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From Adam Kocoloski <kocol...@apache.org>
Subject Re: Preserving seq order through replication
Date Tue, 09 Mar 2010 00:26:09 GMT
On Mar 8, 2010, at 4:20 AM, 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.

True, but when x and y happened at different write masters all bets are off.  Vector clocks
can often maintain an ordering of events across the distributed set of nodes, but not always.
 Best,

Adam
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