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From Robert Elliot <...@lidalia.org.uk>
Subject Re: Multi node topology
Date Mon, 22 Aug 2011 10:23:27 GMT
OK, great.  So my next question is what we need to do to restore after reboting a node.  We
know that the replication information is not persisted.  So if in the scenario I outlined
we restart A, obviously we need to tell it to pull from B, C and D again.  However, do we
also need to tell B, C and D to pull from A?  Or will they have been trying to do that anyway?
 Should we really have told B, C and D to *stop* pulling from A before we stopped A in a deliberate
restart scenario?

Thanks,
Rob

----- Original Message -----
> From: "Adam Kocoloski" <kocolosk@apache.org>
> To: user@couchdb.apache.org
> Sent: Friday, 19 August, 2011 7:29:23 PM
> Subject: Re: Multi node topology
> Hi Robert, no, I wouldn't say that. The projects Paul mentioned can
> simplify some of the setup of a multi-master deployment even if you
> don't take advantage of the sharding, but they're by no means required
> for it.
> 
> To answer your questions, push and pull replications are approximately
> equal in their efficiency these days. The approach you outlined should
> be fine for a cluster of 4 nodes. Cheers,
> 
> Adam
> 
> On Aug 19, 2011, at 2:21 PM, Robert Elliot wrote:
> 
> > Thanks; we're aware of both solutions, but as we do not currently
> > need to partition/shard we are interested in exploring what CouchDB
> > could do by itself, since it supports bi-directional replication.
> >
> > Is the answer "the CouchDB developers recommend not running CouchDB
> > in a multi-master replicated topology"?
> >
> > On 19 Aug 2011, at 18:26, Paul Davis wrote:
> >
> >> Robert,
> >>
> >> There are two projects for running CouchDB in a cluster:
> >> CouchDB-Lounge and BigCouch. CouchDB-Lounge is a combination of an
> >> nginx module and Python proxy that handles managing multiple
> >> backend
> >> CouchDB nodes. BigCouch is a pure Erlang implementation that works
> >> more like Dynamo.
> >>
> >> [1] http://tilgovi.github.com/couchdb-lounge/
> >> [2] http://github.com/cloudant/bigcouch
> >>
> >> On Fri, Aug 19, 2011 at 8:32 AM, Robert Elliot <rob@lidalia.org.uk>
> >> wrote:
> >>> Hi,
> >>>
> >>> We are considering setting up a cluster with more than two nodes.
> >>> There is a lot of documentation regarding two nodes but we
> >>> couldn't find an exact answer for let's say a cluster of 4 nodes.
> >>>
> >>> Would you recommend a multi-master setup where all nodes receive
> >>> writes? This would be simpler to setup and administer, and would
> >>> also be the most fault tolerant (any combination of nodes can be
> >>> shutdown so long as one is still active).
> >>>
> >>> If so, should we use only push replication? Or only pull
> >>> replication? Or a combination of both?
> >>>
> >>> Assuming we are using pull replication within 4 nodes: A, B, C and
> >>> D. Should we set up A to pull changes from B, C and D, B to pull
> >>> changes from A, C and D, C to pull changes from A, B and D and D
> >>> to pull changes from A, B and C? Is this the recommended approach?
> >>>
> >>> Thanks for any guidance,
> >>>
> >>> Rob
> >>>
> >

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