[Openstack] Understanding the Folsom-Quantum

Gary Kotton gkotton at redhat.com
Tue Dec 11 09:29:22 UTC 2012

On 12/11/2012 09:50 AM, Trinath Somanchi wrote:
> Hi-
> I have the following first set of doubts regarding the Folsom Quantum
> [1] With regard of Quantum Plug-in, How does the RPC communication 
> take place between the Agent and the plug-n ? In the source code, 
> ovs_quantum_plugin.py, I find the setup_rpc method and AgentRPCAPI 
> class what does the reverse RPC tasks. Can any one guide me on 
> understanding this.

When the OVS detects that a new interface has been added it will query 
the plugin for the interface details. This will enable it to create the 
relevant networking for the specific interface, for example tags etc. 
The agent requests information from the plugin when it detects that 
there is a new resources.
In addition to this there are cases when the plugin will notify the 
agent - for example if the admin status of a port has changed.

> [2] What is the significance of the file quantum/db/dhcp_rpc_base.py? 
> Many plugins in the quantum/plugins directory use the methods in the 
> class.

This enables the DHCP agent to request information from the plugin.

> [3] With core_plugin configuration being in place, can we have some 
> other plugin too existing in Quantum? Can any one guide me on how to 
> achieve the same, like a Fake plugin?

In V2 there is no fake plugin. There are a number of different plugins 
that make sue of the base DB plugin - for example the linuxbridge, 
openvswitch, NEC, RYU etc.

> [4] Why OVS quantum Plug-in doesn't support create/update/delete of 
> port and subnets?

The OVS plugin inherits the base plugin. If it does not need to make any 
additions then it will use the base methods implementation. If you look 
at https://review.openstack.org/#/c/16210/ you will see that in some 
cases changes need to be made - for example extending the ports to 
support security groups.

> Kindly help me understand these ...

It is all pretty complicated. My suggestion would be to get a evstack 
installation up and running and playing around with the configurations 
and the agents. Once you start to understand how all of the components 
interact it will be easier to follow.

> Thanks in advance
> -- 
> Regards,
> ----------------------------------------------
> Trinath Somanchi,
> +91 9866 235 130
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