[rabbitmq-discuss] Clustering over a WAN

Mon Feb 28 21:59:56 GMT 2011

On Mon, Feb 28, 2011 at 9:57 PM, Michael Bridgen <mikeb at rabbitmq.com> wrote:
>> Another approach is to create federation models in new exchange
>> types.
>
> Why have new exchange types -- why not just federate those that exist
> already?

Yes, that would be spiff too.

>
>> On Mon, Feb 28, 2011 at 5:26 PM, John
>> DeTreville<jdetreville at vmware.com>  wrote:
>>>
>>> Yes, but...
>>>
>>> Some users want geographic distribution, and while that's pretty
>>> much impossible in Mnesia (which even so is already a distributed
>>> database!), it doesn't become a whole lot easier with a different
>>> distributed database.
>>>
>>> One possible approach to building a geographically distributed
>>> messaging system (possibly as an eventual successor or supplement
>>> to RabbitMQ) would be to provide eventual consistency instead of
>>> the stronger consistency currently provided, perhaps building it on
>>> top of an appropriate eventual-consistency database system. This
>>> would unfortunately require pervasive changes in the queuing API.
>>>
>>> In my spare time, I've been thinking a little about the design of
>>> such an API, and I'll post some more details shortly.
>>>
>>> Cheers, John
>>>
>>> On Feb 28, 2011, at 8:37, "Jon Brisbin"<jon at jbrisbin.com>  wrote:
>>>
>>>> Would any of these issues be resolved by using a distributed K/V
>>>> store as the backend for both messages and metadata? I know the
>>>> internals of using mnesia to store all that metadata can't easily
>>>> be abstracted, but if you didn't have that particular hurdle to
>>>> jump, would that make clustering any easier?
>>>>
>>>> Jon Brisbin
>>>>
>>>> http://jbrisbin.com Twitter: @j_brisbin
>>>>
>>>>
>>>> On Feb 28, 2011, at 9:51 AM, Matthew Sackman wrote:
>>>>
>>>>> On Mon, Feb 28, 2011 at 03:27:42PM +0000, Chris Hampson wrote:
>>>>>>
>>>>>> We're currently attempting to maintain a RabbitMQ cluster
>>>>>> over a WAN between some of our sites, 2 in the US, one in the
>>>>>> UK and another in India.
>>>>>
>>>>> That's a bad idea.
>>>>>
>>>>>> For the most part this seems to be working fine, but it seems
>>>>>> a little fragile and we can't seem to get it to recover from
>>>>>> failures very well.
>>>>>
>>>>> Correct. Mnesia, which Rabbit uses to store all sorts of data
>>>>> (though not messages), copes poorly with network partitions.
>>>>>
>>>>>> If anyone can provide any advice to aid our situation we'd be
>>>>>> most grateful (even if it is "don't do that you loony,
>>>>>> separate them out and shovel messages between sites when
>>>>>> necessary")
>>>>>
>>>>> Yeah, the latter's a fair summary of my advice on this ;) We do
>>>>> state quite prominantly that clustering is not for HA, though I
>>>>> admit we state it on http://www.rabbitmq.com/pacemaker.html
>>>>> rather than http://www.rabbitmq.com/clustering.html which is
>>>>> not really as helpful as it could be.
>>>>>
>>>>> The problem is that mnesia, and by extension Rabbit, goes for
>>>>> the Consistency and Availability part of the CAP triangle, and
>>>>> so just does not cope well with partitions ocurring.
>>>>> http://en.wikipedia.org/wiki/CAP_theorem
>>>>>
>>>>> We are working on solving some of these problems in a number
>>>>> of different ways. If the shovel is a viable solution then I'd
>>>>> recommend you use that, otherwise please let us know some more
>>>>> details of your use case and we should be able to advise
>>>>> further.
>>>>>
>>>>> Best wishes,
>>>>>
>>>>> Matthew _______________________________________________
>>>>> rabbitmq-discuss mailing list
>>>>> rabbitmq-discuss at lists.rabbitmq.com
>>>>> https://lists.rabbitmq.com/cgi-bin/mailman/listinfo/rabbitmq-discuss
>>>>
>>>>
>>>>
>>>>
>>>>>
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