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From Dave Cottlehuber <d...@muse.net.nz>
Subject Re: Bidirectional replication and new documents
Date Tue, 26 Oct 2010 18:52:11 GMT
On 27 October 2010 03:50, Antoine Kurukchi <antpky@gmail.com> wrote:
> Hi All,
>
> Been reading a lot about couchdb and am really impressed by it. Great
> work. I have got a few questions about replication and new documents.

Welcome aboard the couch, Antoine.

> A lot is mentioned about continuous replication and bidirectional
> replication but is it possible to have both features working at the
> same time? If it is possible, what happens if there is a disconnection
> between the two database servers and are there any pit falls with this
> approach?

I've had continuous replication running for some time on a small 3-way
replicated couch without any issues, in a multi-master mesh (mmm). I
believe there may be a timeout - can anybody confirm?

If you've got continuous replication, when connectivity is re-established,
your repl kicks in again where it left off.

> I have been assuming that if you get the split brain scenario
> occurring when you have multiple database server and new documents
> (different ones) are inserted into both halves, the system wouldn't
> get into a conflict. Is this correct?

Docs are idempotent, so no, no conflict. It's only updates to existing docs
that matter. If the update is identical then there's also no conflict.

> As an example, if I have 2 servers and the link between them becomes
> non functional. Users add documents to both servers. When the servers
> reconnect and do a bidirectional replication, are all the new
> documents added to both servers?

Yes. There's a nice work-through of replication @ Chris Strom's blog at
http://japhr.blogspot.com/2010/02/couchdb-automated-replication-confusion.html
http://japhr.blogspot.com/2010/03/circular-replication-with-couchdb.html
> Thanks,
>
> Antoine
>

A+
Dave

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