325 lines
13 KiB
Python
325 lines
13 KiB
Python
# Copyright 2011 VMware, Inc.
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# All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import contextlib
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import copy
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import weakref
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from neutron_lib.db import api
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from neutron_lib.db import model_base
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from neutron_lib import exceptions
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from neutron_lib.objects import exceptions as obj_exc
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from oslo_config import cfg
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from oslo_db import exception as db_exc
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from oslo_log import log as logging
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from oslo_utils import excutils
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from osprofiler import opts as profiler_opts
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import osprofiler.sqlalchemy
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from pecan import util as p_util
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import six
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import sqlalchemy
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from sqlalchemy import event # noqa
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from sqlalchemy import orm
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from sqlalchemy.orm import exc
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def set_hook(engine):
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if (profiler_opts.is_trace_enabled() and
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profiler_opts.is_db_trace_enabled()):
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osprofiler.sqlalchemy.add_tracing(sqlalchemy, engine, 'neutron.db')
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context_manager = api.get_context_manager()
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# TODO(ihrachys) the hook assumes options defined by osprofiler, and the only
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# public function that is provided by osprofiler that will register them is
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# set_defaults, that's why we call it here even though we don't need to change
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# defaults
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profiler_opts.set_defaults(cfg.CONF)
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context_manager.append_on_engine_create(set_hook)
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MAX_RETRIES = 10
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LOG = logging.getLogger(__name__)
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def is_retriable(e):
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if getattr(e, '_RETRY_EXCEEDED', False):
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return False
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if _is_nested_instance(e, (db_exc.DBDeadlock, exc.StaleDataError,
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db_exc.DBConnectionError,
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db_exc.DBDuplicateEntry, db_exc.RetryRequest,
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obj_exc.NeutronDbObjectDuplicateEntry)):
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return True
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# looking savepoints mangled by deadlocks. see bug/1590298 for details.
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return _is_nested_instance(e, db_exc.DBError) and '1305' in str(e)
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def _tag_retriables_as_unretriable(f):
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"""Puts a flag on retriable exceptions so is_retriable returns False.
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This decorator can be used outside of a retry decorator to prevent
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decorators higher up from retrying again.
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"""
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@six.wraps(f)
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def wrapped(*args, **kwargs):
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try:
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return f(*args, **kwargs)
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except Exception as e:
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with excutils.save_and_reraise_exception():
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if is_retriable(e):
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setattr(e, '_RETRY_EXCEEDED', True)
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return wrapped
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def _copy_if_lds(item):
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"""Deepcopy lists/dicts/sets, leave everything else alone."""
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return copy.deepcopy(item) if isinstance(item, (list, dict, set)) else item
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def retry_if_session_inactive(context_var_name='context'):
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"""Retries only if the session in the context is inactive.
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Calls a retry_db_errors wrapped version of the function if the context's
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session passed in is inactive, otherwise it just calls the function
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directly. This is useful to avoid retrying things inside of a transaction
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which is ineffective for DB races/errors.
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This should be used in all cases where retries are desired and the method
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accepts a context.
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"""
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def decorator(f):
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try:
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# NOTE(kevinbenton): we use pecan's util function here because it
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# deals with the horrors of finding args of already decorated
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# functions
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ctx_arg_index = p_util.getargspec(f).args.index(context_var_name)
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except ValueError:
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raise RuntimeError("Could not find position of var %s" %
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context_var_name)
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f_with_retry = api.retry_db_errors(f)
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@six.wraps(f)
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def wrapped(*args, **kwargs):
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# only use retry wrapper if we aren't nested in an active
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# transaction
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if context_var_name in kwargs:
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context = kwargs[context_var_name]
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else:
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context = args[ctx_arg_index]
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method = f if context.session.is_active else f_with_retry
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return method(*args, **kwargs)
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return wrapped
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return decorator
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def _is_nested_instance(e, etypes):
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"""Check if exception or its inner excepts are an instance of etypes."""
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if isinstance(e, etypes):
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return True
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if isinstance(e, exceptions.MultipleExceptions):
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return any(_is_nested_instance(i, etypes) for i in e.inner_exceptions)
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if isinstance(e, db_exc.DBError):
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return _is_nested_instance(e.inner_exception, etypes)
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return False
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@contextlib.contextmanager
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def autonested_transaction(sess):
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"""This is a convenience method to not bother with 'nested' parameter."""
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if sess.is_active:
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session_context = sess.begin(nested=True)
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else:
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session_context = sess.begin(subtransactions=True)
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with session_context as tx:
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yield tx
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@event.listens_for(orm.session.Session, "after_flush")
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def add_to_rel_load_list(session, flush_context=None):
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# keep track of new items to load relationships on during commit
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session.info.setdefault('_load_rels', weakref.WeakSet()).update(
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session.new)
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@event.listens_for(orm.session.Session, "before_commit")
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def load_one_to_manys(session):
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# TODO(kevinbenton): we should be able to remove this after we
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# have eliminated all places where related objects are constructed
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# using a key rather than a relationship.
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# capture any new objects
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if session.new:
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session.flush()
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if session.transaction.nested:
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# wait until final commit
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return
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for new_object in session.info.pop('_load_rels', []):
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if new_object not in session:
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# don't load detached objects because that brings them back into
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# session
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continue
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state = sqlalchemy.inspect(new_object)
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# set up relationship loading so that we can call lazy
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# loaders on the object even though the ".key" is not set up yet
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# (normally happens by in after_flush_postexec, but we're trying
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# to do this more succinctly). in this context this is only
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# setting a simple flag on the object's state.
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session.enable_relationship_loading(new_object)
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# look for eager relationships and do normal load.
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# For relationships where the related object is also
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# in the session these lazy loads will pull from the
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# identity map and not emit SELECT. Otherwise, we are still
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# local in the transaction so a normal SELECT load will work fine.
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for relationship_attr in state.mapper.relationships:
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if relationship_attr.lazy not in ('joined', 'subquery'):
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# we only want to automatically load relationships that would
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# automatically load during a lookup operation
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continue
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if relationship_attr.key not in state.dict:
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getattr(new_object, relationship_attr.key)
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if relationship_attr.key not in state.dict:
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msg = ("Relationship %s attributes must be loaded in db"
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" object %s" % (relationship_attr.key, state.dict))
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raise AssertionError(msg)
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# Expire relationships when foreign key changes.
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#
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# NOTE(ihrachys) Arguably, it's a sqlalchemy anti-pattern to access child
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# models directly and through parent relationships in the same session. But
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# since OVO mechanism is built around synthetic fields that assume this mixed
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# access is possible, we keep it here until we find a way to migrate OVO
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# synthetic fields to better mechanism that would update child models via
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# parents. Even with that, there are multiple places in plugin code where we
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# mix access when using models directly; those occurrences would need to be
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# fixed too to be able to remove this hook and explicit expire() calls.
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#
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# Adopted from the following recipe:
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# https://bitbucket.org/zzzeek/sqlalchemy/wiki/UsageRecipes
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# /ExpireRelationshipOnFKChange
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#
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# ...then massively changed to actually work for all neutron backref cases.
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#
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# TODO(ihrachys) at some point these event handlers should be extended to also
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# automatically refresh values for expired attributes
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def expire_for_fk_change(target, fk_value, relationship_prop, column_attr):
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"""Expire relationship attributes when a many-to-one column changes."""
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sess = orm.object_session(target)
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# subnets and network's many-to-one relationship is used as example in the
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# comments in this function
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if sess is not None:
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# optional behavior #1 - expire the "Network.subnets"
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# collection on the existing "network" object
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if relationship_prop.back_populates and \
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relationship_prop.key in target.__dict__:
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obj = getattr(target, relationship_prop.key)
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if obj is not None and sqlalchemy.inspect(obj).persistent:
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sess.expire(obj, [relationship_prop.back_populates])
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# optional behavior #2 - expire the "Subnet.network"
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if sqlalchemy.inspect(target).persistent:
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sess.expire(target, [relationship_prop.key])
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# optional behavior #3 - "trick" the ORM by actually
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# setting the value ahead of time, then emitting a load
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# for the attribute so that the *new* Subnet.network
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# is loaded. Then, expire Network.subnets on *that*.
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# Other techniques here including looking in the identity
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# map for "value", if this is a simple many-to-one get.
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if relationship_prop.back_populates:
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target.__dict__[column_attr] = fk_value
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new = getattr(target, relationship_prop.key)
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if new is not None:
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if sqlalchemy.inspect(new).persistent:
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sess.expire(new, [relationship_prop.back_populates])
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else:
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# no Session yet, do it later. This path is reached from the 'expire'
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# listener setup by '_expire_prop_on_col' below, when a foreign key
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# is directly assigned to in the many to one side of a relationship.
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# i.e. assigning directly to Subnet.network_id before Subnet is added
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# to the session
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if target not in _emit_on_pending:
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_emit_on_pending[target] = []
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_emit_on_pending[target].append(
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(fk_value, relationship_prop, column_attr))
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_emit_on_pending = weakref.WeakKeyDictionary()
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@event.listens_for(orm.session.Session, "pending_to_persistent")
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def _pending_callables(session, obj):
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"""Expire relationships when a new object w/ a foreign key becomes
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persistent
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"""
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if obj is None:
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return
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args = _emit_on_pending.pop(obj, [])
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for a in args:
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if a is not None:
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expire_for_fk_change(obj, *a)
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@event.listens_for(orm.session.Session, "persistent_to_deleted")
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def _persistent_to_deleted(session, obj):
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"""Expire relationships when an object w/ a foreign key becomes deleted"""
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mapper = sqlalchemy.inspect(obj).mapper
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for prop in mapper.relationships:
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if prop.direction is orm.interfaces.MANYTOONE:
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for col in prop.local_columns:
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colkey = mapper.get_property_by_column(col).key
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expire_for_fk_change(obj, None, prop, colkey)
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@event.listens_for(model_base.BASEV2, "attribute_instrument", propagate=True)
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def _listen_for_changes(cls, key, inst):
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mapper = sqlalchemy.inspect(cls)
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if key not in mapper.relationships:
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return
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prop = inst.property
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if prop.direction is orm.interfaces.MANYTOONE:
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for col in prop.local_columns:
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colkey = mapper.get_property_by_column(col).key
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_expire_prop_on_col(cls, prop, colkey)
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elif prop.direction is orm.interfaces.ONETOMANY:
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remote_mapper = prop.mapper
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# the collection *has* to have a MANYTOONE backref so we
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# can look up the parent. so here we make one if it doesn't
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# have it already, as is the case in this example
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if not prop.back_populates:
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name = "_%s_backref" % prop.key
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backref_prop = orm.relationship(
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prop.parent, back_populates=prop.key)
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remote_mapper.add_property(name, backref_prop)
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prop.back_populates = name
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def _expire_prop_on_col(cls, prop, colkey):
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@event.listens_for(getattr(cls, colkey), "set")
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def expire(target, value, oldvalue, initiator):
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"""Expire relationships when the foreign key attribute on
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an object changes
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"""
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expire_for_fk_change(target, value, prop, colkey)
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