[rabbitmq-discuss] RabbitMQ persistence when clustering

Thu Dec 9 23:12:53 GMT 2010

Thanks Alex for the quick reply.

To clarify #3, when a node goes down does any other node temporarily
handle the queues for the down node? Or does the queue just stay
unavailable until the node comes back up? If it stays unavailable, are
there any future plans to ensure high availability of queues?

Thanks,
Nathan

On Dec 9, 3:09 pm, Alexandru Scvorţov <alexan... at rabbitmq.com> wrote:
> Hi Nathan,
>
> > 1. When you cluster, do ram nodes persist messages to their queues? Or
> > only disk nodes?
>
> Ram and disk apply only to whether the cluster configuration is in
> memory or also written to disk.  Nodes of any type may persist messages
> to disk.  The broker will always try to write persistent messages (on
> durable queues) to disk, and may also persist transient messages if it's
> running low on memory.
>
> > 2. What's the state that's replicated across all nodes in a cluster?
>
> Queues, bindings and exchanges.
>
> Note that while all three appear the same on every node in the cluster,
> queues are tied to the node they were declared on.  If that node goes
> down, they'll also go down.
>
> > 3. When a Rabbit node goes down, does its queue become unavailable?
>
> Yes.  If the queue was non-durable, then the queue is deleted and can be
> redeclared on any other node.  If the queue was durable, then it becomes
> unavailable, and attempting to redeclare it will result in an exception.
>
> > 4. What are the conditions (if any) for which there will be lost
> > messages?
>
> If the broker goes down before it's had time to write (persistent) messages
> to disk, those messages will be lost.
>
> Cheers,
> Alex
>
>
>
>
>
>
>
>
>
> On Thu, Dec 09, 2010 at 02:46:58PM -0800, nathanmarz wrote:
> > I'm trying to understand the behavior of a clustered RabbitMQ setup.
>
> > Specifically:
>
> > 1. When you cluster, do ram nodes persist messages to their queues? Or
> > only disk nodes?
> > 2. What's the state that's replicated across all nodes in a cluster?
> > 3. When a Rabbit node goes down, does its queue become unavailable?
> > 4. What are the conditions (if any) for which there will be lost
> > messages?
>
> > Thanks in advance,
> > Nathan
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