1423480fb6
The following spec defines what each project's doc/source directory is supposed to look like: https://specs.openstack.org/openstack/docs-specs/specs/pike/os-manuals-migration.html I had not yet moved existing content to follow this design. This patch does that, moving the devref to the 'contributor' directory. It also moves the CLI related documentation into the 'cli' directory. I have updated the autodoc generation to now create the api documentation in 'doc/source/contributor/api'. This patch also creates a template for future documentation contribution. I have created all of the directories recommended by the spec and have included documentation as to what should go in each directory. The index file is updated to point at the new locations for existing content. 'doc/.gitignore' is updated so that it won't complain about the automatically generated 'doc/contributor/api' directory. Change-Id: I55c50fa0b7c1d06c91e40dbcfd11b1c8e8378aa6
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Copyright 2010-2011 OpenStack Foundation
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All Rights Reserved.
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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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Adding a Method to the OpenStack API
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====================================
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The interface is a mostly RESTful API. REST stands for Representational State Transfer and provides an architecture "style" for distributed systems using HTTP for transport. Figure out a way to express your request and response in terms of resources that are being created, modified, read, or destroyed.
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Routing
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-------
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To map URLs to controllers+actions, OpenStack uses the Routes package, a clone of Rails routes for Python implementations. See http://routes.groovie.org/ for more information.
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URLs are mapped to "action" methods on "controller" classes in ``cinder/api/openstack/__init__/ApiRouter.__init__`` .
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See http://routes.groovie.org/manual.html for all syntax, but you'll probably just need these two:
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- mapper.connect() lets you map a single URL to a single action on a controller.
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- mapper.resource() connects many standard URLs to actions on a controller.
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Controllers and actions
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-----------------------
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Controllers live in ``cinder/api/openstack``, and inherit from cinder.wsgi.Controller.
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See ``cinder/api/v2/volumes.py`` for an example.
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Action methods take parameters that are sucked out of the URL by mapper.connect() or .resource(). The first two parameters are self and the WebOb request, from which you can get the req.environ, req.body, req.headers, etc.
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Serialization
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-------------
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Actions return a dictionary, and wsgi.Controller serializes that to JSON or XML based on the request's content-type.
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Errors
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------
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There will be occasions when you will want to return a REST error response to
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the caller and there are multiple valid ways to do this:
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- If you are at the controller level you can use a ``faults.Fault`` instance to
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indicate the error. You can either return the ``Fault`` instance as the
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result of the action, or raise it, depending on what's more convenient:
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``raise faults.Fault(webob.exc.HTTPBadRequest(explanation=msg))``.
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- If you are raising an exception our WSGI middleware exception handler is
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smart enough to recognize webob exceptions as well, so you don't really need
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to wrap the exceptions in a ``Fault`` class and you can just let the
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middleware add it for you:
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``raise webob.exc.HTTPBadRequest(explanation=msg)``.
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- While most errors require an explicit webob exception there are some Cinder
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exceptions (``NotFound`` and ``Invalid``) that are so common that they are
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directly handled by the middleware and don't need us to convert them, we can
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just raise them at any point in the API service and they will return the
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appropriate REST error to the caller. So any ``NotFound`` exception, or
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child class, will return a 404 error, and any ``Invalid`` exception, or
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child class, will return a 400 error.
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