Open Stack

Hi-

I'm now viewing the code of Openstack from a top level to understand the
process flow of the commands and messages in the system.

I have the following doubts.

[1] What is the role of Quantum-Agent in Controller and Node. How will the
"gw-" and "tap-" interface and ports are created in Controller and Host
integration bridge of ovs.

This is how I understand from my study.

*[Trinath] *The flow as follows


   1. Upon receiving an REST call from Horizon, Nova API collected the
   Networking information from the nova_network and prepares an JSON formatted
   request and update the AMQP Queue.
   2. AMQP sends an Async cast to Nova Compute. Upon receiving the cast,
   Nova Compute issues _create_instance and updates the AMQP queue. AMQP queue
   sends an Async cast to Scheduler.
   3. Upon receiving the cast, Scheduler selects the Compute Node and send
   an async cast to the node. Node using the info in the queue using libvirt
   brings up the instance.
   4. Quantum-Agent at NODE updates the DB at controller with the Vlan
   tagged Port-Vif details.
   5. Quantum-Agent at Controller upon reading the DB on Vlan tagged
   Port-Vif details creates Gateway interfaces in the OVS integration bridge
   so that controller can access the VM's present in remote host.

Please update/correct with the pitfalls in my understanding outlined above.


[2] How AMQP (using RabbitMQ server) work, mean to say. How Controller
communicates with the Node for creating an Virtual instance in view of
AMQP. Wanted to be more clear on what Messages do Controller and Node
exchange to create an Virtual Instance.

*[Trinath]* I'm not good at AMQP. Can you kindly describe on how this works.

[3] I have created a Public and Tenant specific network using "nova-manage
network " command.

For each Virtual Instance, I have seen a Public IP addr, and Tenant
Specific IP Addr. For both IP addrs I'm unable to ping from NODE machine.

Rather for the Tenant specific IP Addrs I'm able to ping from Controller
but not the Public IP Addrs..

Can any one guide me on what has happened in the way...

Thanking you...

-- 
Regards,
----------------------------------------------
Trinath Somanchi,
+91 9866 235 130
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