OpenStack Networking (Neutron)
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# 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 contextlib
import copy
import weakref
from neutron_lib.db import api
from neutron_lib.db import model_base
from neutron_lib import exceptions
from neutron_lib.objects import exceptions as obj_exc
from oslo_config import cfg
from oslo_db import exception as db_exc
from oslo_log import log as logging
from oslo_utils import excutils
from osprofiler import opts as profiler_opts
import osprofiler.sqlalchemy
from pecan import util as p_util
import six
import sqlalchemy
from sqlalchemy import event # noqa
from sqlalchemy import orm
from sqlalchemy.orm import exc
def set_hook(engine):
if (profiler_opts.is_trace_enabled() and
profiler_opts.is_db_trace_enabled()):
osprofiler.sqlalchemy.add_tracing(sqlalchemy, engine, 'neutron.db')
context_manager = api.get_context_manager()
# TODO(ihrachys) the hook assumes options defined by osprofiler, and the only
# public function that is provided by osprofiler that will register them is
# set_defaults, that's why we call it here even though we don't need to change
# defaults
profiler_opts.set_defaults(cfg.CONF)
context_manager.append_on_engine_create(set_hook)
MAX_RETRIES = 10
LOG = logging.getLogger(__name__)
def is_retriable(e):
if getattr(e, '_RETRY_EXCEEDED', False):
return False
if _is_nested_instance(e, (db_exc.DBDeadlock, exc.StaleDataError,
db_exc.DBConnectionError,
db_exc.DBDuplicateEntry, db_exc.RetryRequest,
obj_exc.NeutronDbObjectDuplicateEntry)):
return True
# looking savepoints mangled by deadlocks. see bug/1590298 for details.
return _is_nested_instance(e, db_exc.DBError) and '1305' in str(e)
def _tag_retriables_as_unretriable(f):
"""Puts a flag on retriable exceptions so is_retriable returns False.
This decorator can be used outside of a retry decorator to prevent
decorators higher up from retrying again.
"""
@six.wraps(f)
def wrapped(*args, **kwargs):
try:
return f(*args, **kwargs)
except Exception as e:
with excutils.save_and_reraise_exception():
if is_retriable(e):
setattr(e, '_RETRY_EXCEEDED', True)
return wrapped
def _copy_if_lds(item):
"""Deepcopy lists/dicts/sets, leave everything else alone."""
return copy.deepcopy(item) if isinstance(item, (list, dict, set)) else item
def retry_if_session_inactive(context_var_name='context'):
"""Retries only if the session in the context is inactive.
Calls a retry_db_errors wrapped version of the function if the context's
session passed in is inactive, otherwise it just calls the function
directly. This is useful to avoid retrying things inside of a transaction
which is ineffective for DB races/errors.
This should be used in all cases where retries are desired and the method
accepts a context.
"""
def decorator(f):
try:
# NOTE(kevinbenton): we use pecan's util function here because it
# deals with the horrors of finding args of already decorated
# functions
ctx_arg_index = p_util.getargspec(f).args.index(context_var_name)
except ValueError:
raise RuntimeError("Could not find position of var %s" %
context_var_name)
f_with_retry = api.retry_db_errors(f)
@six.wraps(f)
def wrapped(*args, **kwargs):
# only use retry wrapper if we aren't nested in an active
# transaction
if context_var_name in kwargs:
context = kwargs[context_var_name]
else:
context = args[ctx_arg_index]
method = f if context.session.is_active else f_with_retry
return method(*args, **kwargs)
return wrapped
return decorator
def _is_nested_instance(e, etypes):
"""Check if exception or its inner excepts are an instance of etypes."""
if isinstance(e, etypes):
return True
if isinstance(e, exceptions.MultipleExceptions):
return any(_is_nested_instance(i, etypes) for i in e.inner_exceptions)
if isinstance(e, db_exc.DBError):
return _is_nested_instance(e.inner_exception, etypes)
return False
@contextlib.contextmanager
def autonested_transaction(sess):
"""This is a convenience method to not bother with 'nested' parameter."""
if sess.is_active:
session_context = sess.begin(nested=True)
else:
session_context = sess.begin(subtransactions=True)
with session_context as tx:
yield tx
@event.listens_for(orm.session.Session, "after_flush")
def add_to_rel_load_list(session, flush_context=None):
# keep track of new items to load relationships on during commit
session.info.setdefault('_load_rels', weakref.WeakSet()).update(
session.new)
@event.listens_for(orm.session.Session, "before_commit")
def load_one_to_manys(session):
# TODO(kevinbenton): we should be able to remove this after we
# have eliminated all places where related objects are constructed
# using a key rather than a relationship.
# capture any new objects
if session.new:
session.flush()
if session.transaction.nested:
# wait until final commit
return
for new_object in session.info.pop('_load_rels', []):
if new_object not in session:
# don't load detached objects because that brings them back into
# session
continue
state = sqlalchemy.inspect(new_object)
# set up relationship loading so that we can call lazy
# loaders on the object even though the ".key" is not set up yet
# (normally happens by in after_flush_postexec, but we're trying
# to do this more succinctly). in this context this is only
# setting a simple flag on the object's state.
session.enable_relationship_loading(new_object)
# look for eager relationships and do normal load.
# For relationships where the related object is also
# in the session these lazy loads will pull from the
# identity map and not emit SELECT. Otherwise, we are still
# local in the transaction so a normal SELECT load will work fine.
for relationship_attr in state.mapper.relationships:
if relationship_attr.lazy not in ('joined', 'subquery'):
# we only want to automatically load relationships that would
# automatically load during a lookup operation
continue
if relationship_attr.key not in state.dict:
getattr(new_object, relationship_attr.key)
if relationship_attr.key not in state.dict:
msg = ("Relationship %s attributes must be loaded in db"
" object %s" % (relationship_attr.key, state.dict))
raise AssertionError(msg)
# 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)