Open Stack

On 10/09/2012 09:21 PM, Mark McClain wrote:
> Notifications are only used for plugin -> agent communication.  (Data flows the other way via RPC).  Generally, I am not in favor of using RPC for broadcasting information.  RPC requires the plugin know in advance where that data is routed on the receiver and often results in lots of redundent boilerplate interface code.  Also creating a private interface for notifications, results in another API layer that must be maintained.  Eventually one of the apis will suffer from bit rot without duplicative work to ensure they stay in sync.

I'm not sure what you're suggesting here.  Using rpc fanout_cast results
in the same messaging pattern used with notifications from the plugin to
agent today, but uses an API intended for internal communications.

> Ceilometer consumes notifications across all projects that emit them, so I'm not sure they would back your proposal about privatizing this communication channel.  The summit will feature sessions to discuss the notification framework in common and how to improve it  I'm looking forward to those sessions.

Part of the purpose of this thread was that I wanted to find out if
anything (including Celiometer) uses the notifications from Quantum.  I
certainly am not proposing getting rid of notifications in general.  If
they are only in Quantum for plugin to agent communications, then
notifications are not the ideal API to be using.

-- 
Russell Bryant