[openstack-dev] [Quantum][LBaaS] Service type framework: todo & cleanup

Sumit Naiksatam sumitnaiksatam at gmail.com
Tue Apr 30 16:31:40 UTC 2013

Hi Eugene,

Thanks for bringing this up. We tried to discuss some of these in the
"services chaining, insertion, and steering" session during the summit.
Based on the discussion and feedback (and also from implementing a
prototype involving multiple service "types") my responses inline.


On Tue, Apr 30, 2013 at 8:34 AM, Eugene Nikanorov
<enikanorov at mirantis.com>wrote:

> Hi folks,
> One of the major features that we need to implement during Havana (H-1 at
> best) is true flexible multivendor support.
> There could be different ways of giving tenant ability to choose vendor of
> requested loadbalancer, but we need to evaluate how service types could
> help us on this way.
> The reason I'm writing this is that I'd like to make some terminology
> cleanup and set up key design points to discuss and move forward.
> Let's start with what we have on service types today:
> 1) Description of the feature:
> https://wiki.openstack.org/wiki/Quantum/ServiceInsertion
> 2) Code:
> https://github.com/openstack/quantum/blob/master/quantum/db/servicetype_db.py
> 3) seems to be framework is not used (and doesn't have respective CLI
> code) so changing it would not be painfull if we want to.
> *I'd like to set service insertion problem aside and focus on service
> types as a way to choose vendor.*
> So, on terminology side we have the following enitities (from code and
> docs):
> - Service Type - defines a set of service providers (plugins:drivers)
> - Service Definition - defines one service provider
> - Service Class - a type of service (?!) (LB, FW, VPN)

> 1) So, first of all terminology seems to be quite confusing, especially
> word "type" is overloaded.
> I think we need to propose better names for the these entities just to
> simplify our thinking about the integration with services.
So, my proposal would be:
> - Service Type - LB, FW, VPN
> - Service Type Provider - defines one service provider (former Service
> Definition) (alt: Service Type Definition)
> - Service Group - what used to be Service Type. (alt: Service Set, ??)
Sumit: How about a top level "service_type" class (consistent with current
definition) with attributes like:
- Category, e.g. LB, FW, VPN
- Vendor, e.g. XYZ
- Insertion Model, e.g. L3, L2, Bump-in-the-wire, Tap (I know you mentioned
that you want to keep this aside for now, but I am stating it here for
- Provider, name of the class which implements this service (one per type
as you suggest later)

Until agreed, I'll use old terminology.
> 2) The relationship between Service Types and Service Definitions.
> It is not obvious (nowhere stated or enforced) but Service Type must have
> just one Service Definition of the same Service Class,
> otherwise, Service Type is useless for API call dipatching. E.g. there
> should be 1:1 mapping between Service Type and Service Definition for
> certain Service Class.
Sumit: We also need a base service class definition that can be used across
services. This should support a contract for creating multiple logical
instances of the service (e.g. one more logical Firewalls devices/instances
as requested by a tenant). It should also support the attributes required
to help service insertion (since the service implementor knows how the
service will attach to the network).

> 3) API calls dispatching. The most important question: whether or not to
> support multiple plugins per Service Class.
> In other words, whether to have several Service plugins (several lbaas
> plugins, for ex) loaded simultaneosly.
> My opinion is that we don't need that as multi-vendor support could be
> implemented more simple plugin-side drivers.
> To make this shorter, I'll skip explanation for now.
Sumit: A complementary part of this discussion is the ability for one
plugin to support multiple services. We discussed this briefly during the
summit, and I believe we agreed to fix this in the current implementation.

So in order to move forward I'd suggest we have a meeting with the
> following agenda:
> 1. Terminology
> 2. Service type framework refactoring.
> 3. API calls dispatching: hints and control flow.
> I'll prepare some suggestions/diagrams about this.
> We could have a meeting someday this week at 8:00 - 10:00 AM PST, late
> evening PST will also work for me.
Sumit: 8 - 10 AM PST sounds good to me! ;-)

> Thanks,
> Eugene.
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