200 lines
8.4 KiB
Python
200 lines
8.4 KiB
Python
# Copyright (c) 2012 OpenStack Foundation.
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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 weakref
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from sqlalchemy import sql
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from tacker.common import exceptions as n_exc
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from tacker.db import sqlalchemyutils
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from tacker.openstack.common import log as logging
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LOG = logging.getLogger(__name__)
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class CommonDbMixin(object):
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"""Common methods used in core and service plugins."""
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# Plugins, mixin classes implementing extension will register
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# hooks into the dict below for "augmenting" the "core way" of
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# building a query for retrieving objects from a model class.
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# To this aim, the register_model_query_hook and unregister_query_hook
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# from this class should be invoked
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_model_query_hooks = {}
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# This dictionary will store methods for extending attributes of
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# api resources. Mixins can use this dict for adding their own methods
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# TODO(salvatore-orlando): Avoid using class-level variables
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_dict_extend_functions = {}
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@classmethod
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def register_model_query_hook(cls, model, name, query_hook, filter_hook,
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result_filters=None):
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"""Register a hook to be invoked when a query is executed.
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Add the hooks to the _model_query_hooks dict. Models are the keys
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of this dict, whereas the value is another dict mapping hook names to
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callables performing the hook.
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Each hook has a "query" component, used to build the query expression
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and a "filter" component, which is used to build the filter expression.
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Query hooks take as input the query being built and return a
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transformed query expression.
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Filter hooks take as input the filter expression being built and return
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a transformed filter expression
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"""
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model_hooks = cls._model_query_hooks.get(model)
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if not model_hooks:
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# add key to dict
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model_hooks = {}
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cls._model_query_hooks[model] = model_hooks
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model_hooks[name] = {'query': query_hook, 'filter': filter_hook,
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'result_filters': result_filters}
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@property
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def safe_reference(self):
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"""Return a weakref to the instance.
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Minimize the potential for the instance persisting
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unnecessarily in memory by returning a weakref proxy that
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won't prevent deallocation.
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"""
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return weakref.proxy(self)
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def _model_query(self, context, model):
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query = context.session.query(model)
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# define basic filter condition for model query
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# NOTE(jkoelker) non-admin queries are scoped to their tenant_id
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# NOTE(salvatore-orlando): unless the model allows for shared objects
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query_filter = None
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if not context.is_admin and hasattr(model, 'tenant_id'):
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if hasattr(model, 'shared'):
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query_filter = ((model.tenant_id == context.tenant_id) |
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(model.shared == sql.true()))
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else:
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query_filter = (model.tenant_id == context.tenant_id)
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# Execute query hooks registered from mixins and plugins
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for _name, hooks in self._model_query_hooks.get(model,
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{}).iteritems():
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query_hook = hooks.get('query')
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if isinstance(query_hook, basestring):
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query_hook = getattr(self, query_hook, None)
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if query_hook:
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query = query_hook(context, model, query)
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filter_hook = hooks.get('filter')
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if isinstance(filter_hook, basestring):
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filter_hook = getattr(self, filter_hook, None)
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if filter_hook:
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query_filter = filter_hook(context, model, query_filter)
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# NOTE(salvatore-orlando): 'if query_filter' will try to evaluate the
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# condition, raising an exception
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if query_filter is not None:
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query = query.filter(query_filter)
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return query
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def _fields(self, resource, fields):
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if fields:
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return dict(((key, item) for key, item in resource.items()
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if key in fields))
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return resource
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def _get_tenant_id_for_create(self, context, resource):
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if context.is_admin and 'tenant_id' in resource:
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tenant_id = resource['tenant_id']
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elif ('tenant_id' in resource and
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resource['tenant_id'] != context.tenant_id):
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reason = _('Cannot create resource for another tenant')
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raise n_exc.AdminRequired(reason=reason)
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else:
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tenant_id = context.tenant_id
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return tenant_id
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def _get_by_id(self, context, model, id):
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query = self._model_query(context, model)
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return query.filter(model.id == id).one()
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def _apply_filters_to_query(self, query, model, filters):
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if filters:
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for key, value in filters.iteritems():
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column = getattr(model, key, None)
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if column:
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query = query.filter(column.in_(value))
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for _name, hooks in self._model_query_hooks.get(model,
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{}).iteritems():
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result_filter = hooks.get('result_filters', None)
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if isinstance(result_filter, basestring):
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result_filter = getattr(self, result_filter, None)
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if result_filter:
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query = result_filter(query, filters)
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return query
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def _apply_dict_extend_functions(self, resource_type,
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response, db_object):
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for func in self._dict_extend_functions.get(
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resource_type, []):
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args = (response, db_object)
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if isinstance(func, basestring):
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func = getattr(self, func, None)
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else:
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# must call unbound method - use self as 1st argument
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args = (self,) + args
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if func:
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func(*args)
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def _get_collection_query(self, context, model, filters=None,
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sorts=None, limit=None, marker_obj=None,
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page_reverse=False):
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collection = self._model_query(context, model)
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collection = self._apply_filters_to_query(collection, model, filters)
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if limit and page_reverse and sorts:
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sorts = [(s[0], not s[1]) for s in sorts]
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collection = sqlalchemyutils.paginate_query(collection, model, limit,
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sorts,
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marker_obj=marker_obj)
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return collection
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def _get_collection(self, context, model, dict_func, filters=None,
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fields=None, sorts=None, limit=None, marker_obj=None,
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page_reverse=False):
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query = self._get_collection_query(context, model, filters=filters,
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sorts=sorts,
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limit=limit,
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marker_obj=marker_obj,
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page_reverse=page_reverse)
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items = [dict_func(c, fields) for c in query]
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if limit and page_reverse:
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items.reverse()
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return items
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def _get_collection_count(self, context, model, filters=None):
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return self._get_collection_query(context, model, filters).count()
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def _get_marker_obj(self, context, resource, limit, marker):
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if limit and marker:
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return getattr(self, '_get_%s' % resource)(context, marker)
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return None
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def _filter_non_model_columns(self, data, model):
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"""Remove all the attributes from data which are not columns of
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the model passed as second parameter.
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"""
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columns = [c.name for c in model.__table__.columns]
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return dict((k, v) for (k, v) in
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data.iteritems() if k in columns)
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