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# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
"""Provide forwards compatibility for the handle_error event.
See the "handle_error" event at
http://docs.sqlalchemy.org/en/rel_0_9/core/events.html.
"""
import contextlib
import sys
import six
from sqlalchemy.engine import Engine
from sqlalchemy import event
from sqlalchemy import exc as sqla_exc
from oslo_db.sqlalchemy.compat import utils
def handle_error(engine, listener):
"""Add a handle_error listener for the given :class:`.Engine`.
This listener uses the SQLAlchemy
:meth:`sqlalchemy.event.ConnectionEvents.handle_error`
event, however augments the listener for pre-0.9.7 versions of SQLAlchemy
in order to support safe re-raise of the exception.
"""
if utils.sqla_100:
event.listen(engine, "handle_error", listener)
return
elif utils.sqla_097:
# ctx.engine added per
# https://bitbucket.org/zzzeek/sqlalchemy/issue/3266/
def wrap_listener(ctx):
ctx.engine = ctx.connection.engine
return listener(ctx)
event.listen(engine, "handle_error", wrap_listener)
return
assert isinstance(engine, Engine), \
"engine argument must be an Engine instance, not a Connection"
# use a Connection-wrapper class to wrap _handle_dbapi_exception.
if not getattr(engine._connection_cls,
'_oslo_handle_error_wrapper', False):
engine._oslo_handle_error_events = []
class Connection(engine._connection_cls):
_oslo_handle_error_wrapper = True
def _handle_dbapi_exception(self, e, statement, parameters,
cursor, context):
try:
super(Connection, self)._handle_dbapi_exception(
e, statement, parameters, cursor, context)
except Exception as reraised_exception:
# all versions:
# _handle_dbapi_exception reraises all DBAPI errors
# 0.8 and above:
# reraises all errors unconditionally
pass
else:
# 0.7.8:
# _handle_dbapi_exception does not unconditionally
# re-raise
reraised_exception = e
_oslo_handle_error_events = getattr(
self.engine,
'_oslo_handle_error_events',
False)
newraise = None
if _oslo_handle_error_events:
if isinstance(reraised_exception,
sqla_exc.StatementError):
sqlalchemy_exception = reraised_exception
original_exception = sqlalchemy_exception.orig
self._is_disconnect = is_disconnect = (
isinstance(sqlalchemy_exception,
sqla_exc.DBAPIError)
and sqlalchemy_exception.connection_invalidated)
else:
sqlalchemy_exception = None
original_exception = reraised_exception
is_disconnect = False
# new handle_error event
ctx = ExceptionContextImpl(
original_exception, sqlalchemy_exception,
self.engine, self, cursor, statement,
parameters, context, is_disconnect)
for fn in _oslo_handle_error_events:
try:
# handler returns an exception;
# call next handler in a chain
per_fn = fn(ctx)
if per_fn is not None:
ctx.chained_exception = newraise = per_fn
except Exception as _raised:
# handler raises an exception - stop processing
newraise = _raised
break
if sqlalchemy_exception and \
self._is_disconnect != ctx.is_disconnect:
if not ctx.is_disconnect:
raise NotImplementedError(
"Can't reset 'disconnect' status of exception "
"once it is set with this version of "
"SQLAlchemy")
sqlalchemy_exception.connection_invalidated = \
self._is_disconnect = ctx.is_disconnect
if self._is_disconnect:
self._do_disconnect(e)
if newraise:
six.reraise(type(newraise), newraise, sys.exc_info()[2])
else:
six.reraise(type(reraised_exception),
reraised_exception, sys.exc_info()[2])
def _do_disconnect(self, e):
del self._is_disconnect
if utils.sqla_094:
dbapi_conn_wrapper = self.connection
self.engine.pool._invalidate(dbapi_conn_wrapper, e)
self.invalidate(e)
else:
dbapi_conn_wrapper = self.connection
self.invalidate(e)
if not hasattr(dbapi_conn_wrapper, '_pool') or \
dbapi_conn_wrapper._pool is self.engine.pool:
self.engine.dispose()
engine._connection_cls = Connection
engine._oslo_handle_error_events.append(listener)
class ExceptionContextImpl(object):
"""Encapsulate information about an error condition in progress.
This is for forwards compatibility with the
ExceptionContext interface introduced in SQLAlchemy 0.9.7.
"""
def __init__(self, exception, sqlalchemy_exception,
engine, connection, cursor, statement, parameters,
context, is_disconnect):
self.engine = engine
self.connection = connection
self.sqlalchemy_exception = sqlalchemy_exception
self.original_exception = exception
self.execution_context = context
self.statement = statement
self.parameters = parameters
self.is_disconnect = is_disconnect
connection = None
"""The :class:`.Connection` in use during the exception.
This member is present, except in the case of a failure when
first connecting.
"""
engine = None
"""The :class:`.Engine` in use during the exception.
This member should always be present, even in the case of a failure
when first connecting.
"""
cursor = None
"""The DBAPI cursor object.
May be None.
"""
statement = None
"""String SQL statement that was emitted directly to the DBAPI.
May be None.
"""
parameters = None
"""Parameter collection that was emitted directly to the DBAPI.
May be None.
"""
original_exception = None
"""The exception object which was caught.
This member is always present.
"""
sqlalchemy_exception = None
"""The :class:`sqlalchemy.exc.StatementError` which wraps the original,
and will be raised if exception handling is not circumvented by the event.
May be None, as not all exception types are wrapped by SQLAlchemy.
For DBAPI-level exceptions that subclass the dbapi's Error class, this
field will always be present.
"""
chained_exception = None
"""The exception that was returned by the previous handler in the
exception chain, if any.
If present, this exception will be the one ultimately raised by
SQLAlchemy unless a subsequent handler replaces it.
May be None.
"""
execution_context = None
"""The :class:`.ExecutionContext` corresponding to the execution
operation in progress.
This is present for statement execution operations, but not for
operations such as transaction begin/end. It also is not present when
the exception was raised before the :class:`.ExecutionContext`
could be constructed.
Note that the :attr:`.ExceptionContext.statement` and
:attr:`.ExceptionContext.parameters` members may represent a
different value than that of the :class:`.ExecutionContext`,
potentially in the case where a
:meth:`.ConnectionEvents.before_cursor_execute` event or similar
modified the statement/parameters to be sent.
May be None.
"""
is_disconnect = None
"""Represent whether the exception as occurred represents a "disconnect"
condition.
This flag will always be True or False within the scope of the
:meth:`.ConnectionEvents.handle_error` handler.
"""
@contextlib.contextmanager
def handle_connect_context(handler, engine):
"""Wrap connect() routines with a "handle error" context."""
try:
yield
except Exception as e:
if utils.sqla_100:
raise
if isinstance(e, sqla_exc.StatementError):
s_exc, orig = e, e.orig
else:
s_exc, orig = None, e
ctx = ExceptionContextImpl(
orig, s_exc, engine, None, None,
None, None, None, False
)
handler(ctx)
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