** Changed in: python-openstacksdk
Status: New => Won't Fix
** No longer affects: python-openstacksdk
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https://bugs.launchpad.net/bugs/1705755
Title:
[RFE] Plugin support for API resource attribute extensions
Status in neutron:
Triaged
Status in python-openstackclient:
New
Bug description:
FORWARD
---------------
The purpose of this bug is to facilitate a discussion. While I'm willing to
do all the work to implement the feature request herein, I'd first like some
agreement that:
- We want to solve this problem.
- Core(s) on the respective projects (python-openstackclient and
python-openstacksdk) are willing to provide some guidance on the best
high-level approach.
BACKGROUND
----------------------
Some OpenStack REST APIs such as neutron and nova support API extensions.
While the implementation details for API extensions may differ from project
to project, the basic extension support across all projects includes the
ability for pluggable extensions to augment the REST API in the following ways:
(a) Introducing new RESTful resources (APIs). These may be new top-level
resources (e.g. /v1/theapi/{extension_resource}) or sub-resources (e.g.
/v1/theapi/existing_resource/{extension_subresource}).
(b) Adding new attributes (fields) to existing RESTful resources. For example
neutron's net-mtu extension adds a 'mtu' attribute to networks [1] and nova's
extended status adds attributes to servers [2].
While some API extensions may exist in-tree (e.g. right in neutron or
nova), they can also live in out-of-tree projects that implement
plugins/drivers/etc..
Hopefully we can all agree that a CLI should encompass the means to
support both #a and #b above in some form or another in order to
obtain the pluggability our consumers expect with OpenStack.
PROBLEM DESCRIPTION
------------------------------------
For sake of argument lets consider #a and #b as use cases from an OpenStack
CLI (python-openstackclient and python-openstacksdk) perspective. Albeit we are
talking from a contributor perspective here; but the ability to contribute
drive features users can consume.
(a) This case should already be supported via the existing OSC plugin
model. For example [3].
(b) This case is covered for stadium projects; they can add logic
right into python-openstackclient[sdk] as needed. However for non-
stadium projects, this case is not covered; today there's no easy way
to extend existing OSC resources/actions/options/etc. in a reusable
manner. For example, suppose a non-stadium neutron (plugin) project
implements the network API, extends the network resource with
additional attribute(s) and wants to provide CLI support for these
attributes. Ideally they should be able to reuse the existing neutron
network OSC logic in a pluggable manner such that they need not
reimplement the OSC "actions" and associated logic.
From a technical perspective, case #b roughly requires the ability for
non-stadium projects (with such attribute extensions) to:
(1) Add attributes to python-openstacksdk resource(s). This allows the
extension attributes to be "collected" from an API response body.
(2) Extend existing python-openstackclient commands by;
a) Adding parser options if needed to support the attribute extension(s).
b) Adding custom "take action" logic enabling the extension to process
attribute extension options if needed.
c) Displaying the attribute extension(s).
In neutron alone, the following out-of-tree projects implement extensions
falling under case #b:
- vmware-nsx
- gbpservice
- quark
- networking-cisco
- networking-bigswitch
- networking-h3c
This support was provided in an ad-hoc fashion with the classic python
clients (e.g. python-neutronclient) via it's ability to
pass/handle/display arbitrary key/values. For example an API extension
that adds a 'meta' boolean attribute to networks can be handled with
the neutron client without any changes. The sample output snippets
below show GET and POST (notice the 'meta' attribute that's added by
the sample extension).
-->
stack@bvm2:~/devstack$ neutron --debug net-show my-meta-net
...
RESP BODY:
{"network":{"provider:physical_network":null,"ipv6_address_scope":null,"meta":true,
...
+---------------------------+--------------------------------------+
| Field | Value |
+---------------------------+--------------------------------------+
| admin_state_up | True |
| availability_zone_hints | |
| availability_zones | nova |
| created_at | 2017-07-21T17:31:23Z |
| description | |
| id | e824c797-1707-458c-9b71-8ee52f2c46c7 |
| ipv4_address_scope | |
| ipv6_address_scope | |
| meta | True |
...
stack@bvm2:~/devstack$ neutron --debug net-create meta-net-2 --meta=false
DEBUG: keystoneauth.session REQ: curl -g -i -X POST
http://172.16.78.190:9696/v2.0/networks -H "User-Agent: python-neutronclient"
-H "Content-Type: application/json" -H "Accept: application/json" -H
"X-Auth-Token: {SHA1}4f63823e9b5041c7c2ac209a8068b2637ec717cf" -d '{"network":
{"meta": "false", "name": "meta-net-2", "admin_state_up": true}}'
<--
Using the OSC, there's no way to achieve what was shown with the
neutron client in the snippets above without updating python-
openstacksdk's Network resource to add the attribute and then adding
logic into neutron's network logic in the python-openstackclient.
[1]
https://github.com/openstack/neutron/blob/master/neutron/extensions/netmtu.py#L19
[2]
https://github.com/openstack/nova/blob/master/nova/api/openstack/compute/extended_status.py
[3]
http://codesearch.openstack.org/?q=openstack.cli.extension&i=nope&files=setup.cfg&repos=
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