[rabbitmq-discuss] Clustering over a WAN

[Michael Bridgen]

> Another approach is to create federation models in new exchange
> types.

Why have new exchange types -- why not just federate those that exist
already?

> 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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