34ec3536b2
This patch will add devref for relocating db models and it also explains why that change is required. It will also add a directory named models under tree neutron/db/. Change-Id: I160cecb76fb736307e5937122c84cdc0546207b6 Related-Bug: #1597913
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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Relocation of Database Models
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=============================
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This document is intended to track and notify developers that db models in
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neutron will be centralized and moved to a new tree under neutron/db/models.
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This was discussed in [1]. The reason for relocating db models is to solve
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the cyclic import issue while implementing oslo versioned objects for
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resources in neutron.
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The reason behind this relocation is Mixin class and db models for some
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resources in neutron are in same module. In Mixin classes, there are methods
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which provide functionality of fetching, adding, updating and deleting data
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via queries. These queries will be replaced with use of versioned objects and
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definition of versioned object will be using db models. So object files will
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be importing models and Mixin need to import those objects which will end up
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in cyclic import.
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Structure of Model Definitions
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------------------------------
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We have decided to move all models definitions to neutron/db/models/
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with no futher nesting after that point. The deprecation method to move
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models is already been added to avoid breakage of third party plugins using
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those models. All relocated models need to use deprecate method that
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will generate a warning and return new class for use of old class. Some
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examples of relocated models [2] and [3]. In future if you define new models
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please make sure they are separated from mixins and are under tree
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neutron/db/models/ .
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References
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~~~~~~~~~~
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[1]. https://www.mail-archive.com/openstack-dev@lists.openstack.org/msg88910.html
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[2]. https://review.openstack.org/#/c/348562/
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[3]. https://review.openstack.org/#/c/348757/
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