[Openstack] Messaging reliability/durability expectations

Noel Burton-Krahn noel at pistoncloud.com
Tue Oct 14 21:36:08 UTC 2014


Hi Aaron,

Unfortunately, durable queues don't fix the case where rabbit dies and
restarts on a new host (and loses its durable queue store)

There's a fix here, but it's been waiting a while for a merge

https://review.openstack.org/#/c/109373/

--
Noel




On Tue, Oct 14, 2014 at 1:51 PM, Aaron Knister <aaron.knister at gmail.com>
wrote:

> (Tested in icehouse)
>
> On Tue, Oct 14, 2014 at 4:50 PM, Aaron Knister <aaron.knister at gmail.com>
> wrote:
>
>> For those of you following alone at home--  I just discovered that
>> durable queues are particularly nice for nova scheduler. Without them an
>> outage of either the MQ daemon (qpid in my case) or the scheduler itself
>> can cause the scheduling requests to get dropped on the floor. With
>> durability the instance gets scheduled when the broker or the scheduler
>> come back to life.
>>
>> On Tue, Oct 14, 2014 at 3:32 PM, Gordon Sim <gsim at redhat.com> wrote:
>>
>>> On 10/14/2014 07:36 PM, Aaron Knister wrote:
>>>
>>>> With RabbitMQ if a message is silently dropped by the broker will a
>>>> timeout still occur/exception be raised because no reply/ack was
>>>> received?
>>>>
>>>> With the QPID driver the automatic ack()'s Sandy mentioned don't occur?
>>>> Will the sender eventually become aware that a message was lost? I'll
>>>> take a timeout over a silent message drop any day.
>>>>
>>>
>>> Yes, for an RPC 'call' (i.e. not a cast, which has no reply) the call
>>> will block until the response is received or the timeout expires. In the
>>> latter case an exception is raised. This is independent of which driver is
>>> used.
>>>
>>>
>>
>
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