Open Stack

On Tue, Jul 1, 2014 at 6:39 PM, Xicheng Chang <Xicheng.Chang at huawei.com>
wrote:

>  Greetings,
>
>  This is my first post. Sorry for this beginner's question.
>
>  I have read some docs on how to configure OpenStack to use Highly
> available rabbitmq. Looks like simply configuring services with all queue
> nodes in that HA cluster would work.
>
>  --Do the services that use HA queue ensure the message sequencing?
>
> For example, if message mirroring/syncing between nodes fails or delays
> for some reason, some messages that required to be delivered prior to
> others may get delivered late. Is the service consuming this queue cluster
> ensuring the sequence or does RabbitMQ somehow do it?(this is unlikely as
> messages may get delayed while they are being sent to the queues and the
> queues wouldn't even know so)
>
>  Thank you!
>
>  Xicheng
>
>
>
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>
Xicheng,

When utilizing RabbitMQ's HA capabilities it will ensure that ordering of
messages is preserved, as all transactions against the master are
coordinated with slaves. If replication fails then you will have one queue
that is missing messages, but the ordering up to that point will be
preserved.

The primary scenario in which ordering issues might occur is if you have
multiple consumers working on a queue, and one of those consumers has to
re-queue a message for some reason.

Regards,

Richard
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