Sort of.

Openstack RPC-over-AMQP (oslo.messaging) automatically ack()'s all messages 
that are received. So, it becomes the responsibility of the sender to retry. 
For example, the scheduler in Nova does this. However, if the client fails 
before getting the message, AMQP will automatically requeue it and send it to 
another client. But that's an unlikely occurrence as it's queue-per-host so 
there wouldn't be a second client. Therefore, queues should be configured to be 
durable.

Hope it helps!
-S



________________________________
From: Aaron Knister [aaron.knis...@gmail.com]
Sent: Tuesday, October 14, 2014 12:00 PM
To: Raghu Vadapalli
Cc: <openstack@lists.openstack.org>
Subject: Re: [Openstack] Messaging reliability/durability expectations

Thanks Raghu. I think I might not be asking the right questions. Part of my 
ignorance here comes from not understanding AMQP. I think really what I'm 
trying to figure out is whether openstack expects durable queues. It sounds 
like the answer is no but confirmation of this would be great. Even if it 
doesn't expect durable queues is there a noticeable advantage to openstack to 
have them?

Thanks again!

Sent from my iPhone

On Oct 14, 2014, at 10:12 AM, Raghu Vadapalli 
<rvatspac...@gmail.com<mailto:rvatspac...@gmail.com>> wrote:





—
Raghu

On Tuesday, Oct 14, 2014 at 7:49 AM, Aaron Knister 
<aaron.knis...@gmail.com<mailto:aaron.knis...@gmail.com>>, wrote:
Thanks Remo, could you elaborate a little? Which is part of RabbitMQ? The HA 
layer or the message retransmission? I'm currently using qpid. Also, just so 
I'm clear, is it the openstack code or the low-level messaging drivers (rabbit, 
zmq, qpid) that retransmit on message delivery failure?

Thanks!

​
That should be the job messaging infrastructure provided by rabbit or qpid
Raghu

Sent from my iPhone

On Oct 13, 2014, at 11:59 PM, Remo Mattei 
<r...@italy1.com<mailto:r...@italy1.com>> wrote:

That is part of RabbitMQ and yes it will resend the msg.

Remo
On Oct 13, 2014, at 22:31, Aaron Knister 
<aaron.knis...@gmail.com<mailto:aaron.knis...@gmail.com>> wrote:

Hi Everyone,

I'm building a production-grade cloud where HA is a requirement. I'm currently 
working on implementing HA of the messaging layer and am not clear on what the 
expectations/assumptions are of the messaging layer regarding message 
durability and reliability. I've seen documentation scattered about that 
suggests OpenStack makes no assumptions that messages will be delivered or will 
need to persist for any period of time 
(https://openstack.redhat.com/Highly_Available_Qpid_for_OpenStack).

What's the consequence of RPC message loss within openstack? Is it true that it 
will resend messages?

Thanks!

-Aaron
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