openstack/nova
Code Issues Proposed changes

Update api doc with latest updates in api framework

Browse Source 
api.rst has many stale information now as we have done
many changes in api framework specially removal of
stevedore extensions loading and plain routing.

This commit modify this doc to reflect latest information
and remove v2 specific info which are no longer valid.

Note- in next part we will merge api_2.rst in this doc and
show 'adding api method' step by step.

Change-Id: I0628d8fa0b19c3fb09f1896402fc85dcae90916f
This commit is contained in:
ghanshyam 2017-08-11 15:13:46 +00:00 committed by Ghanshyam Mann
parent 4cd6a3a1b4
commit 796f3036c2
1 changed files with 78 additions and 81 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

159
doc/source/contributor/api.rst
View File

@ -1,36 +1,17 @@
Extending the API Extending the API
================= =================
.. TODO::
Update this to reflect the removal of the legacy v2 API code
Background Background
---------- ----------
Nova has two API plugin frameworks, one for the original V2 API and Nova has v2.1 API frameworks which supports microversions.
one for what we call V2.1 which also supports V2.1 microversions. The
V2.1 API acts from a REST API user point of view in an identical way
to the original V2 API. V2.1 is implemented in the same framework as
microversions, with the version requested being 2.1.
The V2 API is now frozen and with the exception of significant bugs no This document covers how to add API for the v2.1 API framework. A
change should be made to the V2 API code. API changes should only be
made through V2.1 microversions.
This document covers how to write plugins for the v2.1 framework. A
:doc:`microversions specific document <microversions>` covers the details :doc:`microversions specific document <microversions>` covers the details
around what is required for the microversions part. It does not cover V2 around what is required for the microversions part.
plugins which should no longer be developed.
There may still be references to a v3 API both in comments and in the The v2.1 API framework is under ``nova/api`` and each API is implemented in
directory path of relevant files. This is because v2.1 first started ``nova/api/openstack/compute``.
out being called v3 rather than v2.1. Where you see references to v3
you can treat it as a reference to v2.1 with or without microversions
support.
The original V2 API plugins live in ``nova/api/openstack/compute/legacy_v2``
and the V2.1 plugins live in ``nova/api/openstack/compute``.
Note that any change to the Nova API to be merged will first require a Note that any change to the Nova API to be merged will first require a
spec be approved first. See `here <https://github.com/openstack/nova-specs>`_ spec be approved first. See `here <https://github.com/openstack/nova-specs>`_
@ -39,20 +20,19 @@ please refer to the `OpenStack API WG
<https://wiki.openstack.org/wiki/API_Working_Group>`_ <https://wiki.openstack.org/wiki/API_Working_Group>`_
Basic plugin structure Basic API Controller
---------------------- --------------------
A very basic skeleton of a v2.1 plugin can be seen `here in the unittests <https://git.openstack.org/cgit/openstack/nova/tree/nova/tests/unit/api/openstack/compute/basic.py>`_. An annotated version below:: API controller includes the implementation of API methods for a resource.
"""Basic Test Extension""" A very basic controller of a v2.1 API::
"""Basic Controller"""
from nova.api.openstack.compute.schemas import xyz
from nova.api.openstack import extensions from nova.api.openstack import extensions
from nova.api.openstack import wsgi from nova.api.openstack import wsgi
from nova.api import validation
ALIAS = 'test-basic'
# ALIAS needs to be unique and should be of the format
# ^[a-z]+[a-z\-]*[a-z]$
class BasicController(wsgi.Controller): class BasicController(wsgi.Controller):
@ -61,34 +41,66 @@ A very basic skeleton of a v2.1 plugin can be seen `here in the unittests <https
data = {'param': 'val'} data = {'param': 'val'}
return data return data
# Defining a method implements the following API responses: # Define support for POST on a collection
# delete -> DELETE @extensions.expected_errors((400, 409))
# update -> PUT @validation.schema(xyz.create)
# create -> POST @wsgi.response(201)
# show -> GET def create(self, req, body):
# If a method is not defined a request to it will be a 404 response write_body_here = ok
return response_body
# It is also possible to define support for further responses # Defining support for other RESTFul methods based on resouce.
# See `servers.py <http://git.openstack.org/cgit/openstack/nova/tree/nova/nova/api/openstack/compute/servers.py>`_.
class Basic(extensions.V3APIExtensionBase): See `servers.py for ref <http://git.openstack.org/cgit/openstack/nova/tree/nova/nova/api/openstack/compute/servers.py>`_.
"""Basic Test Extension."""
name = "BasicTest" All of the controller modules should live in the ``nova/api/openstack/compute`` directory.
alias = ALIAS
version = 1
# Both get_resources and get_controller_extensions must always URL Mapping to API
# be defined by can return an empty array ~~~~~~~~~~~~~~~~~~
def get_resources(self):
resource = extensions.ResourceExtension('test', BasicController())
return [resource]
def get_controller_extensions(self): The URL mapping is based on the plain list which routes the API request to
return [] appropriate controller and method. Each API needs to add its route information
in ``nova/api/openstack/compute/routes.py``.
All of these plugin files should live in the ``nova/api/openstack/compute`` directory. A basic skeleton of URL mapping in routers.py::
"""URL Mapping Router List"""
import functools
import nova.api.openstack
from nova.api.openstack.compute import basic_api
# Create a controller object
basic_controller = functools.partial(
_create_controller, basic_api.BasicController, [], [])
# Routing list structure:
# (
# ('Route path': {
# 'HTTP method: [
# 'Controller',
# 'The method of controller is used to handle this route'
# ],
# ...
# }),
# ...
# )
ROUTE_LIST = (
.
.
.
('/basic', {
'GET': [basic_controller, 'index'],
'POST': [basic_controller, 'create']
}),
.
.
.
)
Complete routing list can be found in `routes.py <https://git.openstack.org/cgit/openstack/nova/tree/nova/api/openstack/compute/routes.py>`_.
Policy Policy
@ -96,18 +108,16 @@ Policy
Policy (permission) is defined ``etc/nova/policy.json``. Implementation of policy Policy (permission) is defined ``etc/nova/policy.json``. Implementation of policy
is changing a bit at the moment. Will add more to this document or reference is changing a bit at the moment. Will add more to this document or reference
another one in the future. Note that a 'discoverable' policy needs to be added another one in the future. Also look at the authorize call in controller currently merged.
for each plugin that you wish to appear in the ``/extension`` output. Also
look at the authorize call in plugins currently merged.
Modularity Modularity
~~~~~~~~~~ ~~~~~~~~~~
The Nova REST API is separated into different plugins in the directory The Nova REST API is separated into different controllers in the directory
'nova/api/openstack/compute/' 'nova/api/openstack/compute/'
Because microversions are supported in the Nova REST API, the API can be Because microversions are supported in the Nova REST API, the API can be
extended without any new plugin. But for code readability, the Nova REST API extended without any new controller. But for code readability, the Nova REST API
code still needs modularity. Here are rules for how to separate modules: code still needs modularity. Here are rules for how to separate modules:
* You are adding a new resource * You are adding a new resource
@ -138,17 +148,13 @@ corresponding method with the ``validation.schema`` decorator like::
def update(self, req, id, body): def update(self, req, id, body):
.... ....
Nova supports the extension of JSON-Schema definitions based on the Similarly to controller modularity, JSON-Schema definitions can be added
loaded API extensions for some APIs. Stevedore library tries to find in same or separate JSON-Schema module.
specific name methods which return additional parameters and extends
them to the original JSON-Schema definitions.
The following are the combinations of extensible API and method name The following are the combinations of extensible API and method name
which returns additional parameters: which returns additional JSON-Schema parameters:
* Create a server API - get_server_create_schema() * Create a server API - get_server_create_schema()
* Update a server API - get_server_update_schema()
* Rebuild a server API - get_server_rebuild_schema()
* Resize a server API - get_server_resize_schema()
For example, keypairs extension(Keypairs class) contains the method For example, keypairs extension(Keypairs class) contains the method
get_server_create_schema() which returns:: get_server_create_schema() which returns::
@ -159,21 +165,12 @@ get_server_create_schema() which returns::
then the parameter key_name is allowed on Create a server API. then the parameter key_name is allowed on Create a server API.
Support files .. note:: Currently only create schema are implemented in modular way.
------------- Final goal is to merge them all and define the concluded
process in this doc.
At least one entry needs to made in ``setup.cfg`` for each plugin. These are essentially hooks into the servers controller which allow other
An entry point for the plugin must be added to nova.api.v21.extensions controller to modify behaviour without having to modify servers.py. In
even if no resource or controller is added. Other entry points available
are
* Modify create behaviour (nova.api.v21.extensions.server.create)
* Modify rebuild behaviour (nova.api.v21.extensions.server.rebuild)
* Modify update behaviour (nova.api.v21.extensions.server.update)
* Modify resize behaviour (nova.api.v21.extensions.server.resize)
These are essentially hooks into the servers plugin which allow other
plugins to modify behaviour without having to modify servers.py. In
the past not having this capability led to very large chunks of the past not having this capability led to very large chunks of
unrelated code being added to servers.py which was difficult to unrelated code being added to servers.py which was difficult to
maintain. maintain.