Open Stack

> > > 
> > > Some questions we had were:
> > > * Is it possible to use the old-style polling, or to make it optional?
> > > 
> > 
> > 
> > Yes. In the agent configuration file there is a flag 'rpc'. By default 
> > this is True. If you want you can set this as False. This is supported 
> > in the l2 agents. It is not supported by the dhcp agent.
> > 
> 
> 
> 

Still not our ideal fix, but that would care of the agents, but what about the notifications? I presume these are still required even if that rpc flag is off? 
> > There are two type of fanout messages that are used. The first is with 
> > the l2 agents in the event that a port or network is updated. The 
> > second is via the openstack common notifier module.
> > 
> 
> 
> 


The l2 agents are only consuming (not sending) the rpc.fanout messages, yes? I assume they're sending the notifications, though? 
> > The is used by the 
> > dhcp agent. I am not 100% sure if the notifier module supports Zero MQ
> > 
It doesn't. The "rabbit_notifier" is just as it is called. Really, though, the only thing that makes the Rabbit notification driver incompatible with ZeroMQ is that it uses a topic key set as:

 "%s.%s" % (topic, priority) 

The ZeroMQ driver would perceive the priority as a destination host and would try sending all messages to a host named 'INFO' (or 'ERROR', or whatever other priorities are defined)

Where are these notifications being consumed?
> > I have yet to understand the problems with the RabbitMq and Qpid vs 
> > Zero MQ. Are these scale issues, performance, stability? It would be 
> > interesting to try and know what the problems are.
> > > 
> > > 
> > 
> > 
> 
> 
> 

The RabbitMQ and Qpid drivers are fairly similar and share a lot of code, and they're behaviorly similar.  I'd compare their relationship to that of MySQL and PostgreSQL.  The ZeroMQ driver is vastly different, and we're using it in a peer-to-peer model that introduces some challenges around the subscription model.

Regards,
Eric Windisch
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