[rabbitmq-discuss] Cluster Pathology

Dmitriy Samovskiy dmitriy.samovskiy at cohesiveft.com
Wed Feb 11 16:31:33 GMT 2009

Hi Jason,

Jason J. W. Williams wrote:
> I don't expect the messages to get moved when the node comes back
> up....well it would be nice, but I accept that it doesn't happen (in
> fact, if the queue has been redeclared on another node during the
> downtime, the messages "appear" to be lost when the downed node
> returns...I'm sure they could be recovered from the persister log).

I have thought more about it and now I'm wondering if it's even possible to redeclare a 
queue in a cluster that happens to reside on a node that currently is not reachable from 
cluster? Can't test at the moment, since I decommissioned my cluster vms some time ago :)

In theory, doesn't the queue still exist when queue.declare with active=true is attempted? 
The contents might not be replicated, but all metadata are.

Have you actually tried it? I kind of expect that if you don't remove a node from cluster, 
you won't be able to redeclare a queue. Does this sound reasonable?

> doesn't apply to them). The point of our cluster is failover with the
> future possibility of scaling the cluster. But first and foremost,
> fail over. If subscribers on Node B get orphaned, they can't help

I am also primarily looking at cluster for failover capabilities. I am getting better 
failover from unclustered brokers - an alternative approach that Tony described earlier 
today in another thread [1]. YMMV of course.

[1] http://lists.rabbitmq.com/pipermail/rabbitmq-discuss/2009-February/003359.html

- Dmitriy

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