[rabbitmq-discuss] Errors starting RabbitMQ when cluster membership changes

[Tim Watson]

Don't take this as gospel, yet, but my understanding is that you'll be able to make cluster changes like this successfully, but I'll make sure there's a test case to prove this scenario.

On 1 Oct 2012, at 18:07, Matt Pietrek <mpietrek at skytap.com> wrote:

> Hey Tim,
> 
> I was expecting that basic response. Thanks!
> 
> However... I still think there may an issue here that hinders RabbitMQ's deployment in production scenarios. Please correct me if I'm wrong or missing something.
> 
> Hypothetically, what would happen if my 'util' node was zapped by lightning and I had no way to bring it up in a timely manner. Would I be able to start the existing cluster nodes (play, play2) "far enough" to run the proper rabbitmqctl command to remove util from the cluster?
> 
> That is, once I've gotten into a bad situation, can I back out of it gracefully and without message loss? Or is the only option to reset the entire cluster?
> 
> Thanks,
> 
> Matt
> On Mon, Oct 1, 2012 at 3:04 AM, Tim Watson <tim at rabbitmq.com> wrote:
> Hi Matt,
> 
> 
> On 09/28/2012 08:23 PM, Matt Pietrek wrote:
>> For example, at one point I had a three node cluster: play, play2, and util. I then removed util from the cluster, although to be honest, simply by changing the rabbitmq.config file, rather than explicitly running rabbitmqctl stop_app while the cluster is still running.
>> 
> 
> I'm pretty sure you're not supposed to do that! :)
> 
> 
>> My steps:
>> Running as three node cluster, stop all brokers
>> Create a new rabbitmq.config file with just two brokers
>> Attempt to start the new cluster.
> 
> If you don't take util offline using the right procedure, I suspect mnesia will get out of sorts and this isn't something you want to happen. It's important to make cluster changes using the right procedure, as mnesia is rather a fussy beast.
> 
> BTW we've made some improvements that (hopefully) simplify working with clusters and these will be in the forthcoming feature release! 
> 
> Cheers,
> Tim
> 
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