openstack/neutron
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Merge "Remove redundant event listening logic from neutron/db/api"

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Zuul 2019-02-12 08:42:09 +00:00 committed by Gerrit Code Review
commit 561b277983
2 changed files with 0 additions and 146 deletions
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neutron/common/utils.py
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@ -46,7 +46,6 @@ import six
import neutron
from neutron._i18n import _
from neutron.api import api_common
from neutron.db import api # noqa
TIME_FORMAT = "%Y-%m-%dT%H:%M:%SZ"
LOG = logging.getLogger(__name__)

145
neutron/db/api.py
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@ -1,145 +0,0 @@
# Copyright 2011 VMware, Inc.
# All Rights Reserved.
#
# 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.
import weakref
from neutron_lib.db import model_base
import sqlalchemy
from sqlalchemy import event # noqa
from sqlalchemy import orm
# Expire relationships when foreign key changes.
#
# NOTE(ihrachys) Arguably, it's a sqlalchemy anti-pattern to access child
# models directly and through parent relationships in the same session. But
# since OVO mechanism is built around synthetic fields that assume this mixed
# access is possible, we keep it here until we find a way to migrate OVO
# synthetic fields to better mechanism that would update child models via
# parents. Even with that, there are multiple places in plugin code where we
# mix access when using models directly; those occurrences would need to be
# fixed too to be able to remove this hook and explicit expire() calls.
#
# Adopted from the following recipe:
# https://bitbucket.org/zzzeek/sqlalchemy/wiki/UsageRecipes
# /ExpireRelationshipOnFKChange
#
# ...then massively changed to actually work for all neutron backref cases.
#
# TODO(ihrachys) at some point these event handlers should be extended to also
# automatically refresh values for expired attributes
def _expire_for_fk_change(target, fk_value, relationship_prop, column_attr):
"""Expire relationship attributes when a many-to-one column changes."""
sess = orm.object_session(target)
# subnets and network's many-to-one relationship is used as example in the
# comments in this function
if sess is not None:
# optional behavior #1 - expire the "Network.subnets"
# collection on the existing "network" object
if relationship_prop.back_populates and \
relationship_prop.key in target.__dict__:
obj = getattr(target, relationship_prop.key)
if obj is not None and sqlalchemy.inspect(obj).persistent:
sess.expire(obj, [relationship_prop.back_populates])
# optional behavior #2 - expire the "Subnet.network"
if sqlalchemy.inspect(target).persistent:
sess.expire(target, [relationship_prop.key])
# optional behavior #3 - "trick" the ORM by actually
# setting the value ahead of time, then emitting a load
# for the attribute so that the *new* Subnet.network
# is loaded. Then, expire Network.subnets on *that*.
# Other techniques here including looking in the identity
# map for "value", if this is a simple many-to-one get.
if relationship_prop.back_populates:
target.__dict__[column_attr] = fk_value
new = getattr(target, relationship_prop.key)
if new is not None:
if sqlalchemy.inspect(new).persistent:
sess.expire(new, [relationship_prop.back_populates])
else:
# no Session yet, do it later. This path is reached from the 'expire'
# listener setup by '_expire_prop_on_col' below, when a foreign key
# is directly assigned to in the many to one side of a relationship.
# i.e. assigning directly to Subnet.network_id before Subnet is added
# to the session
if target not in _emit_on_pending:
_emit_on_pending[target] = []
_emit_on_pending[target].append(
(fk_value, relationship_prop, column_attr))
_emit_on_pending = weakref.WeakKeyDictionary()
@event.listens_for(orm.session.Session, "pending_to_persistent")
def _pending_callables(session, obj):
"""Expire relationships when a new object w/ a foreign key becomes
persistent
"""
if obj is None:
return
args = _emit_on_pending.pop(obj, [])
for a in args:
if a is not None:
_expire_for_fk_change(obj, *a)
@event.listens_for(orm.session.Session, "persistent_to_deleted")
def _persistent_to_deleted(session, obj):
"""Expire relationships when an object w/ a foreign key becomes deleted"""
mapper = sqlalchemy.inspect(obj).mapper
for prop in mapper.relationships:
if prop.direction is orm.interfaces.MANYTOONE:
for col in prop.local_columns:
colkey = mapper.get_property_by_column(col).key
_expire_for_fk_change(obj, None, prop, colkey)
@event.listens_for(model_base.BASEV2, "attribute_instrument", propagate=True)
def _listen_for_changes(cls, key, inst):
mapper = sqlalchemy.inspect(cls)
if key not in mapper.relationships:
return
prop = inst.property
if prop.direction is orm.interfaces.MANYTOONE:
for col in prop.local_columns:
colkey = mapper.get_property_by_column(col).key
_expire_prop_on_col(cls, prop, colkey)
elif prop.direction is orm.interfaces.ONETOMANY:
remote_mapper = prop.mapper
# the collection *has* to have a MANYTOONE backref so we
# can look up the parent. so here we make one if it doesn't
# have it already, as is the case in this example
if not prop.back_populates:
name = "_%s_backref" % prop.key
backref_prop = orm.relationship(
prop.parent, back_populates=prop.key)
remote_mapper.add_property(name, backref_prop)
prop.back_populates = name
def _expire_prop_on_col(cls, prop, colkey):
@event.listens_for(getattr(cls, colkey), "set")
def expire(target, value, oldvalue, initiator):
"""Expire relationships when the foreign key attribute on
an object changes
"""
_expire_for_fk_change(target, value, prop, colkey)