openstack team mailing list archive

[Russell Bryant <rbryant@xxxxxxxxxx>]

On 09/17/2012 06:11 AM, jeffrey coho wrote:
> Hi,all
>    why there needs two topic queues for nova-compute?The queue with
> routing key:"compute.host"
> is obvious,but what about the queue with routing key "compute"?what is
> this for?when does it use this
> queue?
> Thanks a lot.

I don't think that the 'compute' queue is actually used.  It's there
because the code that sets up the queues is common to all nova services,
so they are all capable of the same set of messaging patterns.

All instances of nova-compute are subscribed to the 'compute' topic.  If
a message were to be sent to that topic, it would go to one instance of
the services, chosen via round-robin.

A realistic example of the use of this topic is the nova-scheduler
service.  Messages to the scheduler are sent to the 'scheduler' topic.
You can run multiple instances of nova-scheduler to scale it out, and it
doesn't matter which one processes each scheduler request.

-- 
Russell Bryant