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From Mark Hammond <skippy.hamm...@gmail.com>
Subject Re: Preserving seq order through replication
Date Mon, 08 Mar 2010 23:43:31 GMT
On 8/03/2010 8:20 PM, Dirkjan Ochtman wrote:
> On Fri, Mar 5, 2010 at 17:56, J Chris Anderson<jchris@gmail.com>  wrote:
>> I don't think this is a bug. Preserving order across replicas is definitely something
that won't scale across a cluster (especially if it is partitioned), so we wouldn't want to
attempt guarantees like that at smaller scales.
>
> I'm not sure why you think it doesn't scale across a cluster. If you
> guarantee this for a single replication connection, doesn't that
> magically scale to all of the cluster? That is, if any message y
> preceded by message x came in at any of the masters, and all
> replication channels preserve this order, then any server that has y
> will be sure to have gotten x before. So I'm not sure why that implies
> changes at larger scale.

I'm not really up on this in any detail, but isn't there the possibility 
that 'y' will have had the same edit performed on 2 different nodes, 
while 'x' was only edited on one of them.  The change to 'y' will not be 
replicated at all between the 2 nodes with identical edits, whereas 'x' 
will - meaning 'x' will be seen to arrive later than 'y' on one of the 
nodes?

Cheers,

Mark

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