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From Alessio Pace <alessio.p...@gmail.com>
Subject Re: Questions about couchDB algorithms
Date Wed, 04 Feb 2009 14:18:49 GMT
Hi,

On Wed, Feb 4, 2009 at 2:59 PM, Paul Davis <paul.joseph.davis@gmail.com>wrote:

> On Wed, Feb 4, 2009 at 4:49 AM, Alessio Pace <alessio.pace@gmail.com>
> wrote:
> > Hi,
> >
> > I have just discovered couchDB and I'm very interested in knowing more
> about
> > the internal details of it, because apart from reading that is
> multi-master
> > and that the system is eventually consistent, I don't see much
> informations
> > about other various key design things (I apologize if I wasn't able to
> find
> > them), like:
> >
> > - update propagation through gossiping: based on any known algorithm?
> >
>
> The current state of affairs in terms of keeping multiple nodes in
> sync uses the baked in replication mechanism. At the moment it is up
> to the user to ensure that nodes are kept in sync via these
> facilities.


Could you formulate a bit more about this?


> There is quite a bit of active development on this front
> so it's best to stay tuned and see what comes out.
>
> > - group membership among the various site: how is it done, through
> > gossiping? If so, based on any known algorithm?
> >
>
> Not sure what you mean here.


I mean: how does it deal with dynamic networks, where nodes join and leave,
and you have to know onto which you can push/pull ? I am obviously talking
about cases in which you can't list the a priori list of few cluster
machines on text file and copy it on all the machines.


>
>
> > - are sites required to accept incoming connections (-> can I replicate
> on
> > nodes behind NAT?)
> >
>
> Replication is both push and pull. So you just need to be able to have
> your nodes behind NAT know when to trigger replication.


You mean that if a public node generates an update, it can't be replicated
to a natted target node unless it pulls the replication itself?


Thank you.

Best regards,
--
Alessio Pace

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