecord` 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` """ def soft_invalidate(self, dbapi_connection, connection_record, exception): """Called when a DBAPI connection is to be "soft invalidated". This event is called any time the :meth:`._ConnectionRecord.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 """ def close(self, dbapi_connection, connection_record): """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 """ def detach(self, dbapi_connection, connection_record): """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 """ def close_detached(self, dbapi_connection): """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 """