Neutron/FlavorFramework

Rationale

The purpose of Flavor Framework is to provide more abstract API that allows user to chose service by it's capabilities rather then by provider/vendor.
User-facing part of Flavor is a group of service parameters. The proposed Flavor notion is similar to what nova has with the difference that Flavor parameters are dynamic (e.g. not fixed or hardcoded)

From implementation point of view, the flavor is an object that is used to bind logical service instance (for whatever service) to a concrete provider that is later to be used to dispatch REST API calls after they pass persistence layer.
Binding process is known as scheduling; it maps flavor chosen for particular resource (at creation) to a provider.

Object model

Flavor Framework defines the following objects:

Flavor

Attributes:

* Service Type - string identifier (LOADBALANCER, FWAAS, L3, VPN, etc)
* Name - name of the flavor
* Parameters - list of (key, value) pairs that define capabilities. Value can be range or integer, or string, or json.
* FlavorType - public or internal

The last attribute - FlavorType defines whether the flavor is publicly available or is internal.
Internal flavors are provided by vendor drivers configured for corresponding services.
Internal flavors are similar to 'provider' notion, plus may have additional parameters that describe service capabilities.
Each driver, including the default one of each service should provide at least their default capabilities object.

API

Public API consist of flavors resource, which user can list or show:

neutron flavor-list
------------------------------------------------------------------------------
|    ID    |   Service Type              |    Name            | Description  |
------------------------------------------------------------------------------
|  UUID    | LOADBALANCER                |    Reference       |  Basic LB    |
|  UUID    | LOADBALANCER                |    Hi-perf         | expensive    |
------------------------------------------------------------------------------

neutron flavor-show UUID
---------------------------------------------------------
|  ID                 |     UUID                        |
| Service Type        |      VPN                        |
| Name                |     ipsec                       |
| Description         |      reference                  |
| Parameters          |     <Parameters>                |
---------------------------------------------------------

create/update/delete commands are available for administrator only.

Migration

Migration from existing configuration is expected to be straightforward.
If service supports Provider Framework, it's service instance object has 'provider' attribute that helps REST API calls dispatching to a proper driver.
From the Flavor Framework perspective, such resources appear to be already scheduled with unknown flavor.
That should not affect their operability and admin status.

From REST API Perspective 'provider' attribute becomes visible for admins only (and it can't be provided for create/update), while flavor attribute is available for create/update operations for regular user.