?So let me make sure I understand this. You want to do a separate service 
plugin for what would normally be separate drivers under one service plugin.  
The reasons for this are:


1. You dont want users the ability to choose the type, you want it always to be 
the same one

2. Some types do want to be the source of truth of the data stored, instead of 
it being the service plugin database.


First, let me address the possibility of a solution using one service plugin 
and multiple drivers per type:


I think that you can overcome #1 in the instantiation of the service plugin to 
check if there are more than 1 provider active, if so you can just throw an 
exception saying you can only have 1.  I'd have to look at it more to see if 
there are any caveats to this, but I think that would work.


For #2, assuming #1 works, then the drivers that are defined can have some 
boolean that they set that will tell the plugin whether they are the source of 
truth or not, and depending on that you can store the data in the service 
plugin's db or just pass the data along, also pass GET requests to the drivers 
as well.


As for making a service plugin for each type, I don't see why that wouldn't 
work.  It seems a bit overkill to me though because you'd probably end up 
having 2 base classes for every service plugin type, one for using the service 
plugin database and another for the data source of truth being external.  
Probably a better way to do this, I'm sure I'm oversimplifying.  I don't see 
much technical reasons why you couldn't do this, though.  It's just 
inconsistent and might cause some confusion.  I'd need to spend some time on it 
to really have an educated opinion.


Thanks,
Brandon

________________________________
From: Mathieu Rohon <mathieu.ro...@gmail.com>
Sent: Tuesday, August 18, 2015 7:13 AM
To: OpenStack Development Mailing List
Subject: [openstack-dev] [Neutron][bgpvpn] Service Plugin vs Service driver

Adding the related subject :)

On Tue, Aug 18, 2015 at 10:35 AM, Mathieu Rohon 
<mathieu.ro...@gmail.com<mailto:mathieu.ro...@gmail.com>> wrote:
Hi all,

The current bgpvpn implementation is using the service type framework, with a 
service plugin and one or more service providers.

After registering the bug [1], I wonder if we would rather use a service plugin 
per implementation type (bagpipe, ODL, OpenContrail, Nuage...) which handles 
API calls, instead of having one service plugin which forwards API calls to a 
service driver depending on the provider chosen by the end user.

I would like to better understand what would be the main drawbacks of such a 
move apart from the fact that a deployment would be tightly coupled to a bgpvpn 
plugin, and multiple implementations of the plugin couldn't coexist.

Thanks,

Mathieu

[1]https://bugs.launchpad.net/bgpvpn/+bug/1485515

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