249 lines
8.5 KiB
Python
249 lines
8.5 KiB
Python
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# sqlalchemy/pool/events.py
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# Copyright (C) 2005-2021 the SQLAlchemy authors and contributors
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# <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: http://www.opensource.org/licenses/mit-license.php
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from .base import Pool
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from .. import event
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from ..engine.base import Engine
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class PoolEvents(event.Events):
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"""Available events for :class:`_pool.Pool`.
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The methods here define the name of an event as well
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as the names of members that are passed to listener
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functions.
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e.g.::
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from sqlalchemy import event
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def my_on_checkout(dbapi_conn, connection_rec, connection_proxy):
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"handle an on checkout event"
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event.listen(Pool, 'checkout', my_on_checkout)
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In addition to accepting the :class:`_pool.Pool` class and
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:class:`_pool.Pool` instances, :class:`_events.PoolEvents` also accepts
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:class:`_engine.Engine` objects and the :class:`_engine.Engine` class as
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targets, which will be resolved to the ``.pool`` attribute of the
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given engine or the :class:`_pool.Pool` class::
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engine = create_engine("postgresql://scott:tiger@localhost/test")
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# will associate with engine.pool
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event.listen(engine, 'checkout', my_on_checkout)
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"""
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_target_class_doc = "SomeEngineOrPool"
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_dispatch_target = Pool
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@classmethod
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def _accept_with(cls, target):
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if isinstance(target, type):
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if issubclass(target, Engine):
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return Pool
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elif issubclass(target, Pool):
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return target
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elif isinstance(target, Engine):
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return target.pool
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else:
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return target
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@classmethod
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def _listen(cls, event_key, **kw):
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target = event_key.dispatch_target
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kw.setdefault("asyncio", target._is_asyncio)
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event_key.base_listen(**kw)
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def connect(self, dbapi_connection, connection_record):
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"""Called at the moment a particular DBAPI connection is first
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created for a given :class:`_pool.Pool`.
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This event allows one to capture the point directly after which
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the DBAPI module-level ``.connect()`` method has been used in order
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to produce a new DBAPI connection.
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:param dbapi_connection: a DBAPI connection.
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:param connection_record: the :class:`._ConnectionRecord` managing the
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DBAPI connection.
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"""
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def first_connect(self, dbapi_connection, connection_record):
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"""Called exactly once for the first time a DBAPI connection is
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checked out from a particular :class:`_pool.Pool`.
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The rationale for :meth:`_events.PoolEvents.first_connect`
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is to determine
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information about a particular series of database connections based
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on the settings used for all connections. Since a particular
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:class:`_pool.Pool`
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refers to a single "creator" function (which in terms
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of a :class:`_engine.Engine`
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refers to the URL and connection options used),
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it is typically valid to make observations about a single connection
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that can be safely assumed to be valid about all subsequent
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connections, such as the database version, the server and client
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encoding settings, collation settings, and many others.
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:param dbapi_connection: a DBAPI connection.
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:param connection_record: the :class:`._ConnectionRecord` managing the
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DBAPI connection.
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"""
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def checkout(self, dbapi_connection, connection_record, connection_proxy):
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"""Called when a connection is retrieved from the Pool.
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:param dbapi_connection: a DBAPI connection.
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:param connection_record: the :class:`._ConnectionRecord` managing the
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DBAPI connection.
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:param connection_proxy: the :class:`._ConnectionFairy` object which
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will proxy the public interface of the DBAPI connection for the
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lifespan of the checkout.
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If you raise a :class:`~sqlalchemy.exc.DisconnectionError`, the current
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connection will be disposed and a fresh connection retrieved.
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Processing of all checkout listeners will abort and restart
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using the new connection.
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.. seealso:: :meth:`_events.ConnectionEvents.engine_connect`
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- a similar event
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which occurs upon creation of a new :class:`_engine.Connection`.
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"""
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def checkin(self, dbapi_connection, connection_record):
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"""Called when a connection returns to the pool.
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Note that the connection may be closed, and may be None if the
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connection has been invalidated. ``checkin`` will not be called
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for detached connections. (They do not return to the pool.)
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:param dbapi_connection: a DBAPI connection.
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:param connection_record: the :class:`._ConnectionRecord` managing the
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DBAPI connection.
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"""
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def reset(self, dbapi_connection, connection_record):
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"""Called before the "reset" action occurs for a pooled connection.
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This event represents
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when the ``rollback()`` method is called on the DBAPI connection
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before it is returned to the pool. The behavior of "reset" can
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be controlled, including disabled, using the ``reset_on_return``
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pool argument.
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The :meth:`_events.PoolEvents.reset` event is usually followed by the
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:meth:`_events.PoolEvents.checkin` event is called, except in those
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cases where the connection is discarded immediately after reset.
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:param dbapi_connection: a DBAPI connection.
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:param connection_record: the :class:`._ConnectionRecord` managing the
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DBAPI connection.
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.. seealso::
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:meth:`_events.ConnectionEvents.rollback`
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:meth:`_events.ConnectionEvents.commit`
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"""
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def invalidate(self, dbapi_connection, connection_record, exception):
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"""Called when a DBAPI connection is to be "invalidated".
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This event is called any time the :meth:`._ConnectionRecord.invalidate`
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method is invoked, either from API usage or via "auto-invalidation",
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without the ``soft`` flag.
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The event occurs before a final attempt to call ``.close()`` on the
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connection occurs.
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:param dbapi_connection: a DBAPI connection.
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:param connection_record: the :class:`._ConnectionRecord` managing the
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DBAPI connection.
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:param exception: the exception object corresponding to the reason
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for this invalidation, if any. May be ``None``.
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.. versionadded:: 0.9.2 Added support for connection invalidation
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listening.
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.. seealso::
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:ref:`pool_connection_invalidation`
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"""
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def soft_invalidate(self, dbapi_connection, connection_record, exception):
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"""Called when a DBAPI connection is to be "soft invalidated".
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This event is called any time the :meth:`._ConnectionRecord.invalidate`
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method is invoked with the ``soft`` flag.
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Soft invalidation refers to when the connection record that tracks
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this connection will force a reconnect after the current connection
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is checked in. It does not actively close the dbapi_connection
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at the point at which it is called.
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.. versionadded:: 1.0.3
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"""
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def close(self, dbapi_connection, connection_record):
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"""Called when a DBAPI connection is closed.
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The event is emitted before the close occurs.
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The close of a connection can fail; typically this is because
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the connection is already closed. If the close operation fails,
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the connection is discarded.
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The :meth:`.close` event corresponds to a connection that's still
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associated with the pool. To intercept close events for detached
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connections use :meth:`.close_detached`.
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.. versionadded:: 1.1
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"""
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def detach(self, dbapi_connection, connection_record):
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"""Called when a DBAPI connection is "detached" from a pool.
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This event is emitted after the detach occurs. The connection
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is no longer associated with the given connection record.
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.. versionadded:: 1.1
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"""
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def close_detached(self, dbapi_connection):
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"""Called when a detached DBAPI connection is closed.
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The event is emitted before the close occurs.
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The close of a connection can fail; typically this is because
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the connection is already closed. If the close operation fails,
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the connection is discarded.
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.. versionadded:: 1.1
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"""
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