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Re: Replicating only a particular database - Londiste, or Bucardo

From: Greg Sabino Mullane <greg(at)endpoint(dot)com>
To: lalit(at)avendasys(dot)com
Cc: pgsql-cluster-hackers(at)postgresql(dot)org
Subject: Re: Replicating only a particular database - Londiste, or Bucardo
Date: 2011-03-17 01:22:07
Message-ID: 20110317012207.GX14351@core.home (view raw, whole thread or download thread mbox)
Lists: pgsql-cluster-hackers
On Wed, Mar 16, 2011 at 02:32:05PM +0530, lalit(at)avendasys(dot)com wrote:
> I have been using Slony-I for PG replication of a particular 
> database in a cluster, while a second database is local and 
> not replicated. This works fine for small number of nodes. 
> But as we are moving to scale - say around 30 nodes, we are 
> seeing that Slony-I replication will not be able take the load - 
> guess since now it would be maintaining a mess of 30 nodes.

Yes. Part of the problem with Slony and that number of nodes is 
all the cross-node communication needed. You can remove all of the 
paths except the direct master->slave ones, but then you can't 
use Slony for things like failover, IIRC.

> PG9 logshipping replication is out of question because it works 
> on entire DB set. So I looked at Londiste, Bucardo. Here are my 
> requirements I would like to know if either of the two would suit well
> - nodes are added on the fly, so first it starts with one node and 
> then some network admin comes and adds another node to form a 
> Publisher-Subscriber node and then adds more nodes(or drops nodes) 
> to have multiple Subscribers. it is a master-slave replication

Everything (Slony, Bucardo, Londiste) should be able to handle this

> - promote a subscriber node to become the Publisher (Slony-I does 
> it slow here as it has to figure out which one in the mess has the 
> latest copy and then finish some replication)

Londiste is pretty much the same as Slony as far as most of these 
questions. All can do this as well, although the Bucardo way is 
quite different

> - if a node is not replicated for sometime(6 hours for Slony-I) 
> it is dropped from the cluster

You mean if it is not reachable at all? That will not work well 
with Bucardo. By "cluster" do you mean the group of slaves?

> We have scripts for Add, Drop, Promote and Reset(a single 
> node when it fails/we want to join it back)
> So my scripts have to be modified for the new replication model, 
> but will I be able to achieve all the above with Londiste, or 
> Bucardo. Or else, is there any better thing which somebody is 
> already using with a model like this ?

It's still not entirely clear what your model is. If you have a 
database that needs to be replicated, why not put it in its own 
cluster and use PG9? Is all of this only for read-only load 
balancing? Under what conditions would a slave become a master?

If you don't get much response on this list (which is not quite 
the right one for this question), try pgsql-general(at)postgresql(dot)org

Greg Sabino Mullane greg(at)endpoint(dot)com
End Point Corporation
PGP Key: 0x14964AC8

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