[rabbitmq-discuss] RabbitMQ persistence when clustering

[Alexandru Scvorţov]

> To clarify #3, when a node goes down does any other node temporarily
> handle the queues for the down node?

Nothing's done automatically.  If the queue was non-durable, a
reconnecting client should be able to redeclare the queue.  If the
original node comes back up, the queue doesn't reappear automatically.

> Or does the queue just stay unavailable until the node comes back up? 

If the queue was durable, the queue is unavailable until the node comes
back online.

> If it stays unavailable, are
> there any future plans to ensure high availability of queues?

I can't really comment on that, but if you want high-availability right
now, you might be interested in our HA guide:

  http://www.rabbitmq.com/pacemaker.html


Cheers,
Alex

On Thu, Dec 09, 2010 at 03:12:53PM -0800, nathanmarz wrote:
> 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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> >
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